Abstract: Objective    To establish a three-dimensional finite element model of the wrist joint and investigate the stress distribution and deformation of the wrist joint and prosthesis at different angles of motion after partial replacement prosthesis of scaphoid with personalized 3D printing,  so as to provide basis for design and optimization of prosthesis for clinical application.   Methods   The CT data of the wrist joint of a patient with left scaphoid fracture and bone defect and the data of a personalized 3D-printed titanium alloy scaphoid prosthesis were imported into finite element analysis software. Relevant material properties were assigned. The overall deformation, stress distribution of the wrist joint, and stress distribution of the prosthesis and screws under different motion directions were analyzed.   Results    With the increasing of motion angle, the overall deformation and stress of the wrist joint increased correspondingly, but there were no obvious stress concentration and shielding. The stress of the prosthesis was concentrated at the scaphoid junction, reaching a maximum value during extreme palmar flexion (264.45 MPa), the stress of the screw was concentrated in the waist, reaching a maximum value during extreme ulnar deviation (116.13 MPa), but did not exceed the material strength.   Conclusions   After the partial replacement of the personalized 3D-printed titanium alloy scaphoid prosthesis, the overall deformation of the wrist joint was small, and the stress distribution was reasonable, without excessive concentration or shielding. The maximum stress was much lower than the yield strength of the prosthesis material. This surgical method can match the anatomical characteristics of the patient, has good biomechanical properties, and is a suitable choice for the treatment of scaphoid nonunion with osteonecrosis of the wrist. 

Key words: Finite element analysis; ,  ,  Scaphoid nonunion; ,  , Scaphoid osteonecrosis; ,  3D printing, Titanium alloy