Evaluation of nucleus pulposus fluid velocity and pressure alteration induced by cartilage endplate sclerosis using a po
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ORIGINAL PAPER
Evaluation of nucleus pulposus fluid velocity and pressure alteration induced by cartilage endplate sclerosis using a poro‑elastic finite element analysis Chaudhry Raza Hassan1 · Wonsae Lee1 · David Edward Komatsu2 · Yi‑Xian Qin1 Received: 31 December 2019 / Accepted: 1 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The nucleus pulposus (NP) in the intervertebral disk (IVD) depends on diffusive fluid transport for nutrients through the cartilage endplate (CEP). Disruption in fluid exchange of the NP is considered a cause of IVD degeneration. Furthermore, CEP calcification and sclerosis are hypothesized to restrict fluid flow between the NP and CEP by decreasing permeability and porosity of the CEP matrix. We performed a finite element analysis of an L3–L4 lumbar functional spine unit with poro-elastic constitutive equations. The aim of the study was to predict changes in the solid and fluid parameters of the IVD and CEP under structural changes in CEP. A compressive load of 500 N was applied followed by a 10 Nm moment in extension, flexion, lateral bending, and axial rotation to the L3–L4 model with fully saturated IVD, CEP, and cancellous bone. A healthy case of L3–L4 physiology was then compared to two cases of CEP sclerosis: a calcified cartilage endplate and a fluid constricted sclerotic cartilage endplate. Predicted NP fluid velocity increased for the calcified CEP and decreased for the calcified + less permeable CEP. Decreased NP fluid velocity was prominent in the axial direction through the CEP due to a less permeable path available for fluid flux. Fluid pressure and maximum principal stress in the NP were predicted to increase in both cases of CEP sclerosis compared to the healthy case. The porous medium predictions of this analysis agree with the hypothesis that CEP sclerosis decreases fluid flow out of the NP, builds up fluid pressure in the NP, and increases the stress concentrations in the NP solid matrix. Keywords Cartilage endplate sclerosis · Disk degeneration · Finite element analysis · Fluid velocity · Fluid pressure
1 Introduction Low back pain is the leading cause of disability worldwide with 9% of the global population suffering some form of debilitation (Vos et al. 2012). Intervertebral disk degeneration (IDD) is a significant risk factor for low back pain, and one of the causes of IDD is alterations in nutrient fluid Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10237-020-01383-8) contains supplementary material, which is available to authorized users. * Yi‑Xian Qin yi‑[email protected] 1
Department of Biomedical Engineering, Stony Brook University, 215 Bioengineering Building, Stony Brook, NY 11794, USA
Department of Orthopaedics, School of Medicine, Stony Brook University, Stony Brook, NY, USA
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supply to the intervertebral disk (IVD) (Urban and Roberts 2003). The IVD is composed of two distinct structures: the nucleus pulposus (NP), an avascular fluid-filled structu
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