Promising Results of Total Knee Arthroplasty in Patients with Severe Varus Deformity with High Constrained Prosthesis: A Prospective Study.

Objectives: The existing literature does not provide a clear definition of the outcomes of total knee arthroplasty (TKA) and prosthesis constraint in patients with severe varus deformity. In this study, for the first time, we evaluated the outcomes of TKA and the relationship between prosthesis constraint and these outcomes in patients with severe varus deformity (>30 degrees). Methods: This prospective cohort study was conducted on 41 patients (54 knees) with varus deformity greater than 30 degrees who underwent TKA between April 2013 and April 2019. The patients were divided into two groups based on the type of prosthesis (high constraint and low constraint). Surgical outcomes were evaluated using the Knee Society Score (KSS), Oxford Knee Score (OKS), range of motion (ROM), and postoperative complications. Results: High-constrained prostheses (HCP) and low-constrained prostheses (LCP) were used in 44 and 10 knees, respectively. The mean follow-up duration was 77.11 ± 6.55 months. The mean KSS, KSS function, OKS, and ROM significantly improved after surgery compared to preoperative values (P<0.05). The mean improvement in the KSS function score after surgery was significantly higher in patients with HCP compared to those with LCP (p = 0.021). No significant differences were observed for the other variables. No cases required revision. Conclusion: This prospective non-randomized study, conducted on 41 patients (54 knees) with severe varus deformity (>30º) who underwent total knee arthroplasty (TKA), demonstrated that the mean improvement in the Knee Society Score (KSS) function score after surgery was greater for high-constrained prostheses (HCP, N = 44) compared to low-constrained prostheses (LCP, N = 10). The HCP group included 40 Legacy Constrained Condylar Knees (LCCK) and four hinged knee prostheses, while the LCP group included posterior-stabilizing (PS) prostheses. The mean follow-up duration was 6.5 years. Given the small sample size, randomized clinical trials are needed to validate our preliminary findings.