The osseous endplates in lumbar vertebrae: thickness, bone mineral density and their associations with age and disk degeneration

Abstract

Introduction: As the gateway of nutrient supply, the vertebral endplate is essential to maintain the integrity and function of the avascular intervertebral disk. While a link between calcium deposition in the endplate and disk degeneration is well established from histological studies, findings on the association between endplate thickness and age and disk degeneration are conflicting. Moreover, the association between endplate bone mineral density (BMD) and disk degeneration remains unexplored in humans.

Objectives: To determine the thickness and BMD of lumbar spine osseous endplates in men and explore their associations with age and disk degeneration.

Methods: From a spine archive, 150 cadaveric lumbar vertebrae (L1-L5) from 48 male human spines (mean age 50 years, range 21-64) were scanned using micro-CT (μCT). The osseous endplates were extracted from the vertebral body to measure the mean thickness and volumetric BMD. The difference between cranial and caudal endplates, associations of endplate thickness and BMD with age and discographic degeneration pathology were examined.

Results: Overall, the mean thickness was 1.03±0.24 mm for cranial (to disk) endplates and 0.78±0.16 mm for caudal endplates. For lumbar intervertebral disks, the cranial endplate was significantly thicker and denser than the caudal endplate (p<0.001-0.05). Thickness and BMD of endplates were independent of age. Based on discography, a trend of more severe disk degeneration associated with greater thickness in both the cranial and caudal endplates was observed, and was most marked in severely degenerated disks (p<0.05). However, no evidence was detected for a link between more severe disk degeneration and elevated endplate BMD (p>0.05).

Conclusions: In the lumbar spine, both the thickness and BMD of endplates were independent of age, which ranged from 21 to 64 years. The endplates cranial to intervertebral disks were thicker and had higher BMD than the corresponding caudal endplates. Judged from discography, more degeneration in the adjacent intervertebral disk was associated with greater endplate thickness, but not higher endplate BMD. Thus, endplate sclerosis, reflecting elevated endplate BMD, may not be a risk factor for disk pathology in men.