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Twin spine study indicates that spine curvature is heritable
Researchers discovered lumbar lordosis was associated with features of disc degeneration.
Research using information from the TwinsUK adult twin registry in the United Kingdom finds that spine curvature is inherited and associated with lumbar disc degeneration.
“The curve highly correlated with adjacent curves, but not with more distant curves and all the curves were heritable and especially by the AE model,”
Williams and colleagues used the registry to identify 246 female twins (110 monozygotic and 136 dizygotic pairs) who had a mean age of 64.3 years. The researchers used pre-existing DEXA scans of each twin, took T2-weighted MRIs and radiographs of their spines, and coded each MRI into subtypes including disc signal intensity, disc height, anterior osteophytes and disc bulge intensity. Then they used SpineView (SpineView, Inc., Fremont, CA) software to calculate the angles of lumbar lordosis and thoracic kyphosis, and analyzed spine curves for their heritability.
They discovered lumbar lordosis and thoracic kyphosis increased with age and spine curvature was heritable at a rate of 59% for lumbar lordosis and 61% for thoracic kyphosis. Spinal curves were correlated with adjacent curves, but not more distant curves, according to Williams.
“Surprisingly, we found the data supported the commonly held clinical view, which is that thoracic kyphosis is most commonly influenced by bone mineral density and that lumbar lordosis was significantly associated with a number of features of disc degeneration including disc signal intensity and osteophyte formation,” she said.
The authors plan to identify genes associated with lumbar disc degeneration to gain a better understanding of the degenerative process. – by Renee Blisard Buddle
Reference:
Williams FMK. Spine curvature is heritable and associated with disc degeneration. Presented at: SpineWeek; May 28-June 1, 2012; Amsterdam.
For more information:
Frances M. K. Williams, PhD, FRCP (Edin), can be reached at The Department of Twin Research & Genetic Epidemiology, King’s College of London, St. Thomas’ Campus, Lambeth Palace Rd., London SE1 7EH UK; email: frances.williams@kcl.ac.uk.
Disclosure: The study was funded by Wellcome Trust and Arthritis Research UK.
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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.
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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).