title: Post-euthanasia micro-computed tomography-based strain analysis is able to represent quasi-static in vivo behavior of whole vertebrae.
abstract: Three-dimensional image-based strain measurement in whole bones allows representation of physiological, albeit quasi-static, loading conditions. However, such work to date has been limited to specimens postmortem. The main purpose of this study is to verify the efficacy of deformable image registration of post-euthanasia strain to characterize the in vivo mechanical behavior of rat vertebrae. A micro-computed tomography-compatible custom loading device was used to apply 75 N load to a three-level caudal motion segment of a healthy rat. Loaded and unloaded micro-computed tomography scans were acquired in vivo and post-sacrifice. A micro-computed tomography-based deformable image registration algorithm was used to calculate vertebral strains live and post-euthanasia. No significant difference was found in the in vivo strains (-0.011 ± 0.001) and ex vivo strains (-0.012 ± 0.001) obtained from the comparisons of loaded and unloaded images (p = 0.3). Comparisons between unloaded-unloaded and loaded-loaded scans yielded significantly lower axial strains, representing the error of the method. Qualitatively, high strains were observed adjacent to growth plate regions in evaluating the loaded-unloaded images. Strain patterns in the loaded-loaded and unloaded-unloaded scans were inconsistent as would be expected in representing noise. Overall, live and dead loaded to unloaded comparisons yielded similar strain patterns and magnitudes. Point-wise differences in axial strain fields also supported this observation. This study demonstrated a proof of concept, suggesting that post-euthanasia micro-computed tomography-based strain analysis is able to represent the in vivo quasi-static behavior of rat tail vertebrae.
authors.affiliation: 1 Orthopaedic Biomechanics Lab, Sunnybrook Research Institute, Toronto, ON, Canada.|2 Institute of Biomaterials and Biomedical Engineering, Toronto, ON, Canada.
authors.forename: Chetan
authors.initials: C
authors.lastname: Choudhari
authors.affiliation: 1 Orthopaedic Biomechanics Lab, Sunnybrook Research Institute, Toronto, ON, Canada.|2 Institute of Biomaterials and Biomedical Engineering, Toronto, ON, Canada.
authors.forename: Ryan
authors.initials: R
authors.lastname: Herblum
authors.affiliation: 3 TECHNA Institute, University Health Network, Toronto, ON, Canada.|4 Department of Surgery, University of Toronto, Toronto, ON, Canada.
authors.forename: Margarete K
authors.initials: MK
authors.lastname: Akens
authors.affiliation: 1 Orthopaedic Biomechanics Lab, Sunnybrook Research Institute, Toronto, ON, Canada.
authors.forename: Sara
authors.initials: S
authors.lastname: Moore
authors.affiliation: 1 Orthopaedic Biomechanics Lab, Sunnybrook Research Institute, Toronto, ON, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Hardisty
authors.affiliation: 1 Orthopaedic Biomechanics Lab, Sunnybrook Research Institute, Toronto, ON, Canada.|2 Institute of Biomaterials and Biomedical Engineering, Toronto, ON, Canada.|4 Department of Surgery, University of Toronto, Toronto, ON, Canada.
authors.forename: Cari M
authors.initials: CM
authors.lastname: Whyne
keywords: Biomechanical testing/analysis; bone biomechanics; bone properties; computed tomography analysis; imaging (biomechanics); spine biomechanics; strain analysis/testing (biomechanics)