Patient-specific medial unicompartmental knee arthroplasty has a greater protective effect on articular cartilage in the lateral compartment

Abstract

ObjectivesPatient-specific (PS) implantation surgical technology has been introduced in recent years and a gradual increase in the associated number of surgical cases has been observed. PS technology uses a patient’s own geometry in designing a medical device to provide minimal bone resection with improvement in the prosthetic bone coverage. However, whether PS unicompartmental knee arthroplasty (UKA) provides a better biomechanical effect than standard off-the-shelf prostheses for UKA has not yet been determined, and still remains controversial in both biomechanical and clinical fields. Therefore, the aim of this study was to compare the biomechanical effect between PS and standard off-the-shelf prostheses for UKA.MethodsThe contact stresses on the polyethylene (PE) insert, articular cartilage and lateral meniscus were evaluated in PS and standard off-the-shelf prostheses for UKA using a validated finite element model. Gait cycle loading was applied to evaluate the biomechanical effect in the PS and standard UKAs.ResultsThe contact stresses on the PE insert were similar for both the PS and standard UKAs. Compared with the standard UKA, the PS UKA did not show any biomechanical effect on the medial PE insert. However, the contact stresses on the articular cartilage and the meniscus in the lateral compartment following the PS UKA exhibited closer values to the healthy knee joint compared with the standard UKA.ConclusionThe PS UKA provided mechanics closer to those of the normal knee joint. The decreased contact stress on the opposite compartment may reduce the overall risk of progressive osteoarthritis.Cite this article: K-T. Kang, J. Son, D-S. Suh, S. K. Kwon, O-R. Kwon, Y-G. Koh. Patient-specific medial unicompartmental knee arthroplasty has a greater protective effect on articular cartilage in the lateral compartment: A Finite Element Analysis. Bone Joint Res 2018;7:20–27. DOI: 10.1302/2046-3758.71.BJR-2017-0115.R2.

Finite Element Study on the Preservation of Normal Knee Kinematics with Respect to the Prosthetic Design in Patient-Specific Medial Unicompartmental Knee Arthroplasty

“…Development of PS UKA. The PS medial UKA was based on previously existing three-dimensional (3D) knee joint model [18][19][20][21][22]. 3D knee joint model was developed using medical imaging data.…”

“…Planes were introduced through the intersection of condyles in both the sagittal and coronal views. [14,18,[23][24][25]. Intersection curves were used to extract the articulating surface geometry in sagittal and coronal plane.…”

“…Intersection curves were used to extract the articulating surface geometry in sagittal and coronal plane. Sagittal geometry of the femoral component was respected to patient's bone, and the resultant sagittal implant radii vary along the anteroposterior dimension of the implant [14,18,[23][24][25]. The coronal curvatures of the patient are measured at multiple positions along the length of the femoral condyle ( Figure 2).…”

“…PS UKA design was also used in the development of the finite element (FE) model. The intact model was previously developed and validated [18][19][20][21][22].…”

“…The interfaces between the articular cartilage and the bones were modeled as fully bonded [21,33]. Six pairs of TF contact between the femoral cartilage and the meniscus, the meniscus and the tibial cartilage, and the femoral cartilage and the tibial cartilage were modeled for both the medial and lateral sides of the joint [18,21]. The heights of the tibial insert for three different designs were matched to the original bone anatomy using a sagittal cross-sectional image, then aligned with the mechanical axis, and positioned at the medial edge with a square (0°) inclination in the coronal plane of the tibia [18,21,34].…”