BACKGROUND Intramedullary telescopic rod fixation has been used for stabilization of the long bones in growing children who have osteogenesis imperfecta. Proximal migration of the rod is the most common complication of telescopic rodding in the femur. The purposes of this study were to evaluate incidence and temporal pattern of proximal migration of the femoral rod, and to investigate factors related to it. METHODS A total of 50 patients with osteogenesis imperfecta, who had femur stabilized by telescopic rod with T-piece, were the subjects of this study. In patients having both the femora stabilized, only 1 femur was randomly selected for analysis. Hence, in 50 femora, migration-free survivorship was analyzed using the Kaplan-Meier method, and association with possible risk factors was analyzed by Cox regression analysis using the proportional hazards model. Factors investigated in the analysis include age at the time of surgery, sex, purpose of the index surgery, residual or developing angular deformity of the femur, rod position at the distal physis, persistent cortical gap at fracture/osteotomy site, Sillence classification, and type of telescopic rod. RESULTS Proximal migration was observed in 7 of 50 femora. Cumulative survival without proximal migration was 0.94 (95% CI, 0.87-1.01) in 1 year, and 0.85 (95% CI, 0.75-0.95) in 6 years. Factors significantly associated with proximal rod migration in Kaplan-Meier survivorship analysis and univariate Cox regression analysis were angular deformity, eccentric rod position at the distal physis, and persistent cortical gap. When these factors were analyzed by multivariate analysis, eccentric rod position at the distal physis was the only significant factor with a hazard ratio of 11.74. CONCLUSIONS The risk of proximal rod migration can be reduced by complete correction of angular deformity and optimal placement of the rod at the distal physis. Our data also suggest that developing angular deformity or persistent osteotomy/fracture gap requires special attention at the possibility of proximal rod migration during follow-up. METHODS Level III, prognostic study.