Over five million Americans suffer from lower back pain, making it the leading cause of lost workdays in the United States. The origin of the low back pain is often the degenerated lumbar intervertebral disc. Current treatment options such as discectomy and/or spinal fusion fail to restore normal biomechanics of the spine. We are investing replacing the nucleus pulposus of the intervertebral disc with polymeric hydrogel implant. The present study reports the effect of polymeric hydrogel implant on the mechanical behavior of the human cadaveric lumbar functional spinal unit in axial compression. The implantation of the hydrogel implant in the denucleated specimen significantly restores the compressive behavior of the functional spinal unit. This implantation of a hydrogel nucleus replacement shows promise in restoring the normal biomechanics of the spine.