An attempt has been made to estimate the number of living people with skeletal dysplasias (osteochondrodysplasias) in Scotland, England and Wales, ascertained through five orthopaedic centres in different parts of Britain. Index patients and their affected relatives were sought and reassessed. Over the 30-year period between 1950 and 1979 inclusive a minimum prevalence was calculated (excluding stillbirths, perinatal deaths, and patients with chromosome anomalies, metabolic bone disease and short stature per se). The results indicate that there were in the community upwards of 10 000 individuals, at various ages over this period, with these largely genetic disorders. A more accurate estimate is of some 6000 of them requiring substantial orthopaedic care, and who were physically handicapped throughout life, about half of them severely so.

Forty-eight patients with achondroplasia and 24 with hypochondroplasia have been reviewed in order to clarify the differences between the two disorders and establish the height, body proportions and other clinical and radiological variations within each group. Some of the "classical" findings in achondroplasia are not always present, and hypochondroplasia at its most severe is indistinguishable from achondroplasia at its least severe. The frequency of spinal stenosis and neurological complications was established in an unselected group of 27 achondroplastic and 12 hypochondroplastic patients aged 10 years and over. Only three of the former were free of symptoms but only three developed serious complications (11 per cent). Measurement of radiographs of the lumbar canal did not in general correlate well with the severity of spinal stenosis symptoms, but it was found that the ratio of interpedicular distances at the first and fourth lumbar vertebrae had some value. Neurological complications were rare in patients with simple narrowing of the spinal canal or with persistence of a thoracolumbar kyphos but when these occurred together there was a high risk of serious neurological involvement.

The aims of this survey were to establish the familial incidence of Perthes' disease, to note any associated developmental anomalies and to collect information on preceding trauma or synovitis, on the pregnancy and birth, and on various sociological factors. Height and weight measurements were obtained for 217 patients, and comparisons made with those of their parents, unaffected sibs and (local) controls. Results showed an extremely low frequency of Perthes' disease among relatives, with no obvious pattern of inheritance. As genetic factors were not apparent, environmental and sociological causes were sought. The disease occurred particularly in children who were third-born or later in the family, and had older than average parents. Many came from low-income families and one in ten had been a breech birth, shown other malposition or had had a version late in pregnancy. Many children were already undersized at the time of developing Perthes' disease and remained short than average throughout life. Neither their parents nor sibs were shorter than normal, indicating that the patients' short stature was not familial. The child who is going to develop Perthes' disease is already constitutionally and socially at a disadvantage, and during the perinatal period and the first few years of life is perhaps more susceptible to trauma than is a normal child.