Acute Versus Delayed Magnetic Resonance Imaging and Associated Abnormalities in Traumatic Anterior Shoulder Dislocations

BACKGROUND: The delayed management of patients with shoulder instability may increase the prevalence and severity of concomitant intra-articular shoulder injuries resulting from persistent subluxations and dislocations. HYPOTHESIS: Patients with a longer delay from the initial dislocation event to undergoing magnetic resonance imaging (MRI) or magnetic resonance arthrography will demonstrate more subluxations or dislocations and a greater amount of intra-articular shoulder damage. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: We performed a retrospective review of 89 patients from a single institution with clinically and radiographically confirmed primary traumatic anterior shoulder dislocations. Patients were divided into 2 groups: those undergoing MRI less than 6 months (n = 44; LT6) or greater than 6 months (n = 45; GT6) from the initial dislocation event. The MRI assessment included evaluation of soft tissue injuries, including the labrum, capsule, rotator cuff, and cartilage damage severity along with bone loss. RESULTS: The delayed MRI group (GT6) demonstrated a greater degree of intra-articular abnormalities compared to the early MRI group (LT6). A greater percentage of superior labral anterior-posterior (SLAP) tears (58% vs 34%, respectively) and cartilage damage (73% vs 27%, respectively) was present in the GT6 group compared to the LT6 group. Cartilage damage was 18% mild, 7% moderate, and 2% severe for the LT6 group as compared to 38% mild, 31% moderate, and 4% severe for the GT6 group. Additionally, more recurrent shoulder dislocations were seen in the GT6 group (n = 6) compared to the LT6 group (n = 2). In the LT6 group, there were more rotator cuff tears (50% vs 24%, respectively) and capsular tears (25% vs 9%, respectively) than the GT6 group. There was no difference in anterior glenoid bone loss, glenoid version, or humeral head subluxation between the 2 groups. CONCLUSION: Patients who undergo MRI greater than 6 months from the time of primary or initial shoulder dislocation had significantly more recurrent shoulder instability events and demonstrated a greater incidence and severity of intra-articular abnormalities, including SLAP tears, posterior labral tears, and anterior glenoid cartilage damage.