Good Mid-Term Implant Survival of a Novel Single-Design Rotating-Hinge Total Knee Arthroplasty

Background: Rotating-hinge knee (RHK) implants are an option for knee arthroplasty in cases of instability or severe bone loss. However, the revision rate can be increased compared to unconstrained implants which mandate improvements in implant design. This study investigates a novel RHK design for total knee arthroplasty (TKA). Methods: Retrospective analysis of a single design RHK TKA (GenuX MK, Implantcast) implanted between 2015 and 2019 including 133 patients (21 primary TKA, 112 revisions). The main indication for revision TKA was second-stage reimplantation following infection. The median follow-up amounted to 30 months (IQR 22-47). Results: In total, 13% (18/133) of patients underwent revision surgery after a mean time of 1 month (IQR 0-6). The main reason for the revision was (re-) infection in 8% of patients. All revisions were performed following revision TKA and none following primary TKA. There were no revision surgeries for loosening or instability. The revision-free implant survival of 83% was (95% CI 75-91%) after five years. A higher number of previous surgeries was associated with a greater revision risk (p = 0.05). Conclusion: Revision and complex primary TKA using a single-design RHK implant results in good implant survival at mid-term follow-up although infection remains a major concern.