Comparison and agreement analysis of Böhler and Gissane angles on radiographs and CT in dry human calcanei

PURPOSE: This study aimed to compare the measurements of Böhler's angle (BA) and the critical angle of Gissane (GA) between lateral radiographs and computed tomography (CT) scans in dry human calcanei, and to assess the inter- and intraobserver agreement for each angle across both imaging modalities. METHODS: A total of 160 dry human calcanei were examined. Both BA and AG were measured on digital radiographs and multiplanar CT reconstructions. Two independent observers - a radiologist and an orthopedist performed all measurements in two separate sessions. Mean values, standard deviations, and agreement metrics were calculated. The inter- and intraobserver reliability were assessed using intraclass correlation coefficients (ICC). Paired statistical tests were used to compare radiographic and tomographic measurements. RESULTS: The mean value of the BA was 31.8° ± 5.8° and 29.7° ± 5.6° on radiographies and CT-scans, respectively. The GA showed mean values of 108.7° ± 9.2° on radiographs and 125.7° ± 10.3° on CT. CT-based measurements of BA demonstrated the highest reproducibility (ICC > 0.90), with excellent inter- and intraobserver agreement. In contrast, GA showed poor agreement across all comparisons, particularly on radiographs (ICC < 0.30). Observer agreement was consistently higher for BA, and CT substantially reduced interobserver variability. CONCLUSION: The BA demonstrated superior measurement reliability compared to the Gissane angle, particularly when assessed by CT. GA measurements demonstrated low reproducibility and should be interpreted with caution, especially when obtained from x-rays. These findings support the preferential use of CT-based BA for morphometric and clinical evaluations of the calcaneus.