CHANGES OF INTERSTITIAL BONE THICKNESS WITH AGE IN MEN AND WOMEN

Mean interstitial bone thickness has been estimated from mean trabecul ar thickness and mean wall thickness (It.Th = Tb.Th-2W.Th) with varyi ng results. Some authors found age-related changes of It.Th while othe rs did not. We measured It.Width (It.Wi, 2D) directly, in cancellous i liac crest bone from 23 women aged 20-78 yrs. and 21 men aged 23-74 yr s. At grid-selected sites coupled measurements were done of Tb.Wi and It.Wi, together with W.Wi. It.Wi was defined as the distance between c ement lines nearest to the surface at both sides of a trabecula. A thi onine stain was used to visualize the cement lines. When the persons s tudied were divided into two age groups: 20-49 yrs (Group 1) and 50-79 yrs (Group 2) significant but opposite age-related trends were seen b oth in men and women. Group 1: Men: r= -.68; p <.02; n = 11; Women: r= -.68; p <.02; n = 11. Group 2: Men: r= .79; p <.01; n= 10. Women: r= .59; p <.05; n = 12 (r= coeff. of correlation). Men: It. Wi 63.3 mum ( 3rd decade [dec.]); 50.8 mum (6th dec.); 67.8 mum (8th dec.). Women: I t.Wi 63.7 mum (3rd dec.); 48.3 mum (6th dec.); 63.8 mum (8th dec.). Me asured It.Wi values appeared considerably larger than their calculated counterparts (mean DELTA: 35%). The decline of It.Wi is interpreted a s a sign of negative bone balance at the BMU level, leading to thinnin g of trabeculae, the subsequent increase has to be the result of both declining resorption depth and disappearance of the thinner trabeculae . Intersection of the two opposite regression lines is situated at the age of about 45 yrs. both in men and women: bone loss may begin earli er in life than generally assumed.