Kinematic alignment in total knee arthroplasty restores the native anatomy, with a joint line parallel to the ground on a standing view

Abstract

Background: Kinematic alignment (KA) total knee arthroplasty (TKA) restores the native alignment of the knee joint. The present study compared the pre-and post-operative limb alignment of patients undergoing KA-TKA. It evaluated joint line orientation and obliquity on weight-bearing radiographs with the ground as reference. Methods: 56 patients treated with KA-TKA from January to December 2022 were prospectively included. The coronal orientation of the TKA was evaluated on pre- and postoperative anteroposterior long-leg weight-bearing radiographs. For each patient, measurements were made of the hip-knee-ankle (HKA) angle, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), arithmetic HKA (aHKA), and joint line obliquity (JLO). Results: The mean LDFA of all patients was 84.6◦ ± 1.7◦ pre-operatively and 84.5◦ ± 1.5◦ post-operatively (P = 0.06). The mean MPTA of all patients was 83.5◦ ± 1.6◦ pre-operatively and 85.1◦ ± 2.1◦ post-operatively (P = 0.07). The mean HKA of all patients was 172◦ ± 2◦ pre-operatively and 175◦ ± 2◦ post-operatively (P = 0.47). The difference in LDFA, MPTA, HKA, JLO and aHKA pre-operatively and post-operatively was not statistically significant. Conclusion: There were no differences in pre- and postoperative radiographic measurements and alignment of the lower limb in patients undergoing KA-TKA, with the joint line orientation parallel to the ground on weightbearing radiographs in all patients. Longer-term follow-up is necessary to assess the functional outcome and study implant survival of KA-TKA.