Relation between subject-specific hip joint loading, stress distribution in the proximal femur and bone mineral density changes after total hip replacement

• Published in: Journal of biomechanics Vol. 41; no. 16; pp. 3405 - 3413
• Main Authors: Jonkers, Ilse, Sauwen, Nicolas, Lenaerts, Gerlinde, Mulier, Michiel, Van der Perre, Georges, Jaecques, Siegfried
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 05-12-2008; Elsevier Limited
• Subjects: Adult; Arthroplasty, Replacement, Hip; Biomechanics; Bone Density; Bone remodelling; Bones; Computer Simulation; Elastic Modulus; Female; Femur; Femur Head - physiopathology; Femur Head - surgery; Finite element; Finite element analysis; Gait; Geometry; Hip; Hip contact forces; Hip joint; Hip Joint - physiopathology; Hip Joint - surgery; Humans; Hydroxyapatite; Load; Male; Middle Aged; Models, Biological; Muscle forces; Musculoskeletal modelling; Physical Medicine and Rehabilitation; Pressure; Prostheses; Stress, Mechanical; Studies; Transplants & implants; Treatment Outcome; Weight-Bearing; Biomechanics; Femur; Gait; Musculoskeletal modelling; Bone remodelling; Bone density; Finite element analysis; Hip contact forces; Muscle forces; Hip; Finite element
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2008.09.011

Abstract In the prediction of bone remodelling processes after total hip replacement (THR), modelling of the subject-specific geometry is now state-of-the-art. In this study, we demonstrate that inclusion of subject-specific loading conditions drastically influences the calculated stress distribution, and hence influences the correlation between calculated stress distributions and changes in bone mineral density (BMD) after THR. For two patients who received cementless THR, personalized finite element (FE) models of the proximal femur were generated representing the pre- and post-operative geometry. FE analyses were performed by imposing subject-specific three-dimensional hip joint contact forces as well as muscle forces calculated based on gait analysis data. Average values of the von Mises stress were calculated for relevant zones of the proximal femur. Subsequently, the load cases were interchanged and the effect on the stress distribution was evaluated. Finally, the subject-specific stress distribution was correlated to the changes in BMD at 3 and 6 months after THR. We found subject-specific differences in the stress distribution induced by specific loading conditions, as interchanging of the loading also interchanged the patterns of the stress distribution. The correlation between the calculated stress distribution and the changes in BMD were affected by the two-dimensional nature of the BMD measurement. Our results confirm the hypothesis that inclusion of subject-specific hip contact forces and muscle forces drastically influences the stress distribution in the proximal femur. In addition to patient-specific geometry, inclusion of patient-specific loading is, therefore, essential to obtain accurate input for the analysis of stress distribution after THR.