Interindividual and intraspecimen variability of 3-D bone microarchitectural parameters in iliac crest biopsies imaged by conventional micro-computed tomography

Bone microarchitecture of the iliac bone is used to characterize the properties of bone tissue in osteoporosis, particularly in pharmacological studies. Trabecular bone is known to be heterogeneous media. For a few years, the analysis of three-dimensional (3-D) bone microarchitecture has been based on micro-computed tomography (micro-CT). To assess the interindividual variability (inter-indVar) and the intrasample variability (intra-sampVar) of iliac crest biopsies, we used a Bordier needle trephine in 35 postmenopausal female cadavers (mean age, 74.4 +/- 10.4 years). Finally, we had at our disposal 32 individual iliac crests to assess the inter-indVar and 21 oriented specimens to assess the intra-sampVar. All the samples were chemically defatted, and the images were performed with a desktop micro-CT with a voxel size of 10.77 mu m. We measured trabecular bone parameters: bone volume/tissue volume (BV/TV %), trabecular thickness and spacing (Tb. Th*, Tb.Sp* mu m), bone surface/bone volume (BS/BV, 1/mm), the trabecular number (Tb.N, 1/mm), structure model index (SMI), trabecular pattern factor (Tb.Pf), and degree of anisotropy (DA). We also measured cortical bone parameters: cortical thickness (Cort.Th), porosity (PoV/TV), and pore diameter (Po.Dm). For the inter-indVar, we analyzed a fixed volume of interest corresponding to 119.8 mm(3) centered on each iliac crest. To assess the intra-sampVar, we divided the whole trabecular volume into three equal height parts (external, middle, internal). BV/TV, Tb.N, and PoV/TV were negatively correlated with age and Tb.Sp* and SMI were positively correlated. The mean difference of absolute individual variations in percentage with the middle area used as a reference, comparatively to external and internal areas, ranged from 6.6% (Tb.Sp*) to 27.8% (BV/TV), except Tb.Pf, which showed large variability. There was no difference between external and internal areas, with a tendency for lower values of BV/TV, Tb.Th*, and Tb.N in the middle of the iliac crest and higher values of Tb.Sp* and BS/BV. The evaluation of bone microarchitecture of iliac crest samples on micro-CT images is reliable. The heterogeneity of bone inside the iliac crest is noticeable as leading to analyzing the largest possible quantity of bone, with standardized location, according to cortex but without any assumption of orientation.