The 6-O'clock Anchor Increases Labral Repair Strength in a Biomechanical Shoulder Instability Model

Abstract

To characterize the additive effect of a 6-o'clock anchor in the stabilization of a Bankart lesion. Twelve cadaveric shoulders were tested on a 6-df robotic musculoskeletal simulator to measure the peak resistance force due to anterior displacement of 1cm. The rotator cuff muscles were loaded dynamically. The test conditions consisted of the intact shoulder, Bankart lesion, Bankart repair (3-, 4-, and 5-o'clock anchors), and Bankart repair with the addition of a 6-o'clock anchor. A 13% anterior bone defect was then created, and all conditions were repeated. Repeated-measures analysis of variance was performed. In the group with no bone loss, the addition of a 6-o'clock anchor yielded the highest peak resistance force (52.8N; standard deviation [SD], 4.5N), and its peak force was significantly greater than that of the standard Bankart repair by 15.8% (7.2N, P= .003). With subcritical glenoid bone loss, the repair with the addition of a 6-o'clock anchor (peak force, 52.6N; SD, 6.1N; P= .006) had a significantly higher peak resistance force than the group with bone loss with a Bankart lesion (35.2N; SD, 5.8N). Although the 6-o'clock anchor did increase the strength of the standard repair by 6.7%, this was not statistically significant (P= .9) in the bone loss model. The addition of a 6-o'clock suture anchor to a 3-anchor Bankart repair increases the peak resistance force to displacement in a biomechanical model, although this effect is lost with subcritical bone loss. This study provides surgeons with essential biomechanical data to aid in the selection of the repair configuration.