Assessing the performance envelop of TKR using subject specific loads during stair ascent

Tan, K.H., Costigan, P. and Taylor, M. (2004) Assessing the performance envelop of TKR using subject specific loads during stair ascent. Transactions of the Annual Meeting - Orthopaedic Research Society, 29.

Abstract

The short and long term performance of total knee replacements are dependent on the mechanical environment of the joint. In particular, excessive polyethylene stresses and abnormal kinematics are likely to accelerate the wear process. In vivo fluoroscopy studies have reported highly variable kinematics for a given activity [1,2]. Total knee designs are likely to be subjected to a wide range of loading conditions in vivo. Morrison [3] and Costigan et al. [4] conducted gait kinematics and kinetic studies and obtained a range of force values within a group of individuals. For example, in Morrison’s study, the maximum knee joint reaction force during level gait was in the range of 2 – 4 times body weight. The majority of pre-clinical finite element studies only model idealized loading patterns, typically based on the ISO loading data of knee wear simulators. Tan et al. [5] examined the performance envelope during level gait by applying subject forces to an explicit FE model of a TKR. The study showed for that particular TKR the kinematics were relatively insensitive to subject specific loads, but the polyethylene stresses showed great variability. Other activities, for example stair ascent, are more demanding for TKR and therefore may produce larger variations in kinematics and polyethylene stresses than observed during level gait. Hence, the aim of this study was to assess the performance envelope of a TKR design when subjected to subjects’ specific loads for stair ascent.

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