Computed tomography-based automated 3D measurement of femoral version: Validation against standard 2D measurements in symptomatic patients

To validate 3D methods for femoral version measurement, we asked: (1) Can a fully automated segmentation of the entire femur and 3D measurement of femoral version using a neck based method and a head-shaft based method be performed? (2) How do automatic 3D-based computed tomography (CT) measurements of femoral version compare to the most commonly used 2D-based measurements utilizing four different landmarks? Retrospective study (May 2017 to June 2018) evaluating 45 symptomatic patients (57 hips, mean age 18.7 +/- 5.1 years) undergoing pelvic and femoral CT. Femoral version was assessed using four previously described methods (Lee, Reikeras, Tomczak, and Murphy). Fully-automated segmentation yielded 3D femur models used to measure femoral version via femoral neck- and head-shaft approaches. Mean femoral version with 95% confidence intervals, and intraclass correlation coefficients were calculated, and Bland-Altman analysis was performed. Automatic 3D segmentation was highly accurate, with mean dice coefficients of 0.98 +/- 0.03 and 0.97 +/- 0.02 for femur/pelvis, respectively. Mean difference between 3D head-shaft- (27.4 +/- 16.6 degrees) and 3D neck methods (12.9 +/- 13.7 degrees) was 14.5 +/- 10.7 degrees (p < 0.001). The 3D neck method was closer to the proximal Lee (-2.4 +/- 5.9 degrees, -4.4 to 0.5 degrees, p = 0.009) and Reikeras (2 +/- 5.6 degrees, 95% CI: 0.2 to 3.8 degrees, p = 0.03) methods. The 3D head-shaft method was closer to the distal Tomczak (-1.3 +/- 7.5 degrees, 95% CI: -3.8 to 1.1 degrees, p = 0.57) and Murphy (1.5 +/- 5.4 degrees, -0.3 to 3.3 degrees, p = 0.12) methods. Automatic 3D neck-based-/head-shaft methods yielded femoral version angles comparable to the proximal/distal 2D-based methods, when applying fully-automated segmentations.