Treatment of physeal arrest with bar removal and placement of interposition materials in young patients has been shown to restore physeal growth. Among the various materials that have been used to prevent early reformation of the physeal bar (fat, silastic, cartilage), Peterson recommended the use of Cranioplast, as this material can prevent bar reformation, and it is radiolucent because it does not contain barium. Peterson suggested steps be taken to prevent migration of the Cranioplast, as migration of the interposition material might allow for reformation of the physeal bar. Although Peterson had not observed cement migration leading to pathologic fracture, he felt that this was a potential concern. We describe the case of cement migration from the epiphysis into the diaphysis, leading to a pathological femur fracture. Despite migration of the Cranioplast, the physeal bridge did not reform, and the patient had nearly normal growth 7 years after the initial physeal arrest procedure.