Remodeling of the calcaneus apophysis in the growing child.

Radiography and computer-aided analysis of tomography of the os calcis in 35 children with Sever's disease and of 52 control children were concurrently evaluated with histologic appearance of six calcanei of victims of road accidents, which were radiographically compatible with the same syndrome. Histology showed abrupt interruption in continuity of the apophysis of perpendicular fibrous plates with evidence of an ongoing reparative process. Computer-aided analysis of orientation of the "fragmentation" lines and histologic data both support the hypothesis of a stress remodeling process owing to excessive bending forces acting on the calcaneal apophysis.

Clubfeet associated with hydrocephalus: new evidence of gradual dynamic development in utero.

Clubfoot, a relatively frequent congenital malformation, may be associated with several genetic syndromes or other malformations, or may appear as an isolated idiopathic anomaly. We describe the intrauterine development of clubfeet subsequent and in parallel to fetal hydrocephalus formation, as followed by serial transvaginal sonographic scans at 11-16 weeks' gestation. The possibility of a causal relationship between the central nervous system malformation and the clubfeet is suggested. To the best of our knowledge, this is the first description of the dynamic, in vivo fetal development of hydrocephalus and clubfeet at 11-16 weeks' gestation.

Ligament and tendon substitution with composite carbon fiber strands.

Carbon fiber strands were used experimentally to substitute for tendons in dogs and clinically to reconstruct tendons and ligaments in human. The investigation was carried out to determine the histologic appearance of the new composite structure and its tensile strength in comparison to the natural structure. The histologic picture disclosed a remarkable structure evolved by continuous irritation of the carbon fibers and consisting of two interrelated components: synthetic carbon fibers and biologic collagenous tissue. This carbon fiber composite structure was composed of long cylindrical units containing concentric layers of collagenous fibers and cells enveloping the core of each carbon fiber. After one year of physiologic use in dogs, the average ultimate tensile strength of the composite structure which replaced the quadriceps and triceps was 372 N, or 88% the strength of the natural tendons. One year after implantation the histologic picture of the composite structure in human showed a relatively dense collagenous architecture. However, a significant proportion of the structure was taken up by histiofibroblasts produced by the irritation of the carbon fibers. Thus, the density of the collagen in the composite structure remained relatively deficient in comparison to the nature tendon, and the structural tensile strength continued to depend entirely on the integrity of the carbon fibers.

A model for inferring the voluntary and involuntary causes of residential segregation.

It is clear that both voluntary and involuntary forces normally contribute to the residential segregation existing between groups. For the most part, the contribution of each dimension has not been determined. Rather, researchers operate as if either one or the other force is operating. In the United States, for example, black-white segregation is assumed to be imposed by whites on blacks, as if the latter were themselves totally indifferent to the racial composition in their areas of residence. On the other hand, it is assumed that segregation between white ethnic groups is at present purely a voluntary matter. In an earlier period, it was assumed that their segregation was both voluntary (reflecting desires to be among copatriots) and involuntary (reflecting the imposition of restrictions on residential movement by other groups as well as economic forces). But it has not been possible for investigators to determine the relative importance of each factor. Using asymmetrical segregation indexes, a rudimentary procedure is proposed for determining the relative importance of voluntary and involuntary forces operating to generate a given level of segregation. Data based on Black, Anglo, and Spanish residential patterns are then considered in terms of the proposed model.

A comparison between Northern and Southern blacks residing in the North.

Differences between Southern and non-Southern blacks living in the North and West are considered for a wide variety of attributes such as employment, occupation, income, marital stability, and offspring's performance in school. Migrant blacks have generally more favorable rates than their Northern- and Western-born compatriots after standard domographic controls are applied to an unusually detailed set of cross-tabulations based on the One-Percent Sample Tapes for 1960. Perhaps the sharpest gap exists with respect to marital conditions; Southern blacks of both sexes are more likely to marry and, among those ever married, live more frequently with their spouses. Some of the results reported by earlier investigators require considerable modification; For example, the fact that Northern black men are less often at work than migrants has led to speculations about regional differences in work orientation among blacks, but a detailed analysis of labor force activity indicates this pattern does not hold for women. Likewise, the migrant income advantage is found to vary by education such that it is confined to those with low educational attainment. The use of sample tapes permits a novel analysis of differences between Northern-born blacks classified by whether they are second or at least third generation residents of the North (children of Southern- or Northern-born parents, respectively). For the attribute measured, school performance, the gap is essentially nil. Finally, an alternative is suggested to the existing causal interpretations of North-South gaps among black residents of the North. Reconsidered in particular are the higher labor force rates of migrant men and their more frequent employment in blue collar jobs;