Computational Modeling of Hip Joint Mechanics

The hip joint is one of the largest weight bearing structures in the human body. While its efficient structure may lend to a lifetime of mobility, abnormal, repetitive loading of the hip is thought to result in osteoarthritis (OA). The etiology of hip OA is unknown however, due to the high loads this joint supports, mechanics have been implicated as the primary factor. Quantifying the relevant mechanical parameters in the joint (i.e. cartilage and bone stresses) appears to be central to an enhanced understanding of this disease. Experimental studies have provided valuable insight into baseline hip joint biomechanics but they require a protocol that is inherently invasive. Numerical modeling techniques, such as the finite element method, open the possibility of predicting hip joint biomechanics noninvasively and could revolutionize the way pathological hips are diagnosed and treated. Unfortunately, hip finite element models to date have used simplified geometry and have not been validated. It can be credibly argued that prior computational models of the hip joint do not have the ability to predict cartilage and bone mechanics with sufficient accuracy for clinical application. The aim of this dissertation is to develop and validate methods that will facilitate patient-specific modeling of hip joint biomechanics. Toward this objective, subjectspecific FE models of the pelvis and entire hip joint were developed. The accuracy of model geometry, i.e. cortical bone and cartilage thickness, was assessed using phantom based imaging studies. FE predictions were compared directly with experimental data for purposes of validation. The sensitivity of the models to errors in assumed and measured model inputs was quantified. Finally, recognizing that acetabular dysplasia may be the single most important contributor of hip joint OA, the validated modeling protocols were extended to analyze patient-specific models to demonstrate the general feasibility of the approach and to quantify differences in hip joint biomechanics between a normal and dysplastic hip joint. The developed modeling methodologies have a number of potential longer-term uses and benefits, including improved diagnosis of pathology, patientspecific approaches to treatment, and prediction of the success rate of corrective surgeries based on preand post-operative mechanics.