Microstructural changes of osteopenic trabeculae in the rat.

We studied the differences in the patterns of trabecular bone loss induced by various kinds of experimental osteopenia in the rat, including ovariectomy, sciatic neurotomy (partial paralysis of hind-limb), hemicordotomy (complete paralysis of hind-limb), and their combinations. The cut surface of the metaphysis of proximal tibiae from osteopenic and control rats was observed by scanning electron microscopy, and morphometric changes of the secondary spongiosa were determined by measurement of percent bone area, and number and width of trabeculae. Percent bone area decreased significantly compared with the Sham group in all operated groups except the sciatic neurotomy group, but the qualitative changes of trabeculae in osteopenia induced using different methods were definitely different. In the Sham-operated group of rats, conversion of rod trabeculae to plate trabeculae and thickening of trabeculae were observed over the course of the nine months following surgery. In the sciatic neurotomy group of rats, neither trabecular number nor width significantly changed at 12 weeks after surgery. In the ovariectomy group of rats at nine months after surgery, a significantly decreased trabecular number but unchanged trabecular width were observed, and disappearance of trabeculae was identified primarily in the central area. In the hemicordotomy group of rats at 12 weeks after surgery, significantly decreased trabecular width with unchanged trabecular number were observed and thinning of trabeculae was noted to be equal in the whole area of the proximal tibial secondary spongiosa. In rats subjected to sciatic neurotomy combined with ovariectomy, and in rats subjected to hemicordotomy combined with ovariectomy, both trabecular number and width were severely decreased in the whole area at 12 weeks after surgery.(ABSTRACT TRUNCATED AT 250 WORDS)