Boehlerʹs angle and the critical angle of Gissane are of limited use in diagnosing calcaneus fractures in the ED

Study Objectives The aim of this study was to determine the use of Boehlerʹs angle (BA) and the critical angle of Gissane (CAG) in diagnosing calcaneus fractures in the ED. Design The study was conducted as a randomized, blinded, case-control trial. Cases One hundred thirty-three patients older than 15 years were included in the study. Sixty-five patients with computed tomography–verified calcaneus fractures (gold standard) and 68 ED patients with lateral foot or ankle x-rays without calcaneus fractures were included in the study. Methods One second-year emergency medicine resident, 1 third-year emergency medicine resident, 2 board-certified emergency medicine attending physicians, and 1 board-certified radiologist prospectively reviewed all films using the Picture Archival and Communication System digital radiology system. Cases and controls were randomized and the participants were blinded to final radiographic diagnoses. Participants determined whether there was a fracture on each x-ray and measured BA and the CAG using the digital angle tool in the Picture Archival and Communication System. Results Emergency physicians were 97.9% accurate in diagnosing calcaneus fractures (range, 97% to 99%). The mean κ value for emergency physicians was 0.96 (range, 0.94-0.985). Receiver operating characteristic curves were constructed for BA and the CAG. When compared with the gold standard, the area under the curve for BA ranged from 0.82 to 0.88. The area under the curve for the CAG ranged from 0.45 to 0.67. BA had an interclass correlation coefficient of 0.84 (95% confidence interval, 0.79-0.87). The CAG interclass correlation was 0.52 (95% confidence interval, 0.43-0.60). One fracture was missed by the radiologist and all of the emergency physicians because it was only visible on computed tomography. Conclusion BA is somewhat helpful and the CAG is not useful in diagnosing calcaneus fractures in the ED. Interrater reliability for BA is excellent, but for the CAG, it is poor. Emergency physicians were 97.9% accurate in making the diagnosis by reviewing the plain films without “assistance” of the angle measurements.