Arthroscopic shoulder stabilization with suture anchors has become an accepted treatment option for management of anterior shoulder instability. In most cases of traumatic instability, a labral tear is present, which requires repair to the glenoid rim with suture anchors. Multiple clinical studies have demonstrated favorable long-term outcomes after instability repair with suture anchor fixation. Despite a more evolved understanding of anterior shoulder instability, failure rates leading to repeat instability events are noted to be as high as 20% to 30% for patients after repair of both acute and recurrent instability. For example, Owens and colleagues recently reported on 40 shoulders undergoing arthroscopic Bankart repair with suture anchors for acute (primary) anterior shoulder dislocations. With an average 11.9 years of follow-up, the authors reported a 14.3% recurrent dislocation rate and a 21% recurrent subluxation rate.26 Similarly, van der Linde reported on 70 shoulders undergoing arthroscopic Bankart repair for traumatic recurrent anterior instability with suture anchors and noted a recurrence rate of 35% after 8 to 10 years after surgery. Such failure rates are clearly problematic, especially given the relatively young average age composing the majority of this patient population.
Given that the typical zone of injury in the setting of anterior instability is in the anterior-inferior glenoid quadrant, the zone of injury is between 3 and 6 o’clock (for a right shoulder). For adequate repair, it is critical for the surgeon to achieve inferior anchor placement to address the inferior component of traumatic instability. The standard mid-glenoid portal, however, can pose difficulty in permitting adequate low anterior-inferior anchor placement. This may be due to the obliquity of the approach, which may ultimately lead to anchor blowout.
Alternative portals and curved drill guide systems have been described to improve inferior anchor placement. The majority of technical articles on arthroscopic Bankart repair describe suture anchor placement with a straight guide through a standard midglenoid portal (above the subscapularis tendon). Other portals, including the percutaneous 5-o’clock trans-subscapularis portal and the 7-o’clock portal, have been advocated to provide more con- sistent placement of inferior anchors on the glenoid. These portals allow for a more perpendicular trajectory for pilot hole preparation and subsequent suture anchor placement. More recently, curved guide systems have been developed to facilitate such inferior anchor placement.
To date, there is a paucity of data available evaluating anchor placement accuracy with regard to both portal and guide choice. This information would be useful in clinically guiding orthopaedic surgeons in their choices of portal and guide utilization in the setting of anterior shoulder instability repair. It is unknown if insertional techniques affect the biomechanical performance of the anchor and, further, whether the anchor remains in bone after insertion. Finally, it is unknown if the surgeon’s intended anchor placement (eg, 3 o’clock) is affected by portal and/ or guide choice. The purpose of this study, therefore, is to evaluate initial biomechanical performance of a conventional glenoid anchor and risk of opposite cortex penetration as a function of portal used and type of guide chosen (straight vs curved). The hypothesis of this study is that use of an accessory trans-subscapularis portal or curved drill guide system will improve low anterior-inferior anchor position and result in improved initial biomechanical properties with lower risk of opposite cortex perforation.