A cost-effective 3D-printed cement spacer reconstruction in a rare case of calcaneal Ewing sarcoma: a case report and surgical technique.

Background: Ewing sarcoma (ES) accounts for 15% of primary bone tumors and is the second most common type seen in children and young adults between ages 5 and 20, with a male-to-female ratio of 1.5 to 1. Around one-third of patients have metastatic disease at diagnosis, while involvement of the foot is rare, accounting for only 5% of cases. For patients without metastases, treatment typically includes neoadjuvant chemotherapy, limb salvage surgery when possible, and adjuvant chemotherapy. Recent advances in 3D printing enable customized, patient-specific reconstruction in complex anatomical sites, such as the calcaneus. Case presentation: A 19-year-old female, previously healthy, presented with progressive left heel pain for 1 year without constitutional symptoms or trauma. Clinical observation revealed a swollen heel with intact overlying skin, no deformity, and no limitation of range of motion or neurovascular deficits. Radiologic local and systemic staging showed a nonmetastatic, aggressive, lytic, ill-defined lesion in the left calcaneus on x-ray, with MRI demonstrating a heterogeneously enhancing calcaneal tumor with soft-tissue extension into the heel fat pad and sinus tarsi. Histopathology of the image-guided true-cut biopsy specimen confirmed the diagnosis of Ewing sarcoma and primitive neuroectodermal tumor with EWSR1-FLI1 translocation. After multidisciplinary tumor board discussion, the patient received neoadjuvant chemotherapy with alternating vincristine, doxorubicin, cyclophosphamide, ifosfamide, and etoposide, resulting in tumor regression and good response on restaging. She then underwent limb salvage total calcanectomy. Reconstruction involved a custom-made, 3D-printed mold to fabricate an antibiotic-impregnated polymethylmethacrylate (PMMA) cement spacer, secured with two cannulated screws to the talus and Achilles tendon reattachment. After initial closure, the patient developed wound dehiscence, requiring a free radial forearm flap. She resumed adjuvant chemotherapy. At 1-year follow-up, the patient ambulated with a cane and a Toronto Extremity Salvage Score of 62.5%. By 2.5 years, she developed a deep surgical site infection (Enterococcus faecalis), managed by multiple irrigations, debridement, and implant removal. The infection resolved, the wound healed, and there were no signs of recurrence or metastasis. Conclusions: This case underscores the feasibility of limb salvage surgery in calcaneal primary malignant neoplasm, using versatile reconstructive options including custom 3D-printed prosthetic implants, cement spacers, and total calcanectomy without reconstruction.