A smaller size of the vertebra can protect against lumbar disc displacement

The human spine has evolved to become structurally weaker over the course of history. A new study of the University of Oulu shows that alongside the disadvantages resulting from this, the small size of the vertebrae may also be advantageous. A smaller cross-sectional area of a vertebra means a lower likelihood of disc herniation.

"The finding is somewhat surprising. One might think that a larger intervertebral disc would be more resilient. However, the study suggests otherwise," says Dr. Juho-Antti Junno, the lead researcher from the University of Oulu.

The study utilized a birth cohort of individuals born in Northern Finland in 1966, with over 1500 participants having their spines MRI-scanned at ages 46–48. Statistical methods were used to control for the effects of gender, education level, body mass index, physical activity, smoking, special diet, and vertebral height. The research was conducted by researchers from the University of Oulu and the Oulu University Hospital.

Various back problems are quite common throughout adulthood. Around one-fifth of the working-age population experiences back pain, often localized to the lower back. A significant cause of lower back pain is disc herniation, which, in addition to causing back pain, can also lead to leg pain and numbness.

The size and shape of vertebrae have changed significantly from, for example, the Middle Ages to the present day. Our vertebrae are now smaller, making the spine more susceptible to vertebral compression fractures in old age. Several studies in the field have shown that smaller vertebral cross-sectional size significantly increases the risk of fractures.

"We began to consider whether a smaller vertebra could potentially offer some benefits in exchange for age-related problems. Now it seems that the weakening of the spine due to the reduction in vertebral cross-sectional size is not solely detrimental to human spinal health. While the risk of vertebral compression fractures in old age does increase, smaller vertebrae could have benefits for spinal health in adulthood," says Dr. Junno.

The research findings may provide a new perspective, particularly for archaeologists studying the long-standing weakening observed in human skeletal robusticy. Relatively smaller and thinner bones might thus offer not only clear disadvantages but, in some cases, also potential health benefits.

The study has been published in the European Spine Journal.