Osteocyte lacunar occupancy in the femoral neck cortex: An association with cortical remodeling in hip fracture cases and controls

In adult humans, osteocytes die and disappear from their lacunae in the cor tex of bones which remodel slowly, such as the proximal femur, and osteocyt e death is particularly prevalent in the elderly. We have investigated the statistical determinants of osteocyte density in microscopic fields (0.71mm (2)) within thin, complete femoral neck cross-sections cut from biopsies em bedded in methyl methacrylate and stained with solochrome cyanine R. Lacuna e were counted under phase contrast and osteocytes within lacunae were coun ted in the same fields under epifluorescence. The percentage of lacunae con taining an osteocyte varied between 12.4% and 99.2%, according to subject a nd quadrantic region of the cortex examined. The microscopic determinants o f field-specific osteocyte density included the porosity measured in the fi eld itself and the regional measurement of the proportion of cortical canal s bearing osteoid. There was significant variation between subjects and, wi thin subjects, between cortical regions. Also the inferior region showed a significantly higher density of lacunae than the superior region (+8.2%; P = 0.013). However, cases of fracture were not significantly different from controls with respect to osteocyte lacunar occupancy after adjusting for os teoid-bearing canals and porosity. It is concluded that in subjects in thei r 7(th)-9(th) decades of age, osteocyte lacunar occupancy is statistically associated with bone turnover, implying that high turnover (locally young b one age) might favor lacunar occupancy (ln% osteoid; P = 0.021). Alternativ e explanations of the association are that porosity reflects a better nutri tional supply via the vasculature or that porosity of the cortex is associa ted with osteocyte density through an effect of osteocytes on bone remodeli ng.