Preoperative tibiofemoral contact point on standing lateral radiograph predicts anteroposterior knee kinematics in total knee arthroplasty.

PURPOSE

This study investigated the tibiofemoral contact point (CP) on standing lateral radiographs in knee osteoarthritis and assessed the relationship between CP and pre- and postoperative knee kinematics in total knee arthroplasty (TKA).

METHODS

The intraoperative knee status of 46 knees with varus deformity that underwent bicruciate stabilized TKA using a navigation system was investigated. The intraoperative anteroposterior (AP) position of the femur relative to the tibia at maximum extension, 15°, 30°, 45°, 60° and 90° was evaluated by the navigation system before and after TKA. The CP, defined as the CP between the femur and tibia, was assessed on standing lateral radiographs at the maximum extension of the knee before and 1 year after TKA. CP was expressed as the ratio of tibial plateau distance on a scale of 0-1, with 0 indicating the most anterior position of the femur relative to the tibia.

RESULTS

The mean CP on standing lateral radiographs was 0.54 ± 0.12 and 0.46 ± 0.08 before and after TKA, respectively. The postoperative CP was significantly more anterior than the preoperative CP ( = 0.0002). The mean AP position of the femur relative to the tibia moved anteriorly during early knee flexion both before and after TKA, representing nonanatomical AP movement. The preoperative posterior CP group (CP > 0.54) showed more nonanatomical AP movement from 15° to 60° before and after TKA compared with the preoperative anterior CP group (CP < 0.54).

CONCLUSION

Preoperative posterior deviation of the femur relative to the tibia in the standing position was a predictive factor for nonanatomical AP knee kinematics. Biomechanical analysis of postoperative knees will be necessary; however, surgeons should focus on preoperative tibiofemoral CP on standing lateral radiographs to predict knee kinematics.

LEVEL OF EVIDENCE

Level Ⅲ.