In order to determine the reliability of the Cobb angle measurement as it is used in the clinical management of scoliosis, a methodological survey was carried out. In the measurement of a Cobb angle two phases can be distinguished: (a) the production of a spinal radiograph and (b) the measurement of the angle itself. In respect of the first phase, the variation in production of the radiographs was calculated on Cobb angle measurements made by one investigator on serial radiographs of patients who underwent spinal fusion for scoliosis and therefore had a fixed spinal curvature. For the second phase, the accuracy of Cobb angle measurement was investigated by comparing measurements on the same radiographs of 46 scoliosis patients obtained by three investigators, namely two orthopaedic surgeons and an orthopaedic fellow who was assigned to a school screening project. Results were expressed as a Spearman correlation coefficient and a standard deviation of the differences. The Spearman correlation coefficient was 0.98 for the repeated radiographs (production variation) and also 0.98 for the repeated measurements on one radiograph (interobserver measurement variation). The standard deviation of the differences in Cobb angle for the repeated radiographs amounted to 3.2 degrees and for the repeated measurements on one radiograph it was 2.0 degrees. Although there is a good reproducibility of the Cobb angle measurement between different investigators, the variation in production of a spinal radiograph is an important source of error. This should be taken into account when making decisions in scoliosis management.

The Netherlands has well-organized school health services, and children are assessed on a regular basis for scoliosis among other disturbances and pathologies. The purpose of this study was to assess the benefits of an annual screening programme for scoliosis in the Netherlands. Three cohorts of 10,000 children sampled at 10, 12 and 14 years of age, respectively, were followed for 3 years. Children with a positive bending sign were referred to a second screening stage, in which external asymmetry was quantified. Children diagnosed via the programme (group 1) were compared with those children who had been referred for treatment independently of the screening (group 2). The total number of children in these groups combined was then compared with the number that would have been expected on the basis of accepted prevalence figures for idiopathic scoliosis given in current literature. Over 30,000 children were screened. Although the programme established a total of 57 cases of definite scoliosis (0.18%), the 34 cases (0.11%) already known, mainly detected by previous school health checks, were more severe regarding the risk of progression and treatment. The annual screening programme did not detect a single case that needed surgery. These figures provide the basis on which to decide for or against adopting an annual screening programme for scoliosis; the decision is a socio-political one. Based on this study, we expect all scoliotic patients needing treatment should be detected in time if periodic health checks will be maintained biennially. On medical grounds, it is our view, that screening for scoliosis should not be performed in the Netherlands annually.

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