The Design Of Positioning And Cutting Guide Plate For Unicompartmental Knee Joint Based On The Musculoskeletal Multibody Dynamics Simulation

Unicompartmental knee arthroplasty(UKA)is an important method for the treatment of human unicondylar knee arthritis.However,the prosthetic malalignment in UKA surgery leads to postoperative prosthetic failure,lateral cartilage degeneration,and other failure issues,which is a worldwide problem that currently limits the development of UKA surgery.Although customized positioning and cutting guide plates for knee joints have been developed and clinically applied,their clinical effects are still controversial.The design basis of customized positioning and cutting guide plates for knee joint is unclear,and the related biomechanical mechanism is unclear,which are the fundamental issues for limiting its promotion of UKA.Exploring the impact of UKA prosthesis installation errors on the mechanical load and joint motion of the knee joint after surgery is of great importance for reducing the rate of revision of knee joint and achieving accurate preoperative planning for UKA.This article established a musculoskeletal multibody dynamics model of UKA,quantitatively analyzed the impact of UKA prosthesis installation errors on the mechanics and kinematics of knee joint,explored the design basis of customized positioning and cutting guide plates for knee joint,and proposed a design method for customized positioning and cutting guide plates for knee joint in UKA.Based on the Force-dependent kinematics modeling method and elastic contact theory,this article established a musculoskeletal multibody dynamics model of UKA.Compared to previous studies,the developed model replaced the original definition of the hinged knee joint,established 11 degree of freedoms of inconformity knee joint,taking into account the elastic contact between femoral cartilage and lateral tibial cartilage,femoral cartilage and patellar cartilage,femoral cartilage and lateral tibial meniscus,and femoral prosthesis and tibial insert.Driven by gait data,the established model can simultaneously predict knee joint contact force,knee joint motion,muscle force and ligament force.Through indirect verification,the developed musculoskeletal multibody dynamics model of UKA could reasonably and effectively predict the mechanics and kinematics of knee joint.Based on the developed musculoskeletal multibody dynamics model of UKA,the effects of various prosthetic installation errors in UKA alignments on postoperative knee contact force and joint motion,such as varus-valgus angle,slope angle,internal-external angle,medial-lateral translation and articular line height,were studied using parametric methods.The study found that the safety range for medial-lateral translation is-2 mm to +3 mm(a/A range: 0.427 to 0.688),the safety range for joint line height is 0 mm to-2 mm,the safety range for slope angle is 0 °to 3 °,the safety range for varus-valgus angle is 0 ° to 3 °,and the safety range for internal-external rotation angle is-3 ° to 3 ° in UKA alignments.The research results provided a basis for the customized design of the positioning and cutting guide plates for knee jointBased on the predicted safety ranges for UKA alignments from musculoskeletal multibody dynamics model of UKA,using a patient’s knee joint imaging data,the cutting angle and cutting thickness for the patient’s knee joint were planned,the design positions for positioning holes of femoral and tibial guide plates were determined,and the surgical positioning and cutting guide plates for UKA was designed,manufactured by 3D printing technology,and tested in vitro environment.Compared to the traditional design method of positioning and cutting guide plates for UKA,the proposed new design method in this article would clearly clarify the control accuracy of prosthesis installation.Based on the musculoskeletal multibody dynamics model of UKA,this article clarified the safety range of UKA prosthesis installation,and proposed a new design method of positioning and cutting guide plates for UKA,provided a theoretical basis for the precision design of positioning and cutting guide plates and precision planning of UKA.