Locations of Initial Failure in the Lower Cervical Spine: A Finite Element Investigation

Document Type

Article

Publication Date

8-19-2015

Abstract

The cervical region of the spine is the superiorly located vertebrae that make-up the neck. Like the thoracic and lumbar vertebrae, it is prone to diseases. The geometry of the vertebral bodies is both intricate and delicate as it includes bony and soft tissue musculature. The cervical vertebrae protect the spinal cord while maintaining flexibility and allowing movement in all directions. Institutional Review Board approval was obtained to access patient charts, computed tomography (CT), and limited magnetic resonance imaging (MRI) data. 15 finite element (FE) models were developed from various CT/MRI images. The FE models were homogenous, continuum, linear elastic models that were separated into two hierarchical structures. A comparison was made between a degenerated disc model and a model that considers a disc replacement with various materials used in artificial disc replacement devices. The models were loaded with2%global strain and analyzed for maximum and minimum principal strains. Strain was analyzed because its uniformity is independent of anatomical position. Yield strain was used as an indicator of failure initiation in the vertebral bodies with benchmark values of 400 and −450 × 10−6 for max and min principal strains, respectively. The results of this FE study show that failure based on yield criteria initiates in the trabecular core, which had higher strain levels than that of the cortical shell. It also indicates that the introduction of the much stiffer disc replacement material increases the strain values of the vertebral bodies by approximately ten times. This information will be important in the development of devices in identifying regions of failure initiation and how endplate materials affect the failure and subsidence of the vertebral bodies.

DOI

10.1088/2057-1976/1/2/025004

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