Biomechanical Evaluation of Isotropic and Shell-Core Composite Meniscal Implants for Total Meniscus Replacement: A Nonlinear Finite Element Study

Loss of meniscal function due to symptomatic meniscal tears or meniscectomy leads to biomechanical instability and articular cartilage degeneration. Synthetic meniscal implants ought to ideally restore normal joint contact mechanics and thus forfending the overlying cartilage from degeneration. The purpose of this study was to quantify the contact stresses in both tibiofemoral compartments and joint kinematics during a gait cycle after implantation of a synthetic meniscal implant. Anatomically-detailed finite element model of the knee joint was developed from magnetic resonance images of a healthy female volunteer. Gait analysis was conducted using a three-dimensional motion capture system and computed the knee joint forces and moments and quadriceps muscle forces for a complete walking cycle. The effects of a synthetic meniscal implant on joint mechanics during gait were studied by conducting finite element simulations for the following meniscus conditions: (i) intact meniscus, (ii) meniscus with complete radial posterior root tear, (iii) total meniscectomy, (iv) isotropic meniscal implant, and (v) shell-core composite meniscal implant. Posterior root tear and total meniscectomy caused substantially increased contact stresses in both tibiofemoral compartments and altered tibial kinematics. Compared to posterior root tear and total meniscectomy, the isotropic and composite meniscal implants reduced the peak contact stresses in both compartments and reduced the cartilage nodes with higher contact stresses by disseminating the load over a large surface area. The shell-core composite meniscal implant resulted in lower contact stresses in the medial compartment relative to the other meniscus conditions. This study demonstrated that posterior root tear and total meniscectomy leads to detrimental changes in joint mechanics. Superseding the injured meniscus with a synthetic meniscal implant restored the joint mechanics close to the intact meniscal state. This novel synthetic meniscal implantation approach appears to be a promising strategy for treating patients with severe meniscal injuries.