Metal Backing Significantly Decreases Tibial Strains in a Medial Unicompartmental Knee Arthroplasty Model

Clinical success of unicompartmental knee arthroplasty (UKA) is on the rise and is dependent on multiple patient, implant, and surgical factors. Tibial subsidence has been clinically reported as a cause of failure in UKA with an all-polyethylene tibial design in the absence of metal backing, yet the role of metal backing UKA tibial components on tibial loading is not fully understood. In this study, composite tibiae were implanted with medial all-polyethylene fixed-bearing or metal-backed UKA tibial components and a 1.5-kN load applied in 3 different contact positions simulating femoral translation during gait. All-polyethylene tibial components exhibited significantly higher strain measurements in each femoral position. This study demonstrates the role that metal backing plays on generating an even loading distribution while diminishing the development localized regions of excessive loading across the medial tibial cortex.