Relationships between static histomorphometry and ultrasound in the human calcaneus

The aim of this study was to explore the relationship(s) between histomorphometric measurements of cancellous bone structure and ultrasound. Ultrasonic measurements were made using a CUBA research system consisting of a pair of 1 Mhz unfocused transducers. Speed of sound (SOS) and broadband ultrasonic attenuation (BUA) were determined in 15 human cadaveric heels, with mean precision for all measurements coefficients of variation (CV) = 0.6% and 12%, respectively. The calcaneus was dissected and a 7.5 mm transcortical cylinder was removed from the path of ultrasound (US) transmission. The cortices were removed and the remaining cancellous core was sectioned into approximately 5 mm blocks, numbered from 1 to 6 (medial-lateral). Histomorphometric measurements were performed on decalcified, 5 microm-thick sections from blocks 1-6 using an automatic color image analysis system. There were significant differences between blocks 1 and 3-6 for BS/TV, BV/TV, Tb.N, and Tb. Sp (all P < 0.001), all decreasing in a medial-lateral direction (except Tb.Sp), implying that the medial portion of the calcaneus had more trabeculae with less spacing between them than the lateral portion. Furthermore, Tb.Th and BS/BV variables were uniform across the calcaneus, suggesting that individual trabeculae were of similar dimension. We found no significant correlations between US and histomorphometric parameters either averaged over all blocks or by using each block region separately. In conclusion, this study does not support the notion that US measurements of SOS and BUA through the heel reflect calcaneal cancellous bone structure, however, further studies using larger sample sizes may be warranted.