Impact of the diaphyseal femoral deformity on the lower limb alignment in osteoarthritic varus knees.

The impact of a diaphyseal femoral deformity on knee alignment varies according to its severity and localization. The aims of this study were to determine a method of assessing the impact of diaphyseal femoral deformities on knee alignment for the varus knee, and to evaluate the reliability and the reproducibility of this method in a large cohort of osteoarthritic patients. All patients who underwent a knee arthroplasty from 2019 to 2021 were included. Exclusion criteria were genu valgus, flexion contracture (> 5°), previous femoral osteotomy or fracture, total hip arthroplasty, and femoral rotational disorder. A total of 205 patients met the inclusion criteria. The mean age was 62.2 years (SD 8.4). The mean BMI was 33.1 kg/m ² (SD 5.5). The radiological measurements were performed twice by two independent reviewers, and included hip knee ankle (HKA) angle, mechanical medial distal femoral angle (mMDFA), anatomical medial distal femoral angle (aMDFA), femoral neck shaft angle (NSA), femoral bowing angle (FBow), the distance between the knee centre and the top of the FBow (DK), and the angle representing the FBow impact on the knee (C'KS angle). The FBow impact on the mMDFA can be measured by the C'KS angle. The C'KS angle took the localization (length DK) and the importance (FBow angle) of the FBow into consideration. The mean FBow angle was 4.4° (SD 2.4; 0 to 12.5). The mean C'KS angle was 1.8° (SD 1.1; 0 to 5.8). Overall, 84 knees (41%) had a severe FBow (> 5°). The radiological measurements showed very good to excellent intraobserver and interobserver agreements. The C'KS increased significantly when the length DK decreased and the FBow angle increased (p < 0.001). The impact of the diaphyseal femoral deformity on the mechanical femoral axis is measured by the C'KS angle, a reliable and reproducible measurement.
Competing Interests: C. Batailler reports a grant from Société francaise de chirurgie orthopédique et traumatologique (SoFCOT), and institutional research support from Groupe Lepine, neither of which are related to this study. A. Naaim and J. Daxhelet report no conflicts of interest. S. Lustig reports consulting fees from Stryker, Smith & Nephew, Heraeus, and Depuy Synthes, and institutional research support from Groupe Lepine and Amplitude, all of which are unrelated to this study. S. Lustig is also on the editorial board for The Journal of Bone and Joint Surgery (Am). M. Ollivier reports consulting fees from Arthrex, Stryker, and Newclip technics, unrelated to this study. S. Parratte reports royalties from Zimmer Biomet and Newclip, and consulting fees from Zimmer Biomet, unrelated to this study. S. Parratte is also the treasurer for the European Knee Society.
(© 2023 Author(s) et al.)