Ivan Mauricio Rodriguez MaciasJuan Fernando ChaustreGabriel Narvaez RodriguezLuis Carlos GomezAndrea FrancoCamilo Soto Montoya2026-01-212026-01-212025-11-26Rodriguez Macias IM, Chaustre JF, Narvaez G, Gomez LC, Franco A, Soto Montoya C. Oncologic reconstruction of the proximal femur in children younger than 9 years using a proximal humerus allograft and a hip prosthesis: Report of two cases and description of the surgical technique. J Orthop Surg (Hong Kong). 2025 Sep-Dec;33(3):10225536251406432. doi: 10.1177/10225536251406432. Epub 2025 Dec 7. PMID: 41353613.DOI: 10.1177/10225536251406432https://hdl.handle.net/20.500.14595/890Osteosarcoma and Ewing sarcoma are the two most common primary bone sarcomas in the pediatric and youngadult population, and because of their location they pose a therapeutic challenge due to the segment’s biomechanical demands and the need for reconstructions that preserve length, support, and mobility.1,2 Comprehensive oncologic management combines chemotherapy, wide resection, and functional reconstruction, and the choice of technique depends on patient age, tumor location, and implant availability.3,4 In very young pediatric patients, conventional modular prostheses have limitations (available sizes, risk of physeal injury, loss of bone stock, or long-term loosening), making their use problematic at extreme ages.5–7 Biologic reconstructions and allograft–prosthetic composites (APCs) are valuable alternatives because they allow the reconstruction of the soft tissues, preserve bone stock, and improve function; nevertheless, they carry risks (resorption, nonunion, fracture, infection).8 In the absence of viable reconstructive options, radical procedures such as amputation or rotationplasty remain considerations, albeit with greater functional and psychosocial implications.9,10 Against this backdrop, developing techniques that broaden reconstructive options in pediatric patients is crucial. The technique we describe—an allograft–prosthetic composite based on a proximal humerus allograft—aims to provide a reproducible and biologically favorable option within the few alternatives available for this challenging segment.Introduction: Proximal femoral tumor resection poses a major challenge in orthopaedic oncology, particularly in very young pediatric patients (<9 years), where the need to preserve function and limb length collides with the limited availability of reconstructive options (3D-printed implants, endoprostheses, biological constructs such as vascularized fibular grafts, and allograft-prosthetic composites) or leads to amputation. Objective: To describe in detail the surgical technique for proximal femoral tumor resection and reconstruction using an allograft-prosthetic composite (APC) with a proximal humerus allograft plus a hip prosthesis, documenting its applicability and outcomes regarding function, allograft survival, and oncologic disease status in two pediatric cases treated at a national cancer referral center in Bogot´a, Colombia. Methods: We report two pediatric cases and detail the surgical technique used for proximal femoral reconstruction after tumor resection, based on an APC (proximal humerus allograft + hip prosthesis). Data were collected from medical records with radiological and functional follow-up. Results: In both patients, proximal femoral reconstruction using our technique yielded a stable construct with preservation of limb function (MSTS >72), documented graft incorporation at 3 months, local disease control, and only one recorded complication (contact dermatitis). Conclusion: Proximal femoral reconstruction using an APC with a proximal humerus allograft is a viable and safe surgical option in pediatric patients with Ewing sarcoma. In our experience, the technique was successfully applied in two patients, allowing limb preservation with a favorable course. Thus, it offers a functional and reliable option for limb salvage in selected cases.en-USewing sarcomafemurreconstructive surgical procedurespediatricsallograftsprostheses and implantsArticle