The goal of kinematically aligned (KA) total knee arthroplasty (TKA) is to restore native knee anatomy. However, there are concerns about patellofemoral tracking problems with this technique that lead to early revision. We measured the differences between preoperative anatomic alignment and postoperative component alignment in a consecutive series of KA TKA and evaluated the association between alignment changes and the likelihood of early revision.
The charts of 219 patients who underwent 275 KA TKA procedures were reviewed. Preoperative anatomic alignment and postoperative tibial and femoral component alignment were measured radiographically. The difference in component alignment compared with preoperative anatomic alignment was compared between patients who underwent aseptic revision and those who did not at a minimum of 12 months of follow-up. Receiver operating characteristic curves were created for statistically significant variables, and the Youden index was used to determine optimal alignment thresholds with regard to likelihood of revision surgery.
Change in tibial component alignment compared with native alignment was greater (P = .005) in the revision group (5.0° ± 3.7° of increased varus compared with preoperative anatomic tibial angle) than in the nonrevision group (1.3° ± 4.2° of increased varus). The Youden index indicated that increasing tibial varus by >2.2° or more is associated with increased likelihood of revision. Preoperative anatomic alignment and change in femoral alignment and overall joint alignment (ie, Q angle) were not associated with increased likelihood of revision.
Small increases in tibial component varus compared with native alignment are associated with early aseptic revision in patients undergoing KA TKA.