Twin spine study indicates that spine curvature is heritable

Alvin H. Crawford, MD

This study presented at Spine Week 2012 comprises data collected from the Twins UK adult twin registry in the United Kingdom and investigates the heritable aspect of sagittal plane deformity in an aged >6o year old monozygotic (110) and dizygotic (136) female population. Most twin studies give valuable information on heritable diseases, and this one is no exception. The model used is in an age group that has significant variables is not included in their abstract. Their findings that sagittal plane deformities increased with age are not new. It is well known that thoracic kyphosis, and lumbar lordosis is most commonly influenced by bone mineral density and the ageing process along with disc degeneration including disc signal changes and osteophyte formation. Some of the age-associated variables would include environmental, occupation, life style, body habitus and, in this population, hormonal and gynecological issues as well as use or none use of bisphosphonates.

Finding of a specific gene is going to be a bit more of a challenge given the fact that the majority of these degenerative disc and subsequent spinal alignment changes could be accounted for by the variables noted in the previous paragraph. None of these factors were identified in the summary abstract.

I salute the author’s investigative work, and it would be of tremendous value to humans if they were to identify gene variants that may shed light on and give rise to therapeutic modalities on these spine problems that affect the majority of our ageing population.

Steven R. Garfin, MD

The authors do not discuss potential environmental epigenetic factors such as work, exercise (impact vs. nonimpact), lifestyles, stress, living conditions, etc. that may also affect degeneration and DNA-related effects. Since the study patients are all women with an average age of more than 64 years, there should have been a reasonable number with degenerative, and perhaps some isthmic or spondylolisthesis. Since they have the studies, it would also be interesting to assess for genetics.

Separately, the authors stated "surprisingly, we found the data supported the commonly held clinical view…" Why is that surprising? Empirical data often provides important clinical information, and should not be overlooked, nor should it be considered "surprising" when it is verified.

I feel their focus on "... identifying gene variance..." is important. I would encourage the authors to continue to explore biologic markers; though this might be challenging as there may be multiple genes and loci with associated activation/suppression proteins (tags).