Purpose The aim of this study was to analyse the coronal alignment of a large population of patients undergoing total knee arthroplasty using a modern classiication of the knee phenotypes found in a population of non-osteoarthritic individuals. Methods Five hundred and four navigated total knee arthroplasties were included in the OA group. The following angles were measured with a computer image-free navigation system: mechanical femorotibial angle measured on the medial side without stress and with maximum manual stress to reduce deformation, and medial distal femoral mechanical angle. The native medial distal femoral and medial proximal tibial angles (coronal orientation of the femoral or tibial joint line after correction of wear) were calculated. The data were analysed as categorical data. These data were then compared with those published in a non-arthritic population, considered as a control non-OA group. The main criterion was the percentage of subjects with normal overall coronal alignment, deined by the association of a normal native medial distal femoral angle and a normal native medial proximal tibial angle. The secondary criteria were the percentages of subjects with normal medial femorotibial mechanical angle, normal native medial distal femoral angle and normal native medial proximal tibial angle. The inluence of gender on primary and secondary criteria in the study group was analysed. The most frequent phenotypes in the study group were identiied. Results Normal overall coronal alignment was found in 66 patients in the OA group (12.7%) and 76 patients in the non-OAgroup (24.7%) (p < 0.01 after adjustment by gender). There were fewer normal patients in the OA-group than in the non-OAgroup for medial femorotibial mechanical angle, native medial distal femoral angle and native medial proximal tibial angle. In females, there were signiicantly fewer normal medial femorotibial mechanical angle. In males, there were signiicantly more cases with native medial distal femoral varus and in females more cases with native medial distal femoral valgus. There was no signiicant inluence of gender on native medial proximal tibial angle. There was a wider distribution of the phenotypes in the OA-group than in the non-OA-group. ConclusionThe distribution of functional phenotypes of the knee in patients undergoing total knee arthroplasty is diferent from those found in a reference non-osteoarthritic population. Level of evidence Level III-retrospective cohort study.

IV, retrospective study.

Purpose The aim of this study was to analyze and quantify the changes in native coronal alignment of a population of TKA patients according to diferent alignment goals. Methods Five hundred and twenty TKAs were analyzed. The following angles were measured using an image-free navigation system prior to prosthetic implantation: medial femorotibial mechanical angle without stress and with maximum manual stress to reduce the deformity, medial distal femoral mechanical angle, medial proximal tibial mechanical angle. The native angles were derived from the osteoarthritic knee angles using a validated correction technique, and the overall, femoral and tibial coronal phenotypes were deined. Five diferent coronal alignment techniques were simulated: mechanical (MA), restricted mechanical (RMA), anatomical (AA), kinematic (KA) and restricted kinematic (RKA). The overall, femoral and tibial coronal phenotypes were compared before and after TKA. The primary endpoint was the binary criterion of whether or not TKA restored the natural overall phenotype. Secondary endpoints were the binary criteria of whether or not the natural femoral and tibial phenotypes were restored by TKA. The rates of restored and non restored phenotypes were compared with a Chi-square test at a 0.05 level of signiicance, with post hoc tests between all pairs of techniques at a 0.01 level of signiicance. ResultsThe overall phenotype was restored signiicantly diferently by the ive alignment techniques: 15% for MA, 23% for RMA, 2% for AA, 100% for KA and 79% for RKA (p < 0.001). There was a signiicant diference between each of the technique pairs (p < 0.01 to p < 0.001), except for the mechanical alignment-restricted mechanical alignment pair. The femoral phenotype was restored signiicantly diferently by the ive alignment techniques: 37% for MA, 58% for RMA, 19% for AA, 100% for KA and 85% for RKA (p < 0.001). The tibial phenotype was restored signiicantly diferently by the ive alignment techniques: 36% for MA, 36% for RMA, 17% for AA, 100% for KA and 88% for RKA (p < 0.001). There was a signiicant diference between each pair of techniques for both femoral and tibial phenotypes (p < 0.01 to p < 0.001). Conclusion Except for the kinematic alignment technique, the various alignment techniques induce signiicant changes in the pre-arthritic anatomy of the TKA patient. The surgeon must be aware of these modiications. The clinical relevance of this alteration still needs to be deined. Level of evidence III.

Purpose It is now well established that the coronal anatomy of the lower limb is highly variable both in non-arthritic subjects and subjects undergoing total knee arthroplasty (TKA). Two new classiications were recently described independently, but never compared: functional knee phenotypes classiication and coronal plane alignment of the knee (CPAK) classiication. The hypothesis of this study was that there was a signiicant diference between the values of the hip-knee-ankle angle (HKA) and the arithmetic hip-knee-ankle angle (aHKA) measures in the same patient at the time of TKA. Methods Five hundred and twenty cases were randomly selected among patients operated on for a TKA with navigation assistance. Anatomical parameters were collected during surgery by a navigation system, and the corresponding data of the CPAK classiication were calculated. The numerical values of measured HKA and aHKA in the same patient were compared. ResultsThe measured HKA had a mean of 3.0° varus (standard deviation of 6.0°). The calculated aHKA had a mean of 1.8° varus (standard deviation 4.8°). There was a signiicant diference between the values of the two measurements in the same subject (p = 0.005) and a weak negative correlation between the values of the two measurements in the same subject. In addition, there was no relationship between HKA values and joint line obliquity values or CPAK class. Conclusion A signiicant diference and a weak correlation between the values of the HKA and aHKA measures in the same subject were observed. The two analysis techniques used provide diferent information, and their correlation is only partial. These two techniques therefore appear to be complementary rather than exclusive. The clinical relevance of using these techniques during TKA remains unknown. Level of evidence III.

No abstract