Subject Specific Finite Element Modeling of the Tibiofemoral Joint Based on CT, Magnetic Resonance Imaging and Dynamic Stereo Radiography Data in Vivo

Abstract

In this paper, we present a new methodology for subjectspecific finite element modeling of the tibiofemoral joint based on in vivo computed tomography (CT), magnetic resonance imaging (MRI), and dynamic stereoradiography (DSX) data. We implemented and compared two techniques to incorporate in vivo skeletal kinematics as boundary conditions: one used MRImeasured tibiofemoral kinematics in a nonweightbearing supine position and allowed five degrees of freedom (excluding flexionextension) at the joint in response to an axially applied force; the other used DSXmeasured tibiofemoral kinematics in a weightbearing standing position and permitted only axial translation in response to the same force. Verification and comparison of the model predictions employed data from a meniscus transplantation study subject with a meniscectomized and an intact knee. The modelpredicted cartilagecartilage contact areas were examined against “benchmarksâ€‌ from a novel in situ contact area analysis (ISCAA) in which the intersection volume between nondeformed femoral and tibial cartilage was characterized to determine the contact. The results showed that the DSXbased model predicted contact areas in close alignment with the benchmarks, and outperformed the MRIbased model: the contact centroid predicted by the former was on average 85% closer to the benchmark location. The DSXbased FE model predictions also indicated that the (lateral) meniscectomy increased the contact area in the lateral compartment and increased the maximum contact pressure and maximum compressive stress in both compartments. We discuss the importance of accurate, taskspecific skeletal kinematics in subjectspecific FE modeling, along with the effects of simplifying assumptions and limitations.