Release of the subscapularis tendon and muscle: a limited gain in length

This study measured in vitro the degree of lateral advancement of the subscapularis tendon achieved by circumferential release. Thirty-eight cadaveric shoulders underwent circumferential subscapularis release with anterior capsulotomy. Release was performed in two phases. The first phase consisted of four stages: 1) cutting the capsule parallel to the superior border of the subscapularis tendon to the level of the glenoid; 2) division of the anterior capsule and blunt dissection along the glenoid neck; 3) safe separation of the capsule and muscle inferiorly; and 4) blunt, with a finger, dissection between the conjoined tendon and the subscapularis to the level of the joint line. The second phase was performed by cutting the coracohumeral ligament and the consistently found fibrous band that connects the superior aspect of the subscapularis tendon to the base of the coracoid. After each phase, 3 kg of traction were applied to the muscle and the lateral advancement of the subscapularis was measured using a millimeter caliper. The lateral advancement of the subscapularis was 5.5 +/- 3.4 mm after the first step and 9.8 +/- 4.5 mm after the second step. The difference was statistically significant (P < .001). These results indicate that, although necessary, anterior soft tissue balancing during shoulder replacement is limited.