Paper 85: Biomechanical Properties of an Arthroscopic Anterior Capsular Shift and an Arthroscopic Suture Anchor Repair in Anterior Shoulder Instability

Abstract

In this biomechanical study, the primary stability of two frequently used arthroscopic shoulder stabilization techniques are compared, the anterior capsular shift, and the bankart repair using suture anchors. Both techniques supply sufficient anterior shoulder stabilization with no decrease of external motion. Experimental biomechanical human cadaver study. We tested 10 fresh human cadaver shoulders in a robot-assisted shoulder simulator (Kuka Roboter GmbH, Augsburg). External rotation, and anterior- and antero-inferior and inferior translation were measured under applied moment and loading of 2 Nm and 20 N respectively, and at 0° and 80° of glenohumeral abduction. All measurements were performed under four conditions: on the non-operated shoulder (physiologic); following the setting of 3 arthroscopic portals (vented); following an arthroscopic anterior capsular shift (shift) using 4 sutures (Fiberwire, Arthrex, Naples); and following a simulated defined bankart lesion (lesion); and finally following an arthroscopic bankart repair (repair) using 3 suture anchors (Fastak Fiberwire®, Arthrex, Naples). The application of three arthroscopic portals resulted in a significant increase of the anterior- (0°: 3,3mm to 7,8mm; p=0.01/80°: 4,8mm to 8,9mm; p=0.004) and antero-inferior translation (0°: 3,8mm to 9,7mm; p=0.03/80°: 5,4mm to 7,8mm; p=0.02) at 0° and 80° abduction, as well as an increase in external rotation at 80° abduction (95,1° to 98,8°; p=0.03). Capsular shift reduced external rotation (p=0.03), but did not significantly decrease translation. Under simulating anterior shoulder instability (lesion) glenohumeral translation significantly increased at 0°and 80° of abduction, ranging from 50% to 279% of physiological translation. Arthroscopic shoulder stabilization resulted in a decrease of translation in all tested directions to approximately physiologic levels. External rotation in 0° abduction was thus decreased significantly (p=0,003) an average of 19° to the physiologic rotation. No decreased external rotation in 80° abduction was found. An arthroscopic anterior capsular shift decreases external rotation without a significant influence on glenohumeral translation. In treating anterior shoulder instability, arthroscopic shoulder stabilization with suture anchors sufficiently restores increased glenohumeral translation but also decreases external rotation in neutral abduction.