Finite Element Analysis of Mobile-bearing Unicompartmental Knee Arthroplasty

Abstract

Background:Controversies about the rational positioning of the tibial component in unicompartmental knee arthroplasty (UKA) still exist. Previous finite element (FE) studies were rare, and the results varied. This FE study aimed to analyze the influence of the tibial component coronal alignment on knee biomechanics in mobile-bearing UKA and find a ration range of inclination angles.Methods:A three-dimensional FE model of the intact knee was constructed from image data of one normal subject. A 1000 N compressive load was applied to the intact knee model for validating. Then a set of eleven UKA FE models was developed with the coronal inclination angles of the tibial tray ranging from 10° valgus to 10° varus. Tibial bone stresses and strains, contact pressures and load distribution in all UKA models were calculated and analyzed under the unified loading and boundary conditions.Results:Load distribution, contact pressures, and contact areas in intact knee model were validated. In UKA models, von Mises stress and compressive strain at proximal medial cortical bone increased significantly as the tibial tray was in valgus inclination >4°, which may increase the risk of residual pain. Compressive strains at tibial keel slot were above the high threshold with varus inclination >4°, which may result in greater risk of component migration. Tibial bone resection corner acted as a strain-raiser regardless of the inclination angles. Compressive strains at the resected surface slightly changed with the varying inclinations and were not supposed to induce bone resorption and component loosening. Contact pressures and load percentage in lateral compartment increased with the more varus inclination, which may lead to osteoarthritis progression.Conclusions:Static knee biomechanics after UKA can be greatly affected by tibial component coronal alignment. A range from 4° valgus to 4° varus inclination of tibial component can be recommended in mobile-bearing UKA.

Three-Dimensional Finite Analysis of the Optimal Alignment of the Tibial Implant in Unicompartmental Knee Arthroplasty

“…On the other hand, Sawatari et al 11 and Iesaka et al 12 reported that valgus alignment is preferable to get a satisfactory stress distribution using analysis of subchondral bone under the tibial component. Zhu et al 13 reported that the middle position is best. Thus, the optimal alignment of the tibial implant in UKA is still controversial.…”

Computational biomechanics of knee joint arthroplasty : a review

“…However, recent studies have focused not only on stress or strain on bone, but also looked at stress on soft tissue. Therefore, modeling not only of the femur, but also of cartilage and the lateral meniscus became required (Innocenti et al, 2014;Innocenti et al, 2016;Kang et al, 2018f;Kang et al, 2019c;Kang et al, 2018h;Kang et al, 2018i;Kang et al, 2018j;Kwon et al, 2014;Kwon et al, 2017;Park et al, 2019;Simpson, Price, Gulati, Murray and Gill, 2009;Wen et al, 2017;Zhu et al, 2015).…”

The effect of implant position on bone strain following lateral unicompartmental knee arthroplasty

“… 7 - 9 While previous biomechanical studies have shown that resection depth, component rotation and sagittal and coronal alignment of the tibial component can significantly affect proximal tibial strain after medial UKA, we are unaware of any published studies that evaluate the effect of implant position on tibial strain after lateral UKA. 10 , 11 …”