There is poor reliability of Böhler's angle and the crucial angle of Gissane in assessing displaced intra-articular calcaneal fractures

•We calculated the inter-observer and intra-observer reliability of Böhler's angle and the crucial angle of Gissane among practicing orthopedic surgeons.•Our data suggest that there is wide disagreement among surgeons regarding Böhler's angle and the crucial angle of Gissane in displaced intra-articular calcaneal fractures.•Calculating the tolerance limit for radiographic measurements may be more informative than intra-class correlation coefficient in determining inter-observer reliability.

BackgroundTwo-dimensional measurements are used to describe displaced intra-articular calcaneal fractures (DIACF). Our study evaluates the performance of Böhler's angle (BA) and the crucial angle of Gissane (CAG) among orthopedic surgeons.MethodsThirty-four pre- and post-operative lateral foot radiographs from patients with DIACF were shown to four orthopedic surgeons who measured BA and the CAG. The intra- and inter-observer reliability were calculated using the intra-class correlation coefficient (ICC). Additionally, we calculated frequency of consensus given an allowed discrepancy. We then determined the tolerance limit for each measurement.ResultsThe ICC for inter-observer reliability of BA was 0.83 in the first session and 0.77 in the second. The ICC for intra-observer reliability ranged from 0.83 to 0.98. For the CAG, the inter-observer ICC was 0.28 and 0.1 in the two sessions. Intra-observer ICC ranged from 0.16 to 0.67. With an allowed discrepancy of 20°, there was lack of consensus for BA in 37.5% and for the CAG in 59% of measurements on average. The 95% confidence interval for 90% agreement in BA involved a range of 76°. For CAG, the 95% confidence interval of tolerance for 90% agreement was 56°.ConclusionsFor BA and CAG, there is frequent disagreement among experienced observers, even given a wide tolerance range. We recommend use of caution when applying BA as currently measured in making treatment decisions for DIACF.Level of Clinical Evidence: Diagnostic, level III.