Comparison of mobile-bearing and fixed-bearing total knee arthroplasty in patients with severe varus deformity: A triple-blind randomized controlled trial

Abstract

BACKGROUND: Total knee arthroplasty (TKA) is a common intervention for end-stage knee osteoarthritis, particularly in cases with severe varus deformity. While mobile-bearing (MB) prostheses are designed to offer biomechanical advantages over fixed-bearing (FB) implants, their clinical superiority remains debated, especially in complex deformities. OBJECTIVE: To compare the clinical and radiological outcomes of MB versus FB TKA in patients with severe varus deformity using the same femoral component design. METHODS: This triple-blind randomized controlled trial included 70 patients with severe varus knee deformity (>5 degrees ), who were assigned to MB (n = 35) or FB (n = 35) TKA groups. All surgeries were performed by a single surgeon using a standardized protocol. Primary outcomes included range of motion (ROM), crepitus, alignment (hip-knee-ankle angle), pain (Visual Analogue Scale) and radiographic evaluations at baseline, and 6 months postoperatively. RESULTS: At 6 months, both groups showed significant improvements in ROM and Visual Analogue Scale (VAS) pain, with no statistically significant differences between them (FB: 121.43 +/- 13.53 degrees , MB: 121.71 +/- 13.45 degrees , P = 0.92 for ROM and FB: 16.57 +/- 11.86 degrees , MB: 20.86 +/- 15.02 degrees , P = 0.19 for VAS pain). However, the FB group had significantly greater residual varus alignment (4.85 +/- 3.97 degrees vs. 2.17 +/- 4.39 degrees , P = 0.008). One case of aseptic loosening occurred in the MB group. CONCLUSION: In patients with severe varus deformity undergoing TKA, MB implants resulted in improved postoperative alignment but yielded similar short-term functional outcomes compared to FB implants. Longer follow-up is necessary to determine the clinical relevance of these radiological differences.