Design,characterisation,and clinical evaluation of a novel porous Ti-6Al-4V hemipelvic prosthesis based on Voronoi diagram

Three-dimensional printed Ti-6Al-4V hemipelvic prosthesis has become a current popular method for pelvic defect reconstruction.This paper presents a novel biomimetic hemipelvic prosthesis design that utilises patient-specific anatomical data in conjunction with the Voronoi diagram algorithm.Unlike traditional design methods that rely on fixed,homogeneous unit cell,the Voronoi diagram enables to create imitation of trabecular structure(ITS).The proposed approach was conducted for six patients.The entire contour of the customised prosthesis matched well with the residual bone.The porosity and pore size of the ITS were evaluated.The distribution of the pore size ranged from 500 to 1400μm.Porosity calculations indicated the average porosity was 63.13±0.30%.Cubic ITS samples were fabricated for micrograph and mechanical analysis.Scanning electron microscopy images of the ITS samples exhibited rough surface morphology without obvious defects.The Young’s modulus and compressive strength were 1.68±0.05 GPa and 174±8 MPa,respectively.Post-operative X-rays confirmed proper matching of the customised prostheses with the bone defect.Tomosynthesis-Shimadzu metal artifact reduction technology images indicated close contact between the implant and host bone,alongside favourable bone density and absence of resorption or osteolysis around the implant.At the last follow-up,the average Musculoskeletal Tumour Society score was 23.2(range,21-26).By leveraging additive manufacturing and Voronoi diagram algorithm,customised implants tailored to individual patient anatomy can be fabricated,offering wide distribution of the pore size,reasonable mechanical properties,favourable osseointegration,and satisfactory function.

Biomechanical Study on the Novel Biomimetic Hemi-Pelvis Prosthesis

A pelvic endoprosthesis is the primary means of pelvic reconstruction after internal hemipelvectomy. In this study, a novel biomimetic hemipelvic prosthesis, including an artificial ilium, an artificial acetabulum, and an artificial pubis, was developed. A Finite Element Method （FEM） was carried out to investigate the biomechanical performance of a pelvis reconstructed with biomimetic hemipelvic prosthesis. Two models, including the reconstructed pelvis and the original pelvis （control model）, were established according to the geometry from CT data of a human male patient with pelvic bone sarcomas. The FE models predict that the biomeehanical function of the pelvic ring can be reestablished using this prosthesis. Results show that the body force loaded on the S 1 vertebra is restored and transferred towards the sacro-iliac joint, and along the ilium onto the bearing surface of the artificial ilium, then to the artificial acetabulum and pubis. Von Mises stresses observed in this reconstructed pelvis model are still within a low and elastic range below the yielding strength of cortical bone and Ti6A14V. The values of deformation and strain of the reconstructed pelvis are close to the data obtained in the original pelvis. With the partial replacement of the pubis, little influence is found towards the pubis symphysis. However, the interface between the prosthesis and pelvic bone may become the critical part of the reconstructed pelvis due to the discontinuity in the material properties, which results in stress shielding and deformation constraining. So a biomimetic flexible connection or inter layer to release the deformation of pelvis is suggested in future designing.