Poster 153: Decreased Coracoid Index in Patients with Recurrent Instability after an Arthroscopic Bankart Procedure: A Retrospective Analysis with a Mean Follow-Up of 12.9 Years
Authors: Pruneski James , Cooper Andrew , Min Kyong 
Published: October 2024

Objectives: Traumatic anterior shoulder instability is a common sports medicine pathology, disproportionally affecting competitive, contact athletic and military populations. Currently, arthroscopic Bankart repair is the gold standard for managing patients with anterior instability and associated labral injury with subcritical bone loss. However, recurrent instability remains common after the index operation, with rates between 5% and 20% reported in the literature. Multiple prognostic calculators and scoring indices have been developed in attempts to proactively determine which cohorts may benefit from a bony (Latarjet or free bone graft) or soft tissue (Remplissage) augmentation procedure to further stabilize the joint and decrease the risk of recurrence. Importantly, there has been a growing appreciation for the effects of coracoid process morphology on shoulder pathology, including subcoracoid impingement and subscapularis tears. However, there is a paucity of literature exploring the effect of coracoid morphology on anterior shoulder instability. Therefore, the purpose of this study was to compare known osseous risk factors for recurrent instability, as well as the coracoid index, between patients with and without recurrent instability after an arthroscopic Bankart repair, and to compare long-term outcomes between the 2 cohorts. Methods: Following institutional review board approval, a retrospective cohort comparison of patients with anterior glenohumeral instability treated at a single academic military medical facility was performed. After identifying the initial cohort, patients were invited to complete Western Ontario Shoulder Instability Index (WOSI) and Single Assessment Numeric Evaluation (SANE) surveys. Inclusion criteria included symptomatic anterior shoulder instability, surgical treatment with arthroscopic Bankart repair, and survey completion. Preoperative MRIs were obtained, and glenoid bone loss, Hill-Sachs interval, and coracoid index were quantified. Patients with recurrent instability at last follow up were age-matched in a 1:2 ratio for comparison with those without recurrent instability. Subsequently, unpaired two-tailed t tests were used to compare anatomic morphologies and patient-reported outcome measures (PROMs) between the 2 cohorts. Finally, linear regression was used to evaluate the relationship between the anatomic measurements and PROMs. Results: At a mean of 12.9 years follow-up, 12 patients were confirmed to have recurrent shoulder instability by survey and chart review and were age-matched to 24 patients without recurrent instability (n = 36; mean age 26.0 ± 5.2 years). Patients with recurrent instability after arthroscopic Bankart repair had lower coracoid indices (by 3.28 ± 1.55 mm; p = .0412), greater glenoid bone loss (by 6.67 ± 1.62%; p = .0002), and larger Hill-Sachs Intervals (by 5.88 ± 2.30 mm; p = .0153) on preoperative MRI. The cohort with recurrent instability had lower SANE scores (by 38.0 ± 9.1; p = .0002), and higher WOSI scores (by 692 ± 174; p = .0003) at final follow-up. Coracoid index, glenoid bone loss and Hill-Sachs interval were not correlated with PROMs at latest follow-up (p > 0.05). Conclusions: To our knowledge, this is the first study to assess coracoid morphology in a cohort of patients with symptomatic shoulder instability. The current study findings suggest that a more laterally-projecting coracoid may be protective against recurrent shoulder instability after an arthroscopic Bankart repair. In accordance with recent literature, the recurrent instability cohort had greater glenoid bone loss and larger Hill-Sachs lesions on their index pre-operative MRI and had worse subjective outcomes at latest follow-up. As the shoulder is a complex joint with static and dynamic stabilizers, it is important to understand the effects of anatomic variation on pathoanatomy, as well as patient symptomatology. These preliminary findings highlight the need for further large cohort studies investigating the role of coracoid morphology on shoulder stability. A clearer understanding of the anatomic risk factors for recurrent instability will improve surgical planning and decision making, as well as minimizing time missed from athletic activities or military service.