Kinematics and Early Clinical Outcomes of Navigated Total Knee Arthroplasty through a Lateral Subvastus Approach

Abstract

A procedure with subvastus lateral approach has been utilized routinely on 60 patients, navigation was used due to the reduced exposure of this technique. Purpose of this study was to evaluate pain, function, and implant kinematics at early follow up of this surgical technique.Tibial and femoral implant planning was based on ligament balance, gaps, and intraoperative kinematics. This approach, on pain and function, was verified at early follow- up. KSS and pain score were obtained at pre-op, 1, 3, 12 months. Data were analyzed with ANOVA for KSS and Chi-square for Pain.No intraoperative complications were registered, no patellar tendon lesion or avulsion was noted. Preoperative average leg alignment was 4±6° varus (range 16; -14), corrected to 0° (range 2; -1). Kinematic analysis showed rollback on lateral compartment, while on medial compartment rollback was lower or negligible until 70° of flexion. Less than 5% had a “Fair” or “Poor” KSS score after 3 months. Preop pain was: 41% severe; 50% moderate; 8% mild and 0% none. At 1 month pain was: 2% severe; 18% moderate; 55% mild and 25% none. After 3 months 50% of patients had mild and 50% had no pain. This data was maintained after 1 year, with 31% of patients with mild and 69% of patients no pain (p<0.05).This approach produced promising early outcomes in terms of pain, ROM and knee function, with less than 5% of patients presenting sub-optimal clinical results at 3- months. On symmetrical implant, medial pivot behavior was observed. Medial ligamental envelope preservation and navigated ligament balancing allow to optimize the medial stability and minimize the post-operative pain.