Prediction of Distal Radius Fracture Redisplacement: A Validation Study.

Objective: To externally validate the Edinburgh Wrist Calculator (EWC) in a population of patients with distal radius fractures at risk of loss of threshold alignment.

Design: A retrospective cohort study.

Setting: One academic hospital.

Patients/participants: All consecutive adult patients with a displaced distal radius fracture with initial dorsal angulation >10 degree and/or an ulnar variance of >3 mm who were treated with closed reduction and cast immobilization between 2009 and 2014.

Main Outcome Measurement: The sensitivity and specificity for diagnosis of loss of threshold alignment within 2 weeks of injury was calculated at the 10%, 40%, and the original 70% probability thresholds. The area under receiver operating characteristic curve was calculated using 2 different thresholds for loss of alignment: Mackenney et al and the Dutch consensus standards.

Results: The EWC predicted a greater than 70% chance of redisplacement for only 3 fractures. Redisplacement within 2 weeks occurred in 61 of 99 (62%) fractures according to the thresholds of Mackenney et al and in 18 of 99 (18%) fractures according to the Dutch thresholds. The sensitivity increased and the specificity decreased using a lower probability threshold for redisplacement. The area under the receiver operating characteristic curve of the EWC was poor the Mackenney's thresholds [0.47; 95% confidence interval (CI): 0.36-0.59] and adequate for the Dutch thresholds (0.71; 95% CI: 0.58-0.84).

Conclusions: The EWC was a poor predictor of fracture redisplacement greater than threshold in displaced distal radius fractures in our patient population.