[Intradiscal pressure forces on cervical intervertebral discs in physiologic and pathologic conditions. In vitro study].

Clinical and experimental studies concerning intradiscal pressure have mainly been carried out using the lumbar spine. It has been shown that degenerative changes in the intervertebral disc and external loads can significantly influence intradiscal pressure. To see if these findings are also relevant for cervical discs, we carried out an in vitro study using human cervical spine specimens. The specimens were tested biomechanically under various conditions with simultaneous recording of intradiscal pressure in two cervical discs. We were able to confirm in vivo measurements of intradiscal pressure reported in the literature. Simulation of muscle force led to a marked increase in intradiscal pressure. Moreover, it was demonstrated that ventral cervical fusion has a significant influence on intradiscal pressure in both adjacent segments. In general, the results improve our understanding of the basic biomechanics of the cervical spine. The experiments with fused specimens could help to explain why degeneration is accelerated in adjacent motion segments after ventral cervical fusion.