Affiliations: [a] Department of Orthopedic Surgery, Yonsei University College of Medicine, Seoul, Republic of Korea | [b] Department of Orthopaedic Surgery, Joint Reconstruction Center, Yonsei Sarang Hospital, Seoul, Republic of Korea | [c] Department of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea | [d] Department of Anesthesiology and Pain Medicine, Hallym University College of Medicine, Kangdong Sacred Heart Hospital, Seoul, Republic of Korea
Correspondence:
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Corresponding author: Kyoung-Tak Kang, Ph.D., Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea. E-mail: tagi1024@gmail.com
Note: [†] Joon-Hee Park and Kyoung-Tak Kang contributed equally to this work and should be considered co-corresponding authors.
Abstract: BACKGROUND:Component malalignment in unicompartmental knee arthroplasty (UKA) has been related to the concentration in tibiofemoral joint of contact stress and to poor post-operative outcomes. Few studies investigated a biomechanical effect of femur component position in sagittal plane. The purpose of this study was to evaluate the biomechanical effect of the femoral components on the sagittal alignment under flexion and extension conditions using computational simulations. METHODS:The flexion and extension conditions of the femoral component were analyzed from 10° extension to 10° flexion in 1° increments. We considered the contact stresses in the polyethylene (PE) inserts and articular cartilage, and the force on the collateral ligament, under gait cycle conditions. RESULTS:The contact stress on the PE insert increased as flexion of the femoral component increased, but there was not a remarkable difference in the amount of increased contact stress upon extension. There was no difference in the contact stress on the articular cartilage upon extension of the femoral component, but it increased in flexion during stance and double support periods. The forces on the medial collateral ligaments increased with the extension and decreased with the flexion of the femoral component, whereas the forces on the lateral collateral ligaments showed opposite trends. CONCLUSIONS:Surgeons should be concerned with femoral component position on UKA not only in frontal plane but also in the sagittal plane, because flexion or extension of the femoral component may impact the PE or opposite compartment along with the surrounding ligaments around knee joint.
Keywords: Unicompartmental knee arthroplasty, malalignment, finite element analysis
