Date Published: September 7, 2011
Publisher: SAGE-Hindawi Access to Research
Author(s): Ghassan S. Skaf, Chakib M. Ayoub, Nathalie T. Domloj, Massud J. Turbay, Cherine El-Zein, Mukbil H. Hourani.
It has been previously suggested in the literature that with aging, degenerative changes as well as disc herniation start at the lower lumbar segments, with higher disc involvement observed in an ascending fashion in older age groups. We conducted a study to investigate this correlation between age and level of disc herniation, and to associate it with the magnitude of the Lumbar Lordotic Angle (LLA), as measured by Cobb’s method. We followed retrospectively lumbosacral spine MRI’s of 1419 patients with symptomatic disc herniation. Pearson’s correlation was used in order to investigate the relationship between LLA, age, and level of disc herniation. Student’s t-test was applied to assess gender differences. Young patients were found to have higher LLA (R = 0.44, P < 0.0001) and lower levels of disc herniation (R = 0.302, P < 0.0001), whereas older patients had higher level herniation in lower LLA group (mean LLA 28.6° and 25.4°) and lower level herniation in high LLA group (mean LLA 33.2°). We concluded that Lumbar lordotic Cobb's angle and age can be predictors of the level of lumbar disc herniation. This did not differ among men and women (R = 0.341, P < 0.0001).
The mechanical properties of the intervertebral discs, as well as the interplay between the vertebral spine curvature and the ligaments and musculature that maintain it, not only impart a resilience that is important in protecting the vertebral column against compressive forces encountered in various postures , but largely determine the changes induced by aging, which are subsequently associated with degeneration , tropism [3, 4], disc herniation , and lordosis . These variations are level  as well as gender specific .
Lumbosacral spine MRIs of 2247 patients suffering from low back and sciatic pain were collected retrospectively. Clinical data was obtained from the American University of Beirut Medical Center neurological archive between 2002 and 2005. Subjects were healthy men and women, with ages ranging from 19 to 84 years old. 63% of the patients (N = 1419) had evidence of lumbar disc herniation, 25% showed disc degeneration without herniation at one or more levels (N = 560), and 12% had normal MRIs (N = 268).
Nowadays, it is estimated that at one time, 80% of the population will be afflicted with low back pain [15, 16]. Disc herniation, and degeneration which were found to increase with age [1, 5] were reported to be significant factors in the genesis of it. These changes can be attributed to trunk muscles imbalance , hypolordosis [6, 12], intervertebral stress distribution , and facet tropism [17, 18].
In conclusion, our study revealed that a crucial association exists between disc herniation level, age, and angle of lumbar lordosis. Disc herniation was found to occur at higher levels of the spine as age increased and lumbar lordotic Cobb’s angle decreased. This finding might be due to flattening of the spine, which begins in the fourth decade at lower lumbar levels and continues till the sixth decade at higher levels. It can also be correlated to trunk muscles imbalance, and the incidence of facet angle asymmetry, which, along with an increase in intervertebral discs stress distribution, would move the lumbar pressure points cranially with load bearing and aging. This would result in disc degeneration and herniation that start initially at the lower lumbar levels, except in cases where lumbar lordosis was found to be outside the predicted measure as implied by age, subsequently leading to unexpected levels of disc herniation.