Harman Patil (Editor)

Stress–strain index

Updated on
Edit
Like
Comment
Share on FacebookTweet on TwitterShare on LinkedInShare on Reddit

The stress–strain index (SSI), of a bone, is a surrogate measure of bone strength determined from a cross-sectional scan by QCT or pQCT (radiological scan). The stress–strain index is used to compare the structural parameters determined by analysis of QCT/pQCT cross-sectional scans to the results of three point bending test.

Contents

Definition

It is calculated using the following formula:

S S I = ∑ i = 0 n r i 2 a ( C D N D ) r m a x

Where:

  • rmax is the distance of voxel from centre
  • CD is the apparent cortical (bone) density
  • ND is the normal (cortical bone) density
  • ri is the pixel position from the centre
  • a is the area of a pixel

    • History and relation to moments of inertia

    It was developed by the manufacturer of a peripheral quantitative CT (pQCT) scanner, and is considered to be by some an improvement over the information provided by calculating the area moments of inertia and polar moments of inertia.

    References

    Stress–strain index Wikipedia
    (Text) CC BY-SA