COMPUTER-PREDICTION OF ADAPTIVE BONE REMODELING AROUND NONCEMENTED FEMORAL PROSTHESES - THE RELATIONSHIP BETWEEN DAMAGE-BASED AND STRAIN-BASED ALGORITHMS

Several mathematical models to predict tissue adaptation have been der ived since Julius Wolff proposed a function-form relationship for bone . These can be formulated as computational procedures (algorithms) to predict bone adaptation around implants. The objective of this paper w as to further develop the damage-adaptive algorithm, to test its valid ity, and to determine the relationship between it and algorithms based on strain energy. This was achieved using finite element models of th e proximal femur, one for the intact case and another for the case whe re a noncemented hip prosthesis is implanted. The finite element model s were generated using CT scan data. Initial bone resorption patterns around a femoral prosthesis following total hip arthroplasty were comp uted for both damage-adaptive and strain-adaptive adaptation rules. It is found that the damage-adaptive algorithm can successfully predict the bone's adaptive behaviour in response to altered mechanical loadin g provided that account is taken of the nonlinear nature of damage acc umulation. Predictions are made using a strain energy stimulus for com parison with the damage stimulus, and a theoretical relationship betwe en the two is proposed. It is shown that an advantage of the damage ap proach over strain-based approach is that the nonlinearity required to replicate clinically observed resorption patterns can be derived theo retically, whereas for strain-adaptive remodelling, empirical relation ships are assumed. (C) 1997 IPEM. Published by Elsevier Science Ltd.