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In long bones, the functional adaptation of shape and structure occurs along the whole length of the organ. This study explores the hypothesis that adaptation of bone composition is also site-specific and that the mineral-to-collagen ratio of bone (and, thus, its mechanical properties) varies along the organ's length. Raman spectroscopy was used to map the chemical composition of long bones along their entire length in fine spatial resolution (1 mm), and then biochemical analysis was used to measure the mineral, collagen, water, and sulfated glycosaminoglycan content where site-specific differences were seen. The results show that the mineral-to-collagen ratio of the bone material in human tibiae varies by <5% along the mid-shaft but decreases by >10% toward the flared extremities of the bone. Comparisons with long bones from other large animals (horses, sheep, and deer) gave similar results with bone material composition changing across tens of centimeters. The composition of the bone apatite also varied with the phosphate-to-carbonate ratio decreasing toward the ends of the tibia. The data highlight the complexity of adaptive changes and raise interesting questions about the biochemical control mechanisms involved. In addition to their biological interest, the data provide timely information to researchers developing Raman spectroscopy as a noninvasive tool for measuring bone composition in vivo (particularly with regard to sampling and measurement protocol).

Original publication





Journal of biomedical optics

Publication Date





Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Oxford, OX11 0FA, United KingdombUniversity College London, Institute of Orthopaedics and Musculoskeletal Science, Stanmore, HA7 4LP, United Kingdom.


Bone and Bones, Animals, Sheep, Horses, Humans, Carbonates, Phosphates, Water, Minerals, Collagen, Spectrum Analysis, Raman, Aged, Aged, 80 and over, Middle Aged, Female, Male