• Cheng-Fei Du, Chun-Jie Liu, Yun-Peng Huang, and Xin Wang.
• Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering, Tianjin University of Technology, Tianjin, China; National Demonstration Center for Experimental Mechanical and Electrical Engineering Education, Tianjin University of Technology, Tianjin, China.
• World Neurosurg. 2020 Feb 1; 134: e878-e884.

ObjectiveTo determine the effect of spiral nucleus implant parameters on the biomechanical behavior of the lumbar intervertebral disc after nucleus replacement under compressive loading.MethodsA finite element (FE) model of nucleus replacement in the L4-5 intervertebral disc was constructed. The effects of a spiral implant parameters, such as elasticity, size, and friction property, on the biomechanical behavior of the disc under a compressive load were determined. The effect of an implant with a sharp edge on disc biomechanics was also examined. The stress distribution and contact pressure on the endplate and AF, axial stiffness of disc, and annular bulge of the nucleus replacement models were investigated.ResultsAxial stiffness, annular bulge, and contact pressure were all insensitive to friction properties. Insertion of the spiral implant reversed the changes in the AF and endplates due to the removal of the nucleus. There was a positive correlation between axial stiffness and elasticity with implant size. Annular bulge was positively correlated with size but negatively correlated with elasticity. Compared with the base model, the implant with a sharp edge caused a decrease in disc axial stiffness but an increase in contact pressure on the AF in an annular bulge in the sagittal and coronal axis, respectively.ConclusionsA spiral implant may provide similar biomechanical behavior as a normal disc during compressive loading, with an optimal modulus of approximately 7 MPa. The spiral implant should fully conform to the nucleus cavity during replacement for the best biomechanical results.Copyright © 2019 Elsevier Inc. All rights reserved.

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