Biomechanical properties of a new 3D-printed customized anatomical total wrist prosthesis : a quasi-dynamic finite element analysis.

Aims: Current total wrist prostheses have defects, and their design requires further refinement. Therefore, we designed a novel customized anatomical total wrist prosthesis (CATWP) using 3D printing techniques, and evaluated its biomechanical properties. Methods: The 3D wrist joint model and the models of the CATWP and Universal2 prosthesis were established based on biomechanical finite element analysis. The mechanical structure, stress distribution, joint surface contact patterns, and centre of rotation (COR) were compared between the designed prosthesis, Universal2 prosthesis, and a normal wrist joint. Results: Compared with the Universal2 prosthesis, the CATWP effectively reduced the stress of the prosthesis (carpal platform and screws: maximum (Max), 65.27 MPa; radial shank: Max, 2.09 MPa) and the adjacent bone tissue (carpal bones: Max, 33.84 MPa), with a more uniform distribution. The contact stress curve of the distal/proximal joint surface became more stable during the ulnar-radial deviation movements than the Universal2 prosthesis (distal: Max, 13.47 MPa; proximal: Max, 16.42 MPa). The COR was located near the curvature centre of the prosthesis. Compared with the Universal2 prosthesis, the displacement fluctuation of the COR was effectively reduced by CATWP. Conclusion: The CATWP may outperform the Universal2 prosthesis in terms of restoring comprehensive wrist joint mobility and achieving a more uniform stress load distribution. However, further studies are required to confirm these findings.