Mechanisms in Muscle Atrophy in Immobilization and Aging

Bar-Shai, Marina; Carmeli, Eli; Coleman, Raymond; Reznick, Abraham Z.

doi:10.1196/annals.1297.086

Cited by 4 publications

(2 citation statements)

References 8 publications

(11 reference statements)

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“…This has been shown to be consistent in many different models of disuse muscle atrophy, including Achilles transection 12 and hindlimb suspension models. 24,25 In our current study, we found that both the supraspinatus and infraspinatus wet weight was significantly decreased at 2 weeks after creation of a massive RCT. Denervation of the muscles increased the amount of atrophy seen in both muscles as well.…”

Section: Discussionsupporting

confidence: 52%

A rat model of massive rotator cuff tears

Liu

Manzano

Kim

2010

Journal Orthopaedic Research

121

152

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Rotator cuff tears (RCTs) are the most common tendon injury seen in orthopedic patients. Massive RCT does not heal spontaneously and results in poor clinical outcomes. Muscle atrophy and fatty infiltration in rotator cuff muscles are major complications of chronic massive RCT and are thought to be the key factors responsible for the failure of attempted massive RCT repair. However, the pathophysiology of rotator cuff muscle atrophy and fat infiltration remains largely unknown, and no small animal model has been shown to reproduce the histologic and molecular changes seen in massive RCT. In this article, we report a novel rat massive RCT model, in which significant and consistent muscle atrophy and fat infiltration were observed in the rotator cuff muscles after rotator cuff tendon transection and denervation. The supraspinatus and infraspinatus muscle lost 25.4% and 28.9% of their wet weight 2 weeks after complete tendon transection, respectively. Six weeks after surgery, the average wet weight of supraspinatus and infraspinatus muscles decreased 13.2% and 28.3%, respectively. Significant fat infiltration was only observed in infraspinatus 6 weeks after tendon transection. Keywords: rotator cuff tear; muscular atrophy; fat infiltration Rotator cuff tears (RCTs) are one of the most common orthopedic conditions treated. Chronic RCTs lead to poor shoulder function, pain, and decreased quality of life.1 In the setting of chronic RCTs, studies have demonstrated that muscle atrophy and fatty infiltration are independent predictors of poor outcome following surgical repair.2,3 Understanding the factors that are responsible for muscle degeneration and atrophy as well as fatty infiltration may lead to pharmacologic treatments that will improve the outcomes of patients with massive RCTs.Massive RCTs, or tears that are greater than 4 cm, have been found to be associated with atrophy of the supraspinatus and infraspinatus muscle, as well as fatty infiltration of the muscle. 4 Cofield et al. 5 found that 94% of patients with a small RCT repair had a good or excellent outcome, compared to only 27% of patients with a massive RCT. Importantly, patients with large RCT with atrophy and fatty infiltration have poorer clinical outcomes than those that do not have atrophy and fatty infiltration. 4 Thus, it appears that the natural history of outcomes of large tears is due to the inelasticity and poor function of the muscle-tendon unit. Despite the importance of muscle quality and function in RCT, a majority of the studies on large and massive RCT have focused on improved repair techniques (i.e., single vs. double row repair 6,7 ) or biologic factors to improve tendon to bone healing. [8][9][10] There is no established small animal model for massive RCT. Although an acute animal model is not appropriate to test the degeneration of the tendon, it is likely appropriate to evaluate the atrophy and fatty infiltration that is seen in the setting of massive RCT. Gupta and Lee 11 have evaluated a rabbit model of RCT and demonstrat...

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