Anterior Shoulder Instability: Outcome of Initial Non-operative Treatment in 739 patients with a mean follow up of 15 years

OBJECTIVES: There remains a paucity of data describing the efficacy of non-operative treatment following an index anterior instability event. The purpose of this study was to describe the long-term outcomes of non-operative treatment following index anterior instability event, define the success rate of initial non-operative treatment for anterior shoulder instability, and describe factors that predict conversion to surgery after initial non-operative management to help guide surgical decision making in these patients. METHODS: An established geographic database was utilized to identify patients under the age of 40 treated for anterior shoulder instability between 1994 and 2016. Patient demographics, comorbidities, injury characteristics, instability history, activity level, x-rays, advanced imaging, treatment course, and outcomes were evaluated. Patients treated non-operatively for the first 6 months following index instability event were analyzed to determine long-term outcomes, success rate of continued non-operative treatment, and factors associated with conversion to surgery. RESULTS: 739 patients met criteria with an average follow-up of 190 months (range 0.13 to 490 months). Average age was 23.8, mean BMI was 25.6, 9.1% had a history of hyperlaxity, and 83.9% of instability events were due to trauma. 29.7% of patients had a Hill-Sachs lesion on index x-ray, and 6.3% had a bony Bankart. 198 shoulders went on to operative treatment (26.8%) with a mean time to surgery of 62.7 months following initial instability event. At final follow-up, 24.0% reported mild pain, 6.2% as moderate, 0.2% as severe. 13.8% of patients had evidence of glenohumeral arthritis on final follow-up x-rays compared to 1.6% on initial radiographs. Factors associated with conversion to surgery included 2 or more dislocations prior to first clinical evaluation (OR=1.75, p<0.001), labor intense occupation (OR=1.49, p=0.031), Hill Sachs lesion on index x-ray (OR=1.31, p=0.034), and MRI findings including: anteroinferior labral tear (OR=2.15, p<0.001), posteroinferior labral tear (OR=1.38, p=0.049), SLAP tear (OR=1.29, p=0.054), Hill-Sachs lesion (OR=1.85, p<0.001), and glenohumeral cartilage injury (OR=1.26, p=0.041). CONCLUSION: The majority of patients less than 40 can be definitively treated non-operatively after an initial 6 month episode of non-operative treatment. A small proportion will report pain over the long-term and/or develop glenohumeral arthritis. Multiple factors upon initial evaluation were associated with future conversion to surgery including: increasing number of prior instability events, occupation, and degree of soft tissue injury on MRI.