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Ankle joint biomechanics applied to computer-assisted total knee replacement Shute, Cameron

Abstract

In total knee arthroplasty, implants are aligned perpendicular to the mechanical axis of the lower limb (the line connecting the centre of the hip to the centre of the ankle). Currently, there is a very precise method for locating the centre of the hip, but not so for the centre of the ankle joint. In this study, I report on the two primary contributions I have made to the problem of locating a meaningful ankle centre for use in the computer-assisted total knee arthroplasty system we are developing at the University of British Columbia. The first contribution I made was by deriving the algorithms for use in fitting mathematical models of the ankle (both ball-in-socket and biaxial) to subject-specific data, and then performing the numerical and physical simulations to identify which algorithms are best suited to each model for use with our computer-assisted surgical system. The second contribution I made was my investigation of locating the ankle centre using these different ankle models mentioned above, in weight-bearing and non-weight-bearing, compared to locating the ankle centre using anatomic digitization. By conducting tests on 12 live subjects to identify the precision of each technique I found that the spherical method of ankle centre localization in the non-weight-bearing was the most reliable method of predicting the location of the ankle centre in weight-bearing.

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