A Comparison in Proximal Tibial Strain Between Metal-Backed and All-Polyethylene Anatomic Graduated Component Total Knee Arthroplasty Tibial Components

Loading in total knee arthroplasty (TKA) is multifactorial and dependent on alignment, ligament balance, patient, and implant factors. Abnormal loading has been linked to clinical failure; however, the respective contribution of each factor to failure is not well known. This study defined the effect of metal backing on loading patterns in the proximal tibia. Composite tibiae were implanted with metal-backed and all-polyethylene Anatomic Graduated Component TKA tibial components (Biomet, Inc, Warsaw, Ind) and coated with photoelastic material allowing full-field dynamic strain quantification. In simulated varus loading distributions, significant increases in measured strain were observed ranging from 40% to 587% for all-polyethylene vs metal-backed tibial components. Higher observed strains in the proximal tibia observed with all-polyethylene tibial components could possibly explain increased clinical failure rates observed with this TKA design.