Orthotropic bone remodelling around uncemented femoral implant: a comparison with isotropic formulation

• Published in: Biomechanics and modeling in mechanobiology Vol. 20; no. 3; pp. 1115 - 1134
• Main Authors: Mathai, Basil, Dhara, Santanu, Gupta, Sanjay
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.06.2021; Springer Nature B.V
• Subjects: Adaptation; Algorithms; Biological and Medical Physics; Biomedical Engineering and Bioengineering; Biophysics; Bone density; Bone remodeling; Bone resorption; Computed tomography; Engineering; Femur; Finite element method; Isotropic material; Material properties; Mathematical models; Mechanical loading; Original Paper; Prostheses; Regression analysis; Strain; Surgical implants; Theoretical and Applied Mechanics; Three dimensional models; Two dimensional models; Finite element analysis; Total hip replacement; Proximal femur; Bone remodelling; Bone orthotropy
• ISSN: 1617-7959; 1617-7940; 1617-7940
• DOI: 10.1007/s10237-021-01436-6

Peri-prosthetic bone adaptation has usually been predicted using subject-specific finite element analysis in combination with remodelling algorithms and assuming isotropic bone material property. The objective of the study is to develop an orthotropic bone remodelling algorithm for evaluation of peri-prosthetic bone adaptation in the uncemented implanted femur. The simulations considered loading conditions from a variety of daily activities. The orthotropic algorithm was tested on 2D and 3D models of the intact femur for verification of predicted results. The predicted orthotropic directionality, based on principal stress directions, was in agreement with the trabecular orientation in a micro-CT data of proximal femur. The validity of the proposed strain-based algorithm was assessed by comparing the predicted results of the orthotropic model with those of the strain-energy-density-based isotropic formulation. Despite agreement in cortical densities ( R = 0.71 ) , the isotropic remodelling algorithm tends to predict relatively higher values around the distal tip of the implant as compared to the orthotropic model. Both formulations predicted 4–8% bone resorption in the proximal femur. A linear regression analysis revealed a significant correlation ( R = 0.99 ) between the stresses and strains on the cortex of the proximal femur, predicted by the isotropic and orthotropic formulations. Despite reasonable agreement in peri-prosthetic bone density distributions, the quantitative differences with isotropic model predictions highlight the combined influences of bone orthotropy and mechanical stimulus in the adaptation process.