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The regionalized vertebral column is a hallmark of mammalian morphology and reflects functional differentiation of the vertebral regions. Mammalian vertebrae are serially homologous and morphologically patterened by Hox expression, but also vary in number and gross morphology across species. The trabecular bone inside vertebral centra is more plastic than gross vertebral bone, and structurally adapts to better withstand forces it experiences during life. However, the functional regionalization of vertebral trabecular bone is poorly examined. Are there trabecular "regions” reflecting the differing functions and in-vivo stress patterns of gross morphological vertebral regions? Or is trabecular morphology homogeneous throughout the spine, suggesting that differences in functional demands are borne exclusively by external characteristics? To address these questions, we collected μCT scans and linear measurements of cervical, thoracic, and lumbar vertebrae in four species of large shrews, including two species of the hero shrew Scutisorex, which has a highly modified vertebral column. We compared linear measurements and trabecular bone characteristics of the cranial and caudal ends of each centrum across species. To detect unique vertebral regions, we executed principal coordinates analysis and segmented regression on three versions of our data set: trabecular bone data only, external measurements only, and the two combined. We found that some regionalization is recovered using only trabecular bone data, but trabecular bone regions do not correspond exactly to gross vertebral regions. This reflects divergence between the functional signals of internal and external vertebral bone morphology, which should be further examined in a kinematic context.
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Automated resolution independent method for comparing in vivo and dry trabecular bone
Abstract ObjectivesVariation in human trabecular bone morphology can be linked to habitual behavior, but it is difficult to investigate in vivo due to the radiation required at high resolution. Consequently, functional interpretations of trabecular morphology remain inferential. Here we introduce a method to link low‐ and high‐resolution CT data from dry and fresh bone, enabling bone functional adaptation to be studied in vivo and results compared to the fossil and archaeological record. Materials and methodsWe examine 51 human dry bone distal tibiae from Nile Valley and UK and two pig tibiae containing soft tissues. We compare low‐resolution peripheral quantitative computed tomography (pQCT) parameters and high‐resolution micro CT (μCT) in homologous single slices at 4% bone length and compare results to our novel Bone Ratio Predictor (BRP) method. ResultsRegression slopes between linear attenuation coefficients of low‐resolution pQCT images and bone area/total area (BA/TA) of high‐resolution μCT scans differ substantially between geographical subsamples, presumably due to diagenesis. BRP accurately predicts BA/TA (R2= .97) and eliminates the geographic clustering. BRP accurately estimates BA/TA in pigs containing soft tissues (R2= 0.98) without requiring knowledge of true density or phantom calibration of the scans. DiscussionBRP allows automated comparison of image data from different image modalities (pQCT, μCT) using different energy settings, in archeological bone and wet specimens. The method enables low‐resolution data generated in vivo to be compared with the fossil and archaeological record. Such experimental approaches would substantially improve behavioral inferences based on trabecular bone microstructure.
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- PAR ID:
- 10449572
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- American Journal of Physical Anthropology
- Volume:
- 174
- Issue:
- 4
- ISSN:
- 0002-9483
- Format(s):
- Medium: X Size: p. 822-831
- Size(s):
- p. 822-831
- Sponsoring Org:
- National Science Foundation
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