Human Dermal Allograft Superior Capsule Reconstruction With Graft Length Determined at Glenohumeral Abduction Angles of 20° and 40° Decreases Joint Translation and Subacromial Pressure Without Compromising Range of Motion: A Cadaveric Biomechanical Study

Purpose: To compare the biomechanical effects of superior capsule reconstruction (SCR) graft fixation length determined at 20 degrees and 40 degrees of glenohumeral (GH) abduction. Methods: Humeral translation, rotational range of motion (ROM), and subacromial contact pressure were quantified at 0 degrees, 30 degrees, and 60 degrees of GH abduction in the scapular plane in 6 cadaveric shoulders for the following states: intact, massive rotator cuff tear, SCR with dermal allograft fixed at 20 degrees of GH abduction (SCR 20), and SCR with dermal allograft fixed at 40 degrees of GH abduction (SCR 40). Statistical analysis was conducted using a repeated-measures analysis of variance and a paired t test (P < .05). Results: A massive cuff tear significantly increased total ROM compared with the intact state at 0 degrees and 60 degrees of abduction. SCR 20 or SCR 40 did not affect ROM. Compared with the intact state, the massive cuff tear model significantly increased superior translation by an average of 4.6 +/- 0.5 mm in 9 of 12 positions (P < .002). Both SCR 20 and SCR 40 reduced superior translation compared with the massive cuff tear model (P < .05); however, SCR 40 significantly decreased superior translation compared with SCR 20 at 0 degrees of abduction (P <= .046). Peak subacromial pressure for the massive cuff tear model increased by an average of 486.8 +/- 233.9 kPa relative to the intact state in 5 of 12 positions (P <= .037). SCR 20 reduced peak subacromial pressure in 2 of 12 positions (P < .012), whereas SCR 40 achieved this in 6 of 12 positions (P < .024). Conclusions: SCR with dermal allograft fixed at 20 degrees or 40 degrees of GH abduction decreases GH translation and subacromial pressure without decreasing ROM.