The purpose of this study was to elucidate kinematic change according to the implant’s specific femoral rotation by using orthosensor (Verasense) implant with three degrees external rotation of femoral rotation rebuilt (Genesis-II) and traditional TKA implant without rebuilt of the femoral rotation (Anthem).
Twenty-eight patients (34 knees) underwent TKA using Anthem (Smith &Nephew, Memphis, TN, USA) and 16 patients (22 knees) underwent TKA using Genesis-II (Smith & Nephew, Memphis, TN, USA). Patients were followed up for at least 1 year. Mean age of patients was 71.1 years (range, 60 to 80 years) at the time of surgery. After implantation of femur and tibial components, we applied Verasense, the orthosensor system, to evaluate femoral rollback of the new artificial joint. Femoral rollback was analyzed using digitized screenshot function of Verasense.
Overall femoral tracking proportion regardless of implants was significantly higher on the medial compartment compared to that on the lateral compartment (13.3 ±8.4% vs. 6.3 ± 5.0%, p < 0.001). Regarding femoral tracking according to each compartment, Genesis-II and Anthem showed 12.1 ± 8.2% and 14.2 ± 8.6% ( p = 0.371) on the medial compartment and 8.0 ± 5.8% and 5.2 ± 4.2% ( p = 0.059) on the lateral compartment, respectively.
Our study showed reverse femoral roll-back movement with higher tracking distance on the lateral compartment during TKA. Genesis-II TKA system with femoral component 3-degree rebuilt showed less roll-back difference between medial and lateral compartments compared to traditional TKA system. Fortunately, both TKA systems had excellent short-term clinical outcomes without having significant difference between the two. With longer follow-up and larger cohort, the advantage and effectiveness of femoral component rotation can be elucidated in the future.