The flexible intramedullary pin technique is currently recognized as the preferred method for treating long bone stem fractures in children. The traditional plate screw internal fixation technique has a long surgical incision, extensive periosteal stripping, slow fracture healing and obvious skin scar; moreover, the surgery to remove the plate screw after fracture healing still requires extensive stripping again, which is more traumatic. The flexible intramedullary pin technique generally uses closed reduction or small incision to assist in fracture reduction, and the intramedullary pin fixes the fracture through the broken end from the medullary cavity without stripping the periosteum, with a small incision and a simple procedure to take out the internal fixation, which is the preferred minimally invasive treatment method for children with long diaphyseal fractures. Typical case: Femoral stem fracture Preoperative X-ray Intraoperative closed reduction Postoperative X-ray The fracture was completely healed 7 months after surgery and internal fixation was taken