Abstract
1. Perthes' disease is an ischaemic lesion of the ossific nucleus of the head of the femur which may vary both in extent and degree. It is probably never quite complete.
2. When part of the ossific nucleus only is affected, as is usually the case, it is almost invariably the antero-lateral part.
3. The process of absorption of the damaged bone is complete radiologically before there is radiological evidence of reossification.
4. Reossification always occurs in Perthes' disease.
5. The aim of treatment must be to see that the mould in which the head is shaped is the right shape when ossification occurs.
6. The deformity of the head of the femur does not occur from pressure alone, but from pressure combined with subluxation. Full unrestricted weight-bearing can be allowed with safety on a femoral head in which there are ischaemic changes provided the femoral head is well contained.
7. The time of treatment can be very greatly reduced by using operation to correct the subluxation instead of relying on external splintage. This can be achieved by subtrochanteric osteotomy with rotation, or rotation combined with varus angulation.
8. Perthes' disease and avascular necrosis of the head of the femur are different conditions with different characteristics.
9. Suggestions are made as to the nature of the disease in relation to absorption, continued growth and reossification.
