Clinical Factors Predicting Fractures Associated with an Anterior Shoulder Dislocation

OBJECTIVES: To identify risk factors for fractures associated with an anterior shoulder dislocation treated in an emergency department (ED). METHODS: A retrospective case-control study over five years of patients with an anterior shoulder dislocation was accomplished in a university-affiliated ED. Chart review identified possible predictors of fractures. Comparing the profile of patients having a clinically important fracture associated with their shoulder dislocation (cases) with those sustaining a noncomplicated dislocation (controls) provided the outcome measure. RESULTS: A total of 334 patients were included in the study. Eighty-five (25.5%) had a clinically important fracture-dislocation, and the remaining 249 (74.5%) sustained a noncomplicated shoulder dislocation. Chi-square, logistic regression, and recursive partitioning analysis showed three significant factors for the presence of fracture-dislocation: 1) age 40 years or older, 2) a first episode of dislocation, and 3) mechanism of injury (i.e., a fall greater than one flight of stairs, a fight/assault episode, or a motor vehicle crash). A multiple logistic regression model estimated the significant adjusted odds ratios (and their 95% confidence intervals [95% CIs]) for each of the three factors: 5.18 (95% CI = 2.74 to 9.78), 4.23 (95% CI = 1.82 to 9.87), and 4.06 (95% CI = 1.95 to 8.48), respectively. A predictive model using any one of the three factors reached a sensitivity of 97.7% (95% CI = 91.8% to 99.4%), a specificity of 22.9% (95% CI = 18.1% to 28.5%), and a negative predictive value of 96.6% (95% CI = 88.3% to 99.6%). CONCLUSIONS: Three risk factors predict clinically important fractures that are associated with shoulder dislocation: age, first episode, and mechanism of dislocation. A prospective validation may lead to standardized use of prereduction radiographs of the shoulder in the ED.