Efficiency of systematic sampling in histomorphometric bone research illustrated by hydroxyapatite-coated implants: Optimizing the stereological vertical-section design

The sampling efficiency of the unbiased stereological vertical-section meth od was analyzed in five hydroxyapatite-coated implants. They were inserted into humans and harvested after 1 year. To find an optimal sampling design for histomorphometric analyses, sampling efficiency was estimated by varian ce analyses at different sampling levels (humans, sections, fields of view, and number of counting items) and intensities. Only minor changes in varia nce were observed when the initial scheme was reduced to include just one o f the two possible implant sides, every third field of view, and half the d ensity of the probe; this reduced the total workload at the microscope to l ess than 10% for all sections. In addition, the number of sections for anal ysis could be reduced to every fourth section per implant (three to four se ctions for evaluation) without significantly increasing variance. The study demonstrated that biological variation contributed to the majority of the total observed variance. Optimizing the sampling design could significantly reduce the workload at the hard-tissue microtome and the microscope withou t reducing the quality of the data that were unbiased and that had low samp ling variance as compared with the true biological variation.