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 1 cm. 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 (52.8 N; standard deviation [SD], 4.5 N), and its peak force was significantly greater than that of the standard Bankart repair by 15.8% (7.2 N, P = .003). With subcritical glenoid bone loss, the repair with the addition of a 6-o'clock anchor (peak force, 52.6 N; SD, 6.1 N; P = .006) had a significantly higher peak resistance force than the group with bone loss with a Bankart lesion (35.2 N; SD, 5.8 N). 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.