Lumbar Disc Degeneration: Epidemiology and Genetics

Abstract

Research conducted over the past decade has led to a dramatic shift in the understanding of disc degeneration and its etiology. Previously, heavy physical loading-often associated with occupation-was the main suspected risk factor for disc degeneration, which was commonly viewed as a wear-and-tear phenomenon exacerbated by the precarious nutritional status of the disc. However, results of studies on twins suggest that physical loading specific to occupation and sport plays a relatively minor role in disc degeneration. Recent research indicates that heredity has a dominant role in disc degeneration, which would explain the variance of up to 74% seen in adult populations that have been studied to date. Since 1998, genetic influences have been confirmed by the identification of several gene forms associated with disc degeneration. This research is paving the way for a better understanding of the biologic mechanisms through which disc degeneration occurs, including specific interactions between genes and environment. Research into disc degeneration and genetics has become more limited by phenotypes or definitions and measures of disc degeneration than by DNA analysis. Standardized, universally accepted definitions of disc degeneration are lacking, in part due to limited knowledge of the process. The measurements that are selected depend on the method used to evaluate the disc and are often qualitative ordinal rating scales, lacking in precision. Although it is generally agreed that disc degeneration is common, the prevalence of specific findings is unclear. A review of the epidemiology of disc degeneration reveals wide-ranging prevalence estimates for various signs of disc degeneration in samples of the general population and in patients with back symptoms. The extreme variations in prevalence rates are likely largely due to inconsistencies in the definitions and measurements of disc degeneration. Such inconsistencies and inaccuracies impede epidemiologic research on disc degeneration.

Mid‐term evaluation of the effects of dynamic neutralization system on lumbar intervertebral discs using quantitative molecular MR imaging

“…The fact that after 2 years DT1 did not further increase in the treated levels, but on the contrary significantly decreased in the adjacent disc levels, supports the hypothesis that the initial worsening in previously normal segments was primarily due to the different load distribution generated by the device, and not by a spontaneously evolving discopathy at multiple lumbar levels in these patients because of their possible genetic disposition (36). Also, our results after 2 years confirm the previous observation that dynamic disc stabilization using Dynesys device seems able to lead to tissue regeneration in the more severely degenerated levels, thus improving GAG disc composition, with objective benefits for the patient.…”

Recurrent adjacent segment disease and cauda equina syndrome

“…Results of exposure-discordant monozygotic and classic twin studies suggest that mechanical factors play a very limited role in segmental spinal degeneration, while constitutional factors and heredity may have a dominant role, explaining 74% of the variance in the adult population studied to date [9]. In vitro studies have found altered biomechanics in the mobile segments adjacent to fusion, including increased mobility and increased intradiscal pressure [10,11].…”

“…It is likely that both genetics and mechanics play a role. Previous studies have shown that genetically determined natural progression of degeneration might be modified to some degree by environmental factors [9]. ASD is likely a consequence of normal degenerative progression influenced by altered biomechanics related to fusion [1,2,4,6,[13][14][15][16].…”

Adolescent disc dysplasia and back pain

“…Validated data for ADD specifically are not available, but prevalence figures for disc degeneration vary from 3 to 56%, with studies of patients with an average age of B21 years reporting a prevalence of up to 24%. The absence of standardized case definitions of disc degeneration hampers comparisons and interpretations of epidemiologic studies of disc degeneration [14]. Gender distribution is unclear, with some studies describing males being more commonly affected, while others report that both sexes are affected equally [14].…”

“…The absence of standardized case definitions of disc degeneration hampers comparisons and interpretations of epidemiologic studies of disc degeneration [14]. Gender distribution is unclear, with some studies describing males being more commonly affected, while others report that both sexes are affected equally [14].…”