Rotator cuff tear: muscle atrophy and fatty infiltration

Work on Understanding Muscle Atrophy and Fatty Infiltration in Massive Rotator Cuff tears has won the 2013 Kappa Delta Young Investigator Award.

The authors point out that after surgery for large or massive tears, patients often sustain recurrent tears and, even if the repair remains intact, have poor muscle function. These poor results may be related to irreversible atrophy and fatty infiltration of the rotator cuff muscles.

They developed a small animal model of rotator cuff tears and used this model to identify the ways in which cuff tears affect the associated muscle. They found an intracellular signaling pathway (Akt/mTOR) that appears to be important in regulating muscle mass in normal muscle also has a central role in the development of muscle atrophy and fatty infiltration. Inhibiting this pathway decreases the development of fatty infiltration.

In a rat model the authors demonstrated that transecting the supraspinatus, infraspinatus, and teres minor tendons created muscle atrophy and fatty infiltration along with muscle fibrosis, changes that were increased by denervation.

They used MRI to quantitate muscle atrophy and fatty infiltration and to evaluate the role of Akt/mTOR and of transforming growth factor-beta (TGF-β) in the development of these changes.

Finally, the authors investigated the cellular source of fibroblasts and adipocytes that infiltrate the muscle causing irreversible changes, suggesting that these cells arise from endothelial lineage stem cells. They are searching for a stimulus or small molecule inhibitors to drive these cells to make muscle instead of fibrous tissue and fat, avoiding atrophy and fatty infiltration.

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Cuff tear size, atrophy and fatty infiltration are related

Supraspinatus atrophy as a predictor of rotator cuff tear size: an MRI study utilizing the tangent sign

These authors performed a retrospective review assessing presence of muscle atrophy, fatty infiltration and the size of rotator cuff tear in 34 patients. The tangent sign is a simple method for characterizing the degree of muscle atrophy. These variables were related. 

These findings again help us understand the challenges faced in trying to achieve a durable, functional repair in large tears with atrophic, fatty infiltrated musculature.

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You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery.


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Revision surgery for failed total shoulder replacement arthroplasty for weakness - our approach, Part 5

If weakness is an issue after shoulder arthroplasty, it may be due to (1) insufficient time and effort at rehabilitation (recognizing that shoulder joint replacement is performed on shoulders that have been 'out of action' for a long period of time with some disuse atrophy of the muscles), (2) technical problems with the arthroplaty, (3) nerve injuries, (4) rotator cuff defects, or (5) subscapularis tendon detachment.

In a technically well done joint replacement and in the absence of some intercurrent injury, persistence of the rehabilitation program will usually lead to progressively more strength and function. If this fails, the shoulder should be scrutinized for evidence of other causes of weakness as listed above.

Failure of the subscapularis reattachment may result from excessive early loading of the repair or from poor quality of the tendon. 

This situation is suggested by weakness of internal rotation and be an increased range of external rotation.

 If there has been an acute injury causing the disruption, a re-repair may be indicated. Otherwise a reconstruction with a tendon graft may be helpful in restoring some of the function of the subscapularis.

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You may be interested in some of our most visited web pages including: shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery.

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