Effect of scapular dyskinesis on supraspinatus repair healing in a rat model

Abstract

Background Rotator cuff tears are common conditions that often require surgical repair to improve function and relieve pain. Unfortunately, repair failure remains a common problem following rotator cuff repair surgery. Several factors may contribute to repair failure including age, tear size, and time from injury. However, the mechanical mechanisms resulting in repair failure are not well understood making clinical management difficult. Specifically, altered scapular motion (termed scapular dyskinesis) may be one important and modifiable factor contributing to the risk of repair failure. Therefore, the objective of this study was to determine the effect of scapular dyskinesis on supraspinatus tendon healing following repair. Methods A rat model of scapular dyskinesis was used. 70 adult male Sprague-Dawley rats (400-450 grams) were randomized into two groups: nerve transection of the accessory and long-thoracic nerves (SD) or sham nerve transection (Sham Control). Following this procedure, all rats underwent unilateral detachment and repair of the supraspinatus tendon. All rats were sacrificed at 2, 4, and 8 weeks after surgery. Shoulder function, passive joint mechanics, and tendon properties (mechanical, histological, organizational, and compositional) were evaluated. Results Scapular dyskinesis alters joint function and may lead to compromised supraspinatus tendon properties. Specifically, diminished mechanical properties, altered histology, and decreased tendon organization was observed for some parameters. Conclusion This study identifies scapular dyskinesis as one underlying mechanism leading to compromise of supraspinatus healing following repair. Identifying modifiable factors that lead to compromised tendon healing will help improve clinical outcomes following repair. Level of evidence Basic Science, in-vivo Animal Study.

The Rotator Cuff Organ: Integrating Developmental Biology, Tissue Engineering, and Surgical Considerations to Treat Chronic Massive Rotator Cuff Tears

“…215 Lastly, scapular dyskinesis, as induced through transection of the accessory and long thoracic nerves, decreased mechanical properties, altered histology, and diminished tendon organization at the enthesis following rotator cuff repair. 216 Taken together, these studies validate the importance of controlled mobilization postoperatively as a means to optimize healing. In the clinical setting, where the practical postoperative loading protocols have been far more constrained than those investigated in animal studies, there is no long-term difference between early mobilization compared to delayed rehabilitation.…”

Genetic lineage tracing of targeted cell populations during enthesis healing

“…The collagen architecture of the insertion is also interdigitated . While there have been numerous excellent studies of rotator cuff degeneration/injuries in rats, genetic perturbations are difficult to achieve in rats due to the paucity of available molecular tools. Recently, a few groups established models of clinically relevant supraspinatus tendon injuries in the mouse, thus opening the door for mechanistic studies enabled by the wide array of genetic tools available for mouse.…”

The Constant score and the assessment of scapula dyskinesis: Proposal and assessment of an integrated outcome measure

“…through improved scapular muscle balance (Merolla et al, 2010). The recent works of Reuther et al (2014Reuther et al ( , 2015 on an animal model also support a causative effect. Whatever the cause-effect relationship, it was shown that dyskinesis deeply affects functional scores (Harris et al, 2012), and it should always be evaluated and accounted for during rehabilitation.…”