Author(s)

D.N. GHISTA, S.C. FAN, I. SRIDHAR & K. RAMAKRISHNA

Abstract

The intervertebral disc (IVD) acts as a shock-absorbing unit and effectively contains its lateral and axial deformations while providing the necessary flexibility to the spine. These attributes are due to the stress-stiffening material (elastic modulus) property of the annulus, caused by the pressure developed in the nucleus pulposus (NP). Hence, one of the biomechanical roles of the NP in the IVD is to stress the annulus while the IVD is loaded. In this paper, a closed-form solution of the IVD (with NP, i.e. a healthy IVD, and without NP, i.e. a nucleotomized IVD) under compressive loading is developed. Based on the analysis, it is observed that the deformations of the IVD do not increase in proportion to the load. Rather, the rate of increase in deformation decreases as the load increases. This is a key optimal feature because it means that deformations are contained and therefore stability is maintained. Further, it is shown that the nucleotomized IVD deforms more than the healthy IVD. This means

Keywords

deformation, internal pressure, intervertebral disc, nucleotomy, nucleus pulposus, stress analysis,