Self-aligned Technique for Tibial Component Placement in Total Knee Arthroplasty Lessening Rotational Malalignment in Measured Resection and Gap-Balancing Techniques.

BACKGROUND

Femorotibial rotational mismatch can occur when there is a rotational malalignment in either the tibial or femoral component. Self-aligned technique was proposed for orienting the tibial component in relation to the femoral prosthesis to reduce rotational malalignment between components. Therefore, we aimed to compare the rotational angle of the femoral and tibial components, as well as the femorotibial rotational mismatch, between the measured resection (MR) and gap-balancing (GB) techniques when combined with a self-aligned technique.

METHODS

We conducted a nonrandomized, experimental study with 50 patients in each group. The femoral rotation was set to 3° external rotation relative to the posterior condylar axis in the MR group, whereas the femur was resected to obtain an optimal rectangular flexion gap in the GB group. The self-aligned method was used to set the tibial rotation in both groups. Femoral and tibial rotational alignments were evaluated compared to a surgical transepicondylar axis of the femur using computed tomography. Rotational mismatch was defined as a difference between the femoral and tibial rotational alignments. A positive value indicated that the component was externally rotated relative to the reference line.

RESULTS

The femoral component of the GB group was more externally rotated than that of the MR group (1.52° ± 1.31° vs 0.28° ± 1.16°, < 0.001). However, the tibial rotational angle was not statistically significantly different between the MR and GB groups (1.28° ± 3.17° vs. 1.86° ± 2.81°, = 0.220), and the rotational mismatch was 1.00° ± 3.28° and 0.34° ± 2.71°, respectively ( = 0.306).

CONCLUSIONS

Although the femoral component of the GB group had a greater degree of external rotation than that of the MR group, the use of a self-aligned technique for tibial component placement resulted in no significant difference in tibial rotational alignment or rotational mismatch. This technique helps align the tibial component with the femoral component and lessen the degree of rotational malalignment in both the MR and GB techniques.