Finite Element Analysis of the Pelvis after Customized Prosthesis Reconstruction

Custom-made pelvic prostheses are normally employed to reconstruct the biomechanics of the pelvis for improving patient＇s life quality. However, due to the large demand of biomechanical performance around the pelvic system, the customized prosthesis needs to be studied for its strength and stability. A hemi-pelvic finite element model, including a custom-made prosthesis and the surrounded main ligaments, was created to study the strength and stability of the system. Based on the developed finite element model, the relationship between the pre-stress of the screws and the biomechanical performance of the reconstructed pelvis was investigated. Results indicate that the pre-stress should not exceed 1000 N during surgery in order to prevent fatigue fractures from happening to screws. Moreover, four screws were removed from the pelvic system without affecting the fixing stability of the system, which provide surgical guidance for surgeons in terms of safety and fixation.

Preclinical Strength Checking for Artificial Pelvic Prosthesis under Multi-activities-A Case Study

Customized prostheses are normally employed to reconstruct the biomechanics of the pelvis after resection due to tumors or accidents.The objective of this study is to evaluate the biomechanics of the pelvis under different daily activities and to establish a functional evaluation methodology for the customized prostheses.For this purposes,finite element model of a healthy pelvis as well as a reconstructed pelvic model after type II+III resection were built for biomechanical study.The biomechanical perfonnance of the healthy and reconstructed pelvic model was studied under routine activities including standing,knee bending,sitting down,standing up,walking,stair descent and stair ascent.Subsequently,the strength and stability of the prosthesis were evaluated under these activities.Results showed that,for the heathy pelvic model,the stresses were mainly concentrated around the upper part of the sacrum and the sacroiliac joint undergoing different activities,and the maximum stress occurred during stair ascent.As for the reconstructed pelvis,the stress distribution and the tendency of the maximum stress variation predicted for the bone part during all the activities were similar to those of the natural pelvic model,which indicated that the load transferring function of the reconstructed pelvis could be restored by the prosthesis.Moreover,the predicted maximum von Mises stress of the screws and prosthesis was below the fatigue strength of the 3D printed Ti-6A1-4V,which indicated the prosthesis can provide a reliable mechanical performance after implantation.

Additive manufactured polyether-ether-ketone implants for orthopaedic applications:a narrative review

Polyether-ether-ketone(PEEK)is believed to be the next-generation biomedical material for orthopaedic implants that may replace metal materials because of its good biocompatibility,appropriate mechanical properties and radiolucency.Currently,some PEEK implants have been used successfully for many years.However,there is no customised PEEK orthopaedic implant made by additive manufacturing licensed for the market,although clinical trials have been increasingly reported.In this review article,design criteria,including geometric matching,functional restoration,strength safety,early fixation,long-term stability and manufacturing capability,are summarised,focusing on the clinical requirements.An integrated framework of design and manufacturing processes to create customised PEEK implants is presented,and several typical clinical applications such as cranioplasty patches,rib prostheses,mandibular prostheses,scapula prostheses and femoral prostheses are described.The main technical challenge faced by PEEK orthopaedic implants lies in the poor bonding with bone and soft tissue due to its biological inertness,which may be solved by adding bioactive fillers and manufacturing porous architecture.The lack of technical standards is also one of the major factors preventing additive-manufactured customised PEEK orthopaedic implants from clinical translation,and it is good to see that the abundance of standards in the field of additive-manufactured medical devices is helping them enter the clinical market.