Metacarpal measurements in X-linked hypophosphataemic rickets.

In 15 girls and 7 boys with hypophosphataemic vitamin D-resistant rickets, midshaft diameter, combined cortical thickness, cortical area and metacarpal length were determined in the second metacarpal on radiographs of the left hand. The values obtained were compared with age-matched and height-matched controls. In a longitudinal study the same bone measurements were taken in these 22 patients and in additional 3 boys. The metacarpal diameter in the patients was increased whereas the combined cortical thickness was decreased. The former feature appeared to have its onset in early childhood. Cortical area was normal for age and increased for height, which was taken to indicate a normal or increased bone mass in these children. Metacarpal length was normal for age and height in the boys and increased for height but still within the normal range in girls. This is in agreement with the normal arm-span that has been found in these children.