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The natural history of Perthes' disease.

1. Eighty-nine cases of Perthes9 disease are reviewed. 2. The prognosis varies with the amount of the epiphysis involved. 3. It is possible to assess the amount of epiphysial involvement by a study of the early radiographs. Cases were allocated to four groups on this basis. 4. It is confirmed that both sex and age at the time of diagnosis influence the final prognosis. The reasons for this are discussed. 5. The concept of "the head at risk" is suggested and radiological signs described to diagnose such cases. 6. It is hoped that the classification suggested may in future act as a basis for comparisons of treatment.