The microanatomy of trabecular bone in young normal and osteoporotic elderly males

Abstract

Normally there is a gradual continual loss of cortical and trabecular bone in both men and women as they age. Osteopenia and osteoporosis are conditions in which the loss results in brittle bones that fracture easily. Males with low testosterone and hypogonadism are predisposed to osteoporosis and prevention tends to be overshadowed by the greater problem in postmenopausal women. The ability of the skeleton to resist external forces depends partly upon the amount of bone present and partly upon other factors including cancellous bone microarchitecture. This is examined in iliac crest bone biopsies from idiopathic osteoporotic men, mean age 60 ± 12 SD years [n = 16]. These were compared with a healthy control group (autopsy samples), mean age 30 ± 8.9 years [n = 28] with the aim of examining the pattern of cancellous atrophy in male idiopathic osteoporosis. Undecalcified specimens were embedded in methylmethacrylate and prepared for histomorphometry. Sections were analysed using an automated trabecular analysis system (TAS), whereby a binary image was created. Area measurements including the trabecular surface and distance measurements including the trabecular width were made. The binary image was thinned to its medial framework and the node and terminus number as indices of trabecular interconnection were recorded, together with the strut length. Results (median (range)) showed a lower percentage bone volume in the elderly osteoporotic male, 10.2% (5.4–23.1) compared to young normals 25.2% (14.6–43.9), p < 0.001. The trabeculae tended to be thinner, 95.7 µm (66.7–170.7) c.f. 120.8 µm (75.8–208.6) and considerably fewer in number, 11.1 (2.1–31.4) c.f. 48.3 (25.4–66.9), p < 0.001 per field and in particular the number of nodes, 2.1 (0.15–14) c.f. 40.6 (10.3–74.1) per field and the node: terminus ratio fell to 0.13 (0.01–1.19) c.f. controls 0.98 (0.24–6.69), p < 0.001. It was concluded that the pattern of cancellous atrophy in male idiopathic osteoporosis differs from normal aging and resembles that in postmenopausal women. Results using the automated TAS confirm previous observations made manually.

Keywords:

• Aging men
• idiopathic osteoporosis
• trabecular microarchitecture