Background: Rotational malalignment of a femoral component may lead to chronic pain, patellar maltracking, knee instability, and early failure of a total knee arthroplasty [TKA]. The transepicondylar axis of the femur is widely accepted as a good reference for rotational alignment of a tibial component, although it is more controversial for a tibial component.

Objective: This study aimed to determine the degree of rotational mismatch between femoral and tibial components implanted using the center-post self-align technique.

Materials and Methods: Patients who underwent TKA for osteoarthritis of the knee were enrolled to have postoperative CT scans for determination of the rotational alignment. The study included 5l patients (60 knees), 5 males and 46 females, with a mean age of 64.0 years (range 58 to 73). The posterior cruciate ligament substituting tibial component position was set using the center-post self-align technique. CT digital images in the supine position with the knee at full extension were evaluated.

Results: Of the 60 TKAs, the mean rotational mismatch between tibial and femoral prostheses was 2.00° (SD+0.34°, range 0.l° to 5.8°). The femoral component was rotated externally and internally
within l.5° while the tibial component was within 2.59° relative to the transepicondylar axis. All knees had good patellar tracking intraoperatively without any lateral release procedure.

Conclusion: The center-post self-align technique can achieve good compatibility of rotational alignment between the femoral and tibial components with low variability, particularly with the knee in the extended position.

Keywords: Total knee arthroplasty; Rotational alignment of tibial component; Rotational mismatch; Self-align technique; Range of movement technique