Differential patterns of altered bone formation in different bone compartments in established osteoporosis

Aim-To investigate the level of bone formation in the different bone compar tments in cases of established osteoporosis, as previous work has concentra ted on trabecular bone alone. Methods-Bone formation rates were measured histomorphometrically, in the pe riosteal (P), cortical (C), subcortical iliac crest biopsies from 159 patie nts with established osteoporosis. The values were standardised using age a nd sex matched control data and patterns of differential change determined by analysis of parametric status (increased, normal, reduced). Results-Mean bone formation was reduced in all four compartments. This was more marked (4.4/4.1 standard deviations below the mean in CIT, v 2.3/0.9 i n P/SC) and more frequent (reduced in 81.5%/ 78.3% in TIG, v 43.3%/44% in P /SC) in the trabecular and cortical compartments than in the periosteal or subcortical bone. Parametric status was equal in trabecular and cortical bo ne in 85.4% of cases, and in periosteal and subcortical bone in 65.7%, but in all four compartments in only 35.1%, indicating differential alteration of bone formation in the two sets of compartments (T/C v P/SC). Conclusions-Altered trabecular bone formation is important in osteoporosis, but there are differential patterns of alteration in the other three compa rtments, emphasising the presence of different microenvironments in bone; t hus the effect on the cortical compartment was similar to that on the trabe cular, while the subcortical and periosteal compartments also showed linkag e. The linkage between the two pairs was divergent, indicating different co ntrol of bone formation, with resultant different patterns of perturbation in osteoporosis.