Biomechanical effects of superior capsular reconstruction in a rotator cuff deficient shoulder - a cadaveric study

Abstract Background Superior capsule reconstruction (SCR) has been gaining popularity as a treatment for irreparable rotator cuff (RC) tears, especially for younger patients. The present biomechanical study aimed to investigate how SCR affects functional abduction force, humeral head migration, and passive range of motion following an irreparable RC tear. We hypothesized that SCR will restore these parameters to near intact shoulder levels. Methods Six fresh-frozen cadaveric shoulders were evaluated using a custom biomechanical testing apparatus. Each shoulder was taken through three conditions: (1) intact/control, (2) irreparable, complete supraspinatus(SS) tear, and (3) SCR. Functional abduction force, superior humeral head migration, and passive range of motion, including axial shoulder rotation, were measured in static condition at 0, 30, and 60° of glenohumeral abduction. Data were analyzed using paired student t-testing and Wilcoxon signed-rank testing, depending on the results of normality testing. Results The irreparable SS tear resulted in significantly lower functional abduction force at 30° abduction(p=0.01) and a trend toward decrease(p=0.17) at 60° when compared to the intact configuration. SCR shoulders produced greater functional force at 0° compared to the tear (p=0.046). Humeral head migration was significantly increased by 4.4 and 3.0mm at 0° and 30° of abduction, respectively, when comparing intact to the SS tear configurations(p=0.001). SCR decreased superior migration down to levels of intact shoulders at 0° and 30° of abduction (p=0.008, 0.013) and was not significantly different from the intact configuration at any angle. SCR decreased passive shoulder extension when compared to the tear configuration and increased abduction when compared to the intact configuration (p=0.007, p=0.03). The overall arc of axial rotation was not significantly different between SCR and the intact configuration at any angle. Conclusions In the setting of an irreparable supraspinatus tear, SCR restores key biomechanical parameters of the shoulder to intact levels. Superior capsular reconstruction should be considered for qualifying patients with irreparable rotator cuff tears.