Precision and accuracy of histomorphometric analysis in the intact and osteopenic femur rat

Background. The postovariectomy osteopenic rat model is widely used to mimic human osteoporosis and to test the efficacy of treatments. Histomorphometric data on cortical bone in rats used for osteoporosis research often derive from diaphyseal cross sections of the femur or tibia without a specific observation site. The aim of the present study is to evaluate along the rat femur diaphysis the site where the histomorphological observations are more appropriate and significant in monitoring the development of osteopenia. Methods. We used 10 intact Sprague Dawley female rats (RI) and 10 rats of the same age 3 months after ovariectomy (OVX). Cross sections of femoral diaphysis (taken every 4 mm from the supracondylar distal line) were morphometrically analyzed in blind and the following parameters were measured: Ct.Wi, Ps.Pm, Es.Pm, Se.Ar, Ct.Ar, Ct.Ar/Se.Ar%, and Me.Ar. Results. The results of the femur mapping showed that the lowest measure variability both in RI and OVX rats is observed at 12 mm from the supracondylar distal line, that seems to be more suitable to evaluate histomorphometric parameters. Finally, at 12 mm the highest difference in Ct.Wi between intact and osteopenic bone was observed. Conclusions. In conclusion, it seems preferable to evaluate histological femur specimens in cross sections at that specific point in order to have the least variability and to obtain the most homogeneity of the measurements with a good discrimination between intact and osteopenic rats. These results support those of a previous study on densitometric map of the rat femur in which we showed a 30% improvement in precision at the bone segment between 8 and 14 mm.