Fig. 1

Radiographs of the different stages of the lengthening procedure and average hip flexion contracture at each measurement period. a Preoperative radiograph of a 16-year-old boy with achondroplasia b) Radiograph during the latency period of the patient. c Radiograph at the early stage of lengthening period of the patient. d Radiograph at the end of lengthening period of the patient. The patient finally gained the length 9.5 cm by femoral lengthening (lengthening percentage of 30.2%). e Radiograph during the consolidation period of the patient. f Radiograph after external fixator removal. The external fixator was removed after a bridging callus was observed at 3 of 4 cortices on plain radiographs. g Diagram of average hip flexion contracture for the entire patients during the each stage of the lengthening process. In the hip flexion contracture group, soft tissue release was performed during the consolidation period (*)