Article: Cresswell, EN; Goff, MG; Nguyen, TM; Lee, WX; Hernandez, CJ; (2016) “Spatial Relationships between Bone Formation and Mechanical Stress within Cancellous Bone”, Journal of Biomechanics, 49 (2): 222-228
Abstract: Bone adapts to mechanical stimuli. While in vivo mechanical loading has been shown to increase the density of cancellous bone, theory suggests that the relationship between tissue stress/strain and subsequent bone formation occurs at the scale of individual trabeculae. Here we examine bone formation one week following mechanical stimulus. Three bouts of cyclic loading (300 cycles/day on 3 consecutive days) were applied to caudal vertebrae of female rats (n=7). Bone formation was determined using three-dimensional images of fluorescent markers of bone formation (0.7 x 0.7 x.5.0 mu m(3)) and local tissue stress/strain was determined using high-resolution finite element models. Three days of mechanical stimuli resulted in an increase in mineralizing surface (loaded: 17.68 +/- 2.17%; control: 9.05 +/- 3.20%; mean +/- SD) and an increase in the volume of bone formed (loaded: 7.09 +/- 1.97%; control: 1.44 +/- 0.50%). The number of bone formation sites was greater in loaded animals (650.71 +/- 118.54) than pinned not loaded controls (310.71 +/- 91.55), a difference that was explained by the number of formation sites at regions with large local tissue strain energy density (SED). In addition, the probability of observing bone formation was greater at locations of the microstructure experiencing greater SED, but did not exceed 32%, consistent with prior work. Our findings demonstrate that bone formation in the week following a short term mechanical stimulus occurs near regions of bone tissue experiencing high tissue SED, although the ability of finite element models to predict the locations of bone formation remains modest and further improvements may require accounting for additional factors such as osteocyte distribution or fluid flow. (C) 2015 Elsevier Ltd. All rights reserved.
Funding Acknowledgement: National Science Foundation [1068560, DGE-1144153, TG-MSS 13011]
Funding Text: Supported by the National Science Foundation Grant no. 1068560 (PI Hernandez). This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant no. DGE-1144153. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant no. TG-MSS 13011. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors(s) and do not necessarily reflect the views of the National Science Foundation.