Biomechanical study of modular hemipelvic endoprosthesis for Type I-IV defect of pelvic tumor

Background： The modular hemipelvic prosthesis has been used in patient of Type I-IV pelvic tumor with good outcomes, but how to keep the stability between the prosthesis and the residual sacrum is a problem. An additional screw-rod system seems to solve it, but its biomechanical characters are still not well understood, which need experimental evaluation. Methods： Six pelvic specimens were prepared in three conditions （normal intact pelvis, ＂normal＂; the pelvis of left Type I-IV defect and implanted with prosthesis without/with additional screw-rod system, ＂rod-＂ and ＂rod＋＂）. Compressing biomechanical experiments （50-500N） were performed in these three conditions, respectively. Results： The loadings during the experiments are in accordance with the linear elastic control mode. Under the increasing loading, the implanted pelvises displaced asymmetrically, unlike normal intact pelvis. The vertical displacement of ＂rod＋＂ changed significantly, whereas ＂rod-＂ did not. For both implanted pelvis, right side displaced less than left side （P values 〈0.05）. Conclusions： The implanted pelvis showed asymmetric displacement under loading, where healthy side displaced more. The implanted pelvis plus screw-rod system showed less displacement at implanted side but more at contralateral side in comparison with those without screw-rod system.

Novel 3D Printed Modular Hemipelvic Prosthesis for Successful Hemipelvic Arthroplasty： A Case Study

In this study, in order to prevent the failure of hemipelvic arthroplasty using a patient-specific Computer-Aided Design （CAD） and Additive Manufacturing （AM） approach, a new design for modular hemipelvic prosthesis was developed. Moreover, the biomechanical properties of the new design were determined. The 3D printed pelvic prosthesis with a sacrum portion that completely matches the back surface of the patient＇s sacrum offers more potential for bone ingrowth between the host bone and prosthesis. The new approach integrated the capabilities of digital medical imaging techniques, CAD and metal AM to realize a modular hemipelvic prosthesis. The patient＇s pelvic Digital Imaging and Communication in Medicine （DICOM） data were imported into Mimics software to construct a digital representative patient model for design of the prosthesis. A physical model was obtained using a Stereolithography （SLA） 3D printer for preoperative planning. The final customized implant was designed by using UG NX 10.0 software. Then a surgically modular hemipelvic prosthesis was fabricated from the Ti6Al4V titanium alloy by electron beam melting technology. The operation was performed according to the preoperative planning. The outcome of the operation was good at the 6-month follow-up. Also, the stress distribution and the relative micromotion revealed positive results based on a finite element model built to detect prosthesis stability. The 3D printed modular hemipelvic prosthesis provided good resolution for the failure of hemipelvic arthroplasty. Personal customization will be important in future surgeries aiming at improving the anatomy and function of the implant.

Design and Application of 3D Printing Based Personalised Pelvic Prostheses

In this paper,we describe the design and surgical process of personalised pelvic prostheses fixation through 3D printing according to different Enneking pelvic tumour zones:the ilium(Zone I),acetabulum(Zone II),and pubis and ischium(Zone III).A 3D model of the pelvis was reconstructed using imaging data,and the parameters on the planes of the acetabulum and pelvic incisal margin were measured.The main body of the pelvic prosthesis was constructed,a porous structure was designed on the bone-prosthesis interface,and the movement paths,lengths,and diameters of screws were planned.By combining the pathological model and osteotomy guide,limb salvage reconstruction was performed in patients with pelvic tumours.Preoperative and postoperative data were compared to verify the prosthesis stability.Our investigation revealed that the long-term survival of pelvic reconstruction prostheses depends on accurate matching with the bone defect area,good initial stability,and a porous structure to allow bone ingrowth.