A histomorphometric determination of iliac bone structure and remodeling in obese subjects.

Quantitative histomorphometric analyses of iliac crest biopsies were performed after tetracycline double labeling in 24 patients with morbid obesity and in 30 age- and sex-matched controls. The amount and structure of bone were determined from measurements of total biopsy length, fractional length of medullary space, fractional trabecular bone volume, trabecular thickness, and the intertrabecular distance. Static and dynamic variables of bone resorption and formation were determined, and the balance of the BMU level was estimated from final resorption depth and mean wall thickness of trabecular structural units. In the obese patients the total biopsy length was increased, with a normal proportion of medullary space to total biopsy length. The mean fractional trabecular bone volume was reduced due to an increased distance between trabeculae of normal mean thickness. The total biopsy length in the obese patients was found to be positively related to the intertrabecular distance and inversely related to the fractional trabecular bone volume. The remaining histomorphometric variables describing bone formation rate at tissue, BMU, and cellular levels, the amount of bone formed, the mineralization process, mineralization lag time, bone resorption, and the balance between resorption and formation were all normal in the obese group.