Hip reconstruction using a customized intercalary prosthesis with the rhino horn-designed uncemented stem for ultrashort proximal femur segments following tumor resection: a combined biomechanical and clinical study

Background Hip-preserved reconstruction for patients with ultrashort proximal femur segments following extensive femoral diaphyseal tumor resection is a formidable undertaking. A customized intercalary prosthesis with a rhino horn-designed uncemented stem was developed for the reconstruction of these extensive skeletal defects. Methods This study was designed to analyze and compare the differences in the biomechanical behavior between the normal femur and the femur with diaphyseal defects reconstructed by an intercalary prosthesis with different stems. The biomechanical behavior under physiological loading conditions is analyzed using the healthy femur as the reference. Five three-dimensional finite element models (healthy, customized intercalary prosthesis with four different stems implemented, respectively) were developed, together with a clinical follow-up of 12 patients who underwent intercalary femoral replacement. Results The biomechanical results showed that normal-like stress and displacement distribution patterns were observed in the remaining proximal femur segments after reconstructions with the rhino horn-designed uncemented stems, compared with the straight stem. Stem A showed better biomechanical performance, whereas the fixation system with Stem B was relatively unstable. The clinical results were consistent with the FEA results. After a mean follow-up period of 32.33 +/- 9.12 months, osteointegration and satisfactory clinical outcomes were observed in all patients. Aseptic loosening (asymptomatic) occurred in one patient reconstructed by Stem B; there were no other postoperative complications in the remaining 11 patients. Conclusion The rhino horn-designed uncemented stem is outstanding in precise shape matching and osseointegration. This novel prosthesis design may be beneficial in decreasing the risk of mechanical failure and aseptic loosening, especially when Stem A is used. Therefore, the customized intercalary prosthesis with this rhino horn-designed uncemented stem might be a reasonable alternative for the reconstruction of SSPF following extensive tumor resection.

Automated summary

Background: Hip-preserved reconstruction for patients with ultrashort proximal femur segments following extensive femoral diaphyseal tumor resection is a challenging procedure. Methods: This study aimed to analyze and compare the biomechanical behavior and clinical outcomes of a customized intercalary prosthesis with a rhino horn-designed uncemented stem for the reconstruction of these extensive skeletal defects. Results: The biomechanical results showed that the rhino horn-designed uncemented stem had better stress and displacement distribution patterns compared to the straight stem. Stem A performed better in terms of biomechanical performance, while the fixation system with Stem B was relatively unstable. The clinical results were consistent with the finite element analysis (FEA) results. Conclusion: The rhino horn-designed uncemented stem offers precise shape matching and osseointegration. This novel prosthesis design may reduce the risk of mechanical failure and aseptic loosening, particularly when using Stem A. Therefore, the customized intercalary prosthesis with this rhino horn-designed uncemented stem may be a suitable option for the reconstruction of ultrashort proximal femur segments following extensive tumor resection.