Upright Cone CT of the hindfoot: Comparison of the non-weight-bearing with the upright weight-bearing position

Objectives To prospectively compare computed tomography (CT) of the hindfoot in the supine non-weight-bearing position (NWBCT) with upright weight-bearing position (WBCT). Methods Institutional review board approval and informed consent of all patients were obtained. NWBCT and WBCT scans of the ankle were obtained in 22 patients (mean age, 46.0+/-17.1 years; range 19-75 years) using a conventional 64-row CT for NWBCT and a novel cone-beam CT for WBCT. Two musculoskeletal radiologists independently performed the following measurements: the hindfoot alignment angle, fibulocalcaneal and tibiocalcaneal distances, lateral talocalcaneal joint space width, talocalcaneal overlap and naviculocalcaneal distance. Significant changes between NWBCT and WBCT were sought using Wilcoxon signed-rank test. P values <0.05 were considered statistically significant. Results Significant differences were found for all measurements except the hindfoot alignment angle and tibiocalcaneal distance. Significant measurement results were as follows (NWBCT/WBCT reader 1; NWBCT/WBCT reader 2, mean +/- standard deviation): fibulocalcaneal distance 3.6 mm+/-5.2/0.3 mm+/-6.0 (P = 0.006); 1.4 mm+/-6.3/-1.1 mm+/-6.3 (P = 0.002), lateral talocalcaneal joint space width 2.9 mm+/-1.7/2.2 mm+/-1.1 (P = 0.005); 3.4 mm+/-1.9/2.4 mm+/-1.3 (P = 0.001), talocalcaneal overlap 4.1 mm+/-3.9/1.4 mm+/-3.9 (P = 0.001); 4.5 mm+/-4.3/1.4 mm+/-3.7 (P < 0.001) and naviculocalcaneal distance 13.5 mm+/-4.0/15.3 mm+/-4.7 (P = 0.037); 14.0 mm+/-4.4/15.7 mm+/-6.2 (P = 0.100). Interreader agreement was good to excellent (ICC 0.48-0.94). Conclusion Alignment of the hindfoot significantly changes in the upright weight-bearing CT position. Differences can be visualised and measured using WBCT. Key Points Cone-beam computed tomography (CBCT) offers new opportunities for musculoskeletal problems Visualization and quantification of hindfoot alignment are possible in upright weight-bearing CBCT Hindfoot alignment changes significantly from non-weight-bearing to weight-bearing CT The weight-bearing position leads to a decrease in the fibulocalcaneal distance and talocalcaneal overlap The naviculocalcaneal distance is increased in the weight-bearing position