Background and study aims <p>Elastic stable intramedullary nailing (ESIN) enables stable osteosynthesis with a low rate of complications in pediatric both-bone forearm fractures. However, repeated unsuccessful attempts at closed reduction can cause unnecessary soft tissue trauma and increased radiation exposure. We conducted a retrospective study of pediatric forearm fracture patients to identify predictors for the need for open reduction when using ESIN.</p> Patients and methods <p>We included 65 pediatric patients who underwent ESIN osteosynthesis for both-bone forearm fractures. We analyzed gender, age at injury, fracture location, fracture type, radiological parameters (shortening, angulation, and translation), the order in which the bones were stabilized, and the type of reduction performed.</p> Results <p>Of the patients, 49 (75.4%) were male and 16 (24.6%) female, with a mean age of 11.5 years. Most fractures (87.7%) occurred in the middle third of the forearm; 4.6% were proximal, and 7.6% distal. Fifteen patients (23%) had an open fracture; the remaining 50 (77%) had closed fractures. Overall, 59.2% (77/130) of fractured bones were fixed after closed reduction, while 40.8% (53/130) required open reduction and fixation. When the radius was the first bone stabilized, significantly greater translation and shortening were observed in cases requiring open reduction. The difference was most pronounced when translation exceeded 100%. When the ulna was the first bone stabilized, significantly greater shortening predicted the need for open reduction.</p> Conclusions <p>When the radius is stabilized first, significant shortening and translation—especially translation over 100%—strongly predict failed closed reduction. When the ulna is first, shortening remains a reliable predictor.</p> Level of evidence <p>Level III (Retrospective comparative study).</p>