Abstract
1. The widespread deformities commonly associated with diaphysial aclasis have been studied in seventy-six patients. Apart from the adaptations of growth due to pressure by neighbouring exostoses, all the deformities of the tubular bones can be explained in terms of the same underlying factor–diminished length of the bones affected by the disease.
2. When the condition first manifests itself the future pattern of bone growth is completely unpredictable except in so far as it is known that the more actively growing ends of the long bones are the more severely affected in each case. It has also been shown in this series that, in general, the bones with the smallest cross-sectional area at the epiphysial plates (such as the ulna and the fibula) are the most severely shortened of all.
3. The cause of this disturbance of growth is still unknown, but there is an undoubted relationship between the presence of exostoses or thickening of the metaphysial region and shortening of the bone involved.
4. The phenomena of migrating exostoses and disappearing exostoses are also described and are shown to be examples of the normal process of bone modelling applied in special circumstances.
5. Although the importance of the cartilage-capped exostoses is not underestimated, it is hoped that this study will stimulate further work on what is probably the basic defect in this disease–namely, the disturbance of bone growth.
