A Biomechanical assessment of anterior shoulder translation after anterior stabilization : The dynamic anterior stabilization using the long head of the biceps versus isolated Bankart repair

Abstract

Background Isolated Bankart repair for shoulder instability has been associated with recurrences. A concept of dynamic anterior stabilization (DAS) by transferring the long head of the biceps (LHB) within a subscapularis split to the anterior glenoid margin, thereby creating a “sling effect” has recently been proposed. Therefore, our purpose was to compare the biomechanical effects of these two procedures. Materials and methods Twenty-four cadaveric specimens were tested at 90° of abduction and external rotation on a custom shoulder simulator. Anterior translation was monitored following an axial force (20, 30 and 40 N) withrotator cuff muscle loading (5 N each line) and long head of biceps loading (10 N). The specimens were tested in the intact state, following Bankart lesion, Bankart repair and DAS, and following each procedure after creation of 10 % and 20 % glenoid bone defects. The reconstruction order was randomized. Results The starting position of the humeral head was more posterior after DAS. Significantly less relative anterior translations after DAS in comparison to Bankart repair were found. However, with large bone defect (20 %) and low axial load (20, 30 N) after DAS procedure, the anterior translation did not reach native starting position (the humeral head remained posteriorly subluxated). Conclusion DAS procedure restores shoulder stiffness and decreases significantly anterior translation compare to Bankart stabilization. DAS might be efficient to decrease postoperative persistent glenohumeral micromotion that has been observed in previous studies. However, DAS can not be recommended for important bone loss.