The effect of nucleus implant modulus on the mechanical behavior of lumbar functional spinal unit: a finite element study

Low back pain is one of the most expensive health care issues today. The origin of the low back pain is often the degenerated lumbar intervertebral disc. Current treatment options include discectomy and/or spinal fusion, both of which relieve pain, but are ineffective in terms of restoring the normal biomechanics of the spine to a normal physiological state. We are investing replacing the nucleus pulposus of the intervertebral disc with polymeric hydrogel implant. The present study reports a validated axisymmetric finite element model of the lumbar functional spinal unit to determine the material properties of the hydrogel implant as a substitute for nucleus pulposus. Effect of hydrogel implant moduli on the mechanical behavior of the lumbar functional spinal unit is observed. Variation of intradiscal pressure with hydrogel implant moduli is predicted. The finite element model gives the range of hydrogel implant modulus as a replacement for degenerated nucleus pulposus.