This Article Full Text Full Text (PDF) Letters to the Editor: Submit a response Alert me when this article is cited Alert me when Letters to the Editor are posted Alert me if a correction is posted Services E-mail this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Rights and Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lee, S.-B. Articles by An, K.-N. Search for Related Content PubMed PubMed Citation Articles by Lee, S.-B. Articles by An, K.-N. Social Bookmarking                   What's this?

Dynamic Glenohumeral Stability Provided by the Rotator Cuff Muscles in the Mid-Range and End-Range of Motion

A Study in Cadavera*

Seok-Beom Lee, M.D., Ph.D., Kyu-Jung Kim, Ph.D, Shawn W. O'Driscoll, M.D., Ph.D., Bernard F. Morrey, M.D. and Kai-Nan An, Ph.D.

Investigation performed at the Biomechanics Laboratory, Division of Orthopedic Research, Department of Orthopedic Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minnesota
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Funds were received in total or partial support of the research or clinical study presented in this article. The funding source was Grant AR41171 from the National Institutes of Health.
Department of Orthopedic Surgery, Hallym University, Sacred Heart Hospital, 896 Pyungchon-dong, Dongan-ku, Kyunggi-do 431-070, Korea.
Biomechanics Laboratory, Division of Orthopaedic Research, Department of Orthopaedic Surgery, Mayo Clinic and Mayo Foundation, 200 First Street S.W., Rochester, Minnesota 55905. Please address requests for reprints to K.-N. An.

Background: Both static and dynamic factors are responsible for glenohumeral joint stability. We hypothesized that dynamic factors could potentially operate throughout the entire range of glenohumeral motion, although capsuloligamentous restraints (a static factor) have been thought to be primarily responsible for stability in the end-range of motion. The purpose of this study was to quantitatively compare the dynamic glenohumeral joint stability in the end-range of motion (the position of anterior instability) with that in the mid-range by investigating the force components generated by the rotator cuff muscles.

Methods: Ten fresh-frozen shoulders from human cadavera were obtained, and all soft tissues except the rotator cuff were removed. The glenohumeral capsule was resected after the rotator cuff muscles had been released from the scapula. A specially designed frame positioned the humerus in 60 degrees of abduction and 45 degrees of extension with respect to the scapula. The compressive and shear components on the glenoid were measured before and after a constant force was applied individually to each muscle with the humerus in five different positions (from neutral to 90 degrees of external rotation). The dynamic stability index, a new biomechanical parameter reflecting these force components and the concavity-compression mechanism, was calculated. The higher the dynamic stability index, the greater the dynamic glenohumeral stability.

Results: In the mid-range of motion, the supraspinatus and subscapularis provided higher dynamic stability indices than did the other muscles (p < 0.05). On the other hand, when the position of anterior instability was simulated in the end-range of motion, the subscapularis, infraspinatus, and teres minor provided significantly higher dynamic stability indices than did the supraspinatus (p < 0.005).

Conclusions: The rotator cuff provided substantial anterior dynamic stability to the glenohumeral joint in the end-range of motion as well as in the mid-range.

Clinical Relevance: A glenohumeral joint with a lax capsule and ligaments might be stabilized dynamically in the end-range of motion if the glenoid concavity is maintained and the function of the external and internal rotators, which are efficient stabilizers in this position, is enhanced.

CiteULike    Connotea    Del.icio.us    Facebook    Technorati    Twitter    What's this?

This article has been cited by other articles:

				K. C. Huxel, C. B. Swanik, K. A. Swanik, A. R. Bartolozzi, H. J. Hillstrom, M. R. Sitler, and D. M. Moffit Stiffness Regulation and Muscle-Recruitment Strategies of the Shoulder in Response to External Rotation Perturbations J. Bone Joint Surg. Am., January 1, 2008; 90(1): 154 - 162. [Abstract] [Full Text] [PDF]

				M. Scheibel, C. Nikulka, A. Dick, R. J. Schroeder, A. G. Popp, and N. P. Haas Structural Integrity and Clinical Function of the Subscapularis Musculotendinous Unit After Arthroscopic and Open Shoulder Stabilization Am. J. Sports Med., July 1, 2007; 35(7): 1153 - 1161. [Abstract] [Full Text] [PDF]

				K. J. Ecklund, T. Q. Lee, J. Tibone, and R. Gupta Rotator Cuff Tear Arthropathy J. Am. Acad. Ortho. Surg., June 1, 2007; 15(6): 340 - 349. [Abstract] [Full Text] [PDF]

				M. Scheibel, A. Tsynman, P. Magosch, R. J. Schroeder, and P. Habermeyer Postoperative Subscapularis Muscle Insufficiency After Primary and Revision Open Shoulder Stabilization Am. J. Sports Med., October 1, 2006; 34(10): 1586 - 1593. [Abstract] [Full Text] [PDF]

				Y. Morag, J. A. Jacobson, B. Miller, M. De Maeseneer, G. Girish, and D. Jamadar MR Imaging of Rotator Cuff Injury: What the Clinician Needs to Know. RadioGraphics, July 1, 2006; 26(4): 1045 - 1065. [Abstract] [Full Text] [PDF]

				C. M Ball, T. Steger, L. M. Galatz, and K. Yamaguchi The Posterior Branch of the Axillary Nerve: An Anatomic Study J. Bone Joint Surg. Am., August 1, 2003; 85(8): 1497 - 1501. [Abstract] [Full Text] [PDF]

Stanford University Libraries' HighWire Press (TM) assists in the publication of JBJS Online.
Copyright © 2000 by The Journal of Bone and Joint Surgery, Inc. Online ISSN: 1535-1386.
The Journal of Bone and Joint Surgery®, JBJS®, JB&JS®, and eJBJS® are registered in the U.S. Patent and Trademark Office.