Evaluation of the role of ligaments, facets and disc nucleus in lower cervical spine under compression and sagittal moments using finite element method

Cervical spinal instability due to ligamentous injury, degenerated disc and facetectomy is a subject of great controversy. There is no analytical inve stigation reported on the biomechanical response of cervical spine in these respects. Parametric study on the roles of ligaments, facets, and disc nuc leus of human lower cervical spine (C4-C6) was conducted for the very first time using noninvasive finite element method. A three-dimensional (3D) finite element (FE) model of the human lower cervi cal spine. consisted of 11,187 nodes and 7730 elements modeling the bony ve rtebrae, articulating facets, intervertebral disc, and associated ligaments , was developed and validated against the published data under three load c onfigurations: axial compression; flexion; and extension. The FE model was further modified accordingly to investigate the role of disc, facets and li gaments in preserving cervical spine motion segment stability in these load configurations. The passive FE model predicted the nonlinear force displac ement response of the human cervical spine, with increasing stiffness at hi gher loads. It also predicted that ligaments, facets or disc nucleus are cr ucial to maintain the cervical spine stability, in terms of sagittal rotati onal movement or redistribution of load. FE method of analysis is an invalu able application that can supplement experimental research in understanding the clinical biomechanics of the human cervical spine. (C) 2001 IPEM. Publ ished by Elsevier Science Ltd. All rights reserved.