Mid-term clinical outcome of constrained condylar knee prosthesis for patients with rheumatoid arthritis

Objectives: This study retrospectively investigated the mid-term outcome of Legacy constrained condylar knee (LCCK) prosthesis in patients with rheumatoid arthritis (RA) having severe varus/valgus deformity, instability, and/or bone loss. Methods: Between January 2000 and December 2015, LCCK prostheses had been performed in 32 knees of 25 patients with RA, and 23 knees of 17 patients of the postoperative follow-up minimum 2 years were analyzed in this study (Primary: 14 knees, Revision: 9 knees). The average of follow-up duration was 6.9 ± 2.7 years, all were female, and the average of age and RA duration at the surgery was 59.0 ± 9.5 years and 26.6 ± 13.5 years, respectively. Clinical result was analyzed by Knee Society Score (KSS) knee and function at preoperative time and final visit. Imaging outcome was investigated by femoral tibial angle (FTA), four component alignment angles, and radiolucent line at pre-/postoperative time. Results: KSS knee/function scores and radiographic FTAs were improved after operation. Radiolucent lines around components were seen in 17 knees (73.9%), of which only one knee (4.3%) has shown aseptic loosening. The seven-year Kaplan-Meier survivorship analysis resulted in 91.7%. Conclusion: LCCK prosthesis in RA patients was achieved to the excellent mid-term clinical and radiographic result.