We prospectively derived a clinical decision rule to guide pre- and postreduction radiography for emergency department (ED) patients with anterior glenohumeral dislocation.

This prospective cohort derivation study took place at 4 university-affiliated EDs over a 3-year period and enrolled consenting patients with anterior glenohumeral dislocation who were 18 years of age or older. We compared patients with a clinically important fracture-dislocation with those who had an uncomplicated dislocation to provide the clinical decision rule components using recursive partitioning. The final rule involved age, mechanism, prior dislocation and humeral ecchymosis.

A total of 222 patients were included in the study. Forty (18.0%) had clinically important fracture-dislocation. A clinical decision rule using 4 factors reached a sensitivity of 100% (95% confidence interval [CI] 89.4%–100%), a specificity of 34.2% (95% CI 27.7%–41.2%), a negative predictive value of 99.2% (95% CI 92.8%–99.9%) and a negative likelihood ratio of 0.04 (95% CI 0.002–0.27). Patients younger than 40 years are at high risk for clinically important fracture-dislocation only if the mechanism of injury involves substantial force (i.e., a fall greater than their own height, a sport injury, an assault or a motor vehicle collision). Patients 40 years of age or older are at high risk only in the presence of humeral ecchymosis or after their first dislocation. Projected use of the rule would reduce the absolute number of prereduction radiographs by 27.9% and of postreduction by 81.9%.

The Quebec shoulder dislocation rule for patients with acute anterior glenohumeral dislocation holds promise to reduce unnecessary imaging, pending validation.