Effect of Rotational Alignment On Patellar Tracking in Total Knee Arthroplasty

TLDR

Forty‑four patients (65 knees) received identical condylar‑type total knee arthroplasties, with the femoral component either neutrally aligned to the posterior condylar axis or externally rotated 3–5° relative to that axis. Externally rotating the femoral component lowered the need for lateral release from 34 % to 6 %, improved patellar tracking, and reduced the mean posterior condylar–transepicondylar angle from 7.9° to 3.2°, potentially decreasing patellofemoral complications.

Abstract

Forty-four consecutive patients (65 knees) who underwent identical condylar type total knee arthroplasty were evaluated retrospectively. In 22 of the patients (32 knees), the femoral component was set parallel to the posterior condylar axis (neutrally aligned group). In the remaining 22 patients (33 knees), it was set in an external rotation position of 3° to 5° relative to the axis (externally aligned group). Of the total knee arthroplasties in the neutrally aligned group, 34% required lateral release, compared with only 6% in the externally aligned group; patellar tracking in the externally aligned group was significantly better than that in the neutrally aligned group. Postoperative measurements performed using computed tomography scans showed that the mean angle between the prosthetic posterior condylar axis and the transepicondylar axis was 7.9° in the neutrally aligned group and 3.2° in the externally aligned group. The external rotation setting of the femoral component diminished the need for lateral retinacular release and may decrease the rate of patellofemoral complications that occur after total knee arthroplasty.