Unbiased stereological estimation of osteoid and resorption fractional surfaces in trabecular bone using vertical sections: sampling efficiency and biological variation.

The conventional stereological procedure for estimating bone surface densities in iliac crest biopsies provides biased estimates because bone substructure is anisotropic and the sectioning of the biopsies is intended to be parallel to the cylindrical axis of the iliac crest biopsy. It has recently been shown that random anisotropic sections with an identifiable axis or direction which is arbitrary but fixed can be used for unbiased estimates of surface areas. The arbitrary axis is called "vertical," a denomination which does not imply anything about its relation to directions in the world's field of gravity. Sampling efficiency and biological variation of fractional osteoid and resorptive surfaces were investigated in 14 paired bone specimens obtained from two females and five males (mean age 64) using an integral anisotropic test system constructed of cycloids. Results obtained at direct microscopy were compared to results obtained with projection onto the table. Mean fractional osteoid and resorption surfaces were 6.2 and 1.4% using direct microscopy and 5.6 and 1.7% using projection. Estimation of variance at each level of sampling showed that the majority of the total observed variance was due to true variance between individuals; for fractional osteoid surface the unavoidable biological variation was 80.5% of the observed variation and for fractional resorption surfaces it was 57%. The efficiency of the estimation procedure is therefore close to optimal and the only way to improve the precision in groups of patients and controls would be to include more individuals in the study.(ABSTRACT TRUNCATED AT 250 WORDS)