Purpose: Previous studies have evaluated the ability of the gap technique to achieve accurate rotational placement in both posterior cruciate ligament (PCL)-retaining and PCL-substituting total knee arthroplasty (TKA). The purpose of the present study was to determine (1) the accuracy of this technique in degrees and (2) whether retention of the PCL affects the rotational alignment of the femoral component relative to the transepicondylar axis during TKA. The hypothesis of this study was that retention of the PCL does not affect the femoral rotational alignment in TKA using a gap-balancing technique because both procedures are reported to have good long-term clinical outcomes.
Methods: The femoral rotation angle (FRA) relative to the transepicondylar axis was examined in 206 patients who underwent primary TKA using either PCL-retaining (104 knees) or PCL-substituting (102 knees) prostheses to determine the effect of PCL retention on FRA. Quantitative three-dimensional computed tomography was used to assess the FRA in both groups. All values are expressed as median (25th percentile, 75th percentile).
Results: Postoperative FRA in the PCL-retaining group was -1.1° (-2.8°, 2.2°) and in the PCL-substituting group was -0.1° (-2.5°, 2.8°). The groups were not statistically different. One outlier was found in the PCL-retaining group, and none was found in the PCL-substituting group.
Conclusions: The gap technique reliably allows accurate rotational alignment of the femoral component during TKA despite the retention of the PCL.
Level of evidence: Therapeutic study, Level II.