Presence of Additional Pathology in Low-Grade Acromioclavicular Joint Injuries

Objective: To determine if additional pathology is present in low-grade acromioclavicular (AC) joint injuries. Design: Prospective case series. Setting: Patients were assessed by primary care sports medicine physicians at a single institution between 2019 and 2023. Patients: Patients aged 18 to 65 years diagnosed with a type I to III AC injury based on clinical and radiographic evaluation. Intervention: Consenting patients underwent magnetic resonance imaging (MRI) evaluation within 21 days of injury. All injuries were treated nonoperatively. Main Outcome Measures: Additional pathologies identified on MRI were reported in a standardized fashion by fellowship-trained musculoskeletal radiologists. Results: Twenty-nine patients (26 men/3 women) were consented with a mean (±SD) age of 28.6 ± 9.5 years. The mean time from injury to MRI was 8.1 ± 5.9 days. Twenty-three injuries were sport related, and 6 were accidental traumas. Based on MRI, injury type was reclassified in 16 of 29 patients, and 13 remained unchanged. Additional pathologies identified included 14 muscle injuries, 5 rotator cuff tears, 5 labral tears, 1 nondisplaced fracture, and 1 intra-articular body. Conclusion: MRI evidence suggests that most AC joint injuries are more severe than clinically diagnosed. Identifying additional pathology may alter diagnostic and treatment guidelines for type I to III AC joint injuries.