Is the Bohler angle reliable for operative reduction of calcaneus fracture?

To evaluate reliability of Bohler angle in doing operative reduction of fractured calcaneus, and compare its value over other image lines of hindfoot when surgeons determine whether the injured calcaneus is reduced close to pre-injured state.

Eighteen of postoperative lateral radiographs were obtained and edited with two versions; one of which anterior of calcaneus erased not to check Bohler angle, the other of which peri-calcaneus structure such as talus erased only to check Bohler angle. Four orthopaedic surgeons were asked to determine the two sets of images whether the injured calcaneus is reduced close to pre-injured state in independent two sessions. Intra-, interobserver reliability, diagnosis test including specificity, sensitivity, positive and negative predictive values were assessed.

Intra- and interobserver reliability, Kappa value, ranged from 0.110 to 0.723 regardless the kind of the test. Sensitivity and specificity of both two tests were not significantly different in both trials, either. Positive and negative predictive values also showed similar pattern. The probability that observer determine the specific image as an acceptable reduction of calcaneus-less than 5 degrees of difference of the Bohler angle between post-reduction and pre-injured state-of two tests, was not significantly different in both trials (p = 0.40, 0.24, respectively).

Bohler angle is known as one of the most objective markers for calcaneus fracture, but was not accurate as a sole reference in intra-operative reduction in this study. Therefore, surgeons should take into account the other radiographic features in surgery.

IV, case series.