Abstract
Introduction
The precise indications for tibial component metal backing and modularity remain controversial in routine primary total knee arthroplasty. This is particularly true in elderly patients where the perceived benefits of metal backing such as load redistribution and the reduction of polyethylene strain may be clinically less relevant. The cost implications for choosing a metal-backed design over an all-polyethylene design may exceed USD500 per primary knee arthroplasty case.
Methods
A prospective randomised clinical trial was carried out at the QEII Health Sciences Centre, Halifax, Nova Scotia, to compare modular metal-backed versus an all-polyethylene tibial component. Outcome measures included clinical range of motion, radiographs, survivorship, Knee Society Clinical Rating System, WOMAC and SF-12.
Results
116 patients requesting primary knee arthroplasty were recruited and randomised between the Smith & Nephew Genesis I non-modular (57) and modular (59) tibial designs between September 1995 and August 1997. At 10 years clinical follow-up, 4 implant revisions or intention-to-revise decisions were recorded in the metal-tray/modular group of which 2 were for aseptic tibial component loosening. 2 implant revisions in the all-polyethylene non-modular group were recorded, neither of which were for tibial component loosening. At 5, 7 and 10 year review; the KSCRS, WOMAC and SF12 scores were similar in both groups. As most patients randomised were over seventy years of age, this impacted significantly on the numbers available for longer term review and data was analysed by comparing pre- and post-operative scores for individual patients.
Conclusion
There was no difference in performance between the all-polyethylene tibial component and the metal-backed tibial component. The case for using the all-polyethylene tibia in elderly patients is justified on both clinical efficacy and cost-containment grounds.
