Abstract
Artificial meniscal implants may replace severely injured meniscus and restore the normal functionality of the knee joint. Implant material stiffness and shape influence the longevity of implantations. This study, using 3D finite element analysis, aimed to evaluate the effects of material stiffness variations of anatomically shaped artificial meniscal implant in the knee joint. Finite element simulations were conducted on five different cases including intact knee, medial meniscectomized knee, and the knee joint with the meniscal implant with three distinct material stiffness. Cartilage contact pressures, compression stresses, shear stresses, and implant kinematics (medial-lateral and posterior-anterior displacement) were evaluated for an axial compressive load of 1150 N at full extension. Compared to the meniscectomized knee, the knee joint with the meniscal implant induced lower peak cartilage contact pressure and reduced the cartilage regions loaded with contact pressures greater than the peak cartilage contact pressure induced by the intact knee. Results of the current study also demonstrate that cartilage contact pressures and implant displacement are sensitive to the implant material stiffness. The meniscal implant with a stiffness of 11 MPa restores the intact knee contact mechanics, thereby reducing the risk of physiological damage to the articular cartilage.
Highlights
The menisci play a crucial role in the knee, by stabilizing the joint and disseminating forces across the articulating surfaces[1]
In the knee joint with implant-1, the femoral and tibial cartilages were not loaded with contact pressures greater than 4.6 MPa and 5.7 MPa, respectively, while in the medial meniscectomized joint, the articular cartilages experienced significantly higher contact pressures (>4.6 MPa for femoral cartilage and >5.7 MPa for tibial cartilage) (Figs 2d, 3a,b,e,f)
The maximum contact pressure induced on the articular cartilages by the knee joint with implant-1 was considerably lower than the medial meniscectomized joint and proximate to the intact knee (4.6 MPa vs. 6.7 MPa vs. 4.6 MPa on the medial femoral cartilage and 5.2 MPa vs. 7.6 MPa vs 5.7 MPa on the medial tibial cartilage)
Summary
The menisci play a crucial role in the knee, by stabilizing the joint and disseminating forces across the articulating surfaces[1]. Meniscal allografts were seen to shrivel and experience collagen remodeling upon transplantation[7, 8], which affects the mechanical strength and may lead to allograft tears, articular instability, and degenerative damage. Studies have shown that a functional synthetic full meniscal implant could conceivably overcome the deficiencies of meniscus allograft transplantation[9,10,11,12]. Since the primary function of the meniscus is to resist and disseminate the forces across the articulating surfaces, the mechanical properties of the meniscal implants play a major role in their function[16, 17]. It is challenging to experimentally study the effect of material stiffness of the meniscal implant on the knee joint contact mechanics after implantation. It is a viable tool in providing physiological insights and assessing critical design parameters of the meniscal implants
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