The Influence of Postoperative Tibiofemoral Alignment on the Clinical Results of Unicompartmental Knee Arthroplasty

PURPOSE To evaluate the influence of postoperative tibiofemoral alignment on the clinical results and failure in patients who underwent unicompartmental knee athroplasty (UKA). MATERIALS AND METHODS We reviewed 246 cases of medial UKA which were followed up for at least 5 years after the operation. The clinical results were compared between 5 groups classified according to the tibiofemoral angle that was measured at 3 months after surgery. We analyzed the relationship between the tibiofemoral alignment and the failure after UKA. RESULTS The preoperative tibiofemoral angle was changed from 0.4° of varus to 5.4° of valgus after surgery and the average correction angle was 5.8°. During the follow-up, which averaged 7 years and 5 months, the knee score and function score were improved significantly in all groups regardless of the tibiofemoral angle (p<0.01). There were no significant difference between the groups in the clinical results (p>0.05). However, there were significant differences in the cumulative survival rate of implants between the groups and the highest rate was found in the group with a tibiofemoral angle of 4° to 6° of valgus (p<0.01). CONCLUSIONS The tibiofemoral angle after UKA had no significant influence on the midterm clinical scores, but there was a significant relationship between the postoperative tibiofemoral angle and failure rate of implant.