Abstract
Background
Computed tomography osteoabsorptiometry (CT-OAM) and micro-computed tomography (µCT) assess bone mineralization of the subchondral endplates and trabecular microstructure. In the lumbar spine, both bone types were analyzed and the results were correlated to understand their relationship in response to bone functional adaptation.
Methods
Using CT scans of 25 lumbar vertebrae, bone mineralization density of the superior (SEP) and inferior (IEP) endplates in six defined regions (left, central and right, at ventral and dorsal aspects) were examined for CT-OAM. For µCT, these regions were 3-dimensionally scanned and subdivided into six volumes of interest (VOI): the cranial and caudal 0–10%, 10–15%, and 25–50%. Five parameters evaluating trabecular architecture were assessed: bone volume fraction (BV/TV), trabecular number (Tb.N), connectivity density (Conn.D), structure model index (SMI) and degree of anisotropy (DA).
Results
Across all lumbar segments, higher bone mineralization (p < 0.01) is seen in the IEP (463 ± 131 HU) than the SEP (384 ± 109 HU). The highest density is lateral in the dorsal side regions (SEP: 430 ± 86 HU, IEP: 574 ± 116 HU). BV/TV, Conn D. and Tb. N. revealed higher values in the endplate-adjacent regions than in the core. Cortical vs trabecular correlations (p < 0.05) were found between the mean Hounsfield Units (HU) of the SEP and the BV/TV (r = 0.36) values of the adjacent cranial 0–10% trabecular layer. Correlations (p < 0.01) were found between the mean IEP HU and the BV/TV (r = 0.56), Tb.N (r = 0.54), Conn D. (r = 0.45), SMI (r=-0.63) and DA (r=-0.50) values of the neighboring caudal 10 − 0% layer.
Conclusions
The IEP has the highest mineralization located dorsally and is accompanied with thicker, denser trabecular architecture. The process of bone functional adaptation occurs on the cortical but also influences the underlying trabecular bone. CT-OAM can be used to predict microstructural adaptation within the vertebral trabecular core.