Congenital femoral deficiency in children can be treated with femoral lengthening. A common complication is fracture soon after removal of the external fixator, often despite prophylactic hip spica cast application. These fractures present special challenges because the patients have tight soft tissues and sclerotic intramedullary canals. We treated nine such fractures in eight children (average age, 5.4 years). Most were 'spontaneous' events resulting in transverse fracture through regenerate bone or pin sites. All were stabilized with intramedullary Rush pins using special insertion techniques. Union was achieved (average, 6 weeks); no significant complications occurred. We describe details of the surgical technique.