Methodology, selection, and integration of fracture healing assessments in mice

Abstract

Long bone fractures are one of the most common and costly medical conditions encountered after trauma. Characterization of the biology of fracture healing and development of potential medical interventions generally involves animal models of fracture healing using varying genetic or treatment groups, then analyzing relative repair success via the synthesis of diverse assessment methodologies. Murine models are some of the most widely used given their low cost, wide variety of genetic variants, and rapid breeding and maturation. This review addresses key concerns regarding fracture repair investigations in mice and may serve as a guide in conducting and interpreting such studies. Specifically, this review details the procedures, highlights relevant parameters, and discusses special considerations for the selection and integration of the major modalities used for quantifying fracture repair in such studies, including X-ray, microcomputed tomography, histomorphometric, biomechanical, gene expression and biomarker analyses.

Histological and bone mineral density analyses of the mandibular lamellar/oblique fracture healing in beagles.

“…A four-point bending test, which involves applying two downward forces on the skeletal scaffold equidistant from the center of the bone, was used in this experiment. This test is crucial for determining the nal fracture repair because it allows a more uniform propagation of the bending moment between the two points where the force is applied [17] . The strains caused by weight-bearing activity or muscle contraction at the fracture site cause interfragmentary movement (IFM), which alters the size of the initial fracture gap and causes interfragmentary strain ε [26] .Moderate-sized IFM can promote bone healing.Axial motion, as opposed to the translational and torsional shear motion, which slows bone healing, is found by some researchers to produce better healing in mechanical simulations and nite element analysis [27] .The maximum mineralized bone crust area, four-point bending experimental stiffness, and mineralized tissue density, on the other hand, were higher in the torsional shear group than in the axial group in Bishop's experiments in a sheep tibial fracture model, suggesting that interfragmentary shear motion does not necessarily delay bone healing but instead stimulates bone crust formation and promotes fracture healing [28] .Our research also supports the notion that shear does not always prevent bone healing because the stiffness and maximum load of the lamina/bevel group were higher in the late phase of fracture healing than those of the linear group.…”

“…As healing time advances, however, there is a steady decrease in collagen bers and an increase in bone tissue. Bone scab size, bone density, and biomechanical qualities are all directly related to brous tissue area and bone tissue area, which are important stage indicators of fracture healing [17] .Cell differentiation and fracture healing may be impacted by changes in the mechanical environment of the fracture end due to the fracture inclination [18] . Ramasamy [19] discovered that the mechanical function of bone in mice is signi cantly in uenced by the orientation of collagen bers in the anatomical loading axis, with longitudinal bers forming a tissue with better tensile properties and maximum strain.…”

Validation of the modified radiographic union score for tibia fractures (mRUST) in murine femoral fractures

“…Additionally, though it is common practice to for biomechanical specimens to undergo a single freeze-thaw cycle ( 29 ), this is a possible explanation for why biomechanical testing parameters had the lowest correlation with mRUST. Alternatively, biomechanical testing is commonly the most variable measurement for murine fracture healing studies ( 13 ). This variability would then be reflected in the correlation analyses.…”

“…Despite the success of mRUST in human studies, there is no accepted methodology for utilizing plain radiographs to assess fracture healing in mouse models. The standard measures of fracture healing in mice include biomechanical testing, μCT analysis, and histomorphometric analysis, which are associated with significant time and costs ( 13 ). Should mRUST scoring show consistent reflection of the more traditionally accepted measures, it could support a new avenue for fracture assessment in mice that is cheaper, faster, and more clinically translatable than current standard measures, making it an appealing prospect for high throughput analysis.…”

Radiological and Histological Analyses of Nonrigid Versus Rigid Fixation for Free Bone Block Procedures in a Rabbit Model of Glenoid Defects

“…General observations of the reconstructed glenoid were identified via H&E staining, including graft-glenoid healing, regenerated tissue ingrowth, morphological characteristics, and vascularity. 18,19,25 Angiogenesis in the graft was quantitatively analyzed by calculating the mean number of microvessels in 10 random 400 × 400–μm regions of the graft. 46 The mean microvessel number was then normalized to the tissue area (number of vessels per mm 2 ) for vascular density analysis.…”