Impact of Tibial Component Coronal Alignment on Knee Joint Biomechanics Following Fixed‐bearing Unicompartmental Knee Arthroplasty: A Finite Element Analysis

Abstract

Objective: Unicompartmental knee arthroplasty (UKA) has indicated a higher rate of revision than total knee arthroplasty (TKA). The success of UKA depends on UKA component alignment, fixation, and soft tissue integrity. The purpose of this study was to investigate the effects of different tibial component alignments in the coronal plane on the stress distribution in UKA. It was hypothesized that the stress distribution would approach native knee when the tibial component was neutrally positioned. Methods:The left legs from two healthy volunteers were considered to represent the geometric native knee models.All bones within the knee joint were extracted from the three-dimensional (3D) computed tomography (CT). MRI was used to generate cartilage, menisci, and four major ligaments. The UKA components were virtually implanted in the medial compartment of the knee model using MIMICS. A total of five different configurations of UKA tibial obliquity in the coronal plane (neutral, 3 varus, 6 varus, 3 valgus, and 6 valgus) were adopted and investigated. Subjectspecific inhomogeneous material properties of bones were used in the finite element analysis (FEA) model. The von Mises stress in the tibia platform and proximal tibia, and the load distribution between the medial and lateral compartments were extracted and compared among the five different configurations. Results:The inhomogeneous material properties of the trabecular bone were closer to real physics than traditional homogeneous methods. Neutral and 3 varus alignments of the tibial component in the coronal plane have better stress distribution between medial and lateral compartment as healthy knee models, and less stress-shielding effects than other UKA configurations. The stress pathway under the medial tibia platform in neutral and 3 varus UKA configurations was similar and more obvious than the other three UKA configurations. Notably, the stress of the medial tibia platform in the 3 varus UKA models was more homogenous than the neutral UKA configuration. The 6 varus, 3 valgus, and 6 valgus UKA models had higher stress at the location of anterolateral and posterolateral tibia platform than other UKA configurations. Conclusion:Neutral or 3 varus positioned in the coronal plane for the tibial component could be the optimal alignment for UKA. Excessive varus or valgus obliquity in the coronal plane lead to significant differences in bone stress transfer and load distribution in the knee, and increase the risk of UKA failure.

Restoration or relative overcorrection of pre-arthritic coronal alignment leads to improved results following medial unicompartmental knee arthroplasty

“…The application of an individualized alignment approach, guided by re‐tensioning of the MCL, has been shown to restore both joint line obliquity and the mechanical axis to its pre‐arthritic state following medial UKA for medial compartment OA [1]. Theoretically, restoration of the natural soft tissue envelope and knee kinematics may translate into reduced postoperative stiffness, better load distribution, and subsequently improved functional outcomes and survivorship [23, 27, 36]. However, supportive evidence on the clinical relevance of a pre‐arthritic alignment strategy remained scarce.…”

Mechanical overloading leads to chondrocyte degeneration and senescence via Zmpste24-mediated nuclear membrane instability

“…Three-node 3D rigid triangular facet elements (R3D3) were used for bony tissues, whereas for other soft tissues a 10-node quadratic tetrahedron (C3D10HM) element was used to improve computational efficiency. Referring to Nie's study 42 on mesh convergence analysis, the mesh size of bones was taken as 2.0 mm, and that of cartilage and ligaments was taken as 0.5-1.0 mm. The three-dimensional mesh model is shown in Figure 1 D. The elastic modulus of the linear elastic model of the cartilage was 15 Mpa, and Poisson's ratio was 0.475.…”

How effective is proximal fibular osteotomy in redistributing joint pressures? Insights from an HTO comparative in-silico study

“…A total force of 750 N was exerted vertically on the proximal head of the femur to replicate the complete weight of an average adult weighing 75 kg [37,46,52,53,[59][60][61][62][63][64].…”