Investigation of failure and failure propagation in the intervertebral disc caused by mechanical overloads

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Acute onset of severe back pain is often caused by herniated intervertebral discs. In the liter-ature and through our own previous work within the framework of this project, it was shown that in particular, complex and dynamic loads increase the risk of intervertebral disc herni-ations in the lumbar spine. The aim of this DFG project was to investigate the mechanisms that might lead to a herniation in the lumbar intervertebral disc. In the course of the project, it was explored which patient activities and previous damage can cause tears in the lumbar intervertebral disc and how these might spread throughout the disc. For this purpose, human donor spines were loaded in an intervertebral disc loading simulator with different dynamic loading protocols. These dy-namic loading protocols reflect patient activities that are often associated with an increased risk of disc herniation, such as lifting heavy loads "with a hunched and rotated back". Using this new method, disc herniations were successfully provoked and studied more in detail in vitro on lumbar sheep and human spinal segments under physiological conditions. In addition to answering a variety of basic scientific questions about the mechanisms of lumbar disc her-niation, this allows to evaluate surgical procedures and new implants under realistic loading conditions. In the course of the current project, it also became apparent that transferring the findings from the lumbar spine to the cervical spine is not as trivial as had been assumed. The disc of the cervical spine differs structurally significantly from the lumbar one and is by far more flexible spinal segment and can therefore perform more extreme and complex movements. In further studies therefore, anatomical and structural differences of cervical motion segments and intervertebral discs in comparison to the lumbar spine will be investigated more in detail. On this basis, the loading protocol will be further developed. The aim of the project continua-tion is to further investigate cervical disc herniations and the mechanism of their origin and development with these loading protocols in order to define risk factors and to propose new therapy approaches. These protocols will then also be used to investigate implants for the cervical spine under realistic load conditions during everyday patient activities.