Fixed-Bearing Posterior-Stabilized Implant versus Constrained Condylar Knee in One-Stage Bilateral Primary Arthroplasty of the Varus Knee: A Randomized Controlled Trial with Minimum 2-year Follow-Up.

Background: Severe varus deformity of the knee poses a technical challenge in balancing the flexion-extension gaps. The use of a varus-valgus constrained prosthesis is a solution to achieve coronal plane stability. The results of constrained condylar knee (CCK) implants in primary total knee arthroplasty are not well known. This study aims to compare the functional outcomes of posterior-stabilized (PS) and CCK implants for primary arthroplasty of the varus knee. Materials and Methods: Twenty patients with bilateral severe osteoarthritis and genu varum of more than 10° were enrolled in this study. One knee was randomly implanted with a fixed-bearing PS implant, whereas the other was implanted with a CCK prosthesis. Pre- and postoperative Knee Society Score (KSS) and Oxford Knee Score (OKS) questionnaires were completed, and knee flexion was measured and compared. Results: The patients were followed for 32 months on average (24-36 months). On the KSS and OKS, both the groups improved significantly, but the difference between them was not statistically significant. Postoperative knee flexion was also not different between the two groups. Furthermore, 18 patients could not distinguish the difference between the two prostheses, whereas two patients preferred the PS one. Conclusion: We demonstrated that a PS prosthesis can achieve comparable functional results to the CCK one in the short term.