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Med Eng Phys. 2019 May;67:96-101. doi: 10.1016/j.medengphy.2019.02.016. Epub 2019 Mar 7.

Preliminary study on a novel minimally invasive extra-articular implant for unicompartmental knee osteoarthritis.

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Department of Mechanical Engineering, Auckland University of Technology, Auckland, New Zealand.
Department of Engineering Science, University of Auckland, Auckland, New Zealand. Electronic address:
Department of Orthopaedic Surgery, Whanganui Hospital, Whanganui, New Zealand.


The purpose of this research was to study the efficacy of a novel implant for osteoarthritic knees. This implant is designed to eliminate excessive loads through the knee and to provide suitable conditions for possible tibiofemoral cartilage repair. The implant was designed for the medial side of the knee joint. Finite Element Analysis (FEA) was performed for an extended knee position of the knee joint. Von Mises stress and contact pressure distributions on the medial and lateral compartments were investigated as well as stress distributions throughout the implant's plates. Comparison of FEA results with and without the implant showed that the maximum von Mises stress and contact pressure experienced by the femoral cartilage were reduced by 40% and 35%, respectively, after introducing the implant. Furthermore, after attaching the implant, the femur was slightly abducted and more stress and pressure were perceived in the lateral compartment compared to the model without implant. The maximum von Mises stress in the implant (96 MPa) was far lower than the yield strength of Ti-6Al-4V (∼900 MPa), the selected material for manufacturing the implant. According to the above points, this initial study shows promise for the new prosthesis.


Extra-articular; Implant; Knee; Minimally invasive; Osteoarthritis

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