To investigate the causes of nonunion and its appropriate modality of treatment by a retrospective review of our cases.

Four cases of established nonunion of the femur neck referred from other hospitals were included and the initial fracture was Delbet type 2 in all cases. Three cases were mobile with marked bony resorption at the nonunion site.

The causes of nonunion include insufficient fixation which did not cross physis in the state of inaccurate reduction, and also insufficient duration of cast immobilization, and early weight bearing. All cases of nonunion were successfully treated by adequate amount of autogenous cancellous bone graft with minimal pin fixation across physeal plate, and followed by sufficient cast immobilization for more than 12 weeks, reinforced by instituting long-term protective weight bearing for at least 6 months until evidence of union on plain roentgenography is shown.

Based on our experience, we propose the followings instead of subtrochanteric valgus osteotomy in the treatment of mobile, osteopenic nonunion of the femur neck in children. The most important considerations are adequate amount of autogenous cancellous bone graft, and prolonged protective weight bearing until bony union is assured as well as less bulky internal fixation crossing the physis.