Comparison of computed tomography-based tibial torsion measurement techniques reveals significant technique-dependent differences

To compare commonly used computed tomography (CT)-based tibial torsion measurement discrepancies and evaluate their intra- and interobserver agreement, as measurement discrepancies between techniques have not been systematically assessed.

CT scans from 20 adult patients were retrospectively analysed. Tibial torsion was calculated using two proximal reference axes (posterior tibial plateau tangent and tibial tuberosity axis) and four distal axes (transmalleolar, ankle joint, Jend and Waidelich). Three observers performed all measurements independently and repeated them after 8-12 weeks. Differences among techniques were assessed using repeated-measures analysis of variance with Bonferroni correction. Reliability was evaluated using intraclass correlation coefficients (ICCs).

All measurement techniques differed significantly (p < 0.05). Mean tibial torsion was 34.1° (standard deviation [SD] 8.6°) for the transmalleolar axis, 31.2° (SD 8.8°) for the ankle joint axis, 44.2° (SD 9.8°) for the Jend axis and 34.9° (SD 9.0°) for the Waidelich axis. Segmental values revealed a mean supratuberositary torsion of 26° (SD 6.7°) and a mean infratuberositary torsion of 7.9° (SD 8.8°) for the transmalleolar axis, 5.1° (SD 8.9°) for the ankle joint axis, 18.1° (SD 10.4°) for the Jend axis and 8.8° (SD 9.1°) for the Waidelich axis. All techniques showed excellent intra- and interobserver reliability (ICC > 0.89).

Tibial torsion values depended strongly on the measurement technique used. Technique-specific normative values are essential, and radiology reports should explicitly identify the technique applied. Clinicians must account for these systematic differences when interpreting torsion values and planning derotational osteotomies.

Level III, retrospective comparative study.