Abstract
The mechanical behaviour of regenerated bone tissue during fracture healing is key in determining its ability to withstand physiological loads. However, the strain distribution in the newly formed tissue and how this influences the way a fracture heals it is still unclear. X-ray Computed Tomography (XCT) has been extensively used to assess the progress of mineralised tissues in regeneration and when combined with in situ mechanics and digital volume correlation (DVC) has been proven a powerful tool to understand the mechanical behaviour and full-field three-dimensional (3D) strain distribution in bone. The purpose of this study is therefore to use in situ XCT mechanics and DVC to investigate the strain distribution and load-bearing capacity in a regenerating fracture in the diaphyseal bone, using a rodent femoral fracture model stabilised by external fixation. Rat femurs with 1 mm and 2 mm osteotomy gaps were tested under in situ XCT step-wise compression in the apparent elastic region. High strain was present in the newly formed bone (εp1 and εp3 reaching 29000 µε and -43000 µε, respectively), with a wide variation and inhomogeneity of the 3D strain distribution in the regenerating tissues of the fracture gap, which is directly related to the presence of unmineralised tissue observed in histological images. The outcomes of this study will contribute in understanding natural regenerative ability of bone and its mechanical behaviour under loading.
Highlights
The fracture healing process has been analysed in a three-dimensional (3D) manner with the use of high-resolution X-ray computed tomography (XCT) (Gabet et al, 2004; Shefelbine et al, 2005; Isaksson et al, 2009; Morgan et al, 2009; Kustro et al, 2018)
The strain induced on the regenerated tissue throughout the compression steps was assessed using digital volume correlation (DVC)
The methodology reported in this study provide a valuable guideline for XCT-based analysis of regenerated fractures and can be used to inform/validate computational models predicting bone regeneration mechanism
Summary
Histology has been widely used to assess bone healing at the microscale throughout the entire process (Manjubala et al, 2009; Mora-Macías et al, 2017) to identify the type of defect (Epari et al, 2006; Zandi et al, 2019), to evaluate fixation efficiency (Claes et al, 2008; Meeson et al, 2019) and to Both 2D and 3D imaging evaluations were only able so far to quantify the morphology of bone regeneration, without any specific information on its quality in terms of mechanical properties
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