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Scientific Articles   |    
Rotator Cuff Strength in Recurrent Anterior Shoulder Instability
Pascal Edouard, MD, MSc1; Francis Degache, PhD1; Laurent Beguin, MD3; Pierre Samozino, PhD2; Giorgio Gresta, MD2; Isabelle Fayolle-Minon, MD1; Frédéric Farizon, MD, PhD2; Paul Calmels, MD, PhD1
1 Department of Physical Medicine and Rehabilitation, Laboratory of Exercise Physiology (LPE EA 4338), University Hospital of Saint-Etienne, 42055 Saint-Etienne CEDEX 2, France. E-mail address for P. Edouard: Pascal.Edouard42@gmail.com.
3 Department of Orthopedics Surgery, Mutualiste Clinic, 42000 Saint-Etienne, France
2 Department of Orthopedics Surgery (G.G., F.F.), Laboratory of Exercise Physiology (LPE EA 4338), University Hospital of Saint-Etienne, 42055 Saint-Etienne CEDEX 2, France
View Disclosures and Other Information
Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

Investigation performed at the Laboratory of Exercise Physiology, Department of Physical Medicine and Rehabilitation,University Hospital of Saint-Etienne, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France

Copyright © 2011 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2011 Apr 20;93(8):759-765. doi: 10.2106/JBJS.I.01791
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Abstract

Background: 

Although rotator-cuff muscle contraction plays an important role in stabilizing the glenohumeral joint, little is known about the role of these muscles in the pathophysiology of recurrent anterior instability. We intended to analyze the association between isokinetic internal rotator and external rotator muscle strength and glenohumeral joint instability in patients with recurrent anterior instability that was not previously treated surgically.

Methods: 

We enrolled thirty-seven patients with unilateral recurrent anterior posttraumatic shoulder dislocation and eleven healthy nonathletic subjects in this controlled study. The association between internal rotator and external rotator strength and shoulder instability was analyzed by side-to-side comparisons and comparisons with a control group. Isokinetic internal rotator and external rotator strength was evaluated with a Con-Trex dynamometer, with the subject seated and the shoulder abducted 45° in the scapular plane. Tests were performed at 180°/s, 120°/s, and 60°/s in concentric mode for both sides. Peak torque normalized to body weight and external rotator to internal rotator ratio were calculated for each angular velocity. Clinical and isokinetic evaluation was done by the same rehabilitation physician.

Results: 

The association between shoulder instability and internal rotator and external rotator strength was associated with side-to-side differences (p < 0.05). Compared with a control group, strength values were lower on the pathological shoulder side of the patients with shoulder instability than on the healthy contralateral shoulder of control subjects at 180°/s and 120°/s (p < 0.05). The side-to-side differences were increased when the nondominant upper-extremity side was involved and were decreased when the dominant side was involved. There was no association between glenohumeral joint instability and external rotator to internal rotator ratio.

Conclusions: 

Internal rotator and external rotator weakness was associated with recurrent anterior instability, and side-to-side differences depended on the side of hand dominance. Use of a control group may help in the analysis of the influence of constraints on shoulder strength. Further prospective studies are necessary to determine whether the weakness is a cause or an effect of the instability.

Level of Evidence: 

Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

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    References

    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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