Age- and region-dependent changes in human lumbar vertebral bone: a histomorphometric study.

STUDY
DESIGN: Histomorphometric evaluation of autopsy material.
OBJECTIVES: To explore region-dependent changes that occur with aging in trabecular and cortical bone of the human vertebral body. SUMMARY OF BACKGROUND DATA: Human vertebral bone is continuously subjected to external forces (loads) that promote changes in inner architecture. This functional adaptability is limited, however, and when lost, vertebral bone progressively deteriorates and becomes subject to injury with increases in mechanical loading.
METHODS: Bone cylinders were drilled with a trephine from three regions (central anterior, central posterior, and lateral) of the third lumbar vertebral bodies of 48 autopsy cases 31 to 76 years old. Two consecutive 5-microm sections obtained 150 microm apart were stained with toluidine blue and Masson trichrome and photographed at x40. Differences in numerous morphometric factors were evaluated by age and region of the vertebra using repeated-measures analysis of variance and Tukey's Honestly Significant Difference test.
RESULTS: Starting at about 50 years of age, significant, linearly progressive decreases occurred in trabecular and cortical bone volume (P < 0.005), trabecular surface area (P < 0.001), number of trabeculae (P < 0.001), and thickness of trabeculae (P < 0.001). Space between trabeculae increased from ages 31 to 70 years and then decreased (P < 0.001). Trabecular deterioration was significantly more pronounced in central versus lateral regions (P < 0.001). Cortical bone thickness decreased significantly with aging in central regions but increased in lateral regions between ages 61 and 70 years (P < 0.001).
CONCLUSIONS: The balance between cortical and trabecular bone maintains the strength of the vertebral body until about the age of 50 years, when irreversible deterioration begins in central regions and subsequently involves lateral regions.