Population frequencies and altered remodeling mechanisms in normal medullary stenosis.

As shown in 2065 women aged 18 to 45 Years from seven countries of Central and North America, the population frequency of normal medullary stenosis ranges from under 2% to nearly 7%. In this condition, endosteal apposition may begin in infancy and continue through the fourth decade with a compensatory reduction in the rate of subperiosteal apposition, leading t o an approximately normal cortical cross-sectional area contained in a smaller subperiosteal envelope. Medullary stenosis, characterized by reduced medullary cavity widths, growth retardation, disorders of calcium metabolism and probably inherited as a simple mendelian dominant has recently been established as a clinical entity (Kenny and Linarelli, '66; Caffey, '67). Reduced medullary cavity widths also exist in apparentlynormal individuals, the frequency of such medullary reduction varies from population to population, and the course of transverse bone growth is then considerably altered from the normal course (Garn, Rohmann and Harshman, '68). Defining medullary stenosis as medullary cavity width in the second metacarpal at midshaft in the adult female less than 1 mm (see fig. 2 ) and as studied in 2065 women from seven countries of Central and North America, there is considerable variation in the frequency of this trait. Among women aged 18 to 45, the frequency of normal medullary stenosis ranges from under 2% in Nicaragua to nearly 7% in Costa Rica (table 1). In four of these countries (Nicaragua, Panama, El Salavador and Guatemala) the frequency of medullary stenosis is significantly smaller than in Costa Rica by x2 test. Costa Rica, then, emerges as the country with the highest frequency of medullary stenosis in the present sense. In a general way, the frequency of medullary stenosis as shown in the metacarpals appears to be a function of the frequency of European genes. Moreover, the high frequency of medullary stenosis in Costa Rica is associated AM. J. PHYS. ANTHBOP., 29: 425-428. with increased size variance of the medullary cavity diameter rather than overall size reduction in this width.' As shown in table 1, Costa Rica has the highest medullary size variance (as measured by oZ), the F test is then positive for all six comparisons and i t is significant at p = 0.05 or better in comparison with Guatemala, El Salvador, Nicaragua, and Panama. Furthermore, analysis of the distributions countryby-country indicates a tendency towards skewness at the bottom end of the medullary size distribution, and, especially in Costa Rica, a secondary mode well below 0.9 mm. Now adult medullary stenosis could be due to a failure of endosteal resorption during childhood, or to an excess of endosteal apposition during adolescence and young adulthood (cf. Garn, Rohmann, Wagner and Davila, '68). To resolve this problem, we have turned to our serial, longitudinal data from Southwestern Ohio, selecting subjects of each sex with the lowest possible fully adult values of medullary width. These included two males, numbers 268 and 112, with medullary widths of 0.60 and 0.45 mm (T17 and T16) at ages 24 and 33 years respectively. It also includes two females (151 and 097) with minimum medullary cavity widths of 0.80 and 0.40mm (T-scores 23 and 22 at ages 18 and 34 years, in turn). These four indi1 Although Costa Rican women include the largest percent with medullary widths under 1.0 mm the mean medullary cavity width is not significantl; different from that for the other populations considered except for El Salvador, where it is actually slightly larger ( t = 2.62).