Böhler's angle - What is normal in the uninjured British population?

Böhler's angle is a radiographic parameter widely used in the detection and assessment of fractures of the os calcis. The normal range in the uninjured British adult population has not previously been established. We analysed 128 lateral radiographs without fracture in order to establish the true value of Böhler's angle. Analysis was performed with respect to age, sex and laterality. Interobserver reliability was also assessed. The mean angle was 36.4° (SD 4.2°, range 24.7-48.9°). The normal range was 28.2-44.5°, which incorporates 95% of subjects. There was no difference with respect to age, sex or laterality. Agreement between independent observers was good (interobserver correlation coefficient=0.72), although there was disagreement of >5° in 40.9% of cases. Given the wide range of normal values we recommend a comparative radiograph of the contralateral side if the presence of fracture is ambiguous.