La Torsion épiphysaire distale du fémur est-elle identique sur les deux genoux d’un même patient ? Étude morphométrique scannographique

Abstract

IntroductionAppropriate rotational positioning of the femoral component is known to be a key factor of success after total knee replacement. However, distal femoral torsion (DFT) varies among individuals. Preoperative CT-measurement of the DFT associated with computer-assisted surgery improves significantly rotational positioning of the femoral implant. Preoperative CT-imaging is costly and exposes to radiations especially in case of bilateral arthroplasty. The goal of our study was to evaluate DFT of both knees of the same patient undergoing bilateral total knee arthroplasty (TKA). We hypothesized that DFT is symmetrical in patients regardless of the frontal deformity. MaterialsIn this retrospective study between December 2008 and March 2015, 82 patients (mean age: 73 years) who had undergone two-stage bilateral TKA (164 knee) were included. DFT was systematically measured on preoperative CT-scans using the posterior condylar angle as described by Yoshioka et al. Two independent observers performed each measurement twice. The intra- and inter- observer reproducibility was evaluated by the Pearson coefficient (r) and the intra-class correlation coefficient (ρ, ICC). ResultsIn the global series, the mean posterior condylar angle was 5.4° (±1.48°) for the right knee and 5.4° (±1.45°) for the left knee. The difference between both knees varied between 0 and 2.2° (p=0.8). 84.6% of the patients (global series) had a right/left difference inferior to 1°. There was no significant difference between both knees regardless of whether there was an important frontal deviation or not (frontal deviation<10°, p=0,7; frontal deviation>10°, p=0.5) and regardless of whether the knee was in varus or valgus (p=0.9 The intra-observer reproducibility was excellent (94%), le The inter-observer reproducibility was moderate to good (60% for left knees, 53% for right knees). DiscussionPreoperative CT-measurement of the DFT on the two arthritic knees of a same patient is comparable and this measurement is reproducible. A single unilateral CT-scan is therefore enough to preoperatively plan appropriately bilateral TKAs. Level of evidenceRetrospective cobort study, level IV.