Clinical biomechanics of the spine in three unsolved problems. A brief analytical review

Abstract

Chronic pathology of the spine, especially its forms, such as degenerative disc disease (DDD), is one of the most common in the human population and a marker for a person. Even though this pathology lacks the burden of mortality, its existence and consequences worsen the quality of life. Hypotheses of the high prevalence of DDD often appeal to a person's upright gait and the function of the spine as a movable vertical support, which means a permanent significant axial load of the intervertebral discs (IVDs). Therefore, finding out the magnitude of such a load, its dependence on the body's position in space, and types of motor activity is an essential practical task of the biomechanics of the spine as a separate interdisciplinary direction of biomedical research.

Despite all the efforts and significant activity during the 70s and 80s of the last century, the central questions of clinical biomechanics of the spine still need to be explored. It is visible from the state of development of three "legendary" problems ‒ elucidation of intradiscal pressure against the background of usual types of physical activity, the role of sitting in the promotion of DDD of the lumbar region, and determination of the role of intra-abdominal pressure in reducing the axial load of this region of the spine. For example, the results of the investigations can state that assessment of intradiscal pressure against the background of human behavioral activity has so far been the focus of a disproportionately small number of works, which, due to the weakness of the accompanying visualization and the technical unreliability of the sensors did not obtain a sufficient empirical base for statistically significant conclusions. Therefore, the urgent task of the future is developing and using a more accurate, reliable, miniature, and durable intradiscal pressure monitoring technique, which would make it possible to evaluate this parameter on large samples of volunteers with conditionally intact IVD and against the background of pathology. In this regard, the assumptions about the role of sitting in the development of DDD of the lumbar spine remain unverified.
Similarly, the research on the phenomenon of intra-abdominal pressure needs to determine under what conditions and mechanisms this factor can affect the magnitude of the axial load on the lumbar spine. Also, constructing more insightful models of the biomechanics of the spine is only possible with expanding ideas about the composition, vascularization, and innervation of the IVD, biology, and pathology of IVD cells. The practical outcome of all these studies is delineation of the most dangerous types of motor activity in the promotion of DDD, which will bring us closer to understanding the drivers of DDD and thus improving the means of preventing and treating this ubiquitous pathology.