Risk Factors for Intra-Articular Bone and Cartilage Lesions in Patients Undergoing Surgical Treatment for Posterior Instability

OBJECTIVES: Patients with posterior shoulder instability often present with significant differences in history of injury and complaints compared to anterior instability that can lead to challenges in diagnosis and treatment. These patients may have bone and cartilage lesions in addition to caspulolabral injuries, though the risk factors for these intra-articular lesions are unclear. The purpose of this study was to describe intraoperative incidence of glenohumeral bone and cartilage lesions in a cohort of patients undergoing primary posterior stabilization using data from a prospectively collected, multicenter shoulder instability cohort. We hypothesized that patients with traumatic posterior instability with greater number of instability events would have higher rate of bone and cartilage injuries compared to those without fewer instability episodes. METHODS: Data from the Multicenter Orthopaedic Outcomes Network (MOON) Shoulder Group instability patient cohort was utilized for this study. This is a multi-center study encompassing a prospective evaluation of patients ages 12 to 99 years of age undergoing primary surgical treatment for shoulder instability by 24 orthopedic surgeons at 11 sites in the United States. Demographic data and specifics regarding the patient’s instability history were recorded, including patient age, sex, body mass index (BMI), history of smoking, and Beighton score. The number of instability events was classified as 0, 1, 2 to 5, or more than 5. The duration of symptoms was classified as <1 month, 1-3 months, 4-6 months, 7-12 months, or greater than 1 year. The glenohumeral joint was evaluated by the treating surgeon at the time of surgical treatment for bone and cartilage injuries, and patients were classified as having a bone or cartilage lesion (BCL) if there was any grade 3 or 4 glenoid or humeral cartilage lesion, reverse Hill-Sachs lesion, bony Bankart lesion, or glenoid bone loss. The effects of number of instability events on the presence of BCLs was investigated using Fisher’s exact tests. Multivariate analysis using logistic regression modeling was performed to investigate the independent contributions of demographic variables and injury-specific variables to the likelihood of having a BCL. Significance was defined as p<0.05. RESULTS: There were 271 patients identified for analysis. Bone and cartilage lesions were identified in 59 patients (21.8%) at the time of surgical treatment (Table 1). The most common lesion was a glenoid cartilage injury, which was identified in 28 patients (10.3%). Patients with BCLs were significantly older and had significantly higher BMI relative to patients without BCLs (Table 2). There was a significant difference between the number of instability events and the presence of BCLs (p = 0.035), with the highest rate observed in patients with 2-5 instability events (33.9%) (Figure 1). Through multivariate logistic regression modeling, increasing age (p=0.002), increasing BMI (p=0.012), and 2 to 5 reported instability events (p=0.001) were significant independent predictors of the presence of BCLs. CONCLUSION: Bone and cartilage lesions are seen significantly more frequently with increasing patient age, increasing BMI, and patients with 2-5 instability events. Early surgical stabilization for posterior instability may be considered to potentially limit the extent of associated intra-articular injury.