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

Abstract

Background: Arthroscopic Bankart repair is currently the most utilized technique in the surgical management of symptomatic anterior shoulder instability. Despite a growing body of literature regarding optimal repair configurations, little is known about inferior suture anchor placement (6 o'clock position). Methods: 12 cadaveric shoulders were tested on a 6 DOF robotic musculoskeletal simulator to measure the peak resistance force due to anterior displacement of 1 cm. The rotator cuff muscles were loaded during testing to simulate physiological conditions. Test conditions consisted of the intact shoulder, Bankart lesion, Bankart repair (3, 4, and 5 o'clock anchors), and Bankart repair with addition of a 6 o'clock anchor. A 13% anterior bone defect was then and all conditions were repeated. Repeated measures ANOVA was used to test for significant differences among groups. Results: In the no bone loss group, the addition of a 6 o'clock anchor yielded the highest peak resistance force (52.8N, SD: 4.5N) and was significantly greater than the standard Bankart repair by 15.8% (7.2N, p = 0.003). With 13% bone loss from the anterior glenoid, both the standard Bankart repair (peak force 49.3N, SD: 6.1N, p = 0.02) and repair with the addition of the 6 o'clock anchor (peak force 52.6N, SD: 6.1N, p = 0.006) had a significantly higher peak resistance force compared to the bone loss with Bankart lesion group (35.2N, SD: 5.8N). While the 6 o'clock anchor did increase the strength of the standard repair by 6.7%, this was not statistically significant (p = 0.9) in the bone loss model. Conclusions: The addition of a 6 o'clock suture anchor to a "standard" Bankart repair increases the peak resistance force to displacement (no bone loss), although this additional strength is lost with creation of a subcritical anterior glenoid bone defect. Clinical Relevance: This study provides surgeons with essential biomechanical data to aid in the selection of repair configuration. The six o'clock anchor does not enhance repair strength in a subcritical bone loss model.

Mapping of the Inferior Glenohumeral Ligament for Suture Pullout Strength: A Biomechanical Analysis

“…Therefore, the pullout strength was dissipated over 3 anchoring points through the capsulolabral tissue rather than a single suture in the IGHL only, as in our study. Interestingly, a recent cadaveric paper by Bokshan et al 5 reported peak resistance of the capsulolabral tissues to 1 cm anterior translation of an intact shoulder as 43.4 N, with 52.8 N for a Bankart repair with 4 anchors (including a 6 o’clock anchor with capsular plication), which is similar to the values reported in our study. However, direct comparisons between the 2 studies are difficult as the authors did not report the mode of failure—they utilized several anchors as opposed to 1 suture; and unlike our study, they did include labral tissue as well as rotator cuff musculature in their model.…”

Editorial Commentary: More Is Better? The 6-O’clock Anchor in Instability Surgery

“…Barber 4 showed that in arthroscopic rotator cuff repair, the dependent variable was not the number of rows but was the number of sutures. This might well generalize to the Bankart repair technique of Bokshan et al 1 and so not require a risky 6-o'clock anchor. Would the surgeon do just as well using double-loaded anchors and so obtain more sutures in this fashion without the risk of the 6-o'clock anchor?…”

“…The first question is the optimal time-zero strength of the repair. Bokshan et al 1 report that the purportedly inferior repair without the 6-o'clock anchor in fact creates a repair with a displacement equal to the original uninjured shoulder. Is it necessary (or even desirable) to create a construct that is 15.8% stronger than the native structure?…”

The New Double‐row Bankart Repair Recovered Shoulder Stability without Excessive Motion Limitation: A Case–Control Study with Single‐row Bankart Repair

“…One review found the recurrence rate of Bankart repair decreased significantly when no less than four anchors were placed 12 . Similarly, Bokshan et al 13 . concluded from their cadaveric study that an additional 6 o'clock anchor could increase the fixation strength of Bankart repair with single‐row suture.…”

“… 12 Similarly, Bokshan et al . 13 concluded from their cadaveric study that an additional 6 o'clock anchor could increase the fixation strength of Bankart repair with single‐row suture. The increased anchors could connect the capsulolabral complex and glenoid neck more tightly and provide more contact area for better union.…”