The case report of a severe osteolytic reaction surrounding the OptiPlug cement restrictor in a 74-year-old male patient initiated a retrospective case series and closer investigation into the OptiPlug and its active compound, PolyActive. Not only did we find several cases of severe osteolysis in our own study population of 284 patients, several articles have lately described potential harmful side effects of the PolyActive material in humans. Although none of the articles have been based on large databases, we cannot guarantee the safety of this product. More research would help in our understanding of this phenomenon. Until then, we cannot recommend the use of the OptiPlug cement restrictor.

A 7-year-old boy developed complaints of pain in the left groin. These complaints started spontaneously. Initial plain radiographs of the pelvis indicated no abnormalities. As the symptoms persisted for 6 weeks, the young patient and his parents visited our institution. Clinical investigation showed a slight extension deficit of the left hip. New radiographs and MRI indicated a fracture line with sclerosis along the inferior border of the left femoral neck. In retrospect, this stress fracture of the femoral neck was also visible on the initial radiographs. Seven months after the onset of complaints in the left groin and prescribed partial weight bearing with crutches, callus formation with consolidation of the femoral neck was observed on radiographs. Eleven months after onset, the patient recovered fully without any residual symptoms. After 21 months, the young patient did not have any complaints or restrictions in physical activity. Because of its highly rare nature, stress fractures of the femoral neck in children are easy to miss initially. This was also applicable in our case. Extensive differential diagnosis of a child with pain in the groin furthermore adds to the difficulty in the diagnosis of a stress fracture of the femoral neck. This case report emphasizes the importance of the evaluation of radiographs and observation in children with hip complaints. Similarly, interdisciplinary consultation and cooperation between the general practitioner, orthopaedic surgeon, radiologist and paediatrician is essential in the diagnosis, evaluation and treatment of these young patients.