55.full.pdf

European Journal of Orthodontics 36 (2014) 5566doi:10.1093/ejo/cjt004Advance Access publication 23 April 2013

The Author 2013. Published by Oxford University Press on behalf of the European Orthodontic Society.All rights reserved. For permissions, please email: [email protected]

The Author 2013. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: [email protected]

SystematicReview

Craniocervical posture and craniofacial morphology

Liliane de C.RosasGomes, Karla O.CarpioHorta, Joo RobertoGonalves and Ary dos Santos-PintoDepartment of Orthodontics, Araraquara School of Dentistry, UNESP Univ Estadual Paulista, Araraquara, So Paulo, Brazil

Correspondence to: Liliane de C.Rosas Gomes, Department of Orthodontics, Faculdade de Odontologia de Araraquara, UNESP Univ Estadual Paulista, Rua Humait, 1680, Araraquara, So Paulo, Brazil, CEP 14801-903. E-mail: [email protected]

SUMMARY The purpose of this study was to investigate the published evidence regarding the association between head and cervical posture and craniofacial morphology. An electronic search was conducted in PubMed, Medline, Embase, Scopus, and Cochrane databases up to 23 March 2012. Abstracts that seemed to correspond with the goals of this review were selected by a consensus between two independent reviewers. The original articles were retrieved and evaluated to ensure they match the inclusion criteria. Only articles that directly compared head and/or cervical posture with craniofacial morphology were included. Atotal of 84 articles were found of which 12 matched all inclusion criteria. Detailed analysis of the methodology in selected articles revealed quality scores ranging from weak to moderate. Nine arti-cles were cross-sectional studies, whereas only three were longitudinal studies. The findings of selected articles were linked together in order to clarify the evidence on sagittal and vertical craniofacial features as well as growth prediction regarding different postures of the head and neck. On the basis of the data obtained from the literature, significant associations were found between variables concerning head and cervical posture and craniofacial morphology. However, the results of this systematic review suggest that such associations should be carefully interpreted, considering that correlation coefficients found ranged from low to moderate. Moreover, conflicting results were observed regarding some postural variables. Further longitudinal studies are required to elucidate the relationship between the development of crani-ofacial morphology and functional aspects of head and cervical posture.

Introduction

Associations between craniofacial morphology and individ-ual variation in head and cervical posture have been reported (Solow and Tallgren, 1976; Marcotte, 1981; Solow etal., 1984; Solow and Siersbaek-Nielsen, 1986, 1992; Hellsing etal., 1987; Showfety etal., 1987; Ozbek and Koklu, 1993; Huggare and Cooke, 1994; Solow and Sandham, 2002; DAttilio et al., 2005), showing that functional principles of cervical spine are of special interest in orthodontics and orthopaedics. However, important issues remain unan-swered. It is still unclear if the craniofacial development is influenced by the posture of the head and cervical column. If so, which sagittal and vertical morphological features would be directly connected with such different postures?

Soft-tissue stretching hypothesis (Solow and Kreiborg, 1977) linked postural-induced stretching of soft-tissue facial layer, craniofacial morphology, and airway adequacy into a cycle of factors related to craniofacial morphogenesis. It stated that the soft-tissue layer of facial skin and muscles would be passively stretched when the head is extended in relation to the cervical column, which would increase the forces on skeletal structures. Such forces would restrict

forward growth of maxilla and mandible and redirect it caudally (Solow and Kreiborg, 1977; Solow and Sandham, 2002).

A study on lip pressure changes following extension and flexion of the head reported such forces in a more accurate way. Bonded strain gauge transducers on upper and lower central incisors revealed that mean differences between pressures obtained during natural head posture and 5, 10, and 20 degrees of extension showed continuous highly significant increase, whereas during 5, 10, and 20 degrees of flexion, upper lip pressure continuously decreased with highly significant values. However, the results were achieved under experimental conditions of short duration. It is still unclear whether the response would be maintained over time (Hellsing and LEstrange, 1987).

It has been shown an association between head and cervical posture with functional factors such as breathing, considering that the maintenance of a sufficient nasopharyngeal space may require postural changes (Ricketts, 1968; Solow et al., 1984). Solow et al. (1984) observed that obstructed nasopharyngeal airways were connected with extension of the head in

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relation to the cervical column. Moreover, such a condition was linked to a specific craniofacial type characterized by mandibular retrognathism and high mandibular planeangle.

Proper understanding of postural mechanism contribu-tion on normal or abnormal craniofacial development is of fundamental importance for diagnosis and treatment plan-ning of morphological and functional disorders of stoma-tognathic system. Therefore, a comprehensive systematic review may contribute to the knowledge of the complex relationship between head/cervical posture and craniofacial morphology, critically analysing whether available evidence is sufficient to support the hypothesis that posture influences growth and development of craniofacial structures.

Materials and methods

The Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement was used to guide this study (Moher etal., 2009) (Supplementary Table1).

Inclusion/exclusion criteria

Longitudinal, cohort, casecontrol, cross-sectional and case series studies that directly compared craniofacial morphol-ogy with head and/or cervical posture were eligible to be part of this review. Case reports and literature reviews were not included. Searches were restricted to English publica-tions involving only humans. The study population con-sisted of healthy child, adolescent or adult subjects of both genders. Patients with any congenital disorder or syndrome as well as those with history of previous head or neck sur-gery were not included. The sample must not have been constituted by patients with a single skeletal facial type, given the fact that different skeletal patterns are required to make it possible the correct analysis of differences related to posture and morphologic facial features. Measurements used to analyse both postural and morphological variables must have been obtained from cephalometric radiographs performed in natural head position (NHP). Articles that pre-sented any questionable information regarding cephalomet-ric measurement were not included. Articles were excluded if they did not match the inclusion criteria.

Search strategy

This systematic review was performed using the following electronic databases: PubMed, Medline, Embase, Scopus, and Cochrane (from 1966 to 2012). For our search query, medi-cal subject headings (MeSH) terms and free text were used in combination to restrict the search. Some of the keywords used in the search were growth and development, craniocervical posture, facial morphology, head position, and craniofa-cial type. Supplementary Table2 shows detailed information regarding specific search terms and combinations.

Two independent reviewers screened the publications found in the databases. After excluding repetitions, a first

selection based on title was performed. Manual search of the references was conducted to find other relevant articles. Another selection on the basis of abstracts was conducted to find potentially useful articles. When divergences occurred in articles selection, reasons were clearly identified, and a consensus achieved. Subsequently, full-text articles were obtained for those references that appeared to match our inclusion criteria. The search was updated on 23 March 2012.

Critical appraisal

Articles were assessed for the quality of their methodology by two examiners. Critical appraisal was performed regard-ing nine criteria (Supplementary Table3). Each study was graded as weak (0 to 15 to 18 points), and strong (>18 points). The kappa () coefficient was used to assess agree-ment between the reviewers.

Results

The initial search yielded 155 PubMed citations, 77 Medline citations, 345 Embase citations, 112 Scopus citations, and 0 Cochrane citations. After excluding repetitions, completely off-topic titles were excluded, which returned 73 articles. Manual search of references revealed 11 additional articles. After abstract reading, 27 off-topic articles and 9 non-English publications were excluded, which resulted in 48 references achieved by a consensus. Subsequently, full-text articles were obtained for those references that appeared to match our inclusion criteria. Out of the 48 topic-related articles selected, 36 did not fit the inclusion criteria. The remaining 12 articles were found relevant for the purpose of the study. The search was summarized in Figure1. Table1 shows detailed informa-tion about each one of the included articles.

Methodological quality of included studies

At the end of the critical appraisal phase, there was an agree-ment of =0.931 (P

CranioCerviCal Posture and CraniofaCial MorPhology 57

reference lines used for craniofacial morphology assess-ment. Considering that a majority of the selected articles used correlation coefficients for assessing the comparison between postural and craniofacial morphology variables, such coefficients were grouped together to make the quan-titative analysis of results feasible. Data were summarized considering the minimum and maximum correlation coef-ficients found among the selected articles, regarding sagittal (Table3) and vertical diagnostic features (Table4).

Sagittal assessment

On the basis of significant correlation coefficients between postural and morphological variables, as well as significant differences among skeletal classI, classII, and classIII groups, it was observed that greater craniocervical and craniovertical angles were related to lower lengths of the maxilla (Solow and Tallgren, 1976) and mandible (Solow and Tallgren, 1976; Showfety etal., 1987), greater maxillary (Solow and Tallgren, 1976; Marcotte, 1981; Showfety etal., 1987; Ozbek and Koklu, 1993) and mandibular retrognathism (Solow and Tallgren, 1976; Marcotte, 1981; Solow etal., 1984, , Showfety et al., 1987; Ozbek and Koklu, 1993; Leitao and Nanda, 2000), and a skeletal class II pattern (Solow and Tallgren, 1976; Solow etal., 1984; Ozbek and Koklu, 1993; Leitao and Nanda, 2000; DAttilio etal., 2005). Lower cervicohorizontal

angles were related to maxillary and mandibular protrusion regarding measurements that considered extracranial reference lines (Ozbek and Koklu, 1993) and large sagittal interjaw discrepancy (Solow etal., 1984; Ozbek and Koklu, 1993). One article reported facial prognathism (Hellsing et al., 1987) in association with increased cervicovertical angles. Cervical spine was significantly straighter in skeletal class III patients (P 0.001) and markedly curved in skeletal class II patients regarding the angle formed by the intersection of the cervical vertebra tangent and the lower segment of the cervical vertebra (CVT/EVT) (P 0.01) (DAttilio etal., 2005). Subjects with lower maxillary length (PNS-vpOK) were associated with a more lordotic cervical curve (Tecco and Festa, 2007). Other authors did not find significant correlations between cervical lordosis (OPT/CVT, CVT/EVT) and craniofacial morphology considering sagittal analysis (Solow and Tallgren, 1976; Hellsing et al., 1987; Ozbek and Koklu, 1993).

Vertical assessment

Greater craniocervical and craniovertical angles were related to large anterior face height (Solow and Tallgren, 1976; Showfety etal., 1987; Leitao and Nanda, 2000), small pos-terior face height (Solow and Tallgren, 1976; Solow etal., 1984) and thereby reduced face height ratio (S-Go/N-Me;

Figure1 Flow chart.


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0.38 r 0.51; P 0.001) and S-Go/ANS-Me propor-tion (0.38 r 0.41; P 0.001; Ozbek and Koklu, 1993). It was also associated with high mandibular plane angle (Solow and Tallgren, 1976; Marcotte, 1981; Solow etal., 1984; Showfety et al., 1987; Ozbek and Koklu, 1993; Leitao and Nanda, 2000), large inclination of the maxilla to anterior cranial base (Solow and Tallgren, 1976; Solow et al., 1984; Ozbek and Koklu, 1993), and high occlusal plane angle (r=0.32; P 0.05) (Marcotte, 1981). Lower cervicohorizontal angles were linked to large anterior face height (Solow and Tallgren, 1976), small posterior face height (Solow etal., 1984) as well as high mandibular plane angle (Solow and Tallgren, 1976; Ozbek and Koklu, 1993). Articles reported decreased lower and total face height and also small inclination of the mandible to anterior cranial base (Hellsing et al., 1987) in association with increased cervicovertical angles. Straightened cervical lordosis assessed by CVT/EVT or OPT/CVT angles was related to high mandibular plane angle and large anterior face height (Solow and Tallgren, 1976; Hellsing etal., 1987).

Head posture and growth prediction

Three longitudinal studies found a clear pattern of associations between head and cervical posture with craniofacial growth determined by structural superimposition method (Solow and Siersbaek-Nielsen, 1986, 1992; Huggare and Cooke, 1994; Table5). Subjects with greater cervicohorizontal and small craniocervical angles were associated with a horizontal facial growth pattern characterized by reduced backward displacement of the temporomandibular joint (TMJ), increased growth in length of the maxilla (Solow and Siersbaek-Nielsen, 1992), increase in maxillary and mandibular prognathism (Solow and Siersbaek-Nielsen, 1992), and larger than average forward true rotation of the mandible (Solow and Siersbaek-Nielsen, 1986, 1992). Subjects with lower cervicohorizontal and large craniocervical angles were associated with a vertical facial development and are likely to exhibit large backward displacement of the TMJ, reduced growth in length of the maxilla (Solow and Siersbaek-Nielsen, 1992), reduction of maxillary and mandibular prognathism (Solow and Siersbaek-Nielsen, 1992), and less than average forward true rotation of the mandible (Solow and Siersbaek-Nielsen, 1986, 1992). Craniovertical angle significantly correlated with mandibular growth direction. The larger the angulation, the more vertical the facial growth pattern in boys (Huggare and Cooke, 1994).

One article developed a prediction model from which it was suggested that children with the angle between the nasion-sella reference line and the odontoid process tangent (NSL/OPT) larger than 113 degrees may exhibit a verti-cal growth pattern of the lower face, whereas children with NSL/OPT smaller than 79 degrees may exhibit a horizontal growth pattern (Solow and Siersbaek-Nielsen, 1992).


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Discussion

The term extension of the head has been used to denote a raised position of the head in relation to the cervical col-umn or the true vertical (Solow and Tallgren, 1976; Hellsing etal., 1987; Showfety etal., 1987; Leitao and Nanda, 2000; Solow and Sandham, 2002). Thus, it was associated with increased craniocervical angles (Solow and Tallgren, 1976; Solow et al., 1984; Solow and Siersbaek-Nielsen, 1986, 1992; DAttilio et al., 2005) and increased cranioverti-cal ones (when considering the downward opening angles

formed in front of the true vertical) (Solow and Tallgren, 1976; Solow etal., 1984; Showfety etal., 1987; Solow and Siersbaek-Nielsen, 1992; Leitao and Nanda, 2000).

An extended head position was also related to cervical spine sloping forward (Solow and Tallgren, 1976; Ozbek and Koklu, 1993; Solow and Sandham, 2002). Therefore, it was linked to decreased cervicohorizontal angles (Solow and Tallgren, 1976; Solow etal., 1984; Solow and Siersbaek-Nielsen, 1986, 1992; Ozbek and Koklu, 1993) and increased cervicovertical ones (when considering the magnitude of downward opening angles formed behind the

Figure2 Cephalometric postural variables. The convention employed for angles related to the true vertical was that downward opening angles formed behind the true vertical (VER) were taken as negative, whereas angles formed in front were positive.

Table2 Critical appraisal scores of included studies.

Study/year Critical appraisal scores Total score Rating

1 2 3 4.1 4.2 5 6 7 8 9

1. Solow and Tallgren (1976) 2 0 1 1 2 2 2 2 2 0 14 Moderate 2. Marcotte (1981) 2 0 1 1 0 2 2 0 2 0 10 Weak 3. Solow etal. (1984) 2 0 0 1 2 2 2 1 2 0 12 Weak 4. Solow and Siersbaek-Nielsen (1986) 2 1 1 0 2 2 2 2 2 0 14 Moderate 5. Hellsing etal. (1987) 2 0 1 1 1 2 2 2 2 0 13 Moderate 6. Showfety etal. (1987) 2 0 1 1 1 2 2 1 2 0 12 Weak 7. Solow and Siersbaek-Nielsen (1992) 2 2 1 1 2 2 2 1 2 0 15 Moderate 8. Ozbek and Koklu (1993) 2 0 1 0 2 1 2 2 2 0 12 Weak 9. Huggare and Cooke (1994) 2 1 0 0 2 1 2 2 2 0 12 Weak10. Leitao and Nanda (2000) 2 0 1 1 2 2 2 2 2 0 14 Moderate11. DAttilio etal. (2005) 2 0 1 2 2 2 2 2 1 0 14 Moderate12. Tecco and Festa (2007) 2 0 1 1 0 2 2 2 2 0 12 Weak

1, Proposition; 2, study design; 3, sample size; 4, selection description (4.1, different facial types; 4.2, gender/age features); 5, method for obtaining NHP; 6, cephalometric analysis; 7, method error analysis; 8, statistical analysis; 9, blind measurement.


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CranioCerviCal Posture and CraniofaCial MorPhology 61

true vertical; Hellsing etal., 1987; DAttilio etal., 2005). On the other hand, the term flexion of the head denotes a forward bent position of the head (Solow and Tallgren, 1976; Showfety et al., 1987) and is generally associated with backward slope of the cervical column (Solow and Tallgren, 1976; Solow and Sandham, 2002), i.e. a vertical cervical posture (Ozbek and Koklu, 1993).

It was observed that, in general, correlations obtained for cervicohorizontal angles showed opposite signs when com-pared with those obtained for craniocervical and craniover-tical angles, which means that an extended head position is actually related to forward cervical posture (Solow and Tallgren, 1976; Solow and Sandham, 2002). However, care must be taken when interpreting the results of correla-tions regarding cervicovertical angles. Conventionally, the downward opening angles formed behind the true vertical were taken as negative, whereas those formed in front were considered positive. Thus, increased cervicovertical angles mean backward inclination of the cervical column.

Authors believe that the craniofacial morphology is often visually masked by the posture of the head and cervical col-umn (Bjork, 1951; Brodie, 1971). Investigators stated that the convex facial profile is masked somewhat by the extension of the head relative to the true vertical, which tends to reduce the facial convexity by increasing the prominence of the chin. Conversely, in those individuals with prognathic facial profiles,

the mandible protrusion tends to be masked by the forward pos-turing of the forehead. The results of correlation coefficients analysis regarding craniovertical angles seem to support this hypothesis (Solow and Tallgren, 1976; Marcotte, 1981; Solow etal., 1984; Showfety etal., 1987; Leitao and Nanda, 2000).

In general, the results of selected articles statistical analysis in this systematic review corroborate the soft-tissue stretching hypothesis (Solow and Kreiborg, 1977). Therefore, an extended head posture and/or forward inclina-tion of the cervical column were related to individuals with high mandibular plane angle and long-face morphology as well as retrognathic profile (Solow and Tallgren, 1976; Marcotte, 1981; Solow etal., 1984; Solow and Siersbaek-Nielsen, 1986; Hellsing etal., 1987; Showfety etal., 1987; Solow and Siersbaek-Nielsen, 1992; Ozbek and Koklu, 1993; Huggare and Cooke, 1994; Leitao and Nanda, 2000; Solow and Sandham, 2002; DAttilio etal., 2005). On the other hand, subjects with short-face morphology and lower mandibular plane angle, as well as those with mandibular prognathism often carry their heads somewhat lowered and/or presented a backward inclination of the cervical column (Solow and Tallgren, 1976; Marcotte, 1981; Solow etal., 1984; Solow and Siersbaek-Nielsen, 1986; Hellsing etal., 1987; Showfety etal., 1987; Solow and Siersbaek-Nielsen, 1992; Ozbek and Koklu, 1993; Huggare and Cooke, 1994; Leitao and Nanda, 2000; Solow and Sandham, 2002).

Figure3 Cephalometric points and reference lines used for craniofacial morphology assessment.


ownloaded from

L.C.R. Gomes etaL.62T

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***P

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