The Journal of Bone and Joint Surgery (American). 2005;87:2662-2670.
doi:10.2106/JBJS.D.02421
© 2005 The Journal of Bone and Joint Surgery, Inc.
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow CME: Take the activities for this article:
 CME 4: October, November, December 2005
Basic Science Test 6: Winter 2006
Right arrow Letters to the Editor: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when Letters to the Editor are posted
Right arrow Alert me if a correction is posted
Services
Right arrow E-mail this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My File Cabinet
Right arrow Download to citation manager
Right arrow Rights and Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Safran, O.
Right arrow Articles by Iannotti, J. P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Safran, O.
Right arrow Articles by Iannotti, J. P.
Related Collections
Right arrow Basic Science
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us   Add to Facebook   Add to Technorati   Add to Twitter  
What's this?

Changes in Rotator Cuff Muscle Volume, Fat Content, and Passive Mechanics After Chronic Detachment in a Canine Model

Ori Safran, MD1, Kathleen A. Derwin, PhD1, Kimerly Powell, PhD1 and Joseph P. Iannotti, MD, PhD1

1 Department of Orthopaedic Surgery and the Orthopaedic Research Center (O.S., K.A.D., K.P., and J.P.I.) and the Department of Biomedical Engineering (K.A.D., K.P., and J.P.I.), The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195. E-mail address for J.P. Iannotti: iannotj{at}ccf.org

Investigation performed at the Department of Orthopaedic Surgery, the Orthopaedic Research Center, and the Department of Biomedical Engineering, The Cleveland Clinic Foundation, Cleveland, Ohio

In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from the Sukenik Family Foundation and DePuy Orthopaedics. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Background: Long-standing tears of the rotator cuff can lead to substantial and perhaps irreversible changes in the affected rotator cuff muscles. We developed a chronic rotator cuff tear in a canine model to investigate and quantify the time-related changes in passive mechanics, volume, and fat of the infraspinatus muscle. We hypothesized that infraspinatus muscle stiffness would increase, volume would decrease, and fat content would increase at twelve weeks following tendon detachment.

Methods: The right infraspinatus tendon of eight adult mongrel dogs were surgically detached from the proximal part of the humerus. The uninvolved left shoulder served as a control. Muscle volume changes were quantified with use of magnetic resonance imaging. At twelve weeks, the passive mechanical properties of the chronically detached and control muscles were determined intraoperatively with use of a custom-designed device. Intramuscular fat was evaluated histologically at the time that the animals were killed.

Results: After twelve weeks of detachment, the stiffness was significantly increased in the detached infraspinatus muscles relative to that in the controls (p < 0.0001). Magnetic resonance image analysis demonstrated that the detached muscle volumes decreased by an average of 32% in the first six weeks and remained constant thereafter. Intramuscular fat increased significantly in the detached muscles and to a greater extent in the lateral regions (p < 0.05).

Conclusions: The chronically detached muscle is not merely a smaller version of the original muscle but, rather, a different muscle. The detached muscle becomes stiffer, and the passive loads required to repair it can become excessive. A significant reduction in muscle volume occurs within days to weeks following tendon detachment (p < 0.0001). The nonuniformity of changes in muscle fat suggests that fat content should be used cautiously as an indicator of muscle quality.

Clinical Relevance: Clinically, chronic large rotator cuff tears are observed to have a qualitatively shorter and stiffer muscle-tendon unit than normal. We developed a chronic rotator cuff model to quantitatively investigate changes in the detached infraspinatus muscle. The passive mechanical properties of a chronically torn rotator cuff muscle-tendon unit may be a useful predictor of repairability and clinical outcome.


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


This article has been cited by other articles:


Home page
 NEJMHome page
F. A. Matsen III
Rotator-Cuff Failure
N. Engl. J. Med., May 15, 2008; 358(20): 2138 - 2147.
[Full Text] [PDF]

Home page
 JBJSHome page
G. Treme, J. A. Hart, and M. D. Miller
What's New in Sports Medicine
J. Bone Joint Surg. Am., March 1, 2007; 89(3): 686 - 696.
[Full Text] [PDF]