A new study appearing in the journal BMC Evolutionary Biology investigates the relationship between intervertebral disc herniation and vertebral shape and concludes that the condition preferentially affects individuals with vertebrae that are towards the ancestral end of the range of shape variation within H. sapiens (ie, closer to that of chimpanzees) and therefore are less well adapted for bipedalism. This finding not only has clinical implications for patients with back pain, but also illustrates the benefits of bringing the tools of evolutionary biology to bear on problems in medicine and public health.
Intervertebral disc herniation is a widespread but poorly understood cause of back pain. It is defined as a prolapse of the gelatinous substance inside the disc, the nucleus pulposus, either horizontally through the fibrous outer disc layers or vertically into the vertebral endplate. The study compared human, chimpanzee, and orangutan vertebrae to examine the links between vertebral shape, locomotion, and Schmorl’s nodes, which are bony indicators of vertical intervertebral disc herniation. The researchers found that human vertebrae with Schmorl’s nodes are closer in shape to chimpanzee vertebrae than are healthy human vertebrae. These results suggest that vertebral shape may be a factor that could help predict an individual’s susceptibility to vertical intervertebral disc herniation. It may be possible for clinicians to investigate an individual’s vertebral shape and identify those who may be at risk of developing the condition. In addition, a better understanding of the role that vertebral variation can play in spinal health could aid physiotherapists in refining activity and exercise regimes.
The journal article and abstract may be read here.