Good clinical and radiological outcomes of the varus-valgus constrained mobile-bearing implant in revision total knee arthroplasty

PURPOSE Knee instability is one of the most common indications for having to undergo revision total knee arthroplasty (RTKA) and can be prevented with adequate implant selection and good surgical technique. Varus-valgus constrained implants (VVC) are indicated for cases of RTKA with absent ligament function in order to provide the necessary stability. While mobile-bearing articulations are thought to decrease the risk of aseptic loosening in comparison to their fixed-bearing counterparts, there is limited data on their outcomes. The purpose of our study is to present the clinical and radiological outcomes for patients undergoing an RTKA procedure with the mobile-bearing VVC implant. METHODS Between January 2008 to January 2018, 93 patients underwent RTKA with the use of varus-valgus mobile-bearing (VVCMB) prosthesis. The main indications for RTKA were instability 38.7% (n = 36), aseptic loosening 31.2% (n = 29), infection in 26.9% (n = 25), and other 3.3%. The mean follow-up time was 56 months. Clinical outcomes were assessed by knee society scores, range of motion, and rate of re-operation. RESULTS The mean knee society score increased significantly from 65.52 pre-operatively to 89.65 post-operatively (p < 0.001). The five year cumulative incidence of re-operation in our study was 7.53% (n = 7). Our study reported no cases of aseptic loosening or mobile-bearing spin-out. The number of flexion contractures decreased from n = 23 (24.7%) pre-operatively to n = 11 (11.8%) post-operatively (p < 0.05). CONCLUSION The VVC mobile-bearing prosthesis demonstrated good clinical outcomes and mid-term survivorship in patients undergoing RTKA. Additional follow-up is required in the long term.