A COMPUTER-MODEL WITH SURFACE FRICTION FOR THE PREDICTION OF TOTAL KNEE KINEMATICS

A computer model was generated which modelled the bearing surfaces of total knees, and predicted the kinematics for a set of input forces an d moments. The model included friction al the bearing surfaces and sof t tissue restraint forces, including the effect of cruciate resection. Predictions from the model were compared with data from a Knee Simula ting Machine. There was close agreement in the shapes of the curves an d in the magnitudes of the displacements and rotations under most cond itions. The model predicted major differences in kinematics when frict ion between metal and polyethylene was included, the differences being even greater at the friction levels associated with small embedded ac rylic particles. Soft tissue restraint was shown to reduce the displac ements and rotations for tibial surfaces of low constraint but for mod erate to high constraint, the soft tissues affected the kinematics onl y slightly. When the model was used to predict the motions for differe nt condylar geometries, widely different contact paths on the tibial s urface were determined. This suggested that condylar geometries which appeared to be generally similar, could have important differences in kinematics, function and wear. Copyright (C) 1996 Elsevier Science Ltd .