Osteoporosis delays intervertebral disc degeneration by increasing intradiscal diffusive transport of nutrients through both mechanical and vascular pathophysiological pathways

Abstract

Several studies have demonstrated an inverse correlation between osteoporosis and degenerative disc disease, so that patients with lower bone mass index, despite presenting greater risks of vertebral fractures, would paradoxically present delayed intervertebral disc degeneration. However the exact pathophysiological mechanisms underlying such phenomenon are not yet completely elucidated. In this article the author provides a general scheme to explain the causal relation between osteoporosis and delayed intervertebral disc degeneration by two main pathophysiological pathways: a vascular and a mechanical one. According to such model, osteoporosis positively affects disc nutrient diffusion through several mechanisms such as: increased endplate vascularization, decreased endplate resistance and decreased intradiscal strain. In the sequence a comprehensive review of the current literature on the issue is performed in order to provide a general overview about the current degree of evidence about the role of each factor postulated to be involved in such pathophysiological scheme. Finally the author provides overall directions for future research on the issue with special attention to the causal links which are supported by weak scientific evidence or by evidence from single studies.