Recently, surgical intervention of the fractures of the humeral shaft was increased due to the severe trauma occuring in the traffic accident and industrial accident, even if closed treatment was appropriate in the humeral diaphysis.

In order to obtain the early mobilization prevention of the nonunion and joint stiffness, rigid fixation of the fracture is needed. To reduce the complication of the open reduction (nonunion, infection, radlal neue palsy), closed intramedullary nail fixation techlnques without opening the fracture site were used.

Eight cases of the fractures of the humeral shaft were treated with nonreamed True/Flex humerus rod system(intramedullary fixation) between Nov.1992 and Apr.1993. And the obtained results were as follows.

1. The normal healing cases were S and its average healing time Is post-op. 9.2 weeks. There were nonunion in 1 case and delayed union in 2 cases.

2. The causes of the injury were traffic accident in 6 cases fall down in 1 case, belt injury in 1 case.

3. The causes of the nonunion and delayed union were as follows distraction(by inappropriate selection of the rod and physical treatment) in 2 cases, insufficient immobilzation in 1 cases.

4. The True/Flex humerus rod seemed to recommand to the patients with multiple, open, segmental fractures and poor qeneral condition.