The Effect of Kinematic and Kinetic Changes on Meniscal Strains During Gait

Abstract

The menisci play an important role in load distribution, load bearing, joint stability, lubrication, and proprioception. Partial meniscectomy has been shown to result in changes in the kinematics and kinetics at the knee during gait that can lead to progressive meniscal degeneration. This study examined changes in the strains within the menisci associated with kinematic and kinetic changes during the gait cycle. The gait changes considered were a 5 deg shift toward external rotation of the tibia with respect to the femur and an increased medial-lateral load ratio representing an increased adduction moment. A finite element model of the knee was developed and tested using a cadaveric specimen. The cadaver was placed in positions representing heel-strike and midstance of the normal gait, and magnetic resonance images were taken. Comparisons of the model predictions to boundaries digitized from images acquired in the loaded states were within the errors produced by a 1 pixel shift of either meniscus. The finite element model predicted that an increased adduction moment caused increased strains of both the anterior and posterior horns of the medial meniscus. The lateral meniscus exhibited much lower strains and had minimal changes under the various loading conditions. The external tibial rotational change resulted in a 20% decrease in the strains in the posterior medial horn and increased strains in the anterior medial horn. The results of this study suggest that the shift toward external tibial rotation seen clinically after partial medial meniscectomy is not likely to cause subsequent degenerative medial meniscal damage, but the consequence of this kinematic shift on the pathogenesis of osteoarthritis following meniscectomy requires further consideration.

Deterioration of Stress Distribution Due to Tunnel Creation in Single-Bundle and Double-Bundle Anterior Cruciate Ligament Reconstructions

“…For the cartilage, the elastic moduli ranging from 5 to 15 MPa have been reported in previous studies. 10,23,28,30,44 The modulus of a viscoelastic material increases with loading rate, 29 thus, the low modulus of the cartilage (5 MPa) was chosen to simulate the quasistatic loading conditions in the present study. For the meniscus, both isotropic and transverse isotropic properties have been applied previously.…”

“…These mismatch volumes are within the range of the MR image pixel resolution (0.469 mm), as explained in literature. 28,44 Briefly, one pixel inferior shift of meniscus could generate a 12.36% volume mismatch for the medial meniscus and a 22.9% volume mismatch for the lateral meniscus. Thus, the developed FE model was verified.…”

“…Equation (1) and the stiff parameters of ACL (both AM and PL bundles), PCL, MCL, and LCL were cited from the literatures. 4,22,28 In addition, the subchondral plate could be a predisposing factor of the articular cartilage degeneration, 5,8,32,33 but it was difficult to identify in the MR images, therefore, the thickness of the subchondral bone was assumed to be 1.5 mm. 27 The subchondral bone was assumed to behave as a linear isotropic elastic material with a Young's Modulus of 1.15 GPa and a Poisson ratio of 0.25.…”

“…The ACL (both AM and PL bundles), posterior cruciate ligament (PCL), medial collateral ligament (MCL), lateral collateral ligament (LCL), and meniscal horns were modeled as bundles of one-dimensional nonlinear elements. 28,44 The material properties for the model were cited from literature. The cartilage was assumed to behave as a linear isotropic elastic material with a Young's Modulus of 5 MPa and a Poisson ratio of 0.35.…”

“…The initial lengths of the four attachments were respectively assumed to be 8.2, 14.7, 14.0, and 9.8 mm, whereas the cross-sectional areas were 8.6, 11.8, 14.8, and 8.63 mm 2 . 28 The ligaments were also simulated as one-dimensional nonlinear elements. Ligament strain was defined as e = DL/L 0 , whereas DL is the deformation of the length, and L 0 is the initial length of the ligament (zero load length).…”