Abstract
BACKGROUND: Posterior shoulder instability is associated with nonspecific symptoms, including pain, subluxation, and functional impairment, which complicate its diagnosis and management. Owing to the rarity of the condition, there are no present decision tools for its diagnosis and treatment. PURPOSE: To investigate demographic, lesional, and surgical factors that influence functional outcomes in patients treated for posterior shoulder instability. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: We analyzed the clinical and radiographic records of 150 patients treated surgically for isolated posterior shoulder instability at 10 centers between 2000 and 2015, of which 144 were eligible for inclusion: 114 men (79%) and 30 women (21%) (mean ± SD age, 28.7 ± 9.6 years). The mean time between onset of symptoms and surgery was 66 ± 75 months. Shoulder instability was of traumatic origin in 115 patients (80%). The primary treatment was bone-block procedures for 65 patients (45%), posterior Bankart repair for 67 (47%), and capsular plication for 12 (8%). Patients were assessed with the Constant and Walch-Duplay scores at a mean follow-up of 51 ± 32 months (range, 12-159 months). Uni- and multivariable regression analyses were performed to determine associations between clinical scores and sex, age, traumatic origin, type of lesion, type of procedure, and follow-up. RESULTS: At final follow-up, subluxations or dislocations recurred in 24 patients (17%). The overall Constant score was 86.2 ± 14.5, with a pain component of 12.6 ± 3.5. The Walch-Duplay score was 79.8 ± 24.2. Multivariable regressions revealed that the presence of a glenoid cartilage lesion was the only factor associated with worse Constant score (beta = -10; P = .013) and Walch-Duplay score (beta = -16.7; P = .024) across all subcomponents. CONCLUSION: The only factor that jeopardized functional outcomes of posterior instability surgery was the presence of glenoid cartilage lesions. Knowing that shoulders with glenoid cartilage lesions are at greater risk of residual pain or instability could help manage patient expectation and justify faster intervention before lesions deteriorate.