Publication

Abstract :

Introduction: Malalignment of prosthesis can compromise the clinical outcome. This is a prospectively designed comparative study of CAS with the conventional jig based ones. Here we measured the efficacy of CAS in reducing the outliers (i.e. from the accepted 3 degrees range) of tibial component alignment by comparing the Varus - valgus angles radiologically.

Material and Methods: We studied a total of 150 knees divided into two cohorts of 75 each operated in our institute. The treatment selection was random and a single surgeon performed most of the surgeries. Tibial tray alignment relative to the long axis of the tibial shaft was measured in the coronal plane in postoperative CT scanograms and/or radiographs. The target coronal alignment was 90° with respect to the tibial shaft axis. A total of 75 antero posterior radiographs and 75 CT scanograms were analyzed.

Results: The mean coronal alignment of the tibial component was 88.72° with a standard deviation of 2.36° in Jig based group and 89.45° ± 1.98° with CAS. Although the mean coronal alignment was not significantly different, the number of outliers was substantially reduced in the CAS group with a statistically significant data. In this study we also made an additional observation of having a better alignment of the femoral anatomic axis with the mechanical axis of the lower limb but needs further statistical confirmation.

Conclusions: Computer-assisted total knee replacement improves the frontal alignment of the tibial component in the coronal plane, and thus, increases the longevity and durability of the joint to improve the long and short-term clinical outcome