Assessment of in vivo gait patterns on wear of total knee replacements

Lifespan of total knee replacements (TKR) is limited due to wear of the polyethylene tibial liner. Knee load and motion are major factors in TKR wear and are highly activity dependent. Gait is the most frequent activity for TKR patients, however, the effects of walking style (defined as 'gait pattern' by knee kinematics and kinetics) on wear are unknown. Existing testing standards (ISO) for prosthesis evaluation may not be representative of the population mean and do not consider variability. This study investigated the effect of gait pattern on TKR wear.;3D kinematic and kinetic profiles during level walking were obtained for TKR subjects. Analyses were conducted to confirm that individual gait adaptations varied within the population Kinematic and kinetic relationships were investigated to identify gait patterns. Knee wear simulation was conducted using the identified gait patterns, including the profile defined by ISO. Location-specific polyethylene wear was quantified using lanthanide tracers. Wear scar details and damage patterns were also recorded.;Gait was shown to be variable within the population and the testing standards were not kinematically representative of the average TKR patient. Two distinct gait patterns were identified based on the relationship between sagittal translation and the peak external flexion moment. These patterns were classified as high and low motion groups (HMG and LMG). Following wear testing, both in vivo gait patterns had higher wear rates (LMG 14.2+/-7.2 mg/mc; HMG 17.5+/-11.2 mg/mc; ISO 10.0+/-6.4 mg/mc, mean+/-SD), higher percentage of backside-to-total wear (LMG 15.9+/-5.5 %; HMG 19.9+/-2.0 %; ISO 2.8+/-1.6 %), larger percentage of worn-to-total wear areas (LMG 55.7+/-2.5 %; HMG 65.8+/-1.2 %; ISO 42.5+/-2.4 %) and visually more severe frontside and backside tibial damage compared with the standard. Additionally, the HMG showed had higher wear and more severe damage patterns compared with the LMG. The in vivo motion groups produced wear scars similar in size and location to retrievals.;In summary, gait pattern impacted TKR wear. Preclinical evaluation according to ISO underestimates wear occurrence in vivo. The international wear testing standards should be revised to represent realistic kinematics to provide accurate wear assessment for improved rehabilitation therapy and implant design.