Human Knee Joint Finite Element Model Using a Two Bundle Anterior Cruciate Ligament : Validation and Gait Analysis

Abstract

Anterior cruciate ligament (ACL) deficient individuals are at a much higher risk of developing osteoarthritis (OA) compared to those with intact ACLs, likely due to altered biomechanical loading [1]. Research indicates the ACL is comprised of two “bundles”, the anteromedial (AM) and posterolateral (PL) bundles [2]. Although the function of both bundles is to restrain anterior tibial translation (ATT), each bundle has their own distinct range of knee flexion where they are most effective [3]. Articular cartilage contact stress measurements are difficult to measure in vivo. An alternative approach is to use knee joint finite element models (FEMs) to predict soft tissue stresses and strains throughout the knee. Initial and boundary conditions for these FEMs may be determined from knee joint kinematics estimated from motion analysis experiments. However, there is a lack of knee joint FEMs which include both AM and PL bundles to predict changes to articular cartilage contact pressures resulting from ACL injuries. The purpose of this study is to develop and validate a knee joint FEM using both AM and PL bundles and subsequently perform a gait analysis of varying ACL injuries. METHODS FEM Development. An FEM of a right knee joint was built from sagittal plane magnetic resonance images (MRIs) (GE Medical Systems, Ideal GRE, TR=7.428ms, TE=4.16ms, slice spacing=1.5mm, flip angle=45°, pixel spacing=.3156) of a healthy, 33 year old male with no prior history of injuries. FEM tissue structures modeled included: femur and tibia bone; medial and lateral menisci; femoral and tibial articular cartilage; ACL, posterior cruciate (PCL), medial collateral (MCL) and lateral collateral (LCL) ligaments. The 3-D solids of the knee structures were created from the MR images using Mimics (Materialise NV, Leuven, Belgium) and were smoothed to remove any imperfections, before importing into SolidWorks (Dassault Systemes, Velizy-Villacoublay, France) to remove any residual overlap between structures. The ACL was divided into AM and PL bundles in SolidWorks based on their reported femoral and tibial attachment sites [4]. Soft tissue structures were meshed in TrueGrid (XYZ Scientific Applications, Inc., Livermore, California, USA) using linear, hexahedral elements. Bones were modeled as rigid bodies with 2-D shell elements. Each mesh was imported into Abaqus (Dessault Systemes, Velizy-Villacoublay, France) for FEM analyses (Figure 1). The articular cartilage and ligaments were attached to bone using tie constraints. The distal portion of the LCL had three sets of spring elements attached, acting in the longitudinal and transverse directions to mimic tension in this ligament [5,6]. The menisci were constrained to the tibia using four sets of spring elements [7]. Articular cartilage (E=15MPa, ν=0.475 [8]) and menisci (E=59MPa, ν=0.49 [9]) were modeled as a linear elastic, homogenous, isotropic materials. Ligaments were modeled as linear elastic, transversely isotropic, homogeneous materials (Table1) [10,11,12]. Table 1: Ligament material properties. EL (MPa) ET (MPa) ν12, ν13 ν23 G12, G13 (MPa) G23 (MPa) PCL,LCL,MCL 153.7 5.1 1.4 .3 1.72 1.9 AM 212.23 7.07 1.4 .3 1.72 1.9

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Cite this paper

@inproceedings{Czapla2015HumanKJ, title={Human Knee Joint Finite Element Model Using a Two Bundle Anterior Cruciate Ligament : Validation and Gait Analysis}, author={Aleksandra Czapla and Meghan K . Sylvia and Felicitas Lerner and David J . Tuttle and J . Schueckler and Scott J . Hazelwood and Monika Klisch}, year={2015} }