Harzem Ozger

Purpose To perform a comprehensive biomechanical comparison of bone recycling methods (autoclaving, pasteurization, irradiation, and liquid nitrogen freezing) with the frozen allograft method using fresh ovine femora as a cortical bone model. Methods A total of 126 ovine femoral specimens with 2 mm cortical thickness and 20–25 cm length were harvested and allocated into six groups (n = 21 each): Control, autoclaving, pasteurization, irradiation, liquid nitrogen, and frozen allograft (stored at − 80 °C for 12 weeks) in vitro. Sterilization protocols were followed according to standard procedures. Each group was further divided into subgroups for biomechanical testing in three-point bending, axial compression, and torsion using the MTS Bionix 858 system. The outcome parameters included the maximum load, stiffness, energy to failure, and shear modulus. All tests were performed under identical conditions and repeated in triplicates to ensure reproducibility. Statistical analysis was performed using ANOVA with Tukey’s post-hoc test. Post-hoc power analysis confirmed an adequate sample size. The Biomechanical Efficiency Index (BEI) was calculated by normalizing the bending, compression, and torsional stiffness values of each group to those of the control group. Results Autoclaving produced the poorest biomechanical outcomes across all parameters, with significantly lower maximum load, stiffness, energy to failure, and shear modulus than those of all other groups (p < 0.001). The pasteurization and irradiation groups preserved mechanical properties moderately better than autoclaving but were significantly inferior to the liquid nitrogen and frozen allograft groups. Liquid nitrogen freezing preserved biomechanical strength most comparable to the control group, with no significant difference in three-point bending, compression, and torsion tests (p > 0.05). The liquid nitrogen group also demonstrated significantly higher stiffness and shear modulus than the autoclaving group (p < 0.001), confirming its superiority. The calculated BEI values for the control, liquid nitrogen, frozen allograft, pasteurization, irradiation, and autoclaving were 100%, 93%, 88%, 85%, 86%, and 53%, respectively. Conclusion Liquid nitrogen freezing and frozen allograft methods provide biomechanical properties closest to untreated bone and are preferable for biological reconstruction after tumor resection. Pasteurization and irradiation remain acceptable alternatives, whereas autoclaving should be avoided because of the severe deterioration of mechanical integrity.

Introduction: Ewing sarcoma (ES) is an aggressive pediatric bone and soft tissue malignancy. Despite advances in multimodal therapy, outcomes remain suboptimal for patients with high-risk features such as large tumor volume, poor histologic response, disseminated disease, or relapse. Maintenance strategies have gained interest in pediatric sarcomas, but evidence in ES is limited. Pazopanib, an oral multi-targeted tyrosine kinase inhibitor, has shown activity in adult soft tissue sarcomas; however, data on its use as maintenance therapy in pediatric ES are scarce. Methods: We retrospectively analyzed six pediatric ES patients who received pazopanib as maintenance therapy following consolidation treatment or, when applicable, after high-dose chemotherapy with autologous stem cell transplantation. Indications included poor-risk localized disease, relapse, or stable residual disease after frontline therapy. Pazopanib dosing, duration, toxicity, and clinical outcomes were reviewed. Results: Pazopanib was administered at doses of 400–800 mg in five patients and 200 mg twice daily in one patient. Hair depigmentation occurred in all patients, and one patient developed reversible hepatotoxicity requiring temporary interruption and dose reduction. At a median follow-up of 47 months (range, 18–53 months), five patients remained in complete remission. One patient with disseminated disease at diagnosis developed intracranial relapse 18 months post-transplant while still receiving pazopanib. Conclusions: In this retrospective cohort, pazopanib was generally well tolerated and may have a potential role as maintenance therapy in selected high-risk pediatric ES patients. However, efficacy cannot be determined from this limited series, and prospective studies are needed to better define its clinical utility in ES.

Objective: This study aimed to evaluate the clinical and functional outcomes of femoral diaphyseal sarcoma resections reconstructed using liquid nitrogen-treated tumor-bearing autografts filled with antibiotic-impregnated polymethylmethacrylate, locked intramedullary nailing with proximal and distal derotation plating, and docking-site grafting. Methods: Between 2004 and 2023, nine patients who underwent femoral diaphyseal resection for osteosarcoma, Ewing’s sarcoma, and small cell sarcoma were retrospectively reviewed. In all cases, tumor-bearing bone segments were devitalized using standardized liquid nitrogen protocol, followed by reimplantation with reconstruction-type intramedullary nailing without incorporating a vascularized graft. A detailed evaluation of postoperative clinical, radiological, and functional outcomes was conducted. Functional outcomes were assessed using the Musculoskeletal Tumor Society Score. Results: The study included nine patients with a mean age of 18.6 years, of whom four were male, five were female. The mean follow-up period was 6.55 years. The mean tumor size was 14.4 cm. Timely union occurred in six patients, while two experienced delayed union and one had nonunion, all of which ultimately healed with or without reintervention. No local or systemic infections, graft fractures, or implant failure were observed. At final follow-up, five patients were disease-free, three were alive with the disease, and one died of the disease. The mean MSTS score was 89.5. Conclusions: Liquid nitrogen-treated autografts offer a safe, cost-effective, and biologically favorable reconstruction option for femoral diaphyseal sarcomas, particularly in young patients with adequate soft tissue coverage. When applied with a standardized technique and careful augmentation, this method results in favorable union rates and long-term functional outcomes.