Evaluation of Mechanical Adaptation on Preoperative Planning for Total Hip Arthroplasty

Bone structure can change by remodeling to adapt to mechanical status. Such change can result in bone affecting the long-term stability of the stem. The objective of this study was to propose a method to evaluate mechanical adaptation for preoperative planning of total hip arthroplasty. Finite element models of preoperative planning were examined in two ways: bone remodeling simulation and initial mechanical status of femur. A mathematical model of remodeling for long-term changes of bone was developed assuming that bone resorption/formation could be distinguished by strain magnitude of bone. Also, initial compatibility between stem and bone was set with four strain levels based on mechanostat theory. The results of bone remodeling simulation were shown average equivalent stress change was mainly observed in Gruen zone 1 and zone 7 where stress shielding or bone resorption could occur. The proportion of this value was the smallest in the first choice of the stem by a specialist surgeon. Also, these are showed same tendency with evaluation of initial strain distribution results that Gruen zone 1 and 7. Initial strain distribution after total hip arthroplasty was correlated with the long-term change of bone structures after total hip arthroplasty. Bone structure changes around prostheses occur due to changes in the mechanical environment, and this is correlated with strain distribution of immediate post-operative model. Findings of this study suggest that biomechanical indices might be useful for exploring difference in long-term fitting among different surgical plans.