Rod diameter prediction in patients with osteogenesis imperfecta undergoing primary osteotomy.

Because the cross-sectional shape of the long bones of patients with osteogenesis imperfecta is often elliptical, the use of preoperative radiographs to determine intramedullary rod diameter in these patients undergoing osteotomy may be misleading. To investigate this, the authors correlated the narrowest inner bone diameter (NID) on preoperative radiographs to the rod diameter (RD) on postoperative radiographs. The authors evaluated 79 bones in 27 patients undergoing primary osteotomy with intramedullary fixation. Only 5% of the bones had an equal NID and RD, with 81% of bones having a smaller RD than the measured NID. Although a positive correlation was found between RD and NID (correlation coefficient 0.76), measurement of the NID on preoperative radiographs did not provide a good prediction of the actual RD used in this series of children with osteogenesis imperfecta.