Femoral bowing affects varus femoral alignment but not patient satisfaction in mechanically aligned total knee arthroplasty.

Abstract

This study evaluated whether patients with particular lower limb morphological factors have femoral and tibial component malpositioning during mechanically aligned total knee arthroplasty (TKA) and lower postoperative satisfaction. This study included 146 knees in 117 Asian patients undergoing TKA for medial osteoarthritis. Preoperative bony morphological factors such as the angle between the femoral mechanical and anatomical axes (MA-AA angle), angle between the anatomical axes of the proximal and distal femur (lateral bowing femoral angle, LBFA), mechanical lateral distal femoral angle, medial proximal tibial angle, and % anatomical axis of the tibia were evaluated, as well as preoperative and 1-year postoperative 2011 Knee Society scores (KSSs). MA-AA angle and LBFA were significantly larger in knees with varus femoral component alignment versus neutral alignment. Preoperative MA-AA angle was underestimated in patients with larger MA-AA angle or LBFA, especially by inexperienced surgeons. Tibial morphological factors did not affect tibial component alignment. Changes in 2011 KSSs were similar among groups by lower limb alignment or femoral and tibial component alignment. Femoral bowing affects varus femoral component alignment by obscuring preoperative planning, but it had little impact on patient satisfaction when mechanical alignment is targeted during TKA.