Design and Fabrication of a New Costumed Intercalary Prosthesis for (Ulna Bone)

Reconstruction of defects resulting from long bone fractures is a real challenge for orthopedic surgeons. However, an intercalary prosthetic technique is a reliable solution for treating these defects that occur as a result of trauma or diseases. This study aimed to design and fabricate a new costumed intercalary prosthesis for the treatment of defects in ulna bone fractures. A Computed tomography (CT) scan of the forearms was performed to identify the extent of the forearm damage. Then, the CT scan data of a patient in (DICOM) file format were converted into computer-aided design models and saved in stereolithographic (STL) format using the 3D slicer (5.0.3) software. Consequently, the STL files are imported by Meshmixer software to create the intercalary prosthesis model design. Finite element analysis (FEA) was applied to validate the strength of the prosthesis during torsion and bending, depicting that the max stresses achieved were 1.29e3 MPa in the torsion test and 1146 MPa in the bending test. To manufacture the prosthesis, a solid rod of Ti6Al4V alloy was selected, and then several machining processes were performed for the rod, including milling, turning, and EDM, respectively, to arrive at the desired design for the current prosthesis. Finally, biomechanical tests were conducted to evaluate the prosthesis strength and compare the results of these tests with the finite element analysis. Starting with a biomechanical test, the specimen was subjected at the beginning to torsion with (0.02 N m) escalating to (10.92 N m) and bending at (0.15 kN) progressively increasing to (2.17 kN) strength. Experimental examinations and analyses proved that the implant had enhanced mechanical properties. Based on the results, it can be concluded that the prosthesis was successfully implanted, and a satisfactory result was obtained by using this design method.