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.