Effect of support on mechanical properties of the intervertebral disc in long-term compression testing

The complex kinematic structure and the method of support of the spinal motion segments significantly influence mechanical properties of the intervertebral disc (IVD). Because of this, the aim of this study was to analyse the effect of support of the spinal motion segment on selected mechanical properties of the intervertebral disc. The research involved two groups of study: with intact segments (IS) and with acutely injured segments (AIS). In a long-term cyclic compression test, the spinal segments were loaded with a force of 150-650 N. The study has shown that in the case of damage to articular processes, intervertebral disc height decreases by 0.09 mm, and this decrease is 50% greater than in the case of intact segments. The most significant increase in the stiffness coefficient, greater by 63% in the case of injured segments, occurs after 50 000 cycles, which leads to pathological changes taking place in the structure of annulus fibrosus. In assessing the mechanical properties presented in this study, we should bear in mind that this is not a description of the properties of the intervertebral disc alone but also of the elements working with it.