Poster 166: Biomechanical Evaluation of Open Bankart and Soft Tissue Bristow Procedures with 10% Glenoid Bone Loss

OBJECTIVES: Chronic anterior shoulder instability can be debilitating for a wide number of individuals from the general populations, high level and recreational athletes, laborers and the members of the military. Glenoid bone loss presents a more difficult problem to treat as it negates the positive results that can be achieved with arthroscopic labral repair alone. The optimal procedure for subcritical bone loss of 10% or less is undetermined. In young competitive contact athletes, there is still a high failure rate with arthroscopic procedures. Therefore, the purpose of this study was to biomechanically characterize the effects of soft tissue Bristow (conjoint tendon transfer) and open Bankart repair in a 10% glenoid defect model. METHODS: Eight fresh cadavers were studied using a custom shoulder testing system. The rotator cuff muscles were loaded to simulate physiologic muscle conditions. Range of motion, anterior-inferior translation at 60° of external rotation with 20, 30 and 40N of force were tested in scapular and coronal planes. Stiffness and the force required to dislocate in the anterior-inferior direction were also quantified in the coronal plane. 4 different states were examined including: (1) intact capsule (2) Bankart lesion with 10% bone loss, (3) soft tissue Bristow (conjoint tendon transfer), and (4) open Bankart repair. Repeated measures ANOVA with Bonferroni correction was used for statistical analysis. RESULTS: The bony Bankart (injury model) increased range of motion in both the scapular and coronal planes. The conjoint tendon transfer had little effect on range of motion, and the Bankart repair decreased the range of motion to a similar state with that of the pre-injury model. The injury state showed increased translation which was decreased with both the conjoint tendon transfer and the Bankart repair (Figure 1A). The conjoint tendon transfer shifts the humeral head posteriorly in 0° and 30° of external rotation in the scapular plane. There was no difference in stiffness during dislocation between conjoint tendon transfer and Bankart repair (Figure 1B). CONCLUSIONS: Both the soft tissue Bristow and the open Bankart repair were noted to decrease anterior translation in this shoulder instability model. Both open repair models significantly decreased anterior translation and are valid surgical options for the treatment of instability with 10% glenoid bone loss. Surgically, an open Bankart repair is more anatomic and may be the preferred technique.