Évolution de la force isocinétique des rotateurs d'épaule avant et à trois mois d'une stabilisation de l'épaule par technique chirurgicale de Latarjet

Functional Performance Tests Reveal Promising Results at 6 Months After Shoulder Stabilization Surgery

BACKGROUND

Although athletes are mostly allowed to return to play 6 months after shoulder stabilization surgery, there are inadequate data about their functional status during this period.

HYPOTHESES

Performance tests would reveal insufficiency in the functional capacity of shoulder 6 months after stabilization surgery.

STUDY DESIGN

Prospective cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

A total of 32 male athletes with arthroscopic anterior capsulolabral repair (AACR) were included in the study. Shoulder internal and external rotator (IR-ER) strength was assessed using isokinetic dynamometer at 60°/s and 180°/s angular velocities preoperatively and 6 months postoperatively. Shoulder function was assessed with closed kinetic chain upper extremity stability (CKCUES) test, Y balance test-upper quarter (YBT-UQ), and unilateral seated shot-put test (USSPT) at 6 months postoperation. Western Ontario shoulder instability index (WOSI) and Tampa scale of kinesiophobia (TSK) were used for the self-assessment of the shoulder. Mixed-model ANOVA was used to analyze the changes in the IR-ER strength on both shoulders. Limb symmetry index (LSI) was calculated for the IR-ER strength, YBT-UQ, and USSPT scores.

RESULTS

Shoulder IR strength was higher at 6 months postoperatively compared with preoperatively. The LSI was 76.4% and 76.6% for ER strength, and 94.2% and 94% for IR strength at 60°/s and 180°/s angular velocities, respectively, at the postoperative 6 month timepoint. The mean CKCUES test score was 21.8 ± 2.6 touches and the LSI was 94.7% for the YBT-UQ and 102.5% for the USSPT. WOSI (P < 0.001) and TSK (P = 0.001) scores were significantly lower at 6 months postoperatively.

CONCLUSION

Functional status of the patients with shoulder stabilization surgery improved considerably 6 months after surgery, yet they did not fully recover function.

CLINICAL RELEVANCE

Exercise programs focusing on shoulder ER strength and shoulder performance should be emphasized after stabilization surgery.

Primary Open Latarjet Procedure Results in Functional Differences but No Structural Changes in Subscapularis Muscle Quality vs the Healthy Contralateral Shoulder at Long-term Follow-up

BACKGROUND

There are concerns that the Latarjet procedure results in loss of glenohumeral rotation and strength and in subscapularis dysfunction. The long-term effects of this procedure on subscapularis quality, glenohumeral rotation, and strength are unknown.

PURPOSE/HYPOTHESIS

To analyze the long-term effect of the primary open Latarjet procedure using a muscle-splitting approach on internal and external rotation and strength, as well as subscapularis muscle quality as compared with the healthy contralateral side. We hypothesized that the primary open Latarjet procedure is associated with a reduction of long-term shoulder strength and function and decreased subscapularis quality.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 42 patients who underwent a primary open Latarjet procedure for recurrent anterior shoulder instability at a mean age of 26 years (range, 18-36) were reviewed after a mean follow-up of 8.4 years (range, 5-12). The subscapularis muscle volume and fat fraction of both shoulders were assessed. Bilateral active internal rotation (IR) and external rotation (ER), as well as IR and ER strength, were assessed by isokinetic testing (concentric, eccentric, and fatigability).

RESULTS

Active IR (0.6-point difference, P < .001) and ER (4° difference, P = .010) were significantly greater in healthy contralateral shoulders. The IR strength of the operated shoulder was significantly less than that of the healthy shoulder in concentric and eccentric testing (range of deficit, 4%-6%; P < .05). Also, the ER strength of the operated shoulder was significantly less than that of the healthy shoulder in concentric testing (11% deficit, P < .05). Subscapularis muscle volume was significantly greater in the operated shoulder (4% difference, P = .022), and there was no significant difference in fat fraction (P = .114).

CONCLUSIONS

The primary open Latarjet procedure was associated with significantly decreased active IR and ER and strength when compared with the healthy contralateral shoulder. The clinical influence of these findings is yet to be defined. There was no increased subscapularis muscle fatty degeneration but a minimal hypertrophy on the operated side at long-term follow-up.

Factors That Influence the Return to Sport After Arthroscopic Bankart Repair for Glenohumeral Instability

Numerous studies have reported high rates of return to sports following arthroscopic Bankart repair (ABR) However, there is enormous controversy regarding the optimal management of these patients in the postoperative period. Controversy issues include rehabilitation, criteria for returning to sports, and the specific management of each athlete according to the sport they practice. Even though there are several rehabilitation protocols published in the literature, wide variability exists concerning the key elements of rehabilitation after an ABR. Regarding criteria for return to sports, there is a wide variation across the different published studies. The type of sports has been shown to affect an athlete’s decision to return to sports. Nevertheless, most research is evaluated by classifications that cluster different sports into categories that may have other influences in return to sports when analyzed separately. Finally, in addition to physical readiness, the athlete’s psychological state is crucial for returning to sports. However, the contribution of psychological readiness to an athlete’s return to sports after shoulder instability surgery remains uncertain and unexplored.

Clinical Outcomes of Revision Arthroscopic Capsulolabral Repair for Recurrent Anterior Shoulder Instability With Moderate Glenoid Bone Defects: A Comparison With Primary Surgery

Background:

The optimal revision surgery for failed primary arthroscopic capsulolabral repair (ACR) has yet to be determined. Revision ACR has shown promising results.

Purpose:

To compare the functional, strength, and radiological outcomes of revision ACR and primary ACR for anterior shoulder instability.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Between March 2007 and April 2017, a total of 85 patients underwent ACR (revision: n = 23; primary: n = 62). Functional outcome scores and positive apprehension signs were evaluated preoperatively, at 1 year, and then annually. Isokinetic internal and external rotation strengths were evaluated preoperatively and at 1 year after surgery.

Results:

The mean follow-up was 36.5 ± 10.2 months (range, 24-105 months). There was no significant difference between the revision and primary groups in the glenoid bone defect size at the time of surgery (17.3% ± 4.8% vs 15.4% ± 5.1%, respectively; P = .197). At the final follow-up, no significant differences were found in the American Shoulder and Elbow Surgeons score (97.6 ± 3.1 vs 98.0 ± 6.2, respectively; P = .573), Western Ontario Shoulder Instability Index score (636.7 ± 278.1 vs 551.1 ± 305.4, respectively; P = .584), or patients with a positive apprehension sign (17.4% [4/23] vs 11.3% [7/62], respectively; P = .479) between the revision and primary groups. There was no significant difference between the revision and primary groups for returning to sports at the same preoperative level (65.2% vs 80.6%, respectively; P = .136) and anatomic healing failure at 1 year after surgery (13.0% vs 3.2%, respectively; P = .120). Both groups recovered external rotation strength at 1 year after surgery (vs before surgery), although the strength was weaker than in the uninvolved shoulder. In the revision group, a larger glenoid bone defect was significantly related to a positive apprehension sign (22.0% ± 3.8%) vs a negative apprehension sign (16.0% ± 3.2%; cutoff = 20.5%; P = .003).

Conclusion:

In patients with moderate glenoid bone defect sizes (10%-25%), clinical outcomes after revision ACR were comparable to those after primary ACR. However, significant glenoid bone loss was related to a positive remaining apprehension sign in the revision group. Surgeons should consider these findings when selecting their revision strategy for patients with failed anterior shoulder stabilization.

Clinical outcome and return to sports activity after surgical treatment for recurrent shoulder instability with a modified Latarjet procedure

INTRODUCTION

The Latarjet procedure is an attractive surgical option for the management of chronic anterior shoulder instability. The original surgical approach involves the vertical tenotomy of the subscapularis tendon. Alternatively, the subscapularis muscle is split longitudinally and the tendon left attached at the lesser tuberosity.

HYPOTHESIS

The hypothesis is that the longitudinal split is of functional advantage and may lead to better functional results and earlier return to sports activities compared to the vertical tenotomy.

MATERIAL AND METHODS

Thirty-two patients were included in this retrospective cohort study. In 14 patients, the subscapularis tendon was vertically incised (group A), whereas in 18 patients, the subscapularis muscle was split longitudinally (group B). Patients were evaluated at 1 year (FU1) and 2 years (FU2) after the Latarjet procedure. Results at follow-up were correlated with patient-specific data and compared with the preoperative status. Primary outcomes were the functional assessment based on Western Ontario Shoulder Instability (WOSI) index and Constant Score (CS) and the assessment of the return to sports activity. Patients' demographics, duration of surgery, and the rate of recurrent dislocations were recorded as secondary variables.

RESULTS

All patients started their sports activities with a mean±SD of 12.41±1.24 weeks. Interestingly, the time from surgery to full recovery of sports activities was significantly longer for group A (mean±SD of 30.17±10.36 weeks) compared to group B (mean±SD of 20.71±3.67 weeks). There is a statistically significant decrease of the WOSI score from the preoperative level compared to FU1 and FU2, indicating a decrease in instability related symptoms during the entire follow up period with no statistically significant difference between group A and B. There is an increase in shoulder function during the entire follow up period based on the CS. Most interestingly, there is a statistically significant difference between group A and B at FU1, indicating a significantly better shoulder function for group B at the early follow up timepoint (FU1). At the later follow up timepoint (FU2), no difference exists in the individual items. However, a significantly better total CS remains in group B, indicating an overall improved function compared to group A.

DISCUSSION/CONCLUSION

The longitudinal split of subscapularis muscle is a safe approach which leads to quicker functional recovery and return to sports activity compared to the vertical tenotomy, which is a benefit especially for active individuals. It is therefore recommended as the standard surgical approach.

LEVEL OF EVIDENCE

III; Retrospective cohort study.

Shoulder Isokinetic Strength Deficit in Patients with Neurogenic Thoracic Outlet Syndrome

Neurogenic thoracic outlet syndrome (NTOS) is an impairing painful condition. Patients usually report upper-limb pain, weakness and paresthesia. Shoulder weakness is frequently reported but has never been described with objective strength evaluation. We aimed to compare isokinetic shoulder strength between patients with NTOS and healthy controls. Patients and controls were prospectively evaluated with an isokinetic strength test at 60 and 180°/s, and an endurance test (30 repetitions at 180°/s) of the shoulder rotators. Patients were functionally assessed with QuickDASH questionnaires. One hundred patients and one hundred healthy subjects were included. Seventy-one percent of patients with NTOS were females with a mean age of 39.4 ± 9.6. They were compared to controls, 73% females and the mean age of 38.8 ± 9.8. Patients' mean QuickDASH was 58.3 ± 13.9. Concerning the peak of strength at 60°/s, the symptomatic limbs of patients with NTOS had significantly 21% and 29% less strength than the control limbs for medial and lateral rotators, respectively (p ≤ 0.001). At 180°/s, the symptomatic limbs had significantly 23% and 20% less strength than the controls for medial and lateral rotators, respectively (p ≤ 0.001). The symptomatic limbs had significantly 45% and 30% less endurance than the controls for medial and lateral rotators, respectively (p ≤ 0.001). These deficits were correlated to the QuickDASH. Patients with NTOS presented a significant deficit of strength and endurance of the shoulder rotators correlated to disability. This highlights the interest in upper-limb strength evaluation in the diagnostic process and the follow-up of NTOS.

Avaliação isocinética do ombro após procedimento cirúrgico de Bristow/Latarjet em atletas

Objectives  To evaluate the muscular strength of the internal (IR) and external (ER) rotators of the shoulder after Bristow/Latarjet surgery.

Methods  Cross-sectional study with 18 patients (36 shoulders). The isokinetic evaluation was performed using the Biodex 3 System Pro dynamometer (Biodex Medical System, Inc., Shirley, NY, USA). The athletic shoulder outcome rating scale (ASORS) and the visual analogue scale (VAS) were applied.

Results  The values of peak torque and maximum work in concentric and eccentric mode on the non-operated shoulder were higher than on the operated side for both the IR and ER ( p  < 0.01). The conventional and functional balance between the ER and IR showed no differences between the operated and the non-operated side. When comparing patients with postoperative time < 1 year or 1 year, no differences were observed in peak torque values at 60°/s and 240°/s and maximum work at 60°/s and 240°/s of the IR to the operated shoulder. However, the peak torque values of 60°/s and 240°/s and maximum work at 60°/s and 240°/s of the ER were higher in subjects with postoperative time ≥ 1 year in all variables ( p  < 0.05).

Conclusions  There was a decrease in the strength of the IR and ER in the operated shoulder compared with the healthy shoulder. However, the conventional and functional balance was maintained.

Changes in Shoulder Rotator Strength After Arthroscopic Capsulolabral Reconstruction in Patients With Anterior Shoulder Instability

Background:

The correlation between isokinetic internal and external rotation (IR and ER) strength and functional outcomes in patients with anterior shoulder instability treated by arthroscopic capsulolabral reconstruction (ACR) has not been studied.

Purpose:

To analyze isokinetic IR and ER strength and their correlation with clinical outcomes in patients with anterior shoulder instability treated by ACR.

Study Design:

Case series; Level of evidence, 4.

Methods:

Between January 2004 and June 2015, a total of 104 patients who underwent ACR for anterior shoulder instability were analyzed. The mean peak torque (PT) in IR (IR_PT) and ER (ER_PT), PT deficit (PTD; %) relative to the opposite healthy shoulder, and PT ratio (PTR; ER_PT/IR_PT) were calculated before and 1 year after surgery. Functional scores were evaluated before surgery and at every follow-up visit. Recurrence and postoperative apprehension during ER at 90° of arm abduction were evaluated at 1 year and the final follow-up (76.6 ± 64.4 months).

Results:

IR and ER strength were measured for 68 of 104 patients at 1 year after surgery. ER_PT and IR_PT were less on the involved side than on the uninvolved side before surgery (0.29 ± 0.10 vs 0.33 ± 0.10 N·m/kg, respectively, for ER_PT [P = .002]; 0.36 ± 0.14 vs 0.41 ± 0.16 N·m/kg, respectively; for IR_PT [P = .01]). At 1 year after surgery, IR_PT on the involved side recovered (0.40 ± 0.20 N·m/kg), whereas ER_PT remained weak (0.30 ± 0.13 N·m/kg) relative to the baseline value. PTD in IR (PTD_IR) improved to 2.2% ± 24.4% (P = .012), whereas PTD in ER (PTD_ER) showed no improvement (13.5% ± 13.8%; P = .569). PTR on the involved side improved from 1.07 ± 1.71 to 0.86 ± 0.23 at 1 year (P < .001). All functional scores improved significantly at the final follow-up. At 1 year, 9 of 68 (13.2%) patients showed positive apprehension. PTD_IR and PTD_ER on the involved side were worse in patients with positive apprehension than in those with negative apprehension (P = .039 and .014, respectively). PTD_ER was worse than PTD_IR in patients with positive apprehension at 1 year (P = .022).

Conclusion:

For those with anterior shoulder instability, preoperative IR and ER strength of the involved shoulder were lower than those of the uninvolved shoulder. IR_PT recovered, whereas ER_PT remained weak after ACR. To prevent positive apprehension after surgery, IR and ER strengthening exercises are important, with more emphasis on exercises for ER.

Isokinetic evaluation of the shoulder and elbow after Latarjet procedure

BACKGROUND/HYPOTHESIS

The Latarjet procedure changes the anatomy of the shoulder, moving the coracoid process distally through an incision in the subscapularis muscle. Some authors have studied the effect of this surgery on shoulder rotator strength. Our hypothesis is that the Latarjet procedure decreases elbow supination and flexion strength.

METHODS

A retrospective case series, evaluating patients submitted to the Latarjet procedure between May 2013 and June 2017. Movements of the elbow (supination, pronation, flexion and extension) and shoulder (internal and external rotation) were evaluated bilaterally using a Biodex System 3 isokinetic dynamometer (Biodex Medical Systems, New York) in concentric/concentric mode.

RESULTS

We evaluated 20 patients with an average follow-up of 36 months. In the elbow, we observed a 9.1% decrease in supination strength at a speed of 60°/s (p=0.044), without statistical difference at 120°/s (p=0.570). In the shoulder, there was a 13.5% decrease in external rotation strength at 60°/s and 4.5% at 180°/s (p=0.009 and p=0.040, respectively). The other movements did not demonstrate any statistically significant differences.

CONCLUSION

After the Latarjet procedure, the supination strength at 60°/s was decreased, as was the external rotation strength of the shoulder at 60°/s and 180°/s. We did not observe any reduction in strength for shoulder flexion or internal shoulder rotation.

LEVEL OF EVIDENCE

IV, case series.

Time to peak torque and acceleration time are altered in male patients following traumatic shoulder instability

BACKGROUND

Numerous authors have evaluated the strength of the rotator cuff muscles in patients with shoulder instability. However, only limited data are available with regard to neuromuscular control in patients with traumatic anterior shoulder instability, in particular at 90° of abduction. This study was designed to assess muscle strength and neuromuscular control ability using time to peak torque and acceleration time in nonathletic patients with traumatic anterior shoulder instability.

METHODS

Isokinetic muscle performance testing was performed in 20 male nonathletic anterior shoulder instability patients compared with 20 side-matched asymptomatic volunteers. Isokinetic muscle performance testing was performed at an angular velocity of 180°/s with 90° of shoulder abduction. Muscle strength and neuromuscular control (time to peak torque and acceleration time) of the internal rotators (IRs) and external rotators (ERs) were measured.

RESULTS

There were no significant differences in muscle strength of the IRs and ERs between the 2 groups. The injured shoulder showed delayed neuromuscular control in both the IRs and ERs in the instability patients compared with the normal control subjects (time to peak torque, P = .023 for IRs and P = .020 for ERs; acceleration time, P = .035 for IRs and P = .021 for ERs).

CONCLUSION

The neuromuscular control of both the IRs and ERs was decreased in male nonathletic patients with traumatic anterior shoulder instability even though muscle strength was not altered. Therefore, clinicians and therapists should implement exercises that aim to restore neuromuscular control in the rehabilitation of nonathletic patients with anterior shoulder instability.

Isolated Rupture of the Teres Major Muscle When Water Skiing: A Case Report and Literature Review

Isolated lesions to the teres major muscle are rare. They generally occur in patients participating in sports such as baseball, tennis, or boxing. We report the case of a sports patient who suffered an isolated injury to the teres major while water skiing. The clinical presentation was confirmed by MRI. Conservative treatment was chosen and consisted of brief analgesic immobilization, followed by rehabilitative treatment. The rapid recovery of this patient with normal isokinetic strength evaluation at 6 months was interesting for objectifying full muscle recovery. Our results and the data from the literature suggest that functional rather than surgical treatment is preferable in isolated lesions to the teres major muscle.

Is the subscapularis normal after the open Latarjet procedure? An isokinetic and magnetic resonance imaging evaluation

BACKGROUND

The Latarjet procedure is considered to be a violation of the subscapularis muscle. This study evaluated the postoperative status of the subscapularis through isokinetic and magnetic resonance imaging analysis after splitting. We hypothesized that compared with a healthy contralateral shoulder, there would be satisfactory recovery of subscapularis strength at the cost of some fatigability and some mild fatty infiltration.

MATERIALS AND METHODS

This was a case-control retrospective study of patients who underwent a Latarjet procedure between January 2013 and January 2015. A total of 20 patients were reviewed at 1 year postoperatively. With the patient seated, strength testing of both shoulders was done (concentric, eccentric, and fatigability) with a dynamometer. Trophicity and fatty infiltration were analyzed by magnetic resonance imaging.

RESULTS

Strength of the internal rotators (IRs) and external rotators (ERs) of the injured shoulder was significantly lower compared with the healthy shoulder in concentric testing at 180°/s and 60°/s (13% for IR and 20% for E, P < .05) and in eccentric testing at 60°/s (19% for IR and 16% for ER, P < .05). A peak torque ratio (ER/IR) of the operated-on shoulder was maintained. The difference in muscular endurance was significant (P < .001). There was no muscle atrophy and minimal or no fatty infiltration of the subscapularis in any patient.

CONCLUSION

At 1 year after the open Latarjet procedure, isokinetic testing showed a combined strength deficit in both internal and external rotation with a conserved muscle balance. Although no significant subscapularis fatty infiltration or atrophy was noted, there was a significant deficit in endurance compared with the healthy shoulder.

Muscle strength and function of shoulders with Bankart lesion after successful arthroscopic treatment: interlimb comparison 24 months after surgery

BACKGROUND

The purpose of this study was to examine outcomes following arthroscopic Bankart repair with the focus on strength after the repair.

METHODS

56 shoulders with Bankart lesion were operated on arthroscopically. Gender, mechanism of the first dislocation, number of dislocations, dominant side, operated side and the number of anchors used for surgery were recorded. DASH and Oxford instability scoring systems were applied preoperatively and compared to scores at the 24-month follow-up. The scoring systems were also applied to contralateral shoulders at the 24th month of follow-up. Range of motion was measured with a goniometer. Muscle strength was analyzed with a dynamometer simultaneously with the muscle activity of four perishoulder muscles. The data were recorded with surface EMG. Range of motion, muscle strength and activity were evaluated according to the contralateral shoulder at the 24th month of follow-up.

RESULTS

Male/female ratio was 42/14 with a mean age of 32 years. The mean number of dislocations was 3 ± 1 and all were traumatic dislocations. The number of mean anchors used was 3.1 and the mean follow-up period was 24 months. In clinical evaluation, the preoperative and postoperative results of the DASH and Oxford instability scores of the unstable shoulders were significantly different. In the comparison between the operated and contralateral shoulders, there was no significant difference in DASH and Oxford instability scores at the 24th month of follow-up. There was no significant loss of range of motion. Only internal rotation strength was significantly reduced and there was no significant change in the EMG patterns.

CONCLUSIONS

Although good clinical results can be achieved, internal rotation strength is reduced after arthroscopic surgery, but daily activities are not affected. There is no guarantee for patients of excellent recovery.

LEVEL OF EVIDENCE

Level III cohort study.

Care pathways in physical and rehabilitation medicine (PRM): the patient after shoulder stabilization surgery

This document is part of the "Care pathways in physical and rehabilitation medicine" series developed by the French Physical and Rehabilitation Medicine Society (SOFMER) and the French Physical and Rehabilitation Medicine Federation (FEDMER). For a given patient profile, each concise document describes the patient's needs, the care objectives in physical and rehabilitation medicine, the required human and material resources, the time course and the expected outcomes. The document is intended to enable physicians, decision-makers, administrators and legal and financial specialists to rapidly understand patient needs and the available care facilities, with a view to organizing and pricing these activities appropriately. Here, patients with shoulder instability requiring surgical stabilization are classified into five care sequences and two clinical categories, each of which are treated according to the same six parameters and by taking account of personal and environmental factors (according to the WHO's International Classification of Functioning, Disability and Health) that may influence patient needs.

Are shoulders with a reverse shoulder prosthesis strong enough? A pilot study

BACKGROUND

It has been suggested that limited active ROM of reverse shoulder prostheses relates to lack of strength. However, the postoperative strength has not been quantified.

QUESTIONS/PURPOSES

We therefore measured joint torques in patients with reverse shoulder prostheses and correlated torques with functional scores.

METHODS

We recruited 33 patients (age, 72 ± 8 years) with a reverse prosthesis (37 shoulders, 21 primary and 16 revisions). We obtained Constant-Murley, DASH, and Simple Shoulder Test ([D]SST) scores, and performed two isokinetic protocols (abduction/adduction and external/internal rotation) at 60° per second. Minimum followup was 4 months (average, 23 months; range, 4-63 months).

RESULTS

Twenty-three patients (24 shoulders; 13 primaries, 11 revisions) were able to perform at least one of the defined tasks. Mean abduction and adduction torques were 15 Nm ± 7 Nm and 16 Nm ± 10 Nm (19%-78% of normal shoulders). External and internal rotation tasks could be performed by only 13 patients (14 shoulders; nine primary, five revisions) generating 9 Nm ± 4 Nm and 8 Nm ± 3 Nm, respectively (13%-71% of normal shoulders). We found moderate correlations between Constant-Murley, DASH and (D)SST (D = Dutch translation) scores and abduction and external rotation.

CONCLUSIONS

Patients with a reverse prosthesis had reduced strength when compared with normal values reported in the literature (only 65% of patients could perform the protocol). This effect was greatest for external rotation and might explain clinical outcomes with which a moderately strong relationship was observed. Our observations suggest limited strength is a major factor in reduced ROM.

Active stiffness and strength in people with unilateral anterior shoulder instability: a bilateral comparison

CONTEXT

Active muscle stiffness might protect the unstable shoulder from recurrent dislocation.

OBJECTIVE

To compare strength and active stiffness in participants with unilateral anterior shoulder instability and to examine the relationship between active stiffness and functional ability.

DESIGN

Cross-sectional study.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Participants included 16 males (age range, 16-40 years; height = 179.4 ± 6.1 cm; mass = 79.1 ± 6.8 kg) with 2 or more episodes of unilateral traumatic anterior shoulder instability.

MAIN OUTCOME MEASURE(S)

Active stiffness and maximal voluntary strength were measured bilaterally in participants. In addition, quality of life, function, and perceived instability were measured using the Western Ontario Stability Index, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, and Single Alpha Numeric Evaluation, respectively.

RESULTS

We found less horizontal adduction strength (t(15) = -4.092, P = .001) and less stiffness at 30% (t(14) = -3.796, P = .002) and 50% (t(12) = -2.341, P = .04) maximal voluntary strength in the unstable than stable shoulder. Active stiffness was not correlated with quality of life, function, or perceived instability (r range, 0.0-0.25; P > .05).

CONCLUSIONS

The observed reduction in stiffness in the unstable shoulder warrants inclusion of exercises in the rehabilitation program to protect the joint from perturbations that might lead to dislocation. The lack of association between active stiffness and quality of life, function, or perceived instability might indicate that stiffness plays a less direct role in shoulder stability.