Biomechanical Basis of Shoulder Osseous Deformity and Contracture in a XXXX Model of @entity5300 .

@entity5300 @entity810 @entity35 @entity85 @entity121
BACKGROUND: The purpose of this study was to investigate the relative contributions of two proposed mechanisms, strength imbalance and @entity121 , to @entity85 in a @entity35 model of @entity5300 ( @entity5300 ). METHODS: Thirty-two @entity35 pups were divided into four groups on the basis of surgical interventions to induce a strength imbalance, impaired growth, both a strength imbalance and impaired growth (a combined mechanism), and a sham condition in the left forelimb. Maximum passive external shoulder rotation angle (ERmax) was measured bilaterally at four and eight weeks postoperatively. After the @entity35 were killed at eight weeks, the glenohumeral geometry (on microcomputed tomography) and shoulder muscle architecture properties were measured bilaterally. RESULTS: Bilateral muscle mass and optimal length differences were greatest in the impaired growth and combined mechanism groups, which also exhibited >15   lower ERmax (p < 0.05; four weeks postoperatively), 14   to 18   more @entity810 (p < 0.10), and 0.76 to 0.94 mm more inferior humeral head translation (p < 0.10) on the affected side. Across all four groups, optimal muscle length was significantly correlated with at least one @entity85 measure for six of fourteen muscle compartments crossing the shoulder on the affected side (p < 0.05). In the strength imbalance group, the glenoid was 5   more inclined and the humeral head was translated 7.5% more posteriorly on the affected side (p < 0.05). CONCLUSIONS: @entity121 and @entity85 were most pronounced in the impaired growth and combined mechanism groups, which underwent neurectomy. Strength imbalance was associated with @entity85 to a lesser extent. CLINICAL RELEVANCE: Treatments to alleviate @entity85 should address mechanical effects of both strength imbalance and @entity121 , with an emphasis on developing new treatments to promote growth in muscles affected by @entity5300 .
