Customized 3D-printed component-preserving reconstruction for femoral neck fracture revision in a long-term survivor of pediatric osteosarcoma: a case report.

Background: Late proximal femoral fractures in long-term survivors with childhood tumor endoprostheses are rare and technically challenging. When the proximal femur lacks a usable medullary canal but the distal tumor prosthesis remains stable, reconstruction is difficult and total femoral replacement may be excessively invasive. Case presentation: A 28-year-old man with a history of distal femoral osteosarcoma treated in childhood with knee tumor prosthesis replacement presented after a fall with severe right hip pain and inability to bear weight. Imaging confirmed a displaced femoral neck fracture, while the distal prosthesis remained well fixed. To preserve the stable distal component, we performed a component-preserving reconstruction using a customized monoblock stem with a socket-type prosthesis-to-prosthesis coupling design. The construct was stabilized with vancomycin-loaded PMMA cement, locking screws, and a lateral anti-rotation plate, and a dual-mobility head was implanted. Postoperative radiographs showed satisfactory alignment and positioning. Limb-length discrepancy improved from approximately 20 cm to 15 cm. At 3 months, the Harris Hip Score was 63; at approximately 6 months, it improved to 81, with continued functional recovery. Conclusion: This case suggests that customized component-preserving reconstruction may be a feasible alternative to total femoral replacement in selected patients with complex proximal femoral defects and retained stable distal tumor prostheses. Longer follow-up is needed to determine durability and late complications.