Primary osteoarthritic knees have more varus coronal alignment of the femur compared to young non-arthritic knees in a large cohort study

Abstract

Purpose Many surgeons are performing total knee arthroplasty (TKA) with an aim to reproducing native anatomical coronal alignment. Yet, it remains unclear if primary osteoarthritic and non-osteoarthritic populations have similar knee coronal alignment. This study aims to describe and compare the distribution of femoral and tibial coronal alignment in a large primary osteoarthritic cohort and a young non-osteoarthritic cohort. Methods This is a retrospective analysis of a monocentric prospectively gathered data, from 1990 to 2019, of 2859 consecutive primary osteoarthritic knees in 2279 patients. Patients underwent standardized long-leg radiographs. Femoral mechanical angle (FMA) and tibial mechanical angle (TMA) were digitally measured using software. Femoral, tibial and knee phenotypes were analyzed, and descriptive data were reported. Data were compared to a young non-osteoarthritic population previously described. ResultsIn osteoarthritic knees, the mean FMA was 91° ± 2.9° (range 86°-100°) and the mean TMA was 87° ± 3.1° (range 80°-94°). No signiicant diference was observed for FMA and TMA between genders. The most common femoral and tibial phenotypes were varus (38.7%) and neutral (37.1%). The most frequent knee phenotype was a varus femoral phenotype with a neutral tibial phenotype (15.5%), which is diferent to the non-osteoarthritic population. Conclusion This study showed the wide distribution of knee phenotypes in a large osteoarthritic cohort. There was more varus distribution of the femoral coronal alignment compared to a non-osteoarthritic population, suggesting consideration and potential adaptation of the realignment strategy of the femoral component during TKA. Level of evidence III.

Patients with varus knee osteoarthritis undergoing high tibial osteotomy exhibit more femoral varus but similar tibial morphology compared to non-arthritic varus knees

“…This study is the first to compare alignment parameters between varus non-arthritic knees and varus OA knees planned for HTO. The wide range of FMA and TMA reported in this study population alludes to a wide variability in knee phenotypes in both osteoarthritic and non-osteoarthritic patients, which is consistent with previous studies that evaluated knee phenotypes [14,24]. Hirschmann et al showed a great variability among knee phenotypes in non-arthritic patients [13][14][15]21].…”

“…This is an important finding which underpins the fact that osteotomy surgeons should question the underlying pathomorphological factors of knee OA and plan patient-specific corrections rather altering what might be normal morphology. This difference in femoral varus between groups was previously reported by Sappey-Marinier et al [24]. In their study, it was found that although the tibial coronal alignment was similar between osteoarthritic and non-arthritic populations, there was a higher degree of femoral varus in the osteoarthritic population.…”

“…To date, there is ambiguity with regard to the differences in phenotypes of alignment between non-arthritic knees and OA knees. One recent study compared the distribution of femoral and tibial coronal alignment in a large primary osteoarthritic cohort destined for total knee arthroplasty with a young non-osteoarthritic cohort [24]. They found that there was more femoral varus in patients with OA [24].…”

Osteoarthritic and non-osteoarthritic patients show comparable coronal knee joint line orientations in a cross-sectional study based on 3D reconstructed CT images

“…Our results are supported by two recent studies. Sappey‑Marinier et al described the alignment of 2859 OA patients based on weight-bearing long leg radiographic (LLR) measurements using the functional knee phenotype classification [ 17 ]. They excluded patients with severe bone loss (Ahlbäck classification > 3) and only reported femoral, tibial and knee phenotypes but not functional knee or limb phenotype.…”

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

“… 6 , 7 Thanks to these analyses, several authors have reported that the varus deformity is mainly due to the femoral axis in the osteoarthritic knee. 8 , 9 Indeed, the tibial coronal alignment was similar between osteoarthritic and non-osteoarthritic populations. 8 By contrast, there was a broader and more varus distribution of the femoral coronal alignment in the osteoarthritic population compared to the non-osteoarthritic population.…”