Intervertebral disc tissue-level mechanics

Fiber-reinforced tissues of the musculoskeletal system, such as the annulus fibrosus (AF) in the intervertebral disc, experience large, complex loads during daily activities. Repetitive or excessive loading of these tissues may initiate structural damage and lead to mechanical failure, causing debilitating pain and reduced mobility. Additionally, the structure and composition of intervertebral disc tissue is known to change with age and disease, which in turn alters the tissue mechanical response. Thus it is essential to comprehensively characterize the structure-function relations and failure mechanisms of these tissues in order to understand and prevent avoidable spinal injuries, particularly those occurring in the context of disease. Additionally, rigorous characterization of healthy tissue mechanics helps to establish design criterion for biological repair strategies that recapitulate native tissue behavior.

Using a combined experimental and computation approach, our lab has developed and validated novel mechanical testing techniques to ensure that tissue failure properties are robustly and consistently measured and reported (Werbner et al 2017). These techniques have since been applied to explore the effects of important physiological factors on the failure properties of the AF with more precision than had been previously possible. These include the effects of tissue hydration, which is known to decrease with age and degeneration, as well as loading rate, which changes under different injury scenarios (Werbner et al 2019). Using both human tissue and animal models, ongoing work continues to apply these techniques, as well as novel biochemical disease-models, to investigate how diseases such as diabetes and chronic kidney disease may increase patients’ susceptibility to disc degeneration and spinal injury. Additionally, years of combined experience assessing the mechanics of soft, fiber-reinforced composites has motivated our ongoing efforts to create a more comprehensive and transparent framework to understand the complex, and often unusual, behavior of such materials.

If you are interested in the most recent IVD tissue-level research updates, please feel free to contact Erin Archibeck (erinarchibeck at berkeley dot edu) or Minhao Zhou (minhao dot zhou at berkeley dot edu).