Skeletal overgrowth with modelling error in neurofibromatosis.

Ten cases of neurofibromatosis, nine involving the lower extremity and one, the upper extremity, were analysed for growth and modelling errors. The elongated bones showed over-tubulation or under-tubulation. Long as well as short bones were affected. Modelling errors mostly affected the metaphysis but, in a few cases, especially where there was isolated involvement of the fibula, the diaphysis was also affected. In two patients the whole length of paired bones of the leg showed evidence of over-tubulation. The rule of polarity which influences growth and modelling was not applicable to these cases of neurofibromatosis. Soft-tissue masses of neurofibromatosis often determined the segment of the bone involved but, in cases without such an external influence, inherent mesodermal dysplasia was thought to be the causative factor.