• Yang Li, Zhenjun Zhang, Zhenhua Liao, Zhongjun Mo, and Weiqiang Liu.
• Department of Mechanical Engineering, Tsinghua University, Beijing, China.
• World Neurosurg. 2017 Oct 1; 106: 932-938.

BackgroundFinite element models have been widely used to predict biomechanical parameters of the cervical spine. Previous studies investigated the influence of position of rotational centers of prostheses on cervical biomechanical parameters after 1-level total disc replacement. The purpose of this study was to explore the effects of axial position of rotational centers of prostheses on cervical biomechanics after 2-level total disc replacement.MethodsA validated finite element model of C3-C7 segments and 2 prostheses, including the rotational center located at the superior endplate (SE) and inferior endplate (IE), was developed. Four total disc replacement models were used: 1) IE inserted at C4-C5 disc space and IE inserted at C5-C6 disc space (IE-IE), 2) IE-SE, 3) SE-IE, and 4) SE-SE. All models were subjected to displacement control combined with a 50 N follower load to simulate flexion and extension motions in the sagittal plane. For each case, biomechanical parameters, including predicted moments, range of rotation at each level, facet joint stress, and von Mises stress on the ultra-high-molecular-weight polyethylene core of the prostheses, were calculated.ResultsThe SE-IE model resulted in significantly lower stress at the cartilage level during extension and at the ultra-high-molecular-weight polyethylene cores when compared with the SE-SE construct and did not generate hypermotion at the C4-C5 level compared with the IE-SE and IE-IE constructs.ConclusionsBased on the present analysis, the SE-IE construct is recommended for treating cervical disease at the C4-C6 level. This study may provide a useful model to inform clinical operations.Copyright © 2017 Elsevier Inc. All rights reserved.

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