Contributions of Muscle Imbalance and Impaired Growth to Postural and Osseous XXXX Following Brachial Plexus Birth Palsy: A  Computational Simulation Analysis.

@entity851 @entity9509 @entity5300 @entity717 @entity85 @entity121 @entity2685
PURPOSE: Two potential mechanisms leading to postural and osseous @entity85 after @entity5300 are @entity121 between functioning internal @entity717 and paralyzed external @entity717 and @entity851 of paralyzed muscles. Our goal was to evaluate the combined and isolated effects of these 2 mechanisms on transverse plane shoulder forces using a computational model of @entity9509 @entity2685 . METHODS: We modeled a @entity9509 injury using a computational musculoskeletal upper limb model. Muscles expected to be denervated by @entity9509 injury were classified as affected, with the remaining shoulder muscles classified as unaffected. To model @entity121 , affected muscles were given no resting tone whereas unaffected muscles were given resting tone at 30% of maximal activation. To model impaired growth, affected muscles were reduced in length by 30% compared with normal whereas unaffected muscles remained normal in length. Four scenarios were simulated: normal, @entity121 only, impaired growth only, and both @entity121 and impaired growth. Passive shoulder rotation range of motion and glenohumeral joint reaction forces were evaluated to assess postural and @entity85 . RESULTS: All impaired scenarios exhibited restricted range of motion and increased and posteriorly directed compressive glenohumeral joint forces. Individually, @entity121 caused worse restriction in range of motion and higher and more posteriorly directed glenohumeral forces than did @entity121 . Combined @entity121 and impaired growth caused the most restricted joint range of motion and the highest joint reaction force of all scenarios. CONCLUSIONS: Both @entity121 and @entity851 contributed to range of motion and force changes consistent with clinically observed deformity, although the most substantial effects resulted from @entity121 . CLINICAL RELEVANCE: Simulations suggest that treatment strategies emphasizing treatment of @entity851 are warranted for @entity85 after @entity5300 .
