The strength of the rotator cuff before and after subacromialinjection of lidocaine

Jin-Young Park, MD,a Woo-Seung Lee, MD,b and Sung Tae Lee, MD,a Seoul, South Korea

The purpose of this study was to evaluate the strength ofthe shoulder before and after the impingement test. Thisstudy included 153 cases of impingement syndrome, 20cases of partial-thickness rotator cuff tear, and 60 casesof full-thickness rotator cuff tear. We divided each of thegroups into 2 subgroups according to the meanpercentage decrease in pain to evaluate the correlationbetween pain and muscle weakness. We also divided theimpingement syndrome group into 2 groups based onstiffness. After the test, the subgroup with stiffness hada greater reduction in pain compared with the subgroupwithout stiffness. The results show no statisticallysignificant difference in the strength of the shoulder,except for increased external rotation strength in patientswith full-thickness rotator cuff tears and increasedsupraspinatus strength in patients with impingementsyndrome with stiffness. In cases in which the continuity ofthe rotator cuff is maintained, pain is not an importantfactor in the cause of shoulder weakness. Preoperativemuscle testing can be done despite pain, but if a full-thickness rotator cuff tear is confirmed, re-examination ofexternal rotator strength is necessary. In patients withimpingement syndrome, particularly with shoulderstiffness, supraspinatus strength can be decreased.(J Shoulder Elbow Surg 2008;17:8S-11S.)

The clinical manifestations of rotator cuff disease in-clude shoulder pain, weakness, and stiffness. Shoul-der weakness may be related to shoulder pain ratherthan a rotator cuff tear.6,11 However, on musclestrength testing, patients often complain of shoulderpain. If the testing is performed after an impingement

From the aDepartment of Orthopedic Surgery, Konkuk UniversitySeoul Hospital, College of Medicine, Konkuk University, and bDe-partment of Orthopedic Surgery, Seoul Veterans Hospital.

Reprint requests: Jin-Young Park, MD, 4-12 Hwayang-dong,Gwanggin-gu, Department of Orthopedic Surgery, Konkuk Uni-versity Seoul Hospital, College of Medicine, Konkuk University,Seoul, South Korea (E-mail: drpark@chol.com).

Copyright ª 2008 by Journal of Shoulder and Elbow SurgeryBoard of Trustees.

1058-2746/2008/$34.00doi:10.1016/j.jse.2007.06.010

8S

test, with the hope that pain will be reduced, the wait-ing period for an outpatient would be long.

The purpose of this study was to evaluate thestrength of the shoulder before and after an impinge-ment test in cases of impingement syndrome, partial-thickness rotator cuff tear, and full-thickness rotatorcuff tear. The hypothesis was that there is no differencein strength before and after subacromial injection oflidocaine.

MATERIALS AND METHODS

Between January 2002 and February 2005, 153 casesof impingement syndrome, 20 cases of partial-thickness rota-tor cuff tear, and 60 cases of full-thickness rotator cuff tearwere enrolled in this study. Impingement syndrome withoutrotator cuff tear was identified by ultrasonography or mag-netic resonance imaging. Partial-thickness rotator cuff tearwas identified by the operative findings, and full-thickness ro-tator cuff tear was identified by ultrasonography, magneticresonance imaging, and the operative findings. Therewere 111 men and 122 women. The mean age was 52.2years (SD, 10.8; range, 18-82 years).

All impingement tests were carried out by an orthopaedicsurgeon. We used 2% lidocaine (lidocaine hydrochloride,7 mL; Kwangmyung Pharmaceutical Company) with a 23-gauge needle. The needle was inserted vertically underthe anterolateral aspect of the acromion (1 cm from the lat-eral aspect of the anterolateral corner) and was passedthrough the deltoid muscle. When it touched the greater tu-berosity, it was slightly withdrawn; then we confirmed thatit was placed in the subacromial space by injecting 2 mLof lidocaine into the subacromial space. After wideningthe subacromial space by inferior traction of the patient’s af-fected arm, the direction of the needle was changed to par-allel, and the needle was advanced from anterior toposterior. The remaining lidocaine was injected at this posi-tion.

Pain caused by Neer’s impingement sign and the painfularc 30 minutes after the test was compared with pain beforethe impingement test. Improvement of pain was representedby the percentage of decreased pain.

Muscle strength testing was performed with the Notting-ham Mecmesin Myometer (Mecmesin Co., NottinghamUK) (Figure 1). The subjects were seated upright. Wechecked the muscle strength of the supraspinatus in theempty-can position and internal and external rotators ofthe shoulder in neutral abduction, before and after the im-pingement test, in the 3 groups.

J Shoulder Elbow Surg Park, Lee, and Lee 9SVolume 17, Number 1S

The relationship between pain and muscle weakness wasanalyzed by use of 2 methods. First, the muscle strength ofeach group before and after the tests was compared. Sec-ond, we divided each of the groups into 2 subgroups basedon the mean percentage of decreased pain to evaluate thecorrelation between pain and muscle weakness. Subgroups1 and 2 included subjects above and below, respectively,the mean percentage of decreased pain. We also dividedthe impingement syndrome group into 2 subgroups accord-ing to stiffness.

All statistics were calculated with the Microsoft Excel2002 program (Microsoft, Redmond, WA) and SPSS soft-ware, version 13.0 (SPSS, Chicago, IL). The difference in de-creased pain before and after the impingement test amongthe 3 groups was evaluated by 1-way analysis of variance.The difference in decreased pain in impingement syndromepatients with or without stiffness was evaluated by the Stu-dent t test. Paired t tests were used to evaluate musclestrength before and after testing. The difference in musclestrength between the 2 subgroups according to the meanpercentage decrease in pain was evaluated by a paired ttest and the Wilcoxon signed rank test.

RESULTS

Pain after the impingement test, compared with thatbefore the test, was 67.1% lower in impingement syn-drome cases, 71% lower in partial-thickness rotatorcuff tear cases, and 64.3% lower in full-thickness rota-tor cuff tear cases. However, the pain decrease afterthe test was not statistically different among the 3groups (P ¼ .35 > .05). After the test, the subgroup

Figure 1 Position of patient during measurement of supraspinatusmuscle strength with Nottingham Mecmesin Myometer.

with stiffness had a greater reduction in pain com-pared with the subgroup without stiffness (Table I).

Isometric muscle testing, followed by the impinge-ment test, showed no statistically significant increasein shoulder strength (P>.05), except for external rota-tion in the full-thickness rotator cuff tear group (P ¼.0006 < .05) (Table II).

The muscle strength in external rotation in subgroup1 of the full-thickness rotator cuff tear group signifi-cantly increased after the impingement test (P ¼.0006< .05). However, there was no difference in ex-ternal rotation in subgroup 2 of that group (P ¼ .06 >.05). Isometric muscle testing in the rest of the groups,followed by the test, showed no statistically significantincrease in strength of the shoulder (P>.05) (Table III).

Supraspinatus strength in the impingement syn-drome group with stiffness was higher after the test(Table IV).

DISCUSSION

History-taking, physical examination, and plain ra-diographs are sufficient to diagnose most shoulder dis-eases causing shoulder pain. However, when thediagnosis is uncertain or when the relative seriousnessof the shoulder disease needs to be determined,

Table I Improvement of pain in impingement syndrome patients afterimpingement test

Group % of decreased pain

Impingement syndrome 67.1Impingement syndrome with stiffness 61.7Impingement syndrome without stiffness 72.0

P > .05.

Table II Evaluation of shoulder strength before and after impingementtest among groups

Strength (mean)

Group Muscle Before test After test P value

Impingementsyndrome

SS 3.76 4.00 .058

ER 5.78 5.95 .614IR 6.07 6.06 .967

Partial-thicknessRCT

SS 4.17 3.70 .368

ER 5.79 5.79 .987IR 6.22 6.02 .596

Full-thickness RCT SS 3.52 3.67 .413ER 5.28 5.95 .001IR 6.26 6.32 .793

SS, Supraspinatus; ER, external rotator; IR, internal rotator.

10S Park, Lee, and Lee J Shoulder Elbow SurgJanuary/February 2008

several additional checkups are required. The im-pingement test with lidocaine is useful in such cases.

Neer9 said that ‘‘injection of 10cc of 1% lidocaineinto the subacromial space will relieve the pain causedby provocative maneuvers. The impingement test isuseful in distinguishing impingement lesions fromother causes of shoulder pain.’’

Pain after the test compared with before the test was71% lower in the partial-thickness rotator cuff teargroup and 64.3% lower in the full-thickness rotatorcuff tear group. However, there was no statistically sig-nificant difference among the 3 groups.

Yamaguchi and Flatow15 stated that ‘‘the patient istold that it is likely that after a year the result (of arthro-scopic subacromial decompression) will be similar tothat obtained (temporarily) from injection’’ and ‘‘thetest is useful for the diagnosis of impingement syn-drome.’’ On the other hand, Kirkley et al7 said that‘‘the impingement test is a poor tool for predicting suc-cess of subacromial decompression.’’

Pain and muscle weakness are important clinicalmanifestations of rotator cuff disease. However, painand rotator cuff atrophy can cause muscle weaknessindependent of a rotator cuff tear. Pain and weaknessare often related in that the painful shoulder is oftenweak—a phenomenon referred to as pain-inhibited

Table III Evaluation of shoulder strength before and after impingementtest between subgroups

Strength (mean)

Group Subgroup MuscleBefore

testAftertest P value

Impingementsyndrome

1* SS 3.85 4.06 .149

ER 5.88 6.21 .051IR 6.08 6.22 .515

2y SS 3.51 3.91 .148ER 5.53 5.79 .211IR 6.02 5.91 .652

Partial-thicknessRCT

1* SS 5.16 4.63 .646

ER 6.37 6.63 .878IR 6.37 6.80 .169

2y SS 3.15 2.97 .594ER 5.00 4.79 .799IR 6.06 5.13 .074

Full-thicknessRCT

1* SS 4.02 4.04 .922

ER 5.63 6.18 .023IR 6.43 6.51 .823

2y SS 3.16 3.25 .715ER 5.20 5.90 .065IR 6.43 6.51 .823

SS, Supraspinatus; ER, external rotator; IR, internal rotator.*Subgroup 1 is the group in which decreased pain is above average.ySubgroup 2 is the group in which decreased pain is below average.

weakness.1,6,11 Hawkins et al6 stated that shoulderpain was one of the important causes of shoulderweakness. They concluded that postoperative func-tional improvement was primarily related to pain reliefand did not correlate well with the size of the tear.

Hawkins et al6 said that ‘‘significant tendon fiberfailure is usually manifested by weakness on manualmuscle testing, aswas reportedbyBrems.2 ’’ Sapega13

reported that ‘‘manual testing of muscular strength,subject to large interobserver variability and bias, isinsensitive.’’

There are isokinetic and isometric muscle tests, inaddition to manual muscle testing, and varying corre-lations have been found between them.4,10 Rockwoodet al said that isometric muscle testing can prevent thelimitations that were induced by symptom due to shoul-der motion in isokinetic muscle testing.12

Kuhlman et al8 reported that there are highly signif-icant differences in shoulder strength (measured isoki-netically and isometrically), angular velocity inisokinetic muscle testing, position of the shoulder,age, and sex. They also reported that slow-speed(90�/s) isokinetic testing gave significantly highervalues for peak torque and more closely approxi-mated isometric peak torque than did high-speed(210�/s) isokinetic testing.

Much has been published in the literature regard-ing shoulder strength in rotator cuff disease.3,5,14

These are mostly studies comparing shoulder strengthpreoperatively and postoperatively or between the af-fected side and the contralateral side. There are fewstudies on the relationship between pain and muscleweakness using the impingement test.

Ben-Yishay et al1 reported on the relationship be-tween pain and muscle weakness in a study of 14 pa-tients with stage II or III impingement syndrome, andisokinetic muscle strength testing was performed witha Biodex isokinetic dynamometer (Biodex MedicalSystems, Shirley, NY) before and after an impinge-ment test. Their results showed significant improvement

Table IV Evaluation of shoulder strength before and after impingementtest according to shoulder stiffness

Strength (mean)

Group Subgroup MuscleBefore

testAftertest P value

Impingementsyndrome

Withstiffness

SS 3.28 3.90 .002

ER 5.55 5.91 .057IR 5.84 5.98 .503

Withoutstiffness

SS 4.11 4.08 .865

ER 5.93 6.17 .173IR 6.22 6.21 .959

SS, Supraspinatus; ER, external rotator; IR, internal rotator.

J Shoulder Elbow Surg Park, Lee, and Lee 11SVolume 17, Number 1S

in shoulder active range of motion and strength in bothforward elevation and external rotation. They alsoconcluded that pain is an important factor in the etiol-ogy of shoulder weakness in patients with impinge-ment syndrome. However, we believe that their studywas less statistically significant because only 14 pa-tients were included.

In this study, including 233 subjects, isometric mus-cle testing followed by the impingement test showedno statistically significant increase in strength of theshoulder, except for external rotation in a full-thicknessrotator cuff tear.

These results show that there is less of a relationshipbetween pain and muscle weakness than has beensuggested by other investigators. The findings suggestthat there are many factors affecting muscle weaknessbesides pain, such as muscle atrophy, fatty degenera-tion, cuff tear size, location, and retraction, whichaffect muscle weakness in combination.

We observed that, in cases in which the continuity ofthe rotator cuff is maintained, pain is not the onlyimportant factor in the cause of shoulder weakness.Preoperative muscle testing can be done despitepain, but if a full-thickness rotator cuff tear is confirmed,re-examination of external rotator strength is neces-sary. In patients with impingement syndrome, particu-larly with shoulder stiffness, supraspinatus strengthcan be lower.

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