Measurement of Neutra1 Cervical and Cervicothoracic Posture in Healthy Adults

Weihe Wang

A thesis subrnitted to the Department of Anatomy and Ce11 Biology in conformity with the requirements for the degree of

Master of Science

Queen's University Kingston, Ontario, Canada

September, 1997

Copyright O Weihe Wang, 1997

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Absîract

Pain in the cervical spine is cornmon in today's society. It has been documented

that head and neck postural abnormalities are associated with cervical pain. Objective

measurement of head and neck posture is important in order to determine the relationship

between neck pain and posture and to monitor tbe effectiveness of education and exercise

programs in improving posture. The purpose of this study was: a) to detennine the

reliability of the PEAK Motion Analysis System in measuring oeutral cervical spine

posture, totai head excursion (THE) and resting head posture (RHP), b) to detect whether

there are differences in cervical spine posture meames between males and females and

between sitting and standing positions, and c) to use measurements obtained with the

PEAK System to define the normal range of cervical posture, THE and RHP in healthy

young adults. The investigation was conducted in 2 phases: phase 1, reliability study:

phase 2, main study. Ten !abjects (5 males, 5 fernales), aged 20-37 years participated in

the reliability study. Thuty two mbjects (17 males, 15 fernales), aged 20-29 years took

part in the main study. The PEAK Motion Analysis System, a video-recording and

cornputer-digitking system, was used tu record head and neck posture from the lateral

side of the subject and to obtah aagular measures by digitizing markers attached to the

head and neck of the subjects. Nine retroreflective markers were placed over bony

landmarks and twelve angle parameten were measured. Subjects performed fully

protracted, neutral and retracted head and neck postures in both sitting and standing

positions without constraint.

Reliability of al1 12 parameters for between trial (intraday) and between-day

(interday ) measures was calculated using intraclass correlation coefficients ICC(2,l) .

Of 72 intraday ICC's, 66 were in the range 0.80-1.00. The other 6, were in the range

0.60-0.80, related to four angles. interday ICC's of 8 angles had acceptable reliability

and these angles were selected for use in the main study. Interday ICC's of THE and

RHP measured by three angles showed acceptable values in the standing position, but

generally Iower values in the sitting position. The sitting position measures of these

parameters were therefore not used in hrther analysis. No significant difference was

detected between genders or between positions in masures of neutrai head and neck

posture (P 20.05). Similarly no significant difference was found between genders with

respect to THE and RHP (Pr0.05). Normal range of neutral head and neck posture in

both positions, and THE and RHP in the standing position, expressed by 95 % natistical

confidence intervals, supplied the normative database for clinical and research use.

The results dernonstrated that the PEAK Motion Analysis System and method used

in this snidy are highly reliable. Neutra1 head and neck posture of normal young adults

is not affected by gender, nor hy position. Head and neck posture is reproducible in

healthy young subjects on two test occasions. Measures of THE and RHP are more

variable and less reproducible in the sitthg than in the standing position. The variation

in measures of head and neck posture, THE and RHP between subjects, detennined by

the 95% confidence intervals around the mean, is generdly quite small in this subject

population. The normative data base obtained can be used in hitute studies to look at

effects of aging and cervical dysfunction on head and neck posture.

Acknowledgements

I would like to express my deep gratitude and appreciation to my supervisors, Dr.

Elsie Culham and Dr. Malcolm Peat, for their guidance, expertise and support throughout

this research project.

1 would also like to express my gratitude to the following individuals for their

assistance throughout this project:

Mr. lan MacBnde, school of Rehabiütation Therapy, for his invaluable assistance

and advice during the data collection and data processing.

Mr. Rick Hunt, Department of Anatomy and Ce11 Biology, for the design and

manufacture of the equipment used for data collection.

Mr. Bob Temkin, Department of Anatomy and Cell Biology, for the taking and

development of the photographs used for this thesis.

Luci Fuscaldi Teixeira for her fnendship, encouragement and heip throughout this

thesis development .

My parents for their unconditional love and support throughout all rny education.

A Special thank you to ail of the subjects who dedicated their time making this

mdy possible.

Finally, a thank you goes to rny husband, Jason J. Li, for his inspiration, support

and love throughout my education; and to Our daughter, Nancy, for her king aiways

with me al1 hard time and good time, and making our whole word full of fun and love.

Table of Contents

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Abstract i

... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements iii

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table of Contents iv

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . List of Figures vii

... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . List of Tables viii

* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . . I Introduction . 1

II . Literature Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.

* * . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Anatomy of Cervical Spine .5 2.1 - 1 The Occipito-Atlanto-Axial Complex (C&-CI) . . . . . . . . .6 .

. . . . . . . . . . . . . . . . . 2.1.2 The lower Cervical Spine (C2-T, ) .8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . a . The vertebrae 8.

. . . . . . . . . . . . . . . . . . . . . . . . b Zygapophyseal Joints .9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . c . Ligaments .1 0.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 The Neutra1 Posture -11 . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Definition and terminology - 1 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 Measurements .13 . . . . . . . . . . . . . . . . . . a . Non-invasive Measurernent .14.

77 b . Invasive Measurement . . . . . . . . . . . . . . . . . . . . . .--. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Forward Head Posture .28.

. . . . . . . . . . . . . . . . . . . . 2.3.1 Defmition and Description .28 . . . . . . . . . . . . . . . . . . . . . . . . 2.3.2 Consequences of FHP .29 .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Summary 31

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III . Methodology .33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Subjects .33.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Ethicai Considerations .34.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Meanirement System .34. 3.3.1 The Peak 2D Motion Analysis System . . . . . . . . . . . . . .34 . 3.3.2 Recision and Accuracy of Peak System . . . . . . . . . . . . .36 .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 -4 Data Collection .37. . . . . . . . . . . . . . . . . . . . . . . . . . 3 .4.1 Expriment Design .37 .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Rocedure .43.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Data Processing .4 4. . . . . . . . . . . . . . . . . . . . . . . . . 3 S.1 Videotape Encoding: .44 . . . . . . . . . . . . . . . . . . . . . . . . 3.5.2 Spatial Mode1 Set Up .45 .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 S . 3 Project S.et Up .45. . . . . . . . . . . . . . . . . . . . . . . 3.5 -4 Automatic Data Capture .45 .

. . . . . . . . . . . . . . . . . . . . . . . . . . . 3 S.5 Data calculation .46. . . . . . . . . . . . . . . . . 3.6 Further Processing on the Calculated Data .47 .

3 .6.1 Correction of marker position . . . . . . . . . . . . . . . . . . .47. . . . . . . . . . . . . . . . . . . . . . . . . 3.6.2 Location of Point M: .50 .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 Outcome measures .50 .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 Statistical Analysis .57. . . . . . . . . . . . . . . . . . . . . . . . . . . 3 .8.1 Reliabiiity Study .57.

. . . . . . . . . . . . . . . . . . . . . . . a . Reliability Theory .57. b . Intraclass correlation coefficient (ICC) . . . . . . . . . . . . 58.

. . . . . . . . . . . . . . . . . . . . . . . c . Models of the ICC .59 . . . . . . . . . . . . . . d . The type of ICC used in this study .59 .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8.2 Main Study .60 .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV Results and Analysis .62. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Reliability Shidy .62

. . . . . . . . . . . . . . . . . . . . . . 4.1.1 Subject Characteristics .62. . . . . . . . . . . . . 4.1.2 Intraday reliability of the measurements .62 . . . . . . . . . . . . . 4.1.3 Interday Reiiability of the Measurements .63.

4.1.4 Total Head Excursion (THE) and Resting Head Posture (RHP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Main Study .69 . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Subject Characteristics .69.

. . . . . . . . . . . . . . . . . . 4.2.2 Effect of Gender and Position -71 . 4.2.3 ûverall Variation of the Angle Parameters . . . . . . . . . . . .73 .

4.2.3.1 Extreme Trial Means . . . . . . . . . . . . . . . . . . .73 . 4.2.3.2 Extreme Set Means . . . . . . . . . . . . . . . . . . . .74.

. . . . . . . . . . 4.2.3.3 Confidence Interval of Set Means .76. 4.2.4 Normal Range of THE and RHP . . . . . . . . . . . . . . . . . .76 .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V . Discussion .79 . . . . . . . 5.1 Intraday Reliability of head and neck posture measurement .79.

5.2 Interday Reliability of neutral head and neck posture measurernents . .80 . . . . . . . . . . . . . 5.3 hterday Reliabiiity of THE & RHP Measurement .84 .

5.4 Neutrai Head and Neck posture . . . . . . . . . . . . . . . . . . . . . . . .85. . . . . . . . . . . . . . . . . . . . . . . 5.4.1 The Effecîs of Position .86 .

5.4.1.1 Neutral Head Posture (Trag/C, ) . . . . . . . . . . . . .86. 5.4.1.2 Measurement of Neck Posture (Cervicd

Inclination} . . . . . . . . . . . . . . . . . . . . . . . . . 89. . . . . . . . . . . . . . . . . . . . . . . . . 5.4.2 The Effects of Gender 90.

5.5 Normal range of neuaal head posture (NHP) . . . . . . . . . . . . . . . .92.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI. Conclusion -94.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References -96.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix 1 . Posted Notice -104.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix 2. Information Sheet .los.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix 3. Consent Form .108.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix 4. Subject Data Sheet -109.

Appendix 5 . An Example of Trial Average Angle Data File . . . . . . . . . . . . .110.

Appendix 6. Sumrnary of Interday Result for Al1 Angles . . . . . . . . . . . . . . . I l l .

Appendix 7. Summary of Data (Mean and Standard Deviation) in Main Study . .114.

Appendix 8. THE and RHP for Al1 Subjects in Main Study . . . . . . . . . . . . .115.

Appendix 9. Angle Variation Ranges at Sittuig and Neutrai Pomire . . . . . . . ,118.

Vita . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,119.

List of Figures

Figure 1 . Iiiustration of Rheault's measurement (a and b are the distances used to

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . calculate angle a.) .16.

Figure.2. Illustration of the angle describing inclination of the tragus to C7 . . . .18.

Figure 3. Illustration of Raine's measurement. . . . . . . . . . . . . . . . . . . . . . -2 1 . Figure 4. Illustration of the angular parameters of cervical and cervicothoracic

posture as reported by Refshauge et al . . . . . . . . . . . . . . . . . . . . 2 3 .

Figure 5. Illustration for reference lines used in Sandham's study . . . . . . . . . .25.

Figure 7. Subject in three test postures . . . . . . . . . . . . . . . . . . . . . . . . . .42.

Figure 8: Illustration of shifting marker to skin on C7 . . . . . . . . . . . . . . . . -48.

Figure 9: IUus?ration of calculation of marker on T. . . . . . . . . . . . . . . . . . -49.

vii

List of Tables

Table 2.1. Projections vs. postures in Awalt's study . . . . . . . . . . . . . . . . . 27.

Table 4.1: Intraday reliability of outcome masures for subjecîs in m d i n g

neutmi posture on &y 1 (n = 10) . . . . . . . . . . . . . . . . . . . . . . . . .64.

Table 4.2 Summary of intraday ICC's for subjects in both positions and al1

postures on day 1 (n= 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65.

Table 4.3 Summary of interday ICC's for subjects in both positions and ai l

postures (n= 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67.

Table 4.4 Summary of interday reliability of Total Head Excursion (THE) in both

sitting and standing positions (n = 10) . . . . . . . . . . . . . . . . . . . . . . .70.

Table 4.5 Summary of interday reliability of Resting Head Posture ( N P ) in

both standing and sitting positions (n = 10) . . . . . . . . . . . . . . . . . . -70.

Table 4.6 Analysis of effects of gender and position on selected angles using

2-factor with one repeated-test ANOVA for subjects in neutral head posture.72.

Table 4.7 Summary of one-way analysis of variance (ANOVA) for effect of

gender on THE and RHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72.

Table 4.8. Extreme mal means and intervals for both male and femaie in standing

position and neutral posture (n = 32) . . . . . . . . . . . . . . . . . . . . . . . -74.

Table 4.9. Extreme set means and intervals for both male and female in standing

and neutral posture (n = 32) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75.

Table 4.10. 95 % confidence interval for subjects (male and female) in main study

in standing and neutral posture (te = 2.040; n = 32) . . . . . . . . . . . . .77. Table 4.1 1. 95 % Confidence Intenta1 for subjects (male and female) in the main

study in sitting and neutral posture(ta = 2.040; n = 32) . . . . . . . . . . . -77.

Table 4.12 The 95% Confidence Intervals of THE & RHP for Subjects

(male and fernale) in standing position (n =32, i=2.040) . . . . . . . . . . .78.

viii

1. Introduction

The unique matornical characteristics and complex biomechmical nature of the

cervical spine gives it a wide range of mobility but cimies the risk of less stability.[6'-' l

For this reason cervical spine problems are common and include trauma to the cervical

spine, particularly as a result of motor vehicle accidents, degenerative joint disease and

abnormal postures resulting in pain and dysfuncti~n.~~ It has been reported that flexion-

extension (whiplash) injuries occur in from 20 to 62 percent of al1 motor vehicle

accidentdn In Kramer's studynlI, of the people who had intervertebral disc diseases, 36.1

percent had problems at the cervical level. Researchers have indicated that neck pain is

a significant problem in today's society. Makela et aLW1 reported, for instance, that 9.3

percent of men and 13.5 percent of women in Fuiland experienced chronic neck pain.

In addition to instability of the cervical spine, life style also plays an important

role in cervical spine dysfunction. Many vocations in today's society require that workers

spend mon of the day sitting at a desk or cornputer terminal, or driving a motor vehicle.

The cervical spine posture adopted during these activities can iead to pain and dysfunction

and therefore, posture is an issue of importance to clinicians in rehabilitation. It has been

recognized that the posture of the head, neck, and shoulders is a factor contnbuting to

the onset and perpetuation of cervical pain dysfunction ~yndromes.~

Head movement within the sagittal plane includes flexion, extension and forward

or backward translation. Forward hransIation of the head in the sagittal plane with the

eyes horizontai is called protraction, while posterior translation with the eyes horizontal

is known as remction. The distaace between complete reiraction and proûaction is cailed

total head excursion (THE).16.U1 The resting head position (RHP) or neutral position falls

within the functional range of THE. Long term deviation from normai RHP is believed

to contribute to pain and dysfunction. Forward head posture is a common posture

assumed by many people. As the tenn implies, the head is deviated forward from the

neutral position. Generally, clinicians use a plumb line or photographs to assess fonvard

head posture. Kendall and McCrearym define normal skeletal alignment in the sagittal

plane as a plurnb Line passing through the foilowing anatornical landmarks: the extemal

auditory rneahis, odontoid process of the a i s , bodies of the cervical vertehra, acromion

process, bodies of the lurnbar vertebra, sacral promontory, slightly posterior to the center

of the hip joint, slightly anterior to the knee joint, slightly anterior to the lateral malleus

and through the calcaneo-cuboid joint. When viewing a subject perpendicularly to the

sagittai plane, a forward head posture is defined in any alignment in which the extemal

auditory meatus is positioned anterior to the plurnb line.m."l

Many researchers have linked fonuard head posture with changes in

musculoskeletal structure and fbnction that can lead to p a i ~ ~ . ~ * * " ~ Forward head pomire

cm occur as a result of cervical pain or may be a source of cervical pain, either of which

makes it an important consideration duriog assessment. Enwemeka er al did a n w e y ,

in which a random sample of physical therapists were polled by means of a mctured

questionnaire. Of the 52 respondents, 32 reporteci that patients with neck pain and spasm

of the upper trapezius often assume a forward head poshwe. In another snidy, 88 healthy

subjects, aged 20 to 50 years, were asked to answer a pain questionnaire and to stand by

a plumb line for assessment of forward head posture. Frequency counts revealed that

postural abnorrnaiities were prevalent (fonvard head posture = 66%). The results of this

study suggested a relationship between the presence of some postural abnomalities and

the incidence of neck pain.m1 Based o n the relationship between cervical posture and

pain, clinicians and therapists have useci postural education and correction as treatment

approaches for aUeviating pain. [16- 32-

Assessrnent of spinal alignment assists in deterxnining faulty posture and

establishing a baseline to assess patient progress.[lq However, clinical evaluation of

posture is generally based on subjective observations by the chician. While improvement

over time may be detected in a specific patient, it is dificult to compare patients to each

other and to quanti9 the improvernent~.~

Various efforts have been made to quantitate both head, neck and shoulder

position and cervical motion, including both subjective and objective analyse^.^^.^. 13- ". 17.

M+0.'63q Most of the reported objective rneasurernent systerns are non-invasive, Uicluding

plumb line techniques, rulers and flexible rulers, goniometen, skin marker methods.

photographs and digitization, and computerized methods."- '- "- '6. 2g. ''- -'. "' invasive methods, such as X-ray radiography['* ')l, and radiographie imagingw- have

aiso been used to meanire cervical posture. For many of these methods, the reliability

of the testing procedures was not reporteci.". 9* .'me of the rnethods require highly

technical equipment and welï lrained personnel[J", or pose health nsks because repeated

rneasurernent of the same subject necessitateci additional exposure to X-ray~.~ ' . '~~

Many reports use neutral cervical posture as a reference when hvestigating various

cervical movements. Clinicians recommend the neutrai posture to their patients as a

standard posture.['q However, the range of normal cervical posture has not been clearly

documentai, and the terminology used to represent this posture has not been standardized.

It has been referred to as neutrai head and neck positionill* normal positiodW , resting

head position (RHP)wl, comf~rtabld~, relaxeci[* position, or the self-balanced

position In limited reports on neutral cervical posture, reliability of measurement

remainS questionable.[6* 7. a. 4 9 . ~ 1 1 It is clear that there is a need for reliable methods to

objectively assess neutrd posture of head and neck. It is essential to defme the variation

of cervical and cervicothoracic posture for healthy people. This will be useful for building

up a standard reference in order to be able to meanire and assess cervical spine posture

objectively. This is important for understanding the relationship between neck pain and

cervical posture, and for monitoring effects of education and exercise programs designed

to improve cervical posture.

The purposes of this study were: (a) to determine the intraday and interday

reliability of various measures of cervical and cervicothoracic spine sagittal plane posture.

total head excursion (THE) and resting head posture (RHP) obtained with the PEAK

Motion Analysis System, in both sitting and standing; (b) to determine whether there are

differences in cervical spine posture measures between males and females and between

sitting and standing positions; (c) to use measurements obtained with the PEAK System

to define the nomal range of cervical and cervicothoracic measures of posture in healthy

young adults.

II. Literature Review

2.1 Anatomy of Cervical Spine

The cervical spine is one of the mon anatomically and kinematically complicated

articular structure of the human body. It permis a wide range of motion of the head in

relation to the trunk.

niere are eight motion segments between the occipital bone (Co) and the frst

thoracic vertebra (T,). in analyzïng the mechanical behaviour of these joints, the region

is often divided into two sections: 1) the occipito-atlanto-axial complex (Co-CI-C2). and

2) the lower cervical spine consisting of the C,-C, to C,-T1 segments."."l This division

is based on the great differences in anatomy and function as weli as the different

biomechmical behaviour existing in the two regions. The upper and lower cervical spine

differ in terms of facet orientation, presence of an intervertebral disc, variations in

ligamentous, capsular. muscular and bony structures and their suhsequent funct ion~.~~~'

Moffattm midied cineradiographic recordings of motions of the cervical spine and

found that even a slight change in the position of the head would change the positions of

al1 the vertebrae relative to one another. The motions of al1 segments appeared to begin

simultaneously . Therefore, it is Wcely that applying active exercise specifically to one area

of the cervical spine will cause motion to occur at other more remote segments.

The upper cervical segments tend to aliow more rotation and the lower segments

less rotation but more lateral flexion.pn This is deterrnined by the orientation of the

zygapophyseal joints. The greatest movement of the lower cervical spine occurs in the C,-

C, s e g r n e n t ~ . ~

Bhalla and SimmonsP1 found that there are only hwo levels, C& and CI-T,.

which demonstrate greater extension than flexion from the neutral position. Al1 other

levels from C, to C, show greater flexion than extension. Bhalla's findings may explain

why cervical intervertebral dix pathology is most muent at the lower levels which do

not have the available range of motion to cope witb the forward head posture which often

develops in sedentary modem people.P1

2.1.1 The Occipito-Atlanto-Axial Complex (C&-Q

The C,,-C& joints are, perhaps, the mon anatomically and kinematically

complicated joints of the spine. The atlas, the first cervical vertehra. has anterior and

posterior arches, relatively large transverse processes and two lateral masses. It has no

body and its spinous process is represented by a tuber~le .~ ' There is no intervertebral

disc between the occiput and atlas and the articulations are synovial. On either side, the

two atlanto-occipitd joints lie between the superior concave articular facet of the lateral

mass of the atlas and the convex occipital condyles, which project downward on each side

of foramen rnagn~rn.["*~~+~ The upper articular facets of C, are elongated from front to

back, with thei. anterior ends closer together than their posterior ends. Their anterior

ends project upward in a curved fashion to a greater extent than their posterior ends. This

provides for much more extension than flexion in the atlanto-occipital joint.la1 The

movernents available at the atlanto-uccipital joint are flexion, extension and a much lesser

degree of lateral flexion.pq Wernpl stated that no rotation occurred at the atlanto-

occipital joint. However, it has k e n reported to have a small amount of r~tation.l '~*~~'

Atlanteoccipital dislocation, or fracture dislocation, can occur in severe injuries.

These injuries are usuaily fatal, because of damage to the junction of the brain stem and

spinal ~ o r d . ~ * ~

The auto-axial joint complex (Cl-Q has three articula. components, two

syrnmetrical lateral articulations and one centrai joint. The central joint is forxned by the

upward projecting dens of the axis (CJ articuiating with the posterior aspect of the

anterior arch of the atlas. The dens also articulates with the strong transverse ligament

posteriorly and with the margins of the foramen magnum via the alar ligamentd4I As

with C&, no intervertebral d i s is present at C& and the articulations are synovial.[61i

The lateral joints are describecl as planar, but while flat in the coronal plane, both

articular surfaces are convex in the sagittal plane, making them incongru ou^.^^^ The

convex nature of the C,-C, articular surfaces dong with their horizontal orientation

provides a large component of cervical axial rotation, which is required for both

voluntary and reflex huning of the head to direct the gaze to the right or lefi. The convex

nature of the articular surface also ailows rocking with flexion and extension in this joint.

Panjabi and Dv~rak"''~ and Panjabi er al recordeci 20 degrees of sagittal plane

movement, compareci to 30 degrees in the atlanto-occipital joint.[61'

The stability of the joint depends on the integrity of the transverse ligament, which

holds the dens in place.'YY The dens acts as the "axis" around which rotation takes place.

The movement is checked by the alar ligaments, which may be injured in rotational

-.['fi

2.1 -2 The lower Cervical Spine (c-TI)

a. The vertebrae

The CrTI vertebrae have distinct vertebral bodies and intervertebral discs making

them anatornically and functionally more like the rest of the vertebral column and less

iike the upper cervical spine. This region is sornetimes divided into middle and lower

cervical spine c o m p ~ n e n t s . ~ ~ Cervical vertebrae have the smallest bodies and the largest

spinal foramina of the vertebral column. A typical cervical vertebra has a small vertebral

body where the upper surface is flat centrally with uncinate processes laterally, and whose

lower surface is concave in the sagittal Posteriorly there are the spinous

processes which are usually bifid at C,, C4 and C,, and more prominent at C, and C,. The

spinous processes between C2 and C, are not easily palpable, but with the subject supine

and muscle relaxed, C, is readily palpable and with care, ail the spinous processes can

usuaily be identified by palpati~n.~'~

in the region of C3 to Cs, upward projections from the lateral margins of the

vertebral bodies articulate with the bodies of the vertebrae above to form the Luschka

joints (uncovertebral joints)."01 Lateral to the junction of the pedicle and laminae are the

articular masses with articular facets on their upper and lower surfaces. The articular

masses from S to T, form an articular coiumn which bars a significant proportion of

axial 10ading.~~ The movement patterns of vertebral joints in the lower cervical spine

are rnainly determined by the orientation of the joint facets and intervertebral dis~s.[~"

Al1 movernents (flexion, extension, lateral flexion and rotation) occur in the lower

cervical spine.

b. Zygapophyseal Joints

The zygapophyseal joints (also called the posterior joints, the joints of the

vertebral arches, facet joints, or apophysial joints) are paired, diarthrodial (i.e., freeiy

rnovable) joints located between the superior and the inferior articular facets of adjacent

vertebrae. They are synovial in nature." In the cervical spine, the highest zygapophyseal

joint is located at the C& level, and the lowest is at the C,-Ti level. The fibrous

capsules are lax enough to permit fairly free movement. The joints are lined with synovial

membrane and articular surfaces are covered with hyaline cartilage. The superior facets

of the joints face forward and downward at an angle of about 45 degrees. The inferior

nirfaces face backward and upward, also at an angle of 45 degree~.~'' It is known that

the joint plane is more horkontally oxiented in the upper cervical spine segments and

more vertically oriented in the lower cervical spine r e g i ~ n . ~ ~ * ~ ~ * ~ The angles between

the zygapophyseal joint plane and the longitudinal axis of the spine Vary from 45 degrees

in the mid-cervical spine region to about 30 degrees in lower cervical pi ne."'^ The

curvatures of the facets do not fit each other perfettiy, which allows the cornplex

movements at these joints on lateral flexion and rotation of the neck. The zygapophyseal

joints are aid in stabilization of the motion segment. Forward displacement of one

vertebra on another is prevented by a fail-safe locking mechanism provided hy the

abutment of the superior leading edge of the inferior facet into the angle of the facet

abo~e . "~~ The facet orientation determines that axial rotation and lateral bending of

ceivical spine always be coupled.

c. Ligaments

The function of ligaments of the cervical spine is to limit movements of the head

and neck and to maintain postural equilibrium between the ~ e r t e b r a e . ~ The antenor and

posterior longitudinal ligaments extend over the entire length of the spine and act as the

major stabilizers of the intervertebral joints. The anterior longitudinal ligament attaches

to the anterior aspect of the axis vertebral body where it extends upward to merge into

the anterior arch of the atlas and anterior atlanto-occipital membrane. The posterior

longitudinal ligament is widest in the upper cervical spine and narrows caudally. Unlike

the anterior longitudinal Ligament, which has a ribbon-like structure, the postenor

longitudinal ligament is waisted over the vertebral bodies and fans out over the

intervertebral discs.lm The anterior longitudinal ligament in the cervical spine is

relatively thin and rather weak compared with that in the lurnber spine. The posterior

longitudinal ligament is dense, thick and wide, and gives some protection to the spinal

cord from a posterior disc protrusion but offers no such protection to the nerve mots

lateraily

The anterior part of the annulus fibrosus and the anterior longitudinal ligament

control extension of the motion segments; the posterior part of the annulus fibrosus, the

posterior longitudinal ligament and the flaval ligaments control flexion. In combination.

they contribute for the postural equilibrium of the cervical pi ne.[^^

The ligaments which maintain the joints between the vertebral arches are: (1) the

supraspinous ligaments, which in the cervical spine have evolved into the ligament

nuchae, (2) the interspinous ligaments, and, (3) the ligament flavum at each level. The

ligamentum nuchae extends from the vertebra prominent (C,) to the extemal occipital

protuberance and is probably a major stabilizer of the head and cervical spine. Its deeper

fibers attach to the spinous process of each of the cervical vertebrae and reinforce the

interspinous Ligaments, which in the neck appear less developed than elsewhere in the

spinal c o l ~ m n . ~ ~ ~ The ligamenta flava are strong, very elastic ligaments spanning the

space between the laminae in pairs, attached to the anteroinferior surface of the lamina

above and the posterosuperior margia of the lamina below. They metch laterally to the

zygapophyseal joint.''' They merge with the interspinous ligaments posteriorly and with

the fibrous capsule of the synovial facet joints antenorly. The ligamenta flava in the

cervical spine has considerable importance as a stabilizer in flexion hecause of its high

content of elastic tissue.fn1 The ligamenta flava stretch under tension and retract and relax

without undue bulging or folding in the normal state.I4I

2.2 The Neutra1 Postwe

2 -2.1 Definition and terminology

The neutral neck position is defmed as that in which the neck muscles are relaxed

and the cervical spine maintains a normal lordotic c ~ r v e . ~ ' ~ ClinÎcally , the term "neutral

head position" (NHP) is an important reference used by clinicians and therapists to

evaluate and examine a patient with a neck problem. Assessrnent of neutral posture of

head and neck has been used in preliminary and foilow-up examinations for numerous

painhl rnusculoskeletal conditions. [6* 16- ' M uch of the existing literahire consists of

meamring head movement such as axial rotation, lateral flexion, protraction and

retraction by various means from a "neutrai" position.[6* '.- A poor head posture, for

example, forward head posture is also related to the "neutral" posture. It has been

observeci that patients with neck pain and spasm of the upper fibers of the trapezius

muscle assume a f o m d head position.Iiq To ensure good postural alignment and to

reduce spasm of the trapezïus muscle, conservative treatment often includes masures to

correct this faulty neck posture. It is believed that the neutral neck position is the correct

position and is effective in reducing pain and muscle spasm.[" Iq

Although the term "neutral" head and neck posture has been defmed hy some

au th or^^'^, it is still diffkult to imagine what the posture look like. There is no clear.

quantitative d e f ~ t i o n of this position to date. The use of the tenn "neutrai" is somehow

confusing. Several terms have been used to indicate this position by different authors in

literatu~eI~.~* 531 , such as "normal " , "neutral " , "cornfortable " , "relaxed " , and self-balanced

head and neck position. While these tems seerningly have similar meaning, each of them

rnay be interpreted or defined by an individual in a different way. Together with the fact

that different methodologies are used when investigating various motion and postures, the

"neutral" posture used by different researchers as a reference may Vary. These may lead

to some inconsistency when comparing data in the literature.

It has k e n considered in some literature that "neutral" head posture is

synonymous with resting head posture (RHP). The RHP is defined as the position of the

head within the functional range of total head excursion (THE) in a particular static

posture. The distance between complete head retraction to protraction is called total head

excursion (THE). The RHP can Vary over time individually. There are currently few

quantitative &ta availahle regarding normal THE, RHP, or where the RHP lies within

THE.

Hanten et al indicated that deviations fkom normal RHP may contribute to pain

and dysfunction. Some researchers observed that numerous painful musculoskeletal

conditions and craniocervical cornplaints are related to a RHP that is close to the

protracted position, where the lower cervical vertebrae are flexed in forward glide. and

the upper cervical complex is e~tended."~ Clinicians frequentiy consider this posture

as forward head posture. Braunm and Raine and Twomey[- reported tbat, in their

shidies subjects adopted what they considered to be natural head posture (without further

explanation). In othersiS3* 5g. "l , subjects were asked to flex and extend their neck

continuaiiy through a decreasing amplitude, before eventually assuming their moa neutral

comfortably relaxed position.

2.2 -2 Measurements

To assess RHP, a clinician views a patient against some standard and takes

measurements, or simply visually inspects the cervical spine to determine its deviation

fi-om the ~ e r t i c a l . ~ ~ 5'1 Whether the patient's posture is judged as normal is a

subjective decision.

Various quantitative methods have been developed to measure head and neck

posture and moverneot. These can be divided into two types: non-invasive measurement

and invasive measurement. Reports using these methods will be separately reviewed in

the following section.

a, Non-invasive Measurement

As described by Kendall and M~Creary~'~, a plumb line is a cord with a plumb

bob atfached to one end. It may be used to represent the projection of the gravity line to

the extemal surface of the body, and used as an aid in analyzing alignment in static

posture. In examining such postures the plumb line must be suspended in line with a fixed

point. This point in a standing posture is at the base where the feet are in contact with

the flmr. In a lateral view of an ideally digned posture, the plumb line will coincide with

the following points or skeletal parts: the external auditory meatus, odontoid process of

the axis, bodies of the cervical vertebra, acromial process, bodies of the lumbar veriehra,

sacral promontory, slightiy posterior to the center of the hip joint, slightly anterior to the

knee joint, slightiy anterior to the laterd malleus and through the calcaneo-cuboid joint.

In their description, a theoretical plumb line divides the body into an anterior and

postenor sections of approximately qua1 weight. In the standard posture, the body

segments are aligned in a way that a minimum of muscular effort is required to maintain

the position. Foward head posture is defined as any alignment in which the extemal

auditory meatus is positioned anterior to the plumb line passing through the shoulder

joint. Kendall and McCrearylm suggested that deviations of head position relative to the

vertically hanging plumb line should be described as slight, moderate, or marked, when

using a plumb line. These subjective descriptions are Iikely to be interpreted differently

by different clinicians.

R~cabado~':~ also measured head and neck posture from a vertical line using a

d e r . The vertical line was suspended at the posterior aspect of the spinous process of

the thoracic spine of the subject. The horizontai distance fiom the vertical linr to the

surface of the rnid-cervical spine was measured. This approach is clinically advantageous

because it produces a quantitative measurement that may be obtained quickly with

minimal equipment. Although Rocabado stated that this distance averages 6 cm in normal

head posture, no mention is made of how he determined this figure, and there is no

assessrnent of intertester retiability .

Another postural measuring device that does not require use of a vertical line is

the flexible ~ l e r . ~ ~ . In the Rheault et al '''I method, data were collected using a

Spinocwe. The Spinocurve is a flexible mler consisting of a bendable metal band

wrrounded hy a plastic casing. The tester fvmly placed the flexible d e r against the

subjects' cervical spine in the sitting position and took a measurement between the

extemal occipital protuberance and the seventh cervical spinous process. The shape of the

Spinocurve was traced on paper with the endpoints clearly marked. The measurements

were also taken in the flexed position. After tracing the cervical curve ont0 the paper. a

mathematical equation was used to calculate the angle of cervical curvanire (Fig. 1).

Rheault and ass~ciates~'~~ exarnined 20 subjects in two different positions: with the cervical

spine in a neutral position and with the spine in a fbily flexed position. They reported that

the correlation between testers for the neutral position was r = f0.8, while the

intertester reliability for the flexed position was r = +0.9. Furthemore, paired-tests

showed that no signifiant difference existed between testers

0.05). The data suggested that the flexible d e r is a reliable

in either position (P >

measuring tool between

Figure 1. Illustration of Rheault's measurement (a and b are the distances used to calculate angle a.)

testers for measurement of ceivical curvature. They also stated that measurements of

cervical spine posture obtained using the flexible mler can indicate postural deviations.

but they did not lin normal values from which one can judge deviations.

Photography has also been used to masure ceMcal posture. As early as 1928.

Schwartz et al devised a senes of measurements analyzing various body angles.["' These

measurements were made directiy on lateml photographs and were an attempt to define

normal sagittal posture. Since that tirne, several authors have employed similar

measurement techniques to examine cervical posture." '.'6.41

Braun and Amundsodq used a photographie method to meawe head and neck

posture. They employed a cornputer-assisted siide digitizing system called the Postural

Analysis Digitiung System (PADS). In their system, a camera, mounted on a tripod, was

used to make 35-mm slides. The slides were anaiyzed using a system composed of a slide

projector, a computer and a pressure-sensitive digitizing pad. A honzontally levelled

plexiglass bar was used as a reference line. During digitiring, the reference line on the

slide served as a horizontal line for calculation of the positional angles. Twenty men were

photographed fiom the side, and angular measurements were taken using lines drawn

between the tragus of the ear, the seventh cervical vertebra, and the horizontal line

passing through the seventh cervical vertebra (Fig.2). They reportai that the average

angle for resting head posture (neutral) to be 5 1.97 degrees. They also provided average

values for the fully proacteci and retracted positions, 28.48 and 62.09 degrees.

respectively. Using these techniques, recent studies have show the average angle for

normal resthg head posture in young adults to be between 49 and 55 degree~.~."."'

Braunm used the same angular method to examine head and neck position (as

shown in Fig.2.). The purpose of his study was to compare the sagittal head posture of

asymptornatic men and women, and to compare the posture of asymptomatic and

symptomatic women. Forty subjects (20 male and 20 female) were involveci, and the

Postural Analysis Digitizing System (PADS), described above, was employed in the

study. Head posture was significantly different between asymptomatic men and women

in the protracted position and neutral position. The men showed a more protracted posture

in hoth the protracted position and neutral position than the women. indicating a more

anterior position of the head in relation to C,. No significant difference was noted

between men and women in head retraction. Head posture was significantly different

between asymptornatic and syrnptomatic women. The symptomatic women were more

protracted in the neutrai position and showed less ability to retract their heads than the

asymptomatic women. These characteristics are consistent with a more forward head

position.

Hanten er al w utilized a honzontally placed metnc mler to measure resting

position of the head in both sitting and standing (RHP,, RHP,), full protraction (P) and

full retraction (R). A reference mark consisting of a small piece of marked tape was

placed approximately 3 cm below the corner of the left eye, on the zygomatic arch. For

meanirements taken while standing, subjects were asked to assume a relaxed. naturai

posture with their scapulae touching the wall. A menic d e r was extended from the wall

to measure the distance from the wall to the reference mark. This distance was recorded

as RHP,. Full protraction (P), reaaction (R) were not measured for the standing

position. When meamring full protraction (P), fuil retraction (R) and RHP,, subjects

were asked to sit on a high-backed wooden chair which was placed close to the wall.

These parameters were measured in a way similar to that for standing position. However.

the RHP, was expressed by a ratio of [Neutral - Retractioa] to [Protraction - Retractionl.

The unit was converted to percentage. Subjects included 21 8 normal adults. Mean percent

distance from full retraction to resting head position in total head excursion in the Sitting

position was 47.4% for women and 43 % for men. This indicated that women have more

fonvard head posture than men in sitting, contrary to the result from Braun's snidy.'''

Mean value of RHP in the standing position was 22.4 cm for men and 19.1 cm for

women. This suggested that men held their heads in a more protracteci posture than

women in standing.

Raine and Twomeylq examined the reliability of measures of physical

characteristics of the head, shoulder and thoracic spine and identifid relationships among

them. Measurements were made from photographs of subjects in "cornfortable" erect

standing (not constrained in any other way). Thhty-nine volunteers (--one female.

eight male) participated in the study. The measurements included angles of a and II. as

illustrated in Fig.3. The position of the head relative to the tnink was measured from the

lateral photograph to describe the position of the head in the sagittal plane. Angle a.

formed between a horizontal line and the line joinhg CI to the tragus of the ear, was used

to represent sagittal plane head alignment. Srnaller values of the a angle would indicate

a forward head posture. Angle B was rneasured relative to FrankfwZ horizontal plane. The

angle between the line joining the midpoint of the posterior margin of the tragus and

infenor margin of orbit and the horizontal line, was rneasured in a counterclock wise

direction. This angle was used to indicate aiignment or tilt of the head from the Frankfurt

horizontal plane, retlecting the position of the upper cervical spine. A R-angle of 180

degrees represented the horizontal position of the head. An angle of Iess than 180 degrees

indicates that the orbit was superior to the tragus, and the upper cervical relatively

extended. An angle greater than 180 degrees indicates that the orbit was inferior to the

tragus and the upper cervical spine relativeiy fiexed. During the measurement, horizontal

--- Measwernents of sagittal plane head alignment; B --- Head dignment fiom the Frankfun plane; C, --- the 7th cervical spinous process; Tr - - Tragus;

Fignre 3. Illustration of Raine's measurement.

and vertical Iines in the subjects' background served as reference Iines. After photography

and digitkation, data were anaiyzed statistically. It was found that extension of the upper

cervical spine as measured by the angle of head alignment from the FradcfWt plane

(angle 8) was not significantly correlated to a forward position of the head as measued

by sagittal plane head alignrnent (angle a). Thus it was concluded that no relationship was

found between forward head position and upper cervical spine extension.

Refshauge a al tq examined the reproducibility of meanires of cervical and

cervicothoracic curvature in an unconstrained standing position in 17 subjects using a

photographie technique. Parameters measured in their study included three angles of

cervical inclination (the angle between the horizontal and a line drawn between C and

C,, G and T,. C, and T,; denoted as C,(G-CI, CJG-TI, CJG-TA, respectively),

cervical lordosis, denoted as C,, and cervicothoracic kyphosis, denoted as ClTe

(Fig.4). The cervical lordosis was defined by the angle subtended by lines drawn from

Cr to C4 and from C4 to C,. The cervicothoracic kyphosis was defined by the angle

subtended by lines drawn through C4 and C,, and through C, and T,. Reliability of these

parameters for within-trial, between-trial (intraday) and between day (one week apart)

meamrements were calculated using intraclass correlation coefficients (ICC). Al1

measurements of cervical inclination, C [ C C , CJC,-T,] , C,[Cl-Tl] were

reproducible as was cervicothoracic kyphosis ( C I T d , but cervical lordosis (Cm*) was

more variable. An expianation for the poorer reliability of this measurement may be the

small distance between the three vertebral leveIs used (C,, C4 and C7)- In this case, minor

digitising errors would produce relatively large changes in angles. These fïndings suggest

that cervicothoracic kyphosis and cervical inclination are appropriate to use for

determinhg the effects of intervention in either clinical practice or research.

b. Invasive Measurement

Cephalometric radiography (radiography for skull measurement) has been used in

head and neck posture and motion studies .Il* l3' Sandhamiul used a cephalometric

radiographie method to investigate repeatability of head posture. The error of the method

Figure 4. Illustration of the angular parameters of cervical and cervicothoracic posture as reported by Refshauge et al

for measurernent of head posture from standardized lateral cephalometric radiographs was

assessed. Twelve subjects, aged between 8 and 15 years (eight male and four fernale).

participated. Lateral skull films were taken in the natural head posture position and then

duplicated. Naturai head position was determined by the wbject's own feeling of natural

balance (sometimes called self-balance position). It was achieved by Ietting the ~ b j e c t

tilt the head backwards and forwards with decreasing amplitude to find the most relaxed

position. Once îhis position was reached the nibjects were asked to look into their own

eyes in a &or placed at least 2 meters away . This final adjustment, called the " mirror

position" was obtained after the self-balance position had been achieved. The patient was

fuially asked to remain still and relaxeci with the teeth in correct intercuspation while the

film was exposed. A silver plumb line was suspended behind the occipital region,

providing a vertical marker on the radiograph. The cephalometric points were marked

with a tracing paper placed over the radiographs on an illuminated viewing box with a

pencil. Angles were meanired with a 25 cm diameter protractor to the nearest 0.1 of 1

degree. In the midy, several reference lines were used to descnbe the head and neck

posture. They were nasion-sella line (NSL), odontoid process tangent (OPT). cervical

vertebra tangent (CVT), tme vertical (VER), and tme horizontal (HOR). The variables

recorded in the study were angles between pain of the above bes , Le. NSLNER,

NSLIOPT, NSLKVT, OPWHOR, CVTEIOR, OPWCVT (see Fig -5) .

Two trials were made on each subject. AU data cornparisons were made between

the two trials. It was reported that the error of the method for the position of the head

to the m e vertical NSL/VER was 3.2', NSUOPT, 2.6', NSLICVT, 2.4', OPT/HOR.

OP7 CVT

- HOR

VER

HOR -- horizontal line; VER -- vertical line; NSL -- nasion-sella; OPT -- odontoid tangent; CVT -- cervical vertebra tangent;

Figure 5. Uustration for reference lines used in Sandham's study

3.8 O , CVT/HOR, 3.3 O , OPTKVT, 0.97'. Therefore, it was concluded that the midy

demonstrateci that a reproducible head posture existed which could be recorded using a

cephalomemc radiographic method with a method mor of oniy a few degrees. For this

method, the measurements were made directfy from the radiophotographs, and the points

were taken from the edges of bones on the film. This is helpfûl to reduce the errors

brought by noninvasive methods in which spines cm not be directly accessed. However.

due to the harmful nature of the X-ray radiography, only very limited tests can be

performed on each subject. In Sandham'spq report, only two trials were made on each

subject. Reliability of the subsequential results from the two trials may stiil rernain

questionable.

The size of the intervertebd foramina of cervical vertebrae in normal and forward

head posture was measured radiographically by Awalt et ai.''' Thirty-two subjects

participated the smdy. Subjects were selected fiom two populations based on their usual

head posture. Seventeen subjects were categorized as having forward head posture and

fifteen subjects were categorized as normal. Head posture was detennined by using a

posture gauge, which consisted of a telescoping r d affixed with a level on one end. A

vertical reference was obtained by attaching the telescoping rod to the postenor aspect of

the spinous processes of the tùoracic spine of the subject. The horizontal distance between

C, and the vertical reference was measured. Subjects with a distance of greater than 6 cm

were assignai to the forward head posture group, while the subjects with a distance equal

to or less thao 6 cm were assigneci to the normal head posture group."ll A senes of

cervical spine radiographs were obtained on each subject. Table 2.1 lists the types of the

---

Table 2.1. Projections vs. postures in Awalt's siudy

Obliques Bilateral

Projection

Lateral

1 StanQrd vertical I Demonstrate bilaterd

intervertebral foramina.

Poque

Relaxed

I . Group A, normal neck subjects. 2. Group B, forward head subjects.

Number of films

I

Obliques A. right'

B. bilatera12

projection, the number of radiographs, and the rationale for each projection used in the

study. It cm be seen From the table that a toM of four projections (one lateral projection

in a relaxed position, two oblique projections of both sides in a standard vertical position.

and one nght oblique projection in a forward head position) were made from each subject

in the normal group. Five projections (one lateral projection in a relaxed position. two

oblique projections of both sides in a standard vertical position, and two oblique

projections of both sides in a relaxed position) were made from the subjects in forward

head posture group. For the oblique views, posterior oblique projections were obtained

with the median sagittal plane of the head and body placed at a 45O oblique to the film

plane and the central ray angled 15' cephalad." For the projections recorded in the

standard vertical head position the mbjects retracted their necks sufficiently to place the

extenial auditory meatus vertically above the acromion process of the shoulder (normal

Projection rationale

Observation of typical headheck posture and f ordotic curve .

A. Jutted foward

B. Relaxed

1

2

Intervertebral size.

Comparative data.

head posture, according to Kendall and McCrearymJ). The a m of the intervertebrai

foramina on the film was measured with the use of a video rnanipulator which is used in

conjunction with a microscope processing system and video camera. The system was

designed to enable the video camera to project the X-ray image onto a monitor. The

intemertebrai foramina were traced on the rnonitor ushg a opticai mouse, then the video

rnanipulator calculateci the area for each intervertebral foramen traceci.''' The data

regarding the size of the intervertebral foramina were derived from the oblique views, as

this is the only view in which the foramina are fully visible. Data analysis showed that

the intervertebral foramina of the cervical spine (C&) increase in size when moving

from the normal to the fomard head posture. This finding is in conflict with Kendall and

McCreary's previous observation of a specific narrowing at Cd-C, and C& levels in

fonvard head posturep1 and lads to the question of the mechanism of pain relief

associated wiîh axial retraction exercises.

2.3 Forward Head Posture

2.3.1 Definition and Description

Kendall and McCrearyml defined fornard head posture as "any alignment in

which the extenial auditory meatus is positioned anterior to the plumb line passing

through the shoulder jointn. Physically, the cervical spine acts as the junction between

the head and the tnink. A fornard head posture necessitates a change in the alignment of

the cervical vertebra. Kendall and McCreaiy believed that the malignment produced by

a forward head posture includes hyperextension of the upper cervical spine and extension

(posterior rotation) of the occiput on the atlas. Damellt121 contended that there is

extension (increased lordosis) of the upper cervical spine and occiput with flexion

(increased kyphosis) in the lower cervical and upper thoracic spine. Passero er aP' was

of the opinion that the typical forward head posture included flexion of the entire cervical

spine. Quantitative data to support these position was not found.

2 -3 -2 Consequences of FHP

Incorrect posture of the head has been associated with chronic rnusculoskeletal

pain in a number of s t u d i e ~ . ~ - Skeletal alignment or changes in alignrnent may

indicate muscle lengthening or shortening, and strength imbalances between muscular

agonists and antagonists. lq Excessive or abnormal muscle tension, required when

abnormal postures are maintained over time, c m lead to muscle spasm and pain.i7."1

Additionally, the posterior cranid rotation of the head on the upper cervical spine that

is suggested to be associated with forward head position may be sufficient to compress

the arteries and nerves exiting the skull suboc~ipitally.~~~ Thus the forward head posture

has been linked to craniofacial pain, headache, neckache, and shoulder pain, together

with a decline in the ranges of cervical joints motion, muscle stiffness, and tenderne~s.(~.

28. 32.461

According to Lezbergp2', when roentgenograms of the cervical spine taken in both

flexion and extension are compared, differences are observeci in the anatomical

relationships between structures. In extension of the cervical spine there is ovemding of

articular processes

separation of the

and impingement

posterior borders

of the

of the

.29.

spinous processes. In flexion, there is

vertebral bodies and widening of the

intervertebral f~rarn ina .~ ' Further anatomical relationships can be found when cornparhg

flexion and extension views with the roentgenograms taken both in correct alignment and

in forward head position. In the correct alignment, the lateral view of the subject

photograph showed that the chi . is retracted and tbe neck is elongated posteiorly

iodicating the flexion of cervical spine. There is more separation and widening of

intervertebral space than in the forward head posture. In forward head posture, the

photograph showed the sagging forward of the jaw and the cervicodorsal roundback.

indicating the extension of the upper and middle cervical spine. With the narrowing of

the intervertebral foramina and reduction of the space through which the cervical nerve

root may pass, the compression of the nerve mot and pain are p r ~ d u c e d . ~ ~ ~

Sirnilarly, Kendall and McCearyP7I specified that in forward head posture there

was a narrowing of the intervertebral space and that it is greatest between C& and C,-

C,. These observations were made by viewing lateral radiographie films, yet the size of

the intervertebral foramina can only be measured using oblique views."I Rocabado er al

p21 listed entrapment of the greater and lesser occipital nerves as they pass between the

occiput, atlas, and a i s (occiput-C&) as a possible cause of the pain associated with

fonvard head posture, due to the decreased functional space between the occiput. CI and

C, as a rewlt of postenor rotation of the craniovertebral joint. Neither Kendall and

McCeary nor Rocabado measured the size of the intervertebral foramina.

As mentioned previously, Awalt et al ['l reported that the interverbral foramina

of the cervical vertebra were shown to iacrease in size when moving from the normal to

the fonvard head posture. Their finding is in conflict with Kendall and McCreary'sC7'

previous observations of a specific narrowing at the C,, and CM levels in forward head

posture, and coniraclictory to Lezberg 's work .O2'

2.4 Summary

The unique anatornical and biomechanic nature of cervical spine make the study

in this a m more complicated than other parts of spine. It has been observed that postural

abnormality is associated with head and neck pain. Several studies have documented a

high incidence of poshual abnorrnalities in a given population.['6* ".UgU' It has dso been

demonstrated that neutral neck posture is a very important reference to the posture and

gross range of motion assessrnent of the cervical spine. However, this position is poorly

defined, and there is little quantitative data on normal values or degree of variation in

'normal " cervical spine posture.

A few studies have investigated the reliabiliiy of measurement of cervical posture.

Some reported studies did not measure the relaxed neutral posture adopted by subjecis.

but have employed different degrees of c~nstraint.~~. While radiographic methods may

measure and describe the posture with a high degree of accuracy and reliabitity. its

harmful effects on human body excludes the application.

The reliability of cervical and cervicothoracic postural measures have not been

extensivel, investigated. Studies of this field have been restncted to the cervical spine

except that of Refshauge et al lU1 who measured cervicothoracic curvature as well.

Although the angular measurement used by Braunm, Braun and Amundson" is a usehl

general descriptor of head position, it may be possible to achieve the same fonvard

position of head with varying cervical spine and cervicothoracic positions.

III. Methodology

3.1 Sobjects

The population of interest for this study was young healthy people. Ten subjects

(5 males and 5 females) participated in the reliability phase of the study and had measures

obtained on two occasions one week apart at approximately the same time of day. Their

ages ranged from 20 to 37 years ( f = 28.9, SD = 5.84 years). The majority of the

10 subjects in the reliability study were graduate students and staff of Queen's University,

Kingston, remited through personal contact and posted notice (Appendix 1). Thirty two

subjects (1 7 males and 15 females) aged from 20 to 29 years ( g = 24.19, SD = 3.02

years) were recruited from students in the Department of Anatomy & Cell Biology and

School of Rehahilitation Therapy for the second phase of the study. They were acquired

on a volunteer basis from poned advertisement (Appendix 1) and in-class requests. The

following is a list of criteria of eligibility.

- age above 18 for the reiiability study; age between 18 and 30 for the main

smdy ;

--- No cervical or thoracic spine problems, pain, injury or surgery;

- No respiratory disease;

--- No central nervous system âisease;

-- No bony abnormalities of the spine and arthritides;

-- Provided informed consent.

3 -2 Ethicai Considerations

There were no serious ethical considerations to this study. There were no risks or

side effects involved in the measurement. Subjects eligible for the snidy received both

verbal and written information reiated to the study (Appendix 2), as well as a written

consent form (Appendix 3). A subject data form was completed including age, gender,

and other important subject information (Appendix 4). Confidentiality of ail records were

maintained. AU subjects' information and data sheet were organized Dy senes code and

kept by the investigator.

3.3 Measurernent System

The Peak 2D Motion Measurement System was the system chosen for

measurement of head, neck and upper thoracic posture. This is a video-recording and

compter-digitizing system designed for motion analysis. It has been reported to have

good accuracy and reliability in rneasuring both static and moving subjects .flL-'i Reports

of using such a system to measure ceMcal posture have not been found.

3 -3.1 The P d 2D Motion Andysis System

The Peak two dimensional (2D) Motion Analysis System, supplieci by PEAK

Performance Technologies, Inc., includes a video camera, VCR and computer system.

It employs a video camera to record a continuous picture of a subject which is captured

on a videotape. The tape is played on a VCR and the image is input to a computer

through an instniment which includes a VCR controller and frame grabber. The frame

grabber board is a high speed A/D converter which takes the analog signal from the

videotape and converts it into a digital format which is stored in the computer memory.

The digital format unit is a pixel. The video controiier sends signals to the VCR which

control the VCR's operations. It also reads and writes frame numbers on the audio track

of the video tape to identify m e s . The image can be digithi manually, semi-manually

or automaticaily using Peak software.

When digitizing, points of interest (centers of markers placed on the subject) are

identified through a mouse pointer. The computer calcuiates horizontal(x) and vertical@)

coordinate data of these points and stores them on a hard disk. The required distance and

angle outcome masures are computed from the digitized coordinate data of the points.

The basic assumption of the Peak 2D motion analysis system is that the distance

between two points on the videotape is directly proportional to that on the subject. This

requires that the optical axis of the video camera lens is perpendicular to the plane of the

subject being videotaped. In this investigation, the video camera was placed such that its

optical axis was perpendicular to the saginal pIane of a subject. Thus, only sagittal plane

position was recorded. Any visible deviation of the head and neck from the sagittal plane

was corrected by the investigator before video taping.

Cornpared with other filming and digitizing techniques, the Peak system has

several advantages. First, it cm record a subject's posture continuously, resulting in a

series of frames or pictures. This function is the same as using a very high speed

cinecamera, but has much lower coa both in time and money than cinematographic

techniques. For a static subject, data of interest c m be obtained by digitizing a number

of frames and obtaining mean values which will improve reliability over data obtained

from a single picture. Second, film processing procedures are not required because the

video tape image can be replayed easily. Digitizing and calculation can be done

automatically by the cornputer, which reduces the total time required for the experiment.

The featwe of being able to view the recorded tape immediately is important to

aiiow imrnediate repetition of unsuccessful trials. This is also very usefül in clinical

assessment, Nice patients often have limited time and tolerance and can not came back

for repeated assessrnent. The characteristic of easy data collection also makes this system

suitable for routine clinical use where many patients may be assessed at one clinical

session. The patient's video taped image, when used with slow movement, freeze h m e

and playback options, is also very helpful and practical in clinical and research use.

3.3.2 Precision and Accuracy of Peak System

Examination of the precision and accuracy of the Peak system, using an electro-

mechanical device has k e n reported b y researchers. "* Sc holz and M i l l f ~ r d ~ ~ ~

exarnioed the accuracy and precision of the PEAK motion analysis system for three-

dimensional angle reconstruction. They videotaped a pendular motion bar, on which 18

retroreflective markers were mounted, at three different orientations @araIlel, and rotated

30 degrees nght and left to a plane). Two standard video cameras were used in their

study . The videotaped motion was digitized and 32 angles between the 18 markers were

calcukted. Intraclass correlation coefficients (ICC's) (1,l) were calcuIated between trials

within each pendulum orientation and across orientations to detemine system precision,

and between randomly selected trials and actual angles to determine accuracy. ICC's in

all cases were greater than 0.99. Within-trial standard deviations ranged between 0.05 -

0.8 degrees for the different angles. Deviations from the actual angle averaged 0.0 - 0.8

degrees across all angles and orientations. The results indicated that this system can be

used to obtain accurate and reliable angular meanirements.

3 -4 Data Collection

3 -4.1 Experiment Design

Nine retroreflective markers were attached to each subject's head, neck and upper

thoracic spine (Fig. 6). Male subjects were asked to take off their shirts, while female

subjects were required to Wear a black sport top. Bony landmarks were identified by

palpation and marked with a skin pend. The same hvestigator located the bony

landmarks and collected the data for al1 subjects. A black board with two retroreflective

markers on the true horizontal h e was put jua behhd the subject's head, neck and upper

thoracic spine in the video camera view serving as a reference frame for data collection

(Fig.6). Two illumination lights were mounted close to the video camera. This produceci

a very good con= so that the markers were easily identified in the recordai image. The

specific marker locations were as follows (Fig.6):

1. Glabella

2. Tragus

3. Mandibular angle

4. E x t d occipital protuberance (EOP)

Figure 6. Marker Locations.

M! -- Glabella M2 -- Tragus M, -- Mandihular angle M, -- Extemal occipital proîuberance M, -- C, spinous process M, -- C, spinous process M, -- Mid point of the acromion process laterally M, -- T4 spinous process level antenorly M9 -- T.$ spinous process level postenorly Mol -- Retroreflective marker on the black board M, -- Retroreflective marker on the black board M -- Middle point of tnink laterally S - The point on the sternum at the level of T,

Solid circle -- represents a real marker; Blank circle -- represents a measured or calculated point.

5. C, spinous process

6. C spinous process

7. Acromion (mid point of lateral border of the acromion process)

8. T, spinous process level antenorly

9. T, spinous process level posteriorly

The location of the T4 spinous process is usually obscured in the laterai view by

the scapulae, rib cage or back muscles. To overcome this problem, a " T" shape light

wooden r d , with a flat bar on the bottom, was used (Fig.6, 7). The flat bar of the rod

was placed over the T4 spinous process using hypoallergenic adhesive tape. The wooden

rod was covered with black material to enhance the contrast between markers and

background. Two reflective markers were fked on the proximal and distal rod

respectively and the position of T, was calculated ftom these markers.

The markers consisted of styrofoam halls (20 mm in diameter) wrapped with

retroreflective tape. The markers were placed ont0 the skin with a small piece of double

side tape which is hypoallergenic and easy to remove.

The location of the rnarken were detected simultaneously fiom the right side using

one video camera. A 60 camera rate (Le. 60 pictureslsec.) and 11 1 OOO shutter speed were

used for data collection. Measures of cervical and cervicothoracic posture were ohtained

with subjects in both relaxed sitting and standing positions. While standing, subjects were

asked to stand r e h e d looking straight ahead horizontally, with their arms hanging at

their sides, their feet comfortably apari and their toes aligned with a fioor marker. For

the sitting position, subjecis were asked to sit on a straight low-back wooden chair with

Figure 7 : Subject in the t e s t positions: A - subject in neutral posture, B - subject in full protraction, C - subject in full retraction.

their feet on the floor, their knees hipwidth apan, and sacmm and scapulae touching the

chair back, and their eyes looking directly ahead. The head and neck were positionrd so

that the subject felt relaxed and nafural. In order to measure the neutral head posture

(NHP) relative to full retraction (FR) and full protraction (FP), the position of the

markers in full protraction and full retraction were obtained in both postures. For

protraction and retraction subjects were asked to protract or retract their heads as far as

possible with their eyes focused straight ahead. The postures (P, N, R) were also

demonstrated for each subject by the investigator before forma1 recording. During

recording. subjects were asked to hold the head posture for a count of 5 seconds.

3 -4.2 Procedure

The snidy took place in the Motion Lab of the School of Rehabilitation Therapy

in Louise D Acton Building at Queen's University. Data were collected with subjects in

hoth sitting and standing positions in each session. Each session included six intraday

sets. while each set represented one of three postures (protraction, neutral and retraction)

and included four aials in the sitting or standing position. To avoid hias. or systematic

error, the order of position (sining and standing) was randomly selected on each test

occasion and postures (proeaction (P), neutral (N), and retraction (R)) were randomly

selected within position. Fig.7 dernonstrates the subject in the tbree different tening

postures. In each trial, the head and neck posture of the ~ b j e c t was recorded for 5

seconds. Data were coiiected at 30 frames (60 pictures) per second. Seventy two

consecutive pictures were selected and digitized for each trial.

Each subject was asked to walk two minutes hoth before starting a forma1 test and

between sets. The waiking before each recording was designed to relax the suhject. and

help himlher to assume a relaxed posture. Before starting each set, a d e r with two

retroreflective markers was placed horizontally in the camera view. The distance of the

two retroreflective markers was known allowing scaling to tnie dimension. Before each

recording, the black board and camera were adjusted to the horizontal lines using a

levelles. The plane of the black board was adjusted perpendicular to the carnera's optical

axis using a predrawn Iine on the floor; sirnilarly, the camera's optical plane was adjusted

perpendicular to the plane of black board using the grid marker on the floor.

3.5 Data Processing

The location of each reflective marker was determined using the computer-

digitizing feature of the Peak system. The steps are summanzed as follows:

3 -5.1 Videotape Encoding :

The tape was encoded in order to analyze a recorded image. The VCR unit

assigned sequential numbers to each video frarne on the tape under the control of the

video controller board in the computer. The encoding numbers were recorded on audio

track. When editing the video tape, the exact h m e which needed to be accessed could

be detennuied via the encoded frame numbers. After encoding, any image on the tape

could then be referred to by its h m e number.

3.5.2 Spatial Mode1 Set Up

The Peak 2D systern allows the user to digitize up to 35 points on a given image.

However, the cornputer needs to know exactiy how many points to digitize. the names

of these points, and how the points are to be comected. The eleven markers (2 markers

on the reference board and 9 markers on the subject) were input as points to be digitized.

3.5.3 Project Set Up

Under this menu, a variety of information regarding the current project was input

including project name. type of camera used. camera's picture rate. pictures per frame.

number of reference points to digitize. and objective d e r length and units.

3.5.4 Automatic Data Capture

In order to determine the position of a point in space, the user must digitizr one

or more frames initially. At this step, the Peak system uses the video frame grahber board

which converts the analog video signal into a digital format. The frame grahber board

"grabsn a video fiame (2 fields or pictures) and converts the frame into 480 horizontal

lines of 512 pixels. These pixel can be accessed by the use of a cursor. which is on the

video frame. By rnoving the cursor with respect to the video frame. a user c m speciQ

which pixel is to be selected as a digitized point.

In this step, the following five parameters were selected: search radius. minimum

and maximum marker outline size, the contrast threshold, and number of frames to

digitize. The Peak system al.iows the user to select a digitization rate of up to 60 picnires

per second of recorded video. The image cm he digitized both manuall~ and

automatically. However, for automatic digitization, the fust three frames were manually

digitized, allowing the program to predict where the markers would appea. in the

following h m e s . Once the parameten were adjusted properly, the cornputer could

automatically trace trajectories of the markers and digitize them in subsequent frames. If

a pixel which exceeded the threshold was found in the search window, then the marker

would be autornatically digitized. Othenvise, the program would prompt the user

indicating that the marker was not found in the specified search window. In this case. the

location of the missing marker was manually digitized by the user. The location of each

reflective marker was measured as raw data for the trial. The raw data were the x. z

coordinates of the centre of each marker. For each picture, there were 1 1 pairs of score$.

representing x, z coordinates of the 1 1 markers. For each trial. 72 consecutive picturer

were digitized. The unit of the raw data was a pixel.

3.5.5 Data calculation

During this procedure, the raw data of displacernent were smoothed. adjusted.

normalized and processeci. If the two reference points on the board were not in the

horizontal line, they were automatically adjusted as were al1 points on the subject. The

calculation procedure also included a smoothing process which reduces noise by selecting

a frequency cut-off. In this study, errors introduced during digitizing were minirnized

using a Butterworth digital filter with a 5 Hz cut-off frequency. During this procedure.

calculated data (CDA) were generated frorn raw data (RDA). For each marker. the

honzontal(x) and vertical(z) coordinates from the origin of coordinate sysrem were

obtained in cm.

3.6 Further Rocessing on the Calculated Data

3.6.1 Correction of marker position

The calculated data gives the location of the center point of the marker which is

1 cm away from the skin of the subject. The points of interest are those points on the skin

where the markers were attached. To get the true location of point on the skin. an

approximate method was employed in which central points of markers were "shified" to

skin. The "shift" included the following:

1) GlabeIla:

The marker location was shifted horizontally hackward hy 1 cm.

2) Extemal occipital protuberance, S:

The markers were shified forward horizontally by 1 cm.

3) C,:

The marker was shified fore-downward 45' degrees From the horimntal Iine. hy

1 cm. Then the shifted distance ia x and z directions were:

Ax = 1 . 0 ~ ~ 0 ~ 4 5 ' = 0.707(cm) Ar = - 1 . 0 ~ ~ 0 ~ 4 5 ' = -0.707(cm)

thus add 0.707 cm to x, mhus 0.707 cm to z (Fig. 8).

4) T, Calculation

The location of T. was calculated using the location of the two markers on the

O -- ccntcr of the markeq r -- radius of the marker.

Figure 8: Illumation of shifang marker to skin on C,

.48.

projector bar attachai to T,, named M8 and M9 (Fig.9). The value of angle 8 was

Figure 9: Illustration of calculation of marker on T,

.49.

calculated using coordinates of points M8 and Mg. then

0 = arc tan[(M9,., - M8,.,)/(M8,., - M9J

T,., = M8,., + L1 * cos0

T,, = MB,,, - L1 * sin8

3.6.2 Location of Point M:

Points S (the point on the sternum at the level of T4) and M (mid point of trunk)

were located using the following method. After T, was located, the thickness of the mnk

at the horizontal level of T4 was measured using a calliper together with a leveller to

ensure a me horizontal distance. r. (the distance between S and T,) (Fig.6). The location

of point M was detennined afier digitizing. The value of the x-coordinate of M equals

to 112 plus that of the T,'x coordinate, and the value of the z-coordinate was the same as

that of the T,' z coordinate. i . e. :

M,,, = TA,,, + t f 2 ;

Mt., = L x ,

3.7 Outcome measures

Twelve measures of cervical and cervicothoracic posture and measures of total

head excursion (TT-IE) and resting head position (RHP) were obtained in the reliahility

phase of the study (Fig.10). Some of the measures chosen in the study have been used

by previous researchers allowing cornparisons between previous research and the current

mdy. ûther measures were added, providing more information and to help find more

usehl parameters which can describe cervical and cervicothoracic posture. Those

measures found to be most reliable in the fnst phase of the study were used in phase two

of the study. The measures, as identifled in Fig. l O are:

1) Angle 1 (GlablTrag)

The angle is subtended by a line drawn from the glabella to tragus, and a

horizontal h e through the tragus. This parameter describes the posture of head and its

relationship to the horizontal line, for example, flexion, extension. It p n m a d y reflects

the upper cervical spine pomire.

2) Angle 2 (GlablMid)

The angle is subtended hy a line drawn from the glabella to point M. which is the

midpint of the luie drawn from T, to sternum (S), and the horizontal line drawn through

point M. This angle is used to descnbe the relationship of the head relative to the mi&.

i . e . flexion, extension, protraction and retraction .

3) Angle 3 (TraglMid)

The angle is subtended by a line drawn from the tragus to point M. and the

horizontal line drawn from M to S. This angle describes the head position relative to the

mid point of rrunk.

4) Angle 4 (TragIC,)

Fig.10: 12 angles describing head and neck posture

EOP -- External occipital protuberance S -- The intersection of the horizontal line passing

through T4 and sternum M -- The middle point of trunk (the middle point of the

horizontal line which through T4 and sternum Al -- Angle 1 (Glab/Trag) A2 -- A n g l e 2 (Glab/Mid) A3 -- A n g l e 3 (Trag/Mid) A 4 -- Angle 4 (Trag/C7) A5 -- Angle 5 (Glab/C7) A 6 -- Angle 6 (Mand/C7) A7 -- Angle 7 (C7/T4) A8 -- Angle 8 (Glab/Acrom) A 9 -- Angle 9 (Trag/Acrom)

A 1 0 -- Angle 10 (EOP/CS) Al1 -- A n g l e 11 (Cer/Ang) A 1 2 -- Angle 12 (C2/C7)

The angle is forrned between the horizontal line and a line through the uagus and

CI. This variahle? as well as the following two describe the relationship hetween the head

and the cervical spine.

5 ) Angle 5 (GlablC,)

The angle is subtended by a line drawn form the glahella to C,, and a horizontal

line through the C7.

6) Angle 6 (MandlC,)

The angle is subtended hy a line drawo from the mandible to C7, and a horizontal

line through the C,.

7) Angle 7 (CJT,)

This angle is subtended hy a line drawn form the C, to T,. and a horizontal lin<:

drawn through Ta. This parameter describes the upper thoracic spine slope.

8) Angle 8 (GlablAcrom)

This is the angle subtended by a line drawn from the glahella to the acromion. and

a horizontal lioe through the arornion(M,). It describes the relationship hetween glahella

and shoulder joint.

9) Angle 9 (TraglAcrom)

This angle is subtended by a line drawn from the tragus to acromion(M,), and a

horizontal line through the acromion. It describes the fonvard position of tragus relative

to the acromion. This meanire can be used to compare with &ta provided by Kendall and

McCreary." In their study, it was reported that in a lateral view of an ideally aligned

posture, the plumb bue should coincide with the extemal auditory rneahis, and the

acromion process. In this situation, the angle should be 90 degrees. It was used to

dininguish fonvard head posture from nomal head posture, as defuied hy Kendall and

McCreary

10) Angle 10 [EOP(external occipital prohiberance)lC2]

This is the angle subtended hy a line drawn from the EOP to C2, and a horizontal

line through C2. This angle descnbes the angulation of the upper C spine.

I I ) Angle 1 1 (CedAng)

This angle describes the cervical lordosis. It is subtended hy Iines drawn From

external occipital protuberance to C I , and through C, and T, (Fig. 10).

i 2) Angle 12 (CJC-,)

Cd(C2-C,) is the angle wbtended by the horizontal and a line between C, and C,.

This angle descnbes the forward position of C, relative to the cen>icothoracic spine. This

rneasure was used by Refshaung et al (Fig . l O) .

13) Total Head Excursion (THE)

Total head excursion (THE) from full protraction to full retraction can be

expressed using the angles which represent the cervical spine inclination. These angles

are Angle 4 (TraglC,), Angle 6 (MandlC,), and Angle 12 (CJC,). The most reliable

angles as determined in the phase one study will be used in the main study. This measure

is determined by angular difference between full retraction and full protraction, i.e.

THE = A,-A,

Where

Aa is the angle value for retracted head posnire;

A, is the angle value for proaaçted head posture.

14) Resting Head Posture (RHP)

Resting head posture (RHP) is expressed using the angles which represeni the

cervical spine inclination. They are Angle 4 (TraglC,), Angle 6 (MandlC,). and Angle

12 (C&). Again, the

was calculated relative

most reliable angles will be

to the full remcted posture

chosen in the main study. The RHP

as a percentage of THE, i . e.

Where

A. is the angle value for retracted head posture;

AI is the angle value for p t i c t e d head posture;

AN is the angle value for neutral head posture.

3.8 Statisticd Analy sis

3.8.1 Reliability Study

a. Reliability Theory

According to classical reliahility theory, an observed measurement or score. X.

is partitioned into two cornponents: a tme component T. and an error cornponent. E. This

theoretical relationship can be expressed in the following equation

X = T & E

The statistical nature of this relationship can be checked hy restating it in terms

of variance (S ' ) . The total variance within a set of ohserved scores (Sx') is a hinction of

both the hue variance between scores (Sr2) and the variance in the errors of measurement

or error variance (S:):

S.' = s: i s,' Theoretically, the me scores should remain constant, that is, we assume that S,

is futed. When we look at a set of perfectly reliable scores, al1 observed differences

hetween each subject's scores should he attributable to m e differences between each pair

of scores, Le., there is no e m r variance. If, h a set of repeated measurements from one

subject, the true response has not been changed, then dl observed variance should be the

result of error. Therefore, reliability is in essence an indication of arnount of enor diai

is present in a set of scores and can be expressed by the ratio:

true variance . true variance - - - - --

tme variance + error variance total variance

In statistical terminology, this relationship c m be expressed as

where r, is the symhol for a reliability coefficient.""

Most measurements in behavioral studies invoive measurement error. Particularly .

studies in which the judgements are made by humans have this prohlem. Sinçe

measurement emor can seriously affect natistical analysis and interpretation. - i t is

important to assess the amount of such error hy calculating a reliahility index. The

intraclass correlation coefficient (ICC) is designed for this purpose. It provides a clear

and accurate index of measurement reliability.

b. Intraclass correlation coefficient (ICC)

An ICC, theoretically, is the ratio of the adjusted between-subjects variability

("true variance") to between-subject variance plus the appropriate error variance. It is a

reliability coefficient that is calculated using variance estimates obtained through an

analysis of variance (ANOVA). Thus, it refiects b t h degree of correspondence and

agreement arnong ratings .

c . Models of the ICC

Poneney and WatkinsIa1 summarized the ICCs into three models and each model

is expressed in two forms, according to whether the scores are single ratings (raters) or

mean ratings (raters). The notation used to describe the different mes of ICCs are: in

model 1: ICC (1,1), ICC (I,k), in model 2: ICC (2,1), ICC (2,k), in model 3: ICC

(3,1), ICC (3 ,k) . There are six different equations for calculating the ICC, classified by

purpose of the reliability study, the design of the study and the type of measurements

taken. The type of ICC is denoted by two numbers in parentheses. The fvst numher

designates the model used ( I ,2 or 3), and the second number signifies the form. using

either a single measurement (1) or the mean of several measurements (k) as the unit of

analysis ( Le., (2,k) where k is the number of judges used in the study and 2 denotes that

a two-way analysis of variance (ANOVA) was used).

d. The type of ICC used in tbis study

The type of ICC used in this study is ICC (2,l). This mode1 is used most often

in interrater reliability studies where al1 a subjects are measured by k raters and these

raters are considered representative of a larger population of similar raters. This model

is based on hw-way analysis of variance (Two-way ANOVA). Reliability of the measures

obtained over trials, sets and days were assessed using interclass correlation coefficients

(ICC's) (2,l). For each postural parameter, intertrial (intraday) comparison was made

among the four trials within each set on single &y. Interday comparison was made

between corresponding mean values of each set on the two different days. The two way

analysis of variance (ANOVA) was computed to obtain the sum of square value for use

in the ICC formula. The formula used to cornpute the ICC (2-1) is:

ICC(2,l) = BMS- EMS

BMS+(k-1)-EMS?k(RMS-EMWn

ICC = intraclass correlation coefficient;

EMS = Error Mean Square;

BMS = Between Subject Mean Square;

RMS = Between Rater Mean Square;

k = Number of hialsldays;

n = Numher of Subjects.

In this study, a high intraclass correlation coefficient is considered as an ICC

value of >0.80, and p r correlation as ~0.50. A moderate correlation lies hetween

these values.pi Ideally, measures with an ICC value of greater than 0.80 in hoth

positions should considered reliahle and would be used in the second phase of the study

(main study).

3.8.2 Main Study

Data for males and females, and for siauig and standing. were compared using

a two factor with one-repeated meanirement analysis of variance (ANOVA) to determine

whether differences existed between genders and between postures. Measures of THE &

RHP in the standhg position were compared between males and females using a one-way

analysis of variance (ANOVA). The normative database of cervical spine postural

masures, THE. and RHP for healthy young adults were determined as the 95%

confidence intervds around the mean for these measurements.

IV. Results and Analysis

4.1 Reliability Study

4.1.1 Subject Characteristics

Ten subjects participated in the fust phase of the snidy, five males and five

females. The mean age of this group was 28.9 years + 5.84 and ranged fiom 20 to 37

years. The mean age for the males and females in this group were 32 yean f 6.44 and

25.8 years 1 1.87 respectively .

4.1.2 Intraday reliability of the measurements

Intraday reliability was calculated using the trial means of each angle over 10

subjects. For each angle, the "trial rneann was the value averaged over 72 pictures

recorded in the trial. For each picture. 12 angles were calculated using the coordinates

of the marken and trunk antenor posterior diameter of the subject. As an example. a file

including trial means of 1 2 angles (subjec t ûO20, day 1 , trial 1 ) is Listed in Appendix 5 .

It can be seen that, for a given angle, the standard deviation (SD) over the 72 pictures

in one trial is very srnall, normally below 0.5 degrees.

The intraday measurements were compared using a two-way analysis of variance

(ANOVA) and an intraclass correlation coefficient, ICC(2,l) . This analysis was aimed

at deteminhg whether systernatic differences existed between the 4 trials within a set.

The between-ûial two-way ANOVA was conducted using angle data averaged within each

trial collected on &y one. The two-way ANOVA was calculated using the mode1

described by Moore and McCabe.I"l The intraclass correlation coefficient(?. 1 ). was

calculated using the data generated hy the ANOVA process.

The means, standard deviations and ICC's of four trials for al1 measurements in

the standing position and neutral posture is presented in Table 4.1. The ICC values in the

table represent the reliability of the measurement between 4 trials on &y one. Al1 of the

twelve ICC values were high ( > 0.8).

The intraday ICC's of each measurement in al1 positions and postures on tea &y

one are presented in Table 4.2. The ICC values in the Sitting position neutral posture are

similar to those obtained in the standing, neuaal posture, Le., ten of twelve ICC values

were greater than 0.80. Two measures in sitting neutral posture demonstrated moderate

reliability (ICC's between 0.5-0.8). The ICC's for the two measures were also in the

moderate range in the sining retracted position.

In summary. ICC's for al1 12 angles in both positions and al1 postures were in

moderate to high range and were considered reliable.

4.1.3 interday Reliability of the Measurements

To fmd interday reliability of the system and method used in the current study.

a two-way ANOVA was carried out on the angle data averaged within each set (Le..

mean value of the four trials in each set) over 10 !abjects. The procedure was similar to

that for intraday ANOVA and ICC calculation, with between-trial replaced by between-

day. The summaries of angle means and standard deviations over the ten subjects on each

&y, and ICC's between the two days for both positions in a11 pomire are presented in

Table 4.1 : Inwday reliability of outcorne masures for Suhjects in standing neutral posture on day 1 (n = 10)

AI1 units are in degrees except the units for ICC value. Trial rnean: average data of 72 pictures. (SD) : standard deviation obtained when calculating tnal mean. ICC: intraclass correlation coefficient.

Table 4.2 Summary of ùitraday ICC's for suhjects in both positions and al1 postures on day 1 (n= 10)

ICC : Insaclass correlation coefficient.

StdP: Subjects are in standing and protraction head posture. StdN: Subjects are in standing and neutml head posture. StdR: Suhject. are in standing and retraction head posture. SitP: Subjects are in sitting and protraction head posture. SitN: Subjects are in sitting and neuaal head posture. SitR: Subjects are in sining and retraction head posture.

SitR

0.853

0.772

0.807

0.917

0.872

O. 866

Angle

1 GlabfTrag

2 GlabtMid

3 TragIMid

4 TragK,

5 GlabfC,

6 Mand/C,

StdP

0.601

0.852

0.926

0.915

0.799

0.892

StdN

0.871

0.943

0.944

0.950

0.900

0.947

StdR

0.907

0.901

0.908

0.942

0.924

0.912

SitP

0.859

0.915

0.936

0.939

0.895

0.929

SitN

0.861

0.869

0.904

O. 943

0.854

O. 945

Appendix 6. The wmrnary of the interday ICC values for al1 subjects involved in the

study in al1 three postures in both positions are presented in Table 4.3.

It can be seen h m Table 4.3 that interday ICC's are not as high as those in the

intraday situation. For the standing position and neutral posture, six of the twelve ICC's

were high ( > 0.80); three were moderate (0.5-0.8); and three were poor ( < 0.5). ICC's

for the sitting position and neutral posture were somewhat better with four angles having

ICC's values above 0.8, seven angles had moderate ICC values (0.5-0.8) and only one

was poor (c0.5)

The ICC's in protraction and retraction postures in both positions in Table 4.3

showed similar trends to ICC values in the neutral posture. The reliahility of these

rneasures was also considered when choosing outcome measures for the main study . For

instance, Angle 1 had poor ICC value in protraction and angles 8 and 9 had low values

in retraction postures in both sitting and standing, as well as in the neutral posture in

standing.

Six of the twelve angles (4, 5 , 6, 10, 11, 12) had moderate or high ICC values

( > 0.5) in both positions and al1 postures and were included in the main midy . Angle 10

(EOP)/C2 and Angle 1 1 (Cer/Ang) had ICC values in the moderate or high range for hoth

positions and al1 postures and it was decided to use these two measuremenü in the second

phase of the study. Angle 12 (C2/C,) had ICC values higher than 0.73 wiîh one exception

in sitting protraction posture (=0.57). This angle was maintained in main study in order

to allow cornparison to the results reported by earlier researcher~.~~ Angle 2 (GlahlMid)

and angle 3 (TraglMid) had low ICC values in the sitting retraction posture but high or

Table 4.3 Surnmary of interday ICC's for subjects in both positions and al1 postures

StdP: Subjects are in standing and protraction head posture. StdN: Subjects are in standing and neutral head posture. StdR: Subjects are in standing and retraction head posture. SitP: Subjects are in sitting and proûaction head posture. SitN: Subjects are in sining and neutral head pomire. SitR: Subjects are in sitting and retraction head posture.

- -

Angle StdP StdN StdR SitP SitN SitR

-0,142 0.717 O. 843 0.27 1 0.609 0.840

ICC: Intraclass correlation coefficient.

2 GlabIMid

3 Trag/Mid

4 TraglC,

5 GlabJC,

0.851

O. 892

0.887

O. 860

0.809

0.864

0.885

0.928

0.706

0.727

0.762

0.820

0.763

0.779

0.882

O. 825

0.662

0.507

0.837

0.827

0.21 1

0.245

0.589

0.651

moderate ICC values in al1 other postures and very close mean values between the mu

days. Therefore. these two angles were maintained in the main study.

In short. the following angles were used in the main midy:

Angle 2 (GlablMid), Angle 3 (TraglMid), Angle 4 (TraglC,),Aagle 5 (GlahlC,) .

Angle 6 (MandfC,) , Angle 10 (EOPICJ, Angle 1 1 (Cer/Ang), Angle 12 (CC).

For convenience of description, the angle number used in Phase 1 was retained

for phase 11 of the study. Angles 1, 7, 8, and 9 were excluded from furiher analysis.

4.1.4 Total Head Excursion (THE) and Resting Head Posture (RHP)

Calculation of THE uses protraction and retraction data. The method was

described in the Section 3.8. The angles chosen to express the rneasurement of THE (total

head excursion) and RHP (resting head position) are the ones which represent the head

and cervical spine inclination, i.e. Angle 4 (TragK,), Angle 6 (MandiCi). and Angle 12

(CJC,). All three angles had acceptable interday reliabiliy (Table 4.3).

To fmd the interday reliability of THE calculated hy three angles (Angle 4. 6 and

12), the between-&y two-way ANOVA was conducted and the ICC(2.1) was calculated.

Tahle 4.4 presents interday ICC values of angles used in measuring THE in both sining

and standing positions. The ICC's of THE measured by three angles showed moderate

values with one exception (angle 12) which had an ICC of 0.865 in standing, and loa

values in sitting.

Calculation of RHP involved three sets of data (protraction, neutral, and

retraction). The method of calculating the RHP is described in the Section 3.8. Table 4.5

presents a summary of interday ICC values of three angles used for RHP in both sitting

and standing positions. The ICC's calculated using two of three angles ( Angle 4 and

Angle 6) showed moderate ICC values and one showed a low vaiue (mgle 12:

ICC =0.295) in standing. Again, the ICC's of RHP in sitting position were low .

In summary, Tables 4.4 md 4.5 demonstrated that the interday ICC for both THE

and RHP in the standing position showed better values than in the sitting position.

Therefore, io main study THE and RHP were measured in the standing position only.

Angle 4, 6 and 12 were chosen for measurernent of THE, while angle 4 and 6 were

selected to meanire the RHP in the main midy.

4.2 Main Study

4.2.1 Subject Characteristics

Thirty-two subjects participated in main study. The mean age for the group was

24.19 I 3.02. Seventeen subjects were males and fifieen were females. The mean age

for males and females in the group were 24.35 + 6.03, and 24.00 t 13.33 respectively .

Table 4.4 Summary of interday reliahility of Total Head Excursion (THE) in hoth sitting and standing positions (n= 10)

. -

M e m e s Day #l 1 Day #2 Day #1

(lZC,/C,) 1 (5.559) ( (5.046) 1 1 (5.790) Ul uni8 are in degrees except the un ts for K C values.

THE: Total head excursion. M m : Value averaged over 10 subjects. SD: Standard deviation over the 10 suhjectç. ICC : Intraclass correlation coeficient .

-1 Day #2 Icc(2,I) II

Table 4.5 Summary of interday reliability of Resting Head Posture (RHP) in hoth standing and sitting positions (n= 10)

Standing

Mean (SD)

Sitting

Mean (SD)

Measures - - -

RHP (4 TragIC*)

RHP (6 MandIC,)

N P : Resting head posnire. Mean: value averaged over 10 suhjects. SD: Standard deviation over the 10 subjects. ICC: Intraclass correlation coefficient.

Day #1

RHP (12 C&)

Day #2

30.752 (1 2.708)

30.669 (1 0.745)

411 units are in percentage except the umts tor ICC values.

38-383 (9.786)

30.540 (14.046)

32.129 (1 1 260)

37.347 (10.297)

0.763

0.667

0.295

33.606 (9.093)

35.049 (8.351)

42.731 (6.196)

32.071 (14. 162)

32.236 (15.373)

0.522

0.308

38.552 (8.475)

0.197

4.2.2 Effect of Gender and Position

The mean values and standard deviations for measures of cervical posture

(neutral), THE and RHP for males and females in both positions is presented in Appendix

7. In order to determine the effect of gender and position on head and neck posture as

well as interaction between these two factors, a twefactor with one-repeated test ANOVA

was conducted. To avoid inaccuracy in calculating the degree of freedom in a non-equal-

test two-factor ANOVA model, an equal-test two-factor ANOVA rn~del [ '~~ was used. In

order to get an equal number of subjects in each group, the fûst two male ~ h j e c t ~ were

dropped during the ANOVA calculation. A significant difference would be considered if

the P-value was less than 0.05. The ANOVA results of the main study are presented in

Table 4.6. No significant difference between positions or between genders for an): angle

was found (P 1 0.05). No significant interaction effect hetween gender and position was

observed (Pr 0.05).

The total head excursion (THE) and resting head posture (RHP) were calculated

for each subject involved in the main study, using Angle 4 (Trag/C,). Angle 6 (Mand/C,)

and Angle 12 (CJC,) based on results of the reliability study. The data of THE and RHP

are tahulated in Appendix 8. Using the data for individual subjects, THE was pooled hy

gender. Measures of THE and RHP were obtained only in standing. A one-way ANOVA

was conducted to determine whether total head excursion (THE) was effected by gender.

A significant difference would be identifiai if the calculated P-value was less than 0.05.

The results of one-way ANOVA of three measurements of THE (using Angles 4, 6, and

12) are presented in Table 4.7. There was no significant difference between genders with

Table 4.6 Analysis of effects of gender and position on selected angles using 2-factor with one repeated-test ANOVA for subjects in neutral head posture

II 1 Position 1 Gender 1 interaction II

Tahle 4.7 S u m m q of one-way analysis of variance (ANOVA) for effect of gender on THE and RHP

P value

0.1911

0.2114

0.9682

0.9274

0.8463

O .9632

0.1348

0.8939

I r - - -

1 Gender

F value

0,003

0.277

0.280

<O.ûûl

3.956

1 -232

0.187

0.488

11 Masures 1 F value 1 P vaIue

THE (4 TraglC,)

THE (6 Mand/C,)

THE Il (12 C J G )

RHP (4 TragC)

THE: Total head excursion RHP: Resting head posture

RHP (6 MandK,)

0.07 1 0.79182

0.241 0.62730

respect to the three measurements (Pr 0.05).

Similarly, a one-way ANOVA was conducted to detect if gender affects resting

head posture (NP). The F-values and P-values of two measurements, Angle 4. and

Angle 6 with respected to RHP are presented in Table 4.7. No significant difference was

found (P 2 0 .OS).

4.2.3 Overall Variation of the Angle Parameters

In order to understand the range and distribution of the angles in the current midy.

three statistical parameters were obtained during the analysis. They are: extreme al

mean values, extreme set mean values, and confidence intervals of the set means. Based

on the-fact that the angle values did not demonstrate significant difference between the

two gender groups. the variation ranges combine data from males and females.

4-2.3.1 Extreme Trial Means

For each angle, extreme values were searched for al1 subjects in the main study

by using a special module in the software. The pair of maximum and minimum extreme

values within al1 trials for al1 abjects was obtained. These two exaeme values cover an

overall range of the angle for a specified position and posture, presumahly for the whole

population investigated. Table 4.8 presents the extreme values for each angle, and

intervals between the extreme values. for the standing position and neutral posture. The

extreme trial means for the sitting position and neutral posture are presented in Appendix

9.

-p.

Table 4.8. Exuerne trial means and intervals for both male and female in standing position and neutral posture (n =32)

Min: Minimum averaged trial value over 32 subjects; Max: Maximum averaged aial value over 32 subjects; Interval: Maximum - minimum; Al1 units are in degrees.

Angle

2 Glab/Mid

It can he seen from Table 4.8 that at a specific position and posture. each angle

measured in a trial may fa11 into a large range, for different subjects. It is apparent that

using the extreme oial means to define a "normal rangen for each angle concerned wauld

introduce inaccuracy. It can be expected that set means would give a better description

of such normal range for each angle. This will be described in next section.

4-2.3.2 Extreme Set Means

A simifar method was used to search extreme values of set rneans from normalized

files for al1 subjects. The result of this searching was a pair of extrerne values, averaged

over 4 trials within a set. For a given position and pomire. every angle has a maximum

.74.

Min

48.05

Max

67-52

Interval

19-47

and minimum set mean value. The pair of the extreme values forms an intemal. The

extreme set means and correspondhg intervals for subjects in standing neutrai posture are

liaed in Table 4.9. The sirnilar table for subjects in the sitthg position and neutrai

posture is presented in Appendix 9.

Table 4.9. Extreme set means and intemals for botb male and fernale in standing and neutral posture (n = 32)

Min: Minimum average set value over 32 subjects; Max: Maximum average set value over 32 subjects: Interval: Maximum - minimum; Al1 units are in degrees.

Cornparhg data in Tables 4.8 and 4.9, it can be seen that the intervals composed

of extreme set means are smaller than those made by extreme trial means. However. set

means for each angle at a given posture still Vary over a large range. The range is

normally larger than 15 degrees, and is as high as 30 to 40 degrees for some angles.

In tervals

16.55

19.91

16.78

16.15

Max

65.95

78.05

54.52

49.85

Angle

2 Glab/Mid

3 trag/Mid

4 TraglC,

Min

49.40

58.15

37.74

5 GlablC, 33.70

4.2-3-3 Confidence interval of Set Means

While the range for a given angle can be defmed hy the interval between a pair

of extreme values, it is necessary to fuither describe its features with confidence intervals

which are related to probability distribution. The 95 % confidence interval was calculated

for each angle concerned, using set means of the angle.

The rneaning of the 95% confidence interval cm be interpreted as: if we masure

an angle on any subject frorn the population we investigated, there would he 95%

possihility of obtaining a value falling into the interval calculated. Normally, the higher

the confidence level, the wider the confidence interval will be. Table 4.10 gives 95%

confidence intervals for angles measured in the standing, neutral head posture.

It cm be seen that the 95% confidence intervals in Table 4.10 are much smaller

than the intervals formed by two extreme set means in Table 4.9. It is clear that,. for

normal young adults, the angles concemed would frequently Vary in a limited range.

within 2.92 - 7.54 degrees.

Sirnilarly , Table 4.1 1 gives 95 R confidence intervals for the sitting position and

neutral posture. The intervals for corresponding angles are similar to those for the

standing position and neutral pomire, ranged from 3 -37 to 9.00 degrees.

4.2.4 Normal Range of THE and RHP

The normal range of total head excursion (THE) and resting head posture (RHP)

are expressed by 95 95 confidence intervals. The results are presented in Table 4.12. It

cm be seen from the table that the 95 % confidence intervals of THE encompasses a small

- -

Table 4.10. 95% confidence interval for suhjects (male and female) in main study in standing and neutral posture (tg = 2.040; n = 32)

Angle Lower Mean

2 GlablMid 56.04 57.49

Al1 units are in degrees. Mean: Angle value averaged over 32 subjects: SD: Standard deviation over the 32 sub-jects.

U P P ~ ~ Interval SD

58.95 2.92 4.04

Table 4.1 1. 95% Confidence Intenta1 for suhjects (male and female) in the main stuc& in sitting and neutral posture(t* = 2.040: n = 32)

AU units are in degrees. Mean: Angle value averaged over 32 subjects;

Angle

2 GlahIMid

SD: Sta&d d e v i a over th- subficu.

.77.

Lower

53.76

Mean

55.44

U P P

57.12

Interval

3.37

SD

4.67

range. The width of the interval is from 3.62-5.42 degrees. The width of the confidence

interval of RHP is 9.5456 for Angle 4 (TraglC7), and 10.32% for Angle 6 (MandIC7).

Table 4.12 The 95% Confidence Intervals of THE & RHP for Subjects (male and fernale) in standing position (n = 32, r' = 2.040)

The uni& of THE are in degrees, and the units of RHP are in percentage. THE: Total head excursion; RHP: Resting head posture; Mean: Averaged set data over 32 subjects; SD: Standard deviation over the 32 subjects.

-

SD

5.68

5.01

7.5 1

13.23

14.30

Upper

24.88

21.82

33.22

36.70

34.82

Mean

22.83 THE (4 Trag/C7)

Interval

4.10

3.62

5 -42

9.54

10.32

Lower

20.78

THE (6 MandlC,)

THE ( 1 2 C:/C7)

RHP (4 TragG)

RHP (6 Mand/C7)

18.20

27.80

27.16

24.50

20.01

30.5 1

31.93

29.66

V , Discussion

5.1 Iotraday Reliability of head and neck posture measurement

Intraday reliability, determined by repeated testing on a single day, demonstrated

consistently high or moderate reliability (al1 ICC > 0.60) across the 10 subjects in three

postures (P.N.R.) and two positions (sitting and standing). For ail the angles concerned.

there was no significant difference between trials (intraday). Furthermore, it was observed

that for each subject in each trial, the standard deviation of each parameter showed very

small values ( < 0.5 degrees). The results suggest that the PEAK Measurement System

and method used in cwrent midy are highly reliable for objective head and neck posture

assessrnent .

Carehl examination of intraday ICC values reveals that five of seven moderate

ICC's were for the angles which use the marker on the acromion process. Four of them

were in the sining position, and one of them in the standing protracted posture. These

lower ICC values may be related to the location of the acromion process. The acromion

process is not in the same plane as the glahella and tragus. Values of the angles which

include the acromion process are determined not oniy by head and neck posture. but also

by shoulder posture. This could introduce higher variance which causes lower ICC

values.

The lowest intraday ICC value was obtained for angle#l (Glab/Trag) in the

standing position and protraction posture on day one, (ICC=O.oOl). The result was

relatively lower than all other ICC values. A possible reason for this lower ICC is that

the distance between glabella and tragus is relatively small. Thus if there was minor error

in digitizing, it could lead to relatively large variation in the angle value. However. when

the day one value was compared with the same angle, position, and posture on day NO.

the lower ICC appeared to be an exceptional variation, rather than a tme indicator of

lower reliability of measure.

Some previous researchers who studied the consistency of cervical spine posture

(inclination of the tragus to C,) have reported conflicting htraday rewlts. Braun and

Amundsonr6' reported an intra-session ICC of 0.39, while Refshauge et al reprted

an intra-session reliability for a measure cervical inclination (C&) of>0.90. In the

present study, the high intraday(inter-mal) reliability for the measures tragus/C, and

cervical inclination(Cz/C,) were found. supporthg the results reported hy Refshauge er

5.2 Interday Reliability of neutral head and neck posture measurements

Reliahility , as determined hy test-retest on separate days. showed variable results .

Sorne of the angles measured demonstrated high ICC values. whilr others showed

moderate or low ICC values. Two angles had small negative values. The angular

measures demonstrating high ICC values for set (4 trials) cornparisons hoth in the sitting

aad standing positions in the neutral posture were: Angle #4, TraglC, (ICC in standing

= 0.89, in sitting = 0.84); Angle #5, GlabfC, (ICC in standing = 0.93, in sitting =

0.83); and Angle #6, MandlC, (in standing, = 0.90, in sitting = 0.88). The consistent

high ICC values indicated that these angles are highly reproducible and useful in hoth

clinical and research practice in describing head and neck posture.

Four angles showed high ICC in one position and moderate ICC value in the other

position. They were Angle #2, GIab/Mid (in standing = 0.8 1 , in sining = 0.66); Angle

#3, TraglMid (in standing = 0.86, in sinuig = 0.5 1); Angle #IO, EOP/C2 (in standing

= 0.86, in siaing = 0.79); and Angle # I l , CerfAng (in standing = 0.78, in sitting =

0.80). Further examination of the data revealed that the ICC's of these angles in ail

positions and postures dernonstraed moderate or high values. In general, despite some

moderate values, ICC's were considered high.

Angle #12. (CJC,) had a moderate ICC value in both positions in the neutral

posture (in standing = 0.73, in sitting = 0.75). and was kept in main study in order to

make cornparison with previous midies.

Some angles showed Iow ICC values and were excluded from the main sud!.

Angle #1 (GIablTrag) had Ion ICC in protraction in botb positions and Angle #8

(GlahlAcrom) and #9 (TraglAcrom) showed low [CC's in the neutral and retraction

postures in both positions. As discussed in Section 5.1. the factors which may contribute

to the low intraday ICC values may also affect interday ICC's. Angle #7 (C,/T,) showed

generally low ICC's in both positions. A possible reason for this is that the T, was

calculated from position of two markers (Marker 8 and 9), thus more enor may have

been introduced.

In Table 4.3, two angles, Angle #8 (GlablAcrom), and Angle #9 (TragfAcrom).

showed small or even negative ICC values of 0.059 and -0.045 respectively in the

standing neutrai position. It was indicated by Porteney and Watkin~~'~' that in fact. it is

possible for ICC values to range from negative to positive infinity. By checking the

formula used for calculating the intraclass conelation coeficient, it can he found that if

mean square error (EMS) is larger than mean square of between subjects (BMS). a

negative ICC value would be prodriced. In other words, if suhject's scores were

homogeneous, the actual limits of the ICC will not match the theoretical lirnits of 0.00

and 1 .00.L451

Cornparisons can be made between the current study and previously reported

results. Braun and Amundsodq measured head inclination (tragus to C,) on 2 test

occasions and reponed an intersession ICC of 0.56. Twenty male subjects aged from 22

to 45 participated the midy. Refshauge et al examined seventeen subjects (6 males

and 11 fernales) aged from 23 to 62 years and reported an interday ICC of 0.85 for

meamernent of cervical inclination (C,/C,)(P < 0.05). The different metbods adopted hy

the researchers can account for the differences in results. However, it is hteresting to

note that Braun and Amundson"' found hetter intersession reliability than intrasession

reliability (ICC=0.39). In the present study, the high interday reliahiliq of angle 4

(TraglC,) of 0.89 in standing and 0.84 in sining was found. For angle 12 (C,IC7). which

represents cervical inclination, only a moderate ICC value of 0.73 in standing and 0.75

in Sitting were found. One possible reason for this slightiy lower ICC value for Angle 12

is that there may have been some errors in locating the C2 landmark. It is known thar

locating @alpaWg) C, is more dificult than locating the tragus. thus it is easy to

introduce enor during palpation of C,. In this case, a rninor locating error can result in

relatively large angle differences.

Some parameters investigated in the current study have not been used before. For

example, the glabeila and rnandibular angle were used to describe the cervical inclination.

Le. Angle 5 (GlabfC,) and Angle 6 (MandlC,). These two angles were investigated

because these measures cm also reflect the relationship behveen the head and neck. and

these landmarks are easy to palpate. The outcome of these measures cm also serve as

reference for cornparison to measures obtained using the tragus (TragfC,). High ICC

values were obtajned for angles measured using these parameters. It seems clear that

angle 5 (GlahlC,) and Angle 6 (Mand/C,) are reliable and usehl postural parameters in

describing head and neck posture for both research and clinical practice.

In Refshauge et al's mdyW , the angle representing cervical lordosis (Ce) was

investigated. The interday ICC value for this angle was only moderate (ICC=O.63). Their

explanation for this was that the distance between the three vertebral levels used (C,. CL

and CI) was small. In this case, minor digitising enors could produce relatively large

differences in the angle measured. In the present study , a similar parameter (Cer/Ang ).

was investigated to descrihe the cervical lordosis. Instead of using landmarks CL. CI and

C,, landmarks of EOP. C, C, and T4 were used. The angle was defmed hy lines drawn

From the extemal occipital protuberance (EOP) to C2, and through C and T4 (Fig. 10).

The ICC values for this masure were higher (0.78 and 0.80 for standing and sitting

respectively) than that of the similar angle (C,) used in Refshauge et al's study. Based

on this result, it would appear that the landmarks used in current study are more suitahle

than those used by Refshauge et al. In other words, angle # I l (Cerhng), can be

considered a usehl postural parameter to describe cervical lordosis.

Some of the parameters showed low interday ICC values. Several factors might

have contributed to this. First, some landmarks used for describing the posture were

difficult to locate. This would affect the interday reliability. This is a common prohlem

when rneasures rely on palpation of bony landmarks. Slight error in locating a landmark

could cause relatively large differences in the angle measured on different test occasions.

Second, coordinates of one landmark calculated using data of more than one

marker might have larger error. For example, the location of T4 was calculated using data

from Marker 8 and Marker 9. The error in the T, location should be greater than error

of the coordinations of either Marker 8 or Marker 9 individually. This may explain why

angles related to T, have lower ICC values.

Another important factor contributing to the varied reliability is the testing

posture. Few of the previous midies investigated a natural relaxed posture. A chest swap

or stahilizing chair were used in most previous tud dies.^.'.^'^ WhiIe constraining subjects

might enhance reliability, it does not reflect a natural relaxed posture; thus the data

produced from that kind of midy may not reflect the tme neutral posture. In the current

mdy. subjects were unconstrained, reflecting their m e natural posture.

Finally, the lower interday ICC values might also indicate that a subject's posture

varied h m day IO day , especially in the sitting position. However, some measures were

reliable indicating that cervical posture is quite consistent when measured on two different

days particularly in the standing position.

5.3 Interday Reliability of THE & RHP Measurement

The interday ICC's of total head excursion (THE) demonmted moderate and high

values (0.71 -0.86) for al1 three angles used to calculate this parameter in the standing

position, but showed low values in the sitting position. The ICC's of resting head posture

(RHP) had a similar trend, moderate ICC's in the standing and low values in the sining

.84.

position. Such low ICC's for both THE & RHP in the sining position may he due to the

lower interday ICC's of these angles for protraction and retraction in the sitting position.

indicating that head and neck posture is not so reproducible in the sitting position as in

the standing position. As described in section 3.8, the value of THE was calculated using

both protraction and retraction angle data, while RHP came fiom data of three postures.

Thus, low ICC V & U ~ S in protraction and rebaction will cause a lower iCC value for botb

THE and RHP. The three angles used in calculation of THE and RHP had only moderate

interday ICC values in protraction and retraction postures in the sitting position. For this

reason, the interday ICC values of THE and RHP in the sitting position are much lower

than those in standing position. It can be concluded that subjects do not assume a

consistent protracted and retracted head and neck postures in the siaing position over

time. A likely explanation for this is that suhjects have more support for the spine in the

sitting than in the standing position, and thus have more options for head and neck

posture and movement.

There are currently few studies availahle regarding objective measurement of THE

and RHP.[6.'*w"1 No study was found regarding the reliahiliv of measures of THE and

RHP. Thus, the cornparison is not applicable.

5.4 Neutrd Head and Neck posture

In most reports, head and neck posture has generally been determined by

meamring the inclination to the horizontal of a line drawn between the tragus and C, as

demonstrated in Fig.2 .16. '* "* " Although this masure is a usefbi general descriptor of

head and neck posture, it gives oniy limited information. It is possible to achieve the

same head position with different cervical postures. The present study was intended to

ohtain more information by utilizing more measures to describe the cervical spine. For

convenience, the parameters which were investigated in this snidy were divided into three

groups 1) three angles which describe head inclination (TraglC,, Glab/C,, MandlC,); 2 )

one angle of cervical spine inclination (C21C7,); and 3) one angle of cervical Iordosis

(Cerfking). Mon of these measures have not been investigated before, thus cornparisons

with reported studies are remicted. Cornparison between the current study and previous

reports cm only be made for measures in neutral head and neck posture.

5.4.1 The Effects of Position

It was surprising that the present snidy found no significant difference between

sitting and standing positions in measures of neutral head and neck posture. although

there was slight difference between interday ICC values for sining and standing in the

reliahility study. Examination of data in Appendix 7 revealed that the mean values for the

angles concemed in hoth positions are very close. Cornparisons hetween this smdy and

reported results will be made below.

5.4.1 -1 Neutra1 Head Posture (TragiC,)

The parameter used m o a frequently by previous researchers to describe the neutral

head posture was (head inclination) angle Trag/C,, an angle between a horizontal fine and

a line through tragus and C7.16- 7 w 1144.611 This angle, which rneasures the inclination of

the head relative to C,, reflects the relationship between head and cervical spine. In the

present study, the mean value of this parameter for male mbjects in the standing position

was 45.7414.55 degrees, and in the sitting position was 44.88k5.24 degrees. This

finding is similar to that reported by Braun and A m u n d ~ o n . ~ ~ They reported an angle of

51 -97 k5.77 degrees for 20 male subjects 22-45 years of age in the sitting position when

using a cornputer-assiste. siide digitiMg systern caiied the Postural Analysis Digitizing

System (PADS). In Braun and Amundson's ~ tudy[~ , the neutral head posture was achieved

by using a chest strap around the abjects thorax and a pelvic belt across the subject's hip

to secure the subject's testing position. These differences in methodology and age range

may account for the difierence in the angle measured.

In the current study, the mean value of the same angle for female subject in the

standing position was 45.54 k4.72 degrees, and in the sitting position was 45.87 k4.62

degrees. The fmding is very close to those reported by Watson and Trott."] A mean

value of 49.1 k2.9 degrees was ohtained on 30 fernales, aged 25-40 (mean age 30 years)

in the sitting position in Watson and Trott's midy. The angle was measured in degrees

directly fiom a photograph using a protractor image and a straight edge. The method

described by Solow and Tallgren'*l was used by Watson and Tron to attain neutral head

posture ( "NHP") or called "the self-balance position". In their rnethod, the "self-balance

position" was achieved by asking the subject to perform large amplitude cervical flexion

and extension, graduafly decreasing in range until the head came to reg in the most

cornfortable balanced position. The different methods used in the ovo studies could be

possible reason for the slight ciifference of the angle.

A comparison of results of the current study in the standing position can he made

with Raine and Twomey." In th& study, the measurements of head posture were made

from photographs of wbjects in cornfortable erect standing in the sagittal plane. The

study involved 39 subjects (31 fernales, 8 males), ranging in age from 17-48 years, with

a mean age of 22 years. Three photographs were taken at one al and hwo trials were

obtained on the same day. They reported a mean value of 5 1.9f 4.5 degrees for angle

TragIC,. In the present study, the mean value for the sarne angle in standing was

45.65 t4 .56 degrees. This suggests that there were some differences between the two

groups of subjects andlor the different methods used in two studies. The method used to

locate the markers by different investigators could be a factor introducing different result.

While results of these four studies are very similar. the small differences may he

due to not only suhjects (age range) but also the methods used. Neutra1 (resting) head

posture. as the rem suggests, should be a posture in which the subject is in a totally

relaxed and neutral condition without using any remaining device and method. In other

words, the posture adopted in the study should be a posture assumed hy the suhject in the

normal daily living and working activities. Any consuaints to the posture may change the

RHP considerably. For instance, if one is placed in a very erect sitting position with a

strap to hold the thoracic and lumber spine close to the back of the chair, the desired

neutral resting head posture may be in a more retracted posture than when suhjects sit in

a relaxed position without restmining devices, thus allowing some degrees of mnk

flexion. Also, different insbuctions given to the subjects in positioning could cause some

changes in subject ' s normal neutral posture, thus introducing different results .

Additionally, the methoci used to locate the markers by different investigators is also a

factor accounted for the different results.

5.4.1.2 Measurement of Neck Posture (Cervical Inclination)

The postural parameter which was investigated in the current study to represent

the cervical inclination was Angle 12 (C JC,). It was found that Angle 12 demonstrated

consistently high reliability in bot . intraday and interday testing. This suggested that this

angle is the useful poshiral parameter in describing cervical inclination.

The mean value of Angle 12 found in present study was 73.87k6.65 degrees in

standing and 73.22k7.06 degrees in sitting. The extreme trial means of this angle in

standing ranged from 60.20 degrees to 89.05 degrees. The mean value of the measure

in standing is close to that found by Refshauge et ~ l . ' " ~ They reported a mean value of

69.3 degrees in 17 subjects (6 males, I l females). ranging in age from 23 to 61 years

(mean age 36.8 years) using a photograph method. In their sh~dy. the range of values for

CJC, inclination varied from 52.5 degrees to 91.5 degrees. This is approximately 10

degrees larger than the range of variation in the current study. The possible factors

contributhg to this variation could he the wider range of subject's age. as well as errors

introduced dunng their measurement. For example, the coordinate of a landmark in their

study was calculated using the data of two points on a 30 mm-long aluminum bar attached

to the landmark. An error of the coordinate could be easily introduced during digitizing

and calculation.

5.4.2 The Effects of Gender

The present study showed no significant difference hetween males and females in

neutral head and neck posture in either the standing or sitting position. This mean1 that

males did not show more forward head posture than females, and vice venu. Hanten el

al reported that men and women had different rening head postures (significant Ievel:

a =O.OS). They found that, in standing, men held thei heads in a more protracted

position than women, whereas in sitting, women held their heads more fonvard than men.

In their study, head posture of a subject was measured by the horizontal distance beoveen

his (her) zygomatic arch and the vertical wall hehind him (her). (Details of method and

procedure have been described in Section 2.2.2). Due to the fact that different measures

(angles vs linear distance) were used to descrihe head and neck posture in the current and

Hanten er al's snidy, detailed cornparison is not possible.

The effects of gender in the current study support the result reponed by Raine and

Twomeylq, who used curvamre of upper thoracic spine to descnbe head posture. Their

study involved thirty-nine subjects (3 1 female, 8 male), aged from 17-48 years (mean age

22 years). The measurements were obtained by using a photograph method. A forward

head position was related to the cwature of the upper thoracic spine. It was reported that

there was no significant difference between males and females in head posture, and no

significant difference was observed in the measurement of upper thoracic cwature

between males and females. The results in the present study are in agreement with this

conclusion, although

Disagreement

rnethods and parameters used are different.

with respect to the effect of the gender exists in cornparison to the

snidy of Braun." Braun used the parameter TraglC, to descrihe the head posture and

found that head posture was significantly different between men and women in the

protracted and the neutral position. Men showed a more anterior position of the head in

relation to C, in a Sitting position indicating a more protracted head posture. The finding

conflicts witb the report by Hanten et al in which women held their head more

foward than men, and the current sîudy which showed no significant difference between

gender. However, the methodological differences between these midies made the

comparison difficult.

In the current study, the mean value of angle TragIC, for males and females in

the standing position were 45.74k4.55 and 45.5414.72 degrees respectively. In the

sitting position the value were 44.8815.24 and 45.8714.62 degrees for males and

females respectively. The fernale subject's mean value is close to that found hy Daltod"'

on subjects ranging from 23-34 years of age. Twenty-five fernales took part in the midy

and one photograph was taken for each subject . A mean value of 49.5 +_ 3.5 degrees for

angle TraglC, in the sitting position was obtained directly from the photographs. The

neutral head posture was achieved by using the rnethod described by Solow and

TaIlgren.wl The different instmctions given to subjects rnay have resulted in a different

head posture thus caused the difference in mean value.

The results of cunent study are slightly different fiom the measurement reponed

by Braun? In the current snidy, the mean value of angle TraglC, for males and females

in the siaing position were 44.88 + 5.24 degrees and 45.87 2 4.62 degrees respectively .

In the Braunm study, the mean value of the angle TraglC, for males and females

mea~u~ed in sitting position were 5 1.888 k4.181 degrees and 55.360 k4.549 degrers

respectively, for 20 males and 20 females. The mean age for males and females were 29

and 28 yean respectively. The method and equipment used in the study was the same as

that deScnbed by Braun and Amund~on.[~ The fact tbat the present study did not

constrain the subjects in any way may be the most probable reason for differences in the

resufîs.

5.5 Normal range of neutral head posture (NHP)

Previous studies investigating normal range of neutral head and neck posture have

not k e n found. Studies on this topic have ken limited to reporting the mean value and

standard deviation of parameters of interest. Although this simple description of head and

neck posture cm give general information, it does not show overall range of "normalw

head and neck posture; neither does it reflect the compiex nature of the cervical spine.

It can be seen fiom results of the current study that in fact normal head and neck postural

measures Vary within a Lirnited range. It is reasonable to describe the head and neck

posture by a range of variation.

The "normal rangen of the angles for healthy young adults has been analyzed and

described in three different ways:

1) the interval formed by two extreme hiai means;

2) the interval formed by two extreme set means; aad

3) the 95 % confidence interval.

Each of these methods gives a description of the "normal range". It would be

inappropriate to say which description is the ben. Rather, each of them can be used in

different situations. m e the intervals describe. with methods 1) and 2) are fairly large

(Table 4.7,4.8), it is probable that, for mon subjecîs, the angles concemed will fat1 into

the s d l ranges defmed by the statistical confidence interval (Table 4.10, 4.1 1 ) . The

intervals for ail angles listed in Tables 4.10, 4.11, and 4.12 cm be used as a standard

definition of the "normal range" for healthy young adults, in describing head and neck

posture. The data aiso can be used in future studies investigating the effect of aging.

disease or trauma on cervical spine posture and effect of instruction designed to improve

nec k posture.

VI, Conclusion

The current snidy involved two phases: a reliability study and a main study. The

following three conclusions can be obtained from the reliability midy:

1) The Peak 2D Motion Analysis System and the method used in the present study

are highly reliable. Interday ANOVA and ICC results show that some angles have

good consistency, while others do not. The lower reproducibility of some angles

may result from two main reasons:

i) error introduced during palpation;

ii) small error in digitizing resulting in large angle differences, particularly in

cases when two markers are in close together.

2) More than half of the angles analyzed had high interday reliability. These angles

should be recomrnended to serve as a clinical and research standard or reference.

These angles are: Angle 2 (GlabfMid), Angle 3 (TmglMid), Angle 4 (TraglC,).

Angle 5 (GlablC,), Angle 6 (MandIC,), Angle 10 (EOPIQ, Angle 1 1 (Cer/Ang).

and Angle 1 2 (C,/C,).

3) Normal young adults do not assume a consistent protracted and retracted head and

neck posture in the sitting position on different test occasions . Angle 4, 6, and 12

are reliable in measuring total head excursion in the standing position, and angle 4

and 6 are reliable in measuring resting head posture in the standing position.

The above eight angles were used in the second phase of the study. A normal

range of each angle was expressed by extrerne trial means, extreme set means. and

confidence interval of set means. A two-way with one-repeated meanvernent ANOVA

was conducted to detect the effect of gender and position on head and neck posture as

weli as interaction between these two factors over all 32 nibjects. The following

conclusions can be obtained from the main study:

4) The neuaal head posture of normal young adults is not affected by gender oor by

position (sitting and standing). This holds tnie for al1 angles concerned.

5) Each of the angle parameters used to represent neutral cervical posture in this

study may Vary over a large range, fiorn subject to subject. The variation is usually

larger than 20 degrees in terms of aial mean value, or larger than 16 degrees in

tems of set mean value. However, the statistical 95% confidence intervals are

relatively small, nonnally between 3 to 9 degrees. This means that most healthy

young adults assume a similar neutral ceMcal posture. The data can serve as a

standard reference for normal young adults for head and neck postural assessment.

6) Significant differences of THE or RHP between male and female groups were not

observed. The variation in range of THE and RHP for normal young adults can be

desaïbed using 95 1 confidence intervals, and it is usually 3.6-5.4 degrees for THE

and 9.5-10.396 for RHP.

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Appendix 1. Posted Notice

Volunteers Needed

For Research

Looking for volunteers between the ages of 18 and 30 with no present or past

cervical and head injury or disease.

Participation in this midy is a one hour cornmitment and involves several head and

neck posture exercises while nine styrofoam markers placing on your head, neck and

upper thoracic vertebra are detected with a video carnera.

This is a non-invasive, non-electrical study to determine normal range of cervical and

cervicothoracic posture in healthy young adults and whether there is difference between

males and fernales.

The results of this study will be used clinically to determine the effect of diseases or

trauma on the neck and to evaluate the eficacy of treatment designed to improve the head

and neck posture.

If you meet the above criteria and are interested in participating in this midy or just

want to know more, please call:

Ms. Weihe Wang, B. Sc. at 53 1-9843

.IM.

Appeadix 2. Information Sheet

Principal Investigator: Weihe Wang M. Sc. Candidate

Dept. of Anatomy and Ce11 Biology Phone: 531-9843

Supervisors: Dr. Elsie Culham Assistant Professor

School of Rehabilitation Therapy, and Dept. of Anatomy and Cell Biology

Phone: 545-6727

Dr. Malcolm Peat

Professor, Associate Dean and Director

School of Rehabilitation Therapy

Phone: 545-6104

Title of Project:

Measurement of Neutra1 Cenicd and Cervicotboracic Posture

Please r a d through this information sheet and feel free to ask the reseatcher any

question(s) you have.

This research has been designed to investigate the reliability of measurements of

posture of the head and neck in healthy young adults. The posture of head and neck is

a very important issue and concern in modem society. There is a relationship between

poor posture and neck pain, and hedth a r e practitioners ofien advocate postural

correction in treatrnent of patients with neck pain. However, there has been little research

into what constitutes normal neck and head posture and this needs to be measured

objectively and defined ptecisely. This information will be used to determine the effect

of disease or trauma on the neck and head to evaluate the efficacy of treatments designed

to improve posture.

Participation in this study involves one or two sessions in the Motion Laboratory in

the Louise D Acton Building. Each session wili take approximately 1 hour. Nine

reflective markers (20 mm in diameter, made from styrofoam) will be placed on your

head, neck and tmnk to indicate anatomical landmarks. They will be held in place using

double sided tape. The position of these markers will be recorded using a video carnera

when you sit or stand in a cornfortable, relaxed position for 3, 10 seconds trial.

Recording wiU be repeated three times for both the sitting and standing position, with 2

minutes of fke wakng behveen the recording sessions. Various measures of head and

neck posture will be obtained from the video recording.

The first ten participants will be asked to retum on another day to repeat the same

procedure. This information is needed to determine the reliability of the measurement

system.

This study will provide no direct benefit to you nor does it provide any risk of injury.

You rnay withdraw your consent and discontinue participation in the study at any time

without prejudice to you.

The data obtained during testing and any personal information obtained will be

stnctly confidential. A nle number d l be assigned to your data and this record kept

under lock and key. Subject identification will subsequently be known only to the

investigator and her supervisors and will not be released under any circumstance.

Your participation in this shidy is voluntary and you are free to withdraw from the

study at any time without prejudice. There is no financial compensation for participation

.106.

in this study.

Please retain this information sheet and a copy of the consent form for your records.

If you have questions or concerns regardhg the project, please contact the investigator,

or supervisors at the number listed, or Dr. M. Joneja, the head of the Dept. of Anatomy

and Ce11 Biology at 545-2600.

Appendix 3. Consent Form

1 have read and understood the information sheet for this

study. The purpose, procedure and my participation in the

study have been fully explained to me. I have been provided

with the opportunity to have my questions answered. 1 am

voluntarily signing this consent form to participate as a

subject in this study. 1 understand that 1 may withdraw from

the study at any time without prejudice to me. I understand

that 1 have the right to discuss any questions regarding this

research project with the research supervisors Dr. Elsie

Culham and Dr. Malcolum Peat, or with Dr. M. Joneja, the Head

of the Dept. of Anatomy and Ce11 Biology.

By signing this consent f o m , 1 am indicating that I agree

to participate in the study.

Signature of Participant Date

1 have carefully explained the nature of the above

research. 1 certify that, to the best of my knowledge, the

subject understands the nature and demands of this study.

Signature of Researcher Date

Procedure :

Standing:

Sitting:

Appendix 4. Subject Data Sheet

Code: Name:

Address:

Phone:

Sex :

Height:

Date of Test:

Posture

Date of Birth:

Weight :

Number

Posture Number

Trunk Thickness (at T4 level) :

Appendix 5. An Example of Trial Average Angle Data File

Subject GOZO, Day 1, Trid 1:

G0200101: Angle 1 : Angle 2: Angle 3: Angle 4: Angle 5: Angle 6: Angle 7: Angle 8: Angle 9: Angle 10: Angle 1 1 : Angle 12:

Max 39.829 63.887 71.848 45.785 43.777 30 -470 72.698 63.970 74.348 70.009 142.377 65.570

Min 38.482 62.819 70.739 44.473 42.552 29.261 71 378 62.835 72.893 68.186 140.520 64.109

Subject G020, Day 1, Trial 2:

G0200102: Angle 1:

Angle 2: Angle 3: Angle 4: Angle 5: Angle 6: Angle 7: Angle 8: Angle 9: Angle 10: Angle 1 1 : Angle 12:

Max 42.004 65.537 73.393 47.482 45.573 32.121 73.324 66.156 76.660 66.201 139.373 66.395

Min 41.280 65.178 72.988 46.952 45.140 3I .607 73 .O82 65.682 76.006 65.141 138.238 65.687

Note: Max (Min) - Maximum (minimum) vahies among the 72 pictures within one aial.

Appendix 6. Sumrnary of Interday Result for Al1 Angles (Set Means. Sd's & ICC's)

Standing & Protraction: ------_--------------------------- ---____--_-_---C----------IC------

Ange Day#l Day#2 ICC(2.1) 1 Glab-Trag 32.722 (4.386) 35.778 (2 -586) -0.142 2 Glab-Mid 47.249 (5 -340) 48.132 (6.03) 0.851 3 Trag - Mid 53.229 (8.139) 52.834 (8.1 89) 0.892 4 Trag-Ci 32.222 (8.075) 32.148 (7.959) 0,887 5 Glab-C7 32.336 (5.084) 33.262 (5.326) O. 860 6 Mand-C7 15.760 (6.690) 15 -208 (7 -757) 0,915 7 C7-T4 59.495 (5.451) 60.216 (4.581) 0.417 8 Glab - Acr 45.856 (4.475) 48.491 (5.1 11) 0.670 9 Trag-Acr 5 1 -480 (6.300) 53.642 (7.241) 0.779 10 EOP-C2 87.406 (12.420) 83.678 (15.127) 0.901 11Cer-mg 146.901(11.967) 143.893(11.399) 0.821 12 C2-C7 59.981 (7.001) 61.184 (6.721) O. 864 -_ - - - - - - - - -_ - - - - -_ - - - - - - - - - - - - - - - - - - - - - - - - - - - _ _ _ - A - - - C - - - - - - - - - - - - - -

Standing & Neutra1 -------A---&---------------------- ---------------------------------- Angle Day#l Day#2 ICC(2,I ) 1 Glab-Trag 3 1.972 (6.069) 34.145 (5.719) 0.717 2 Glab - Mid 57.983 (4.223) 58.153 (4.198) 0.809 3 Trag-Mid 68.806 (4.874) 67.494 (5.1 19) 0.864 4 T r a g 9 48.554(5.252) 47.1 74 (5.696) 0.885 5 Glab-C7 42.546 (3 .486) 42.695 (4.343) 0.928 6 Mand-Cî 30.780 (5.020) 29.076 (6.410) 0.903 7 C7 - T4 64.758 (6.295) 65 -045 (3.978) 0.394 8 Glab-Acr 56.613 (3.222) 58.805 (2.934) 0.059 9 Trag-Acr 67.833 (3.282) 69.286 (4.029) -0.045 iOEOP-C2 66.662(6.801) 65.309 (10.371) 0.855 IlCer-mg 131.420(8.185) 130.354(8.809) 0.782 12 C î - 77.786 (5.719) 79.1 12 (6.183) 0.732 ------_----------------------+---- ---------_-_--------------_-------

(Appendix 6 , continued)

Angle 1 Clab-Trag 2 Glab-Mid 3 TracMid 4 Trag-C7 5 Glab-Ci 6 ManddC7 7 C7 - T4 8 Glab-Acr 9 Trag-Acr 10 EOP-C2 1 1 Cer-ang 12 C2-C7

Sitting & Protraction - - - - - - - -A - - - - - - - - - - - - - - - - - - - - - - - - - ---------------------------------- Angle Day# I Day#2 ICC(2,l) 1 Glab-Trag 34.487 (5.636) 36.406 (4.031) 0.271 2 Glab - Mid 46.766 (4.499) 47.354 (4.690) O. 763 3 Trag - Mid 5 1.963 (6.428) 51.651 (6.199) 0.779 4 TraggC7 3 1 -776 (5.956) 32.150 (6.522) 0.882 5 Glab - C7 32.624 (3.975) 33 .524 (4.573) 0.825 6 Mand-C7 1 5 . 0 (5.458) 14.778 (6.452) 0.890 7 C7 - T4 56.817 (4.659) 56.888 (4.604) O. 523 8 Glab-Acr 45.326 (3.787) 48.418 (3.774) 0.546 9 Trag - Acr 49.994 (5 .O 14) 53.435 (5.526) 0,634 1 O E O P 3 2 86.40(12.434) 82.366(16.012) 0.855 11 Cer-mg 143.217 (12.737) 139.253 (15.209) 0.800 12C2-C7 58.640(5.585) 60.618 (5.409) O. 566 - - - - - - - - - - - - - - - - - - - - - - -A- - - - - - - - - - ----------------------------------

Sitting & Neutral __- - - -_ - - - - - - - - - - - - - - - - - - - - - - - - - - - __-------------------------------- Angle Day#l DayR ICC(2,l) 1 Glab-Trag 32.739 (5.906) 35.063 (7.265) 0.609 2 Glab - Mid 56.873 (3 .080) 57.242 (2.892) 0.622 3 Trag - Mid 67.224 (3.563) 66.022 (3.1 16) 0.507 4 Trag-C7 47.605 (4.2 14) 47.033 (4.637) 0.837 5 G labJ7 42.163 (2 -992) 42.916 (4.050) O. 827 6 Mand-cl 29.427 (4.217) 28.517 (5.469) O. 876 7 C7J4 61.889 (5.401) 61 A46 (5.172) 0.610 8 Glab-Acr 56.638 (2.349) 59.019 (2.713) 0.438 9 Trag-Aa 67.838 (2 -903) 69.375 (3.232) 0.619 10 EOP - C2 66.561 (7.288) 64.388 (12.298) 0.790 1 1 C e y g 128.450 (8.763) 126.034 (12.903) 0.803 12C2C7 75.715(5.380) 78.183 (5 .288) O. 747 ------------------A--------------- ----------------------------------

Sitting & Retraction __- - - - - - -_ - - - - - - - - - - - - - - - - - - - - - - - - _ - - - - - - - - - - - - - - - - - - - - - - - - - - - c - c - - -

Angle Day#1 Day#2 ICC(2.1) 1 Glb-Trag 3 1 .7 14 (8.164) 33.013 (6.846) 0.840 2 Glab-Mid 63.122 (3.598) 62.586 (3.983) 0.21 1 3 Trag - Mid 76.285 (4.000) 74.176 (4.261) O. 245 4 Trag-C7 56.001 (6.477) 54.185 (5.852) 0.589 5 Glab-C7 46.894 (5 -503) 46.660 (5.085) 0.65 1 6 Mand - C7 37.406 (4.676) 35.272 (6.013) 0.67 1 7 C 7 T 4 - 67.814(5.649) 67.808 (6.735) 0.600 8 Glab-Acr 61.814 (4.144) 64.808 (3.829) 0.38 1 9 Trag-Acr 76.303 (4.057) 78.890 (4.250) 0.441 10EOPCî - 61.143(11.014) 61.072(11,961) 0.818 1 1 Cer-mg 128.957 (13.466) 128.880 (13 .O39) 0.837 12C2-7 88.681(6.075) 89.227 (5.686) 0,882 ---------------------------------- - - - - - - - - - - - - I -C--C-C-- - - - - - -C-- - - -

Appendix 7. Sornmary of Data (Mean and Standard Deviatioa) in Main Study

1 Standing (Neutd) 1 Sitting (Neuîrai)

Measures

Angle #2 (GlabiMid)

Angle #3 (TraglMid)

Angle #4

( T w w )

Angle #5 (GlabfC7)

Male

57.5 f (4.86)

66.64 (5.67)

45.74 (4.55)

Angle #6 (MandK7)

THE 24.30 1 21.66

Fernale

57.48 (3 -02)

66.88 (3.63)

Male

54.92 (5.79)

63-80 (6.92)

41 -74 (3 -77)

Angle #10 (EOPK2)

Angle # I 1 (Cerl Ang )

Female

56.03 (3 -03)

65.11 (3.71)

45.54 (4.72)

26.33 (5.30)

I 1

66.96 (7.96)

132.93 (1 1.54)

THE (Angle #12)

RHP (Angle #4)

RHP (Angle #6)

44.88 (5.24)

41 -63 (3 -46)

28.21 (5.95)

45.87 (4.62)

64.53 (6.89)

133.93 (9 -45)

31.36

(7.90)

32.52 (9.16)

30.84 (9.61)

40.75 (4.11)

24.56 (6-40)

41.79 (3.29)

28.17 (5.61)

68.49 (8.21)

128.43 (13.97)

29.54 (7.20)

31 -26 (17.05)

28.32 (1 8.54)

63 -44 (7.07)

127.58 (1 1 .03)

- -

30.49 (7.80)

38.83 (7.99)

37.68 (8.28)

30.16 (7.5 1)

33.61 (19.19)

31.18 (20.46)

Appendîx 8. THE and RHP for Ail Subjects in Main Study

Subject Go3 1 Go32 Go33 Go34 Go35 0 3 6 Go37 Go38 Go39 Go40 Gu41

Go42 Go43 Go44 Go45 Go46 Go47 Go48 Go49 Go50 GO5 1 GO52 Go53 Go54 Go55 GO56 Go57 GO58 Go59 Go60 Go61 Go62

P N R R-P R-N W(%) 28.57 49.69 57.23 28.66 7.54 26.31 33.50 49.06 50.74 17.24 1.68 9.73 33.06 47.20 52.12 19.06 4.91 25.78 29-26 44.04 51.58 22.33 7.55 33.80 32.08 42.68 51.03 18.95 8.35 44.07 26-49 41.42 47.50 21.02 6.08 28.94 34.23 49.21 57.12 22.89 7.91 34.57 37.65 47.69 57.54 19.89 9.85 49.54 34.11 45.69 54.10 19.99 8.41 42.07 27.60 44.92 53.20 25.60 8.28 32.34 35.92 45.36 53.51 17.59 8.15 46.36 29-02 52.83 62.58 33.56 9.76 29.07 26.32 41.15 51.84 25.52 10.69 41.90 30.22 37.74 46.39 16.17 8.65 53.49 23.95 39.92 53.92 29.98 14.00 46.70 35.95 52.69 59.53 23.58 6.84 29.01 21.70 41.73 52.35 30.65 10.62 34.65 36.30 54.52 64.99 28.69 10.47 36.48 23.85 40.97 45.33 21.48 4.36 20.30 33.37 52.52 60.52 27.15 8.01 29.49 22.36 40.39 45.84 23.48 5.45 23.22 23.58 46.09 56.70 33.12 10.61 32.02 33.92 50.90 48.46 14.53 -2.44 -16.79 33.44 48.68 55.97 22.53 7.29 32.35 31.07 44.28 49.80 18.73 5.52 29.46 26.01 39.46 46.38 20.37 6.92 33.98 28.74 44.62 46.62 17.89 2.01 11.21 25.87 44.15 53.01 27.14 8.85 32.63 30.08 38.82 45.07 14.99 6.25 41.70 32.31 51.35 61.81 29.50 10.45 35.44 39.13 45.36 49.89 10.76 4.53 42.13 26.27 45.58 53.76 27.49 8.18 29.75

P N R R-P R-N NP(%) 9.95 27.95 34.17 24.22 6.21 25.66 16.11 29.46 30.65 14.53 1.18 8.13 18.40 32.73 34.40 16.01 1.67 10.46 14.58 27.85 31.81 17.22 3.95 22.96 15.60 26.40 33.49 17.89 7.08 39.60 9-24 23.52 30.55 21.32 7.03 32.97 13.33 25.53 30.76 17.43 5.23 29.99 22.67 31.94 39.54 16.87 7.60 45.05 18.59 29.40 36.18 17.59 6.78 38.55 13.00 29.85 36.17 23.18 6.32 27.27 17.96 27.36 34.02 16.06 6.66 41.50 9.76 29.64 39.93 30.17 10.30 34-12 10.43 24.03 33.56 23.14 9.53 41.19 8.04 13.26 20.29 12.25 7.03 57-37 6.36 19.47 31.34 24.99 11.87 47.51 20.65 39.05 43.99 23.35 4.94 21-17 3.83 20.81 27.49 23.66 6.68 28.22 19.66 35.55 43.44 23.79 7.89 33.18 3.41 19.43 23.39 19.97 3.96 19.83 15.88 32.85 38.80 22.92 5.95 25.96 4.18 19.31 23.82 19.64 4.51 22.96 6-40 26.42 37.00 30.60 10.58 34.57 18.14 33.60 30.95 12.81 -2.65 -20.70 13.98 26.58 32.77 18.79 6.19 32.94 13.60 24.04 27.97 14.37 3.92 27.32 10.84 23.41 31.36 20.52 7.95 38.73 11.88 28.10 30.31 18.43 2.21 11.98 13.28 31.08 36.79 23.51 5.71 24.31 12.92 20.61 26.95 14.03 6.34 45.17 17.30 35.24 44.82 27.52 9.58 34.80 24.94 31.1 1 35.27 10.33 4.16 40.28 8-08 25.22 31-28 23.20 6.06 26.10

Subject GO3 1 GU32 Go33 Go34 Go35 Go36 Go37 Go38 Go39 Go40 Go41 Go42 Go43 Gu44 Go45 Go46 Go47 Go48 Go49 Go50 GO5 1 Go52 GO53 GO54 Go55 ûû56 Go57 Go58 Go59 Go60 Go61 0 6 2

P N R R-P R-N RHP(%) 56.88 82.68 95.25 38.37 12.58 32.78 57.93 76.70 83.62 25.69 6.92 26.92 57.10 70.78 79.07 21.97 8.29 37.72 55.32 76.05 90.23 34.91 14.18 40.61 49.54 62.82 66.91 17.37 4.10 23.58 56.13 70.33 84.45 28.32 14.12 49.85 75.20 87.49 103.12 27.92 15.63 55.99 61.08 74.29 88.47 27.40 14.18 51.76 63.55 76.35 93.89 30.34 17.54 57.80 53.30 71.22 83.11 29.81 11.88 39.86 58.80 72.23 82.55 23.75 10.33 43.47 59.78 80.33 95.42 35.64 15.09 42.34 54.50 61.95 84.24 29.74 22.29 74.95 56.95 64.01 75.50 18.55 11.49 61.91 52.80 72.03 96.42 43.62 24.39 55.90 60.20 79.24 88.27 28.07 9.03 32.15 49.49 72.02 91.10 41.60 19.08 45.85 62.83 82.77 102.01 39.18 19.24 49.10 59.85 82.29 92.54 32.69 10.25 31.35 65.67 86.61 101.07 35.40 14.46 40.84 53.33 73.12 84.70 31.37 11.57 36.90 47.09 72.46 94.15 47.06 21.70 46.10 63.12 78.70 84.98 21.86 6.28 28.73 59.83 70.93 86.39 26.55 15.46 58.21 58.94 71 -34 80.87 21.93 9.53 43.46 46.86 60.97 79.96 33.10 18.99 57.37 55.76 75.49 84.51 28.76 9.02 31.38 56.47 75.87 93.41 36.94 17.54 47.49 52.93 65.20 80.29 27.36 15.09 55.15 54.36 74.69 92.89 38.53 18.19 47.22 63.90 72.11 81.27 17.37 9.16 52.76 51.60 70.61 86.72 35-12 16.1 1 45.86

------------------------------- - -A- - - - - - - - - - - - - - - - - - - - - - - - - - - -

Note: P = protraction, N = neutral, R = retraction

Appendix 9. Angle Variation Ranges at Sitting and Neutral Posture

Extreme Trial Means and Intervals for Sitting and Neutral Posture (n=32)

- - ----c----- ---------- Angle Min 1 Glab-Trag 2 1.57 2 Glab-Mid 44.54 3 Trag-Mid 50.86 4 Trag-C7 35 .O7 5 Glab-CI 3 1.87 6 Mand_C7 10.46 7C7T4 - 42.72 8 Glab-Acr 5 1.41 9 Trag-Aix 62.07 10 EOP-C2 51.14

----_------------ ----_------------ Max Interval 51.3 1 29.74 68.64 24.10 80.82 29.97 59.07 24.00 51.15 19.28 40.28 29.82 78.90 36.18 71.77 20.36 87.63 25.57 82.39 31.25

Extreme Set Means and Intervals for Sitting and Neutral Posture (n =32)

Angle Min 1 Glab-Trag 26.28 2 Glab-Mid 45.54 3 Trag - Mid 52.8 1 4 Trag-C7 37.6 1 5 Glab-cl 33.28 6 Mand-Ci 12.40 7C7T4 - 44.11 8 Glab-Acr 52.44 9 Trag - Acr 63.41 10 EOP-C2 51.82 11 Ce-g 108.06 12C2-c7 59.94

Max 47.79 66.53 78.84 56.9 1 49.68 39.27 77.84 69.87 86.84 81.90 151.87 87.65