Subject‐specific finite element analysis of the human medial collateral ligament during valgus knee loading

Abstract

The objectives of this study were (1) to develop subject-specific experimental and finite element (FE) techniques to study the three-dimensional stress-strain behavior of ligaments, with application to the human medial collateral ligament (MCL), and (2) to determine the importance of subject-specific material properties and initial (in situ) strain distribution for prediction of the strain distribution in the MCL under valgus loading. Eight male knees were subjected to varus-valgus loading at flexion angles of O", 30", and 60". Three-dimensional joint kinematics and MCL strains were recorded during kinematic testing. Following testing, the MCL of each knee was removed to allow measurement of the in situ strain distribution and to perform material testing. A FE model of the femur-MCL-tibia complex was constructed for each knee to simulate valgus loading at each flexion angle, using subject-specific bone and ligament geometry, material properties, and joint kinematics. A transversely isotropic hyperelastic material model was used to represent the MCL. The MCL in situ strain distribution at full extension was used to apply in situ strain to each MCL FE model. FE predicted MCL strains during valgus loading were compared to experimental measurements using regression analysis. The subject-specific FE predictions of strain correlated reasonably well with experimentally measured MCL strains (R' = 0.83, 0.72, and 0.66 at O", 30°, and 60", respectively). Despite large inter-subject variation in MCL material properties, MCL strain distributions predicted by individual FE models that used average MCL material properties were strongly correlated with subject-specific FE strain predictions (R' = 0.99 at all flexion angles). However, predictions by FE models that used average in situ strain distributions yielded relatively poor correlations with subject-specific FE predictions (R' = 0.44,0.35, and 0.33 at flexion angles of O", 30". and 60", respectively). The strain distribution within the MCL was nonuniform and changed with flexion angle. The highest MCL strains occurred at full extension in the posterior region of the MCL proximal to the joint line during valgus loading, suggesting this region may be most vulnerable to injury under these loading conditions. This work demonstrates that subject-specific FE models can predict the complex, nonuniform strain fields that occur in ligaments due to external loading of the joint.

Permeability of human medial collateral ligament in compression transverse to the collagen fiber direction

“…Second, because of its planar geometry and size, the MCL is ideal for harvesting transverse samples for direct measurement of permeability. Finally, the results of the present study may compliment existing experimental data on the quasi-static and viscoelastic material properties of the human MCL (Bonifasi-Lista Gardiner and Weiss, 2003;Haridas et al, 2001;Quapp and Weiss, 1998) for future investigations of the origins of ligament viscoelasticity. Five unpaired human knees (donor age 55716 yr, 4 males, 1 female) were obtained within 24 h of death and stored in sealed plastic bags at À20 1C.…”

“…Assuming that the direction of uniaxial tensile loading is the 1-direction, the normal stresses T 22 and T 33 are zero, which yields p ¼ T 11 =3: If the material is incompressible, which represents the time-zero behavior of a biphasic material, the pressure can be calculated analytically. Using published material coefficients for human MCL (Gardiner and Weiss, 2003), tensile strains of 1%, 3%, 5% and 10% along the fiber direction result in pressures of 0.26, 1.40, 4.44 and 19.00 MPa. The pressure gradients used in this study ranged from 0.17 to 2.76 MPa, corresponding to uniaxial tensile strains along the fiber direction of about 0.5-4%.…”

“…This is common for ligaments of the knee (Bendjaballah et al, 1997;Li et al, 2002;Sakane et al, 1999), and in particular the MCL (Gardiner and Weiss, 2003). Although our laboratory has performed subject-specific finite element simulations of the human MCL under valgus knee loading (Gardiner and Weiss, 2003), it is impossible to separate the pressure generated by the wrapping of the MCL around the tibia and femur from the pressure that is generated due to tensile stretch along the fiber direction, since the latter stretch is responsible for the wrapping.…”

FE analysis of stress and displacements occurring in the bony chain of leg

“…As in other vertebrates the tibia is one of two bones in the lower leg, the other being the fibula, and is a component of the knee and ankle joints. Gabriel et al 8 Table 4. As shown in table, displacements of tibia, found in this paper, result lower than literature ones, while the stresses are comparable, the same considerations can be done for the stress calculated on the feet.…”

Effect of six degrees of freedom knee kinematics on ligament length and moment arm in an intact knee model

“…For instance, computer modeling of the knee joint and surrounding tissues has been useful [15]. Finite element analysis may help describe the stress-strain characteristics of the knee joint and surrounding tissues, but is unsuitable for assessing high DOF motion associated with ligament length changes and moment arms due to the high computational and time costs [16][17][18][19]. Multibody dynamics software studies may be used to simulate the effect of ligament deficiencies on the knee and provide faster joint analyses over wide ranges of motion [20].…”