Long-term results of Rotating Hinge Prosthesis

Ashok Rajgopal
Rotating Hinge Knee (RHK) has been considered as a salvage procedure in revision TKA and also in difficult primary arthritis. The usual indications included moderate to severe bone loss, collateral deficiencies, significant knee instability and severe of varus, valgus or flexion deformity. The failure rates of hinge knee designs were high in the earlier designs due to higher rigidity of the construct leading to excessive torsional and shearing forces at the bone-cement interface causing aseptic loosening and wear. Infection, peri-prosthetic fractures, patellar instability, etc are other major causes of failure. The RHK design allows for flexion-extension movement to be combined with rotation of tibial polyethylene liner on the metallic tibial tray. This decreases the stress transfer at the bone-prosthesis interface.The system allows fro antero-posterior and varus-valgus constraint while allowing flexion-extension and rotation movements. The tibial and femoral components are compatible with stem extensions and augments. Our experience with NexGen RHK prosthesis has been extremely satisfactory. In our study involving 46 knees at an average follow-up of 62 months, there was significant improvement in the mean flexion range (from 65⁰ to 96⁰) and the Knee Society Score (from 45 to 81) at final follow-up with low incidence of significant complications in the follow-up period.