Brief communication: Reevaluating osteoporosis in human ribs: the role of intracortical porosity

Osteoporosis is a major health concern in modern society and is continually being evaluated in past populations by quantifying bone loss. Cortical area measures are commonly used in anthropological analyses to assess bone loss in the ribs, but these values are typically based on endosteal expansion and do not account for intracortical bone loss. The objective of this study is to evaluate the effectiveness of using absolute cortical area, compared to traditional cortical area measures to describe global bone loss in elderly ribs. Transverse sections were prepared from sixth ribs of ten elderly subjects, and bone area measurements were made from 100× magnification composites of each rib for calculation of cortical area (Ct.Ar) and percent cortical area (% C/T). In addition, all areas of intracortical porosity were measured and percent porosity area (% Po.Ar) calculated. Absolute cortical area (Ct.Ar(A)) was calculated by subtracting porosity area from cortical area, and a percent absolute cortical area (% C(A)/T) calculated. ANOVA results reveal significant interindividual variation in percent porosity area (% Po.Ar). Percent cortical area and percent absolute cortical area values were compared and results show a mean difference of 4.08% exists across all subjects, with a range of 1.19-11.73%. This suggests that intracortical porosity is variable and does play a role in age-associated bone loss in the rib. All future investigations of osteoporosis should account for intracortical porosity in bone loss.