Cortical Bone Structure

Sectioning & Imaging

Click image to enlarge.

Sectioning

Cross-sections of the diaphysis are usually prepared using a grinding system rather than a microtome. Attempting to cut a cross-section of the diaphysis with a microtome usually causes the section to disintegrate even when resin-embeded. Typically, a 100 micron slab is cut with a saw then mounted on a plastic slide. Then slab is then ground and polished down to a thickness of about 30 microns.

Imaging

Sections may be given a light surface stain. Sections taken from mice are normally imaged with a 20X objective. Section from large animals such as mini-pigs are normally imaged with a 10X objective.

Imaging of the section is generally done in bright field. Fluorescence may be used in cases where labels have been given to the animals as can be the case in studies that use 3-point bending to look at response to mechanical loading. Polarized light may sometimes be used to help visualize the borders of osteons tunneled through lamellar bone.

Referent Data

cortical area, thickness, & periosteal surfacE

In this example, a digital scan of the section has been used. BIOQUANT zooms out so the entire cross-section is visible within the field of view. Based on a threshold of the cortical bone, BIOQUANT collects the cortical area, the cortical thickness, and the periosteal surface.

  • Ct.B.Ar/Tt.Ar

  • Ec.Ar/Tt.Ar

  • Mean Ct.Wi

  • Ps.Pm

FYI - The Referent Data Tool can be used on a large scan of the tissue, zoomed out to fit in the Image window as show above. It can also be used field-to-field at higher magnification. You do not need a scan or tracking device to use BIOQUANT, although they do save you time.

2nd moment of AREA

Relative to the X axis of the image, BIOQUANT also computes the 2nd moment of area for the cross-section. This is a measure of the distribution of cortical bone in section. To be comparable to one another, sections must be images in a consistent anatomical orientation.

Anterior / Posterior / Medial / Lateral Zone Data

Click image to enlarge.

Cortical Thickness along Anatomical Axes

The software provides tools for the direct measurement of cortical thickness at preferred anatomical orientations. Typically, four thickness measurements are made: anterior, posterior, media, and later.

  • Anterior Ct.Wi

  • Posterior Ct.Wi

  • Medial Ct.Wi

  • Lateral Ct.Wi

Sampling Along Anatomical Axes 

Sampling Areas at the four orientations are defined using a standardized Region of Interest tool that allows strips of standardized shape to be analyzed at higher magnification.

  • Sa.Ct.Ar Sampled Cortical Area

Osteon Data

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Osteon Area / Osteon Perimeter

Since there is no specific staining at the border of an osteon, the boundary is drawn by hand. Once, drawn the boundary is analyzed for both area and perimeter.

  • On.Ar Osteonal Area

  • On.Pm Osteonal Perimeter

  • On.N Osteon Number

  • OPD Osteon Population Density

  • Ha.Ar Haversian Canal Area

  • Ha.Pm Haversian Perimeter

  • On.Fg.Ar Osteon Fragment Area

  • On.Fg.N Osteon Fragment Number

  • On.Ar/Sa.Ar

  • Ha.Ar/Sa.Ar

  • On.Fg.Ar/Sa.Ar

  • Po.Ar Pore Area

  • Porosity

Click image to enlarge.

Osteon Diameters & Wall Thickness

Similarly, the major and minor diameters of the osteon as well as the wall thickness along the minor diameter of the osteon are manual measurements.

  • Min.On.Dm Minimum Osteon Diameter

  • Max. On.Dm Maximum Osteon Diameter

  • W.Wi Osteon Wall Width

Osteocyte Data

Click image to enlarge.

BIOQUANT automatically counts osteocytes using color, size, and shape to identify them. The Measure Cells tool ensures that no osteocyte is counted twice and that only osteocytes within the sampling area are counted.

  • Ot.N Osteocyte Number

  • Ot.N/Sa.Ar

Bone Formation Rate Data

Click image to enlarge.

Auto Surface tool for single labeled surfaces

Using the Auto Surface tool, BIOQUANT automatically measures the single labeled surface. Manual editing of the labeled surface threshold is easily done with the Draw and Erase tools.

  • sL.Pm Single Labeled Surface

Specialized Double Labeled Surface tool

Pairs of labeled surfaces are traced manually. The dLS tool then automatically measures the interlabel width and the length of the double labeled surface. This data is combined with single labeled surface and bone surface to automatically calculate

  • dL.Pm Double Labeled Surfae

  • M.Pm Mineralizing Perimeter

  • M.Pm/BS

  • BFR/B.Pm

Citations of BIOQUANT in the Analysis of Cortical Bone

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