Abstract
Bone healing has been traditionally described as a four-phase process: inflammatory response, soft callus formation, hard callus development, and remodeling. The remodeling phase has been largely neglected in most numerical mechanoregulation models of fracture repair in favor of capturing early healing using a pre-defined callus domain. However, in vivo evidence suggests that remodeling occurs concurrently with repair and causes changes in cortical bone adjacent to callus that are typically neglected in numerical models of bone healing. The objective of this study was to use image processing techniques to quantify this early-stage remodeling in ovine osteotomies. To accomplish this, we developed a numerical method for radiodensity profilometry with optimization-based curve fitting to mathematically model the bone density gradients in the radial direction across the cortical wall and callus. After assessing data from 26 sheep, we defined a dimensionless density fitting function that revealed significant remodeling occurring in the cortical wall adjacent to callus during early healing, a 23% average reduction in density compared to intact. This fitting function is robust for modeling radial density gradients in both intact bone and fracture repair scenarios and can capture a wide variety of the healing responses. The fitting function can also be scaled easily for comparison to numerical model predictions and may be useful for validating future mechanoregulatory models of coupled fracture repair and remodeling.
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Acknowledgements
The preclinical studies from which this data was obtained were funded by the Johnson & Johnson Family of Companies. The authors wish to thank Beat Lechmann (Johnson & Johnson Family of Companies) for agreeing to grant access to the ovine study data for our analyses. This material is based upon work supported by the National Science Foundation under Grant No. 1943287. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the Johnson & Johnson Family of Companies or the National Science Foundation.
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BvR is a paid consultant and receives research support as a principal investigator from Johnson & Johnson Family of Companies. The other authors report no conflicts relevant to this work.
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Ren, T., Klein, K., von Rechenberg, B. et al. Image-based radiodensity profilometry measures early remodeling at the bone-callus interface in sheep. Biomech Model Mechanobiol 21, 615–626 (2022). https://doi.org/10.1007/s10237-021-01553-2
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DOI: https://doi.org/10.1007/s10237-021-01553-2