Does metal backing improve fixation of tibial component in unicondylar knee arthroplasty? A randomized radiostereometric analysis

In a prospective, randomized study, patients with medial gonarthrosis stage I to III according to Ahlback were allocated to a unicondylar knee arthrop lasty (Miller-Galante, Zimmer. Inc., Warsaw. IN) with an all-polyethylene t ibial component or metal-backed tibial component of the same design. The pu rpose of the study was to evaluate if metal backing enhanced tibial compone nt fixation. A total of 45 knees (42 patients; 23 metal-backed components a nd 22 all-polyethylene components) were examined. We used radiostereometric analysis to measure micromotion of the tibial component over a period of 2 years after surgery. Hospital for Special Surgery score was used for clini cal evaluation. We found no statistically significant differences in clinic al results or migration of the tibial component over a 2-year follow-up per iod. These findings do not support better fixation of metal-backed tibial c omponents. Because of these findings, we advocate all-polyethylene tibial c omponents in unicondylar knee arthroplasties because of optimal biomechanic al strength at a given height of tibial component, avoiding potential probl ems of modularity and minimizing the amount of interfaces, at a lower cost.