Can robotic arm-assisted total knee arthroplasty be applied to valgus deformity

Total knee arthroplasty (TKA) in valgus knees is challenging. Optimal ligament balance, implant neutral or moderate valgus alignment are crucial but conventional instrumentations usually lead to outliers. Robotic arm assisted TKA (RATKA) advantages could answer this challenge. Objectives were to assess RATKA frontal alignment accuracy for valgus knees, rotational femoral component reliability, revision surgery rate and functional outcomes for this population.

This study is based on a continuous series of 454 RATKA. Implants were positioned according to a patient-specific alignment and postero-stabilised inserts were used. Valgus values, range of motion, KOOS and revision surgery rates were assessed at one-year postoperative. Femoral component rotation was analysed intraoperatively.

MAKO navigation system confirmed valgus preoperative deformity for 34 patients. Mean postoperative valgus value was - 1.5°±1.53 (range, -5 to 1), 85% patients had a residual valgus between 0 and - 3°, 97% of patients had a difference < 3° between valgus planned and valgus measured at one year postoperatively. Mean femoral rotation was + 2.65°±1.87 (range, 0 to 6.8°) of external rotation related to posterior condylar angle. No revision surgery has been performed. Mean KOOS value at one year was 80.79. 76% of patients (n = 26) had a good (70-80) or excellent (> 80) KOOS score. Mean flexion value was 133°±12 (range, 100 to 140).

RATKA can be applicable in valgus knee, offering high precision in component positioning with very few outliers. It also facilitates component rotation positioning, providing excellent functional results and ROM.