Nanoscale Examination of Microdamage in Sheep Cortical Bone
April 2013 SSRL Science
Summary by Lori Ann White, SLAC Office of Communications
Lead-uranyl acetate staining of damage morphologies in notched bone samples. (A, B) Staining of lacunae and canaliculi in the compressive region seen in 20 of the 23 samples; (C, D) Cross hatching damage around notch tip in the tensile region observed in 10 of 23 samples; (E, F) Crack propagating from notch tip in the tensile region in a single sample. Staining appears white due to high attenuation of lead-uranyl acetate, with bone tissue appearing grey and voids black. Scale bar: A,C,E = 50 μm; B,D,F = 5 μm. Sample created in the longitudinal plane of the bone.] |
An important factor contributing to bone fractures is the accumulation of
damaged tissue. Micro-damage can occur in bone tissue simply through the
activities of daily life, which can reduce the tissue’s strength,
stiffness and energy dissipation properties. In normal bone such damage is
believed to stimulate bone remodeling and new bone formation. But diseases
characterized by low bone mass such as osteoporosis alter bone remodeling and
may weaken the tissue, leading to an increased risk of fracture. Current
treatment costs for osteoporosis in the United States alone are in the tens of
billions of dollars per year and are expected to grow.
A study recently published in PLoS
ONE by researchers from Cornell University, Hospital for Special
Surgery, New York, and SSRL describes nanoscale visualization of micro-damage
in cortical bone tissue using x-ray negative staining and synchrotron-based
x-ray imaging. The first study to examine bone damage at the nanoscale using
full-field x-ray imaging in cortical bone, it provides new insights into bone
damage and propagation of fractures. The method itself could have future
applications for visualization of damage at the nanoscale, leading to greater
knowledge of skeletal damage mechanisms.
In the study, beams created from sheep bones were damaged by applying either
a monotonic or a fatigue load, then stained with x-ray negative stains of
lead-uranyl acetate and sectioned to 50-micron thickness (much thicker than can
be imaged with electron microscopy). The data were obtained using full-field
transmission x-ray microscopy (TXM) at SSRL Beam Line 6-2, creating nanoscale
images of micro-damage throughout this thickness with 30-nm resolution. Images
revealed increased staining (pointing to damage), cross hatching and
micro-cracks in the fatigue-loaded bone samples (Figure 1). In both cases
staining was localized to existing bone structures, with limited new surfaces
created. The images were compared with lower-resolution images obtained using
micro-computed tomography (microCT), a standard technique for imaging
micro-damage in bone; the structures revealed by the TXM images were not
discernible in the microCT images and the damage manifested diffusely,
appearing larger than in the TXM images. MicroCT analyses of micro-damage may,
therefore, overestimate the damage present. Thus nanoscale TXM imaging through
these relatively thick specimens can provide crucial details needed to discern
features relevant to bone disease.
Primary Citation
G. R. Brock, G. Kim, A. R. Ingraffea, J. C. Andrews, P. Pianetta, M. C. H. van der Meulen, "Nanoscale Examination of Microdamage in Sheep Cortical Bone Using Synchrotron Radiation Transmission X-ray Microscopy", PLoS ONE 8, e57942 (2013)Related Links
- Science Highlight – HTML / PDF
- SSRL Science Highlights Archive
- SSRL Beam Lines
Contacts
Garry R. Brock, Cornell UniversityJoy C. Andrews, Stanford Synchrotron Radiation Lightsource
Marjolein C. H. van der Meulen, Cornell University
