Using Triple-Density Bone Analog to Evaluate the Initial Fixation of a Cementless Tibial Implant

To achieve stable initial fixation and longevity of a cementless tibial implant, low relative motion between implant and bone is vital. Although many studies have been conducted to evaluate the micromotion in-vivo and in-vitro, the methods have been either too complicated to repeat consistently or too simple to truly represent proximal tibial behavior. In this investigation, an experimental micromotion test method was developed to test a commercially available cementless tibial implant using a 3-layer bone analog simulating subchondral, trabecular, and cortical bone and the results compared with the micromotion measurement from a single density polyurethane foam. The results indicate that there is a significant difference in micromotion between the single density foam and the 3-layer bone analog when an applied tipping moment increases.