Histomorphometry of iliac crest bone in 346 normal black and white South African adults.

We examined undecalcified transiliac bone samples from 346 normal black and white South African adults (age range 21-83 years) by routine histomorphometry. The results were analysed for race-, age- and sex-dependent characteristics of trabecular microstructure (bone volume, trabecular thickness, trabecular number, trabecular separation) and static bone turnover variables (osteoid surface, osteoid volume, osteoid thickness, erosion surface). Trabecular thickness was greater in blacks than in whites, and bone volume was greater in black males, but not in black females, than in their white counterparts. Values for osteoid surface, volume and thickness, and for erosion surface were greater in blacks than in whites. Age-related changes were: a decline in bone volume in all race/sex groups; a decline in trabecular thickness in all groups except black males; a decline in trabecular number in all groups except black females; and a rise in trabecular separation in all groups except black females. There was an increase with age in osteoid surface in all groups except white males, in osteoid volume in all groups, and in erosion surface in blacks only. When correcting for age there were no sex-dependent differences in microstructure but values of some osteoid variables were greater in males than in females. If the greater osteoid and erosion values in blacks reflect greater bone turnover, then trabecular bone in blacks would be renewed more frequently, be subjected to fewer loading cycles and be less prone to fatigue failure. Blacks may thus have trabecular bone of better quality and sturdier microarchitecture. These features could contribute to the lower spontaneous fracture rate in blacks.