Activities of Daily Living and Their Impact on Total Knee Replacement Wear.

摘要

There are multiple factors affecting the wear performance of total knee replacement (TKR) polyethylene tibial components. The prosthesis (materials and design), the patient (height, weight, joint loading during daily activities and their frequency) and the surgeon (implant alignment and soft tissue balancing) all influence the wear performance. While many of these factors have been investigated, the contributions of patient factors, such as daily physical activities and activity level, are not fully understood.;This thesis investigated the effect of various daily physical activities on wear of TKR tibial components. In order to compare the contact damage patterns of in vivo and in vitro worn components, a neural network model has been developed with the aim of investigating how closely current ISO standards simulating level walking recreate in vivo damage patterns. It was hypothesized that various daily physical activities contribute considerably to the overall wear scar features of the tibial liner, and therefore, components tested under ISO conditions will not be fully representative. This was confirmed using a neural network model, which grouped the simulator wear scars with wear scars from retrieved components. Simulator tested components were clustered together, non-centrally into the periphery of the feature map.;To gain more knowledge about frequencies and durations of daily physical activities and their transitions, a sample TKR population was followed throughout the day. External knee moments and internal knee motions were estimated for the most frequent physical activities. The knee moments and motions were used to calculate knee contact forces using a parametric modeling approach. Two previously proposed wear models, based on sliding distance or crossshear motion, were used to assess the wear impact of different physical activities. An in vitro methodology to accelerate the creation and assessment of wear scars generated by different physical activities was also developed. This method was used to compare the wear scar characteristics of each physical activity with wear scars generated in vivo..;Among the various physical activities conducted throughout the day, those related to chair and stair were the most frequent and were therefore further investigated. In comparison to ISO walking, the loads and motions generated during chair and stair maneuvers were larger and applied for a longer period of time. Results from the sliding distance and cross-shear wear models indicated that the wear impact of chair and stair activities was substantial; going from 13% of the daily physical activity contribution to 29%, thus indicating that standardized preclinical wear evaluation may, in the worst case, only account for about 70% of the wear generated in vivo. Implementing stair ascent/descent and chair sitting/rising into the simulator protocol generated wear scars that were placed more centrally on the feature map when feeding the wear scar images into the neural network. The wear scar features produced by chair and stair activities shared more similarities with in vivo worn components than with those components tested according to ISO.;In conclusion, the results of this thesis suggest that daily physical activities, such as those related to chair and stair, should be included in standardized wear testing protocols for the preclinical wear evaluation of TKR prosthesis. Such a multi-activity wear testing protocol may generate wear conditions that better recreate those occurring in vivo..;Keywords: total knee replacement (TKR), polyethylene wear, daily physical activities, knee kinetics and kinematics, wear modeling.