Viscoelastic Behaviour of the Human Spinal Disc

An intradiscal pressure transducer (IDPT) and a set of intervertebral pressure transducer (IVPT) were developed to measure the pressures in the nucleus pulposus and around the annulus. Human lumbar spinal segments were loaded up to 2.0 kN and following parameters were recorded: applied compressive load as a function of time, intradiscal pressure as a function of time, intervertebral pressure as a function of time for anterior and lateral edges of the vertebra, strain as a function of time for anterior and lateral right and left sites of the vertebra, stress-relaxation of the complete segment as a function of time. All show very similar response to loading and stress-relaxation. However, annulus pressure did not respond to stress-relaxation. This was due to functional aspect of annulus.