Functional Outcomes of Robotic-Assisted Total Knee Arthroplasty in Severe Varus Deformities of the Knee in the Indian Population.

PURPOSE

Correction of severe coronal plane deformities while performing a total knee arthroplasty (TKA) is challenging. The use of functional alignment (FA) strategy along with image-based robotic technology during TKA makes it possible to restore a patient's constitutional alignment with minimal or no soft tissue release. The present study aims to report the functional outcomes of robotic-assisted TKA in Indian patients with severe varus deformity.

METHODS

This retrospective study included 82 primary TKA performed by a single senior arthroplasty surgeon from January 2022 to December 2022. The Visual Analogue Score for Pain (VAS-P) and the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR) were used to assess functional outcomes. A comparison between mild and severe varus deformities was done using Student's t-test.

RESULTS

The mean age was 66.35 ± 9.21 years. There were 79 (96.34%) knees with a mean preoperative varus hip-knee-ankle angle (HKA) of 12.85° ± 6.03° (range = 177°-148°). Postoperative limb alignment was achieved in the range of HKA 174° to 180°, with mean HKA being 175.78° ± 1.35°. The VAS-P improved significantly from a mean of 7.87 ± 0.81 preoperatively to 1.96 ± 1.43 at 18 months. KOOS-JR improved from 41.22 ± 7.6 preoperatively to 88.44 ± 8.23 at 18 months. A total of 73 (89.02%) cases achieved the minimal clinically important difference (MCID) for VAS-P and 77 (93.9%) cases achieved the MCID for KOOS-JR in our study. Functional outcomes were comparable among the mild (<10°) and severe (>10°) varus deformity cases at 18 months follow-up (p-value > 0.05). There was a significant difference in bone resection from the medial tibial and medial distal femoral condyle (p-value < 0.05) with less bone resected in the severe varus group. The amount of bone resected from the lateral tibial, distal lateral femoral, and posterior femoral condyles was comparable among the two groups (p-value > 0.05). FA was more bone conserving even in severe varus-deformed knees when compared to mechanical alignment (MA).

CONCLUSION

The use of FA with robotic assistance to correct severe varus deformities in TKA showed a significant reduction in VAS-P scores and an improvement in KOOS-JR scores. The functional outcomes were comparable with TKA in mild varus deformities. FA helps in preserving bone from the lateral tibial condyle and distal femur.