The predictive value of quantitative computed tomography for vertebral body compressive strength and ash density

Whole lumbar vertebral sections (L2 and L3) were obtained from 30 elderly individuals aged 43-95 years, mean 81 years (13 females, 17 males). None of the subjects had had malignant diseases. Quantitative computed tomography (QCT) was performed on an EMI 7070 scanner. One 8 mm slice parallel to the end-plates was obtained from the center of each vertebral body. The trabecular bone mass in each slice was outlined interactively by means of a tracer-ball. A CT-histogram was recorded inside this area, and average CT-values were expressed in Hounsfield Units (HU). The whole vertebral body (L2) was compressed in a materials testing machine. From the central part of L3, vertical cylindrical pure trabecular bone specimens were obtained. The biomechanical competence of these specimens was also assessed by means of a materials testing machine. Finally, all bone specimens were incinerated for determination of apparent ash-density. Highly significant positive correlations were found between average CT-values and (a) stress values of the trabecular bone (r = 0.81, p less than 0.001) and (b) ash-density of the pure trabecular bone (r = 0.81, p less than 0.001). Furthermore, a significant positive correlation was found between CT-values and (a) total vertebral body load (r = 0.72, p less than 0.001), (b) total vertebral body stress (load/cross-sectional area) (r = 0.55, p less than 0.001) and (c) ash-density of the whole vertebral body (r = 0.76, p less than 0.001). It is concluded that quantitative computed tomography gives valid predictions of both vertebral trabecular bone mass and mechanical competence.(ABSTRACT TRUNCATED AT 250 WORDS)