Long-term outcomes of one single-design varus valgus constrained versus one single-design rotating hinge in revision knee arthroplasty after over 10-year follow-up

BACKGROUND: The appropriate degree of constraint in knee prosthetic revision is unknown, necessitating the use of the lowest possible constraint. This study aimed to compare the long-term clinical and survival results of revision with rotation hinge knee (RHK) VS constrained condylar constrained knee (CCK) implants. METHODS: Overall, 117 revision case were prospectively reviewed and dividing into two groups based on the degree of constraint used, using only one prosthetic model in each group (61 CCK vs 56 RHK). All implants were evaluated for a minimum of 10 years. Survival of both implants at the end of follow-up, free from revision for any cause, aseptic loosening, and septic cause was compared. RESULTS: Better results were seen with use of the RHK in joint ranges of (p = 0.023), KSCS (p = 0.015), KSFS (p = 0.043), and KOOS (p = 0.031). About 22.2% of the cases required repeat surgery (11.7% RHK vs 29.6% CCK, p = 0.023). Constrained condylar implants had a significantly lower survival rates than rotating hinge implants (p = 0.005), due to a higher aseptic loosening rate (p = 0.031). CONCLUSION: Using a specific RHK design with less rotational constraint has better clinical and survival outcomes than implants with greater rotational constraint, such as one specific CCK.