Optimization Design And Finite Element Analysis Of 3D Printing Bionic Sacral Osseointegration Prosthesis

Background:The pelvis is one of the most common locations for bone tumors.Due to the complex anatomical structure of the pelvis,it is a challenge for bone oncologists to reconstruct the function of the hemipelvis after pelvic tumor resection.For Enneking I+II+III zone pelvic malignancies.Due to a series of problems such as excessive resection,difficult fixation methods,adjacent important neurovascular,and high clinical complications,the task of reconstruction is particularly difficult.With the continuous development of 3D printing technology,a variety of 3D printed individualized prostheses have been applied clinically.Through the optimization design of the prosthesis structure and finite element analysis,a new solution for the design of hemipelvic prosthesis is provided.The stability of the sacroiliac interface and the symphysis pubis interface of the hemipelvic prosthesis can maintain the mechanical stability of the prosthesis and protect the interfacial bone integration.The stability of the sacroiliac interface plays a major role.There are different fixation methods at the sacroiliac interface.However,there is no comparative study on the influence of different fixation methods on the biomechanical stability of prosthesis.Method:Based on the three-dimensional finite element model of normal pelvis,four kinds of semi-pelvic prosthesis replacement models were established.A: 3 screws between the prosthesis and the sacral auricular surface,with a diameter of 7.5mm,a length of S1 75 mm,S2 90 mm,S390mm;b: Based on single interface,the ventral side of the sacrum was fixed with a hook of 12 mm long,10 mm wide and 2 mm thick.C:Based on single interface,L4 and L5 screws were fixed,with a diameter of 7.5 mm and a length of 65 mm.D: On the basis of single interface,sacral dorsal screw fixation,diameter 7.5mm,length S1 30 mm,S225mm,S3 20 mm.Result:Four fixed three-dimensional finite element models of sacroiliac interface of semi-pelvic prosthesis were established.Through the analysis of stress distribution and micro-motion cloud map,it is found that the stress distribution of A and B interface is concentrated,mainly around the screw hole.Among them,the maximum stress of A transverse nail is 368.3 MPa,the maximum stress of B transverse nail is 318.4 MPa,the maximum stress of C transverse nail is 300.1 MPa,and the maximum stress of D transverse nail is 253 MPa.The proportion of the area of the sacroiliac interface fretting greater than 28 microns in the four fixation methods of A,B,C and D was 9.12 %,4.37 %,4.66 % and3.90 %,respectively.Conclusion:The single-interface fixation of the auricular surface of the semi-pelvic prosthesis can reduce the maximum stress by assisting the sacral hook fixation,the auxiliary screw-rod system fixation and the auxiliary sacral dorsal fixation,and reduce the proportion of micro-motion greater than 28 microns.