The design and manufacturing of a Patient-Specific wrist splint for rehabilitation of rheumatoid arthritis

Wrist splint is a device for immobilising the wrist to facilitate the healing of wrist injury. However, conventional splint designing strategies lack consideration of biomechanical interaction with wrist joints, resulting in mechanical failure of splints or causing patient injuries. A novel design and optimisation method of customised functional wrist splints is needed clinically. In this study, we proposed a splint design method combining topology optimisation and additive manufacturing, based on the biomechanical analysis, to enable advanced customisation regarding functionality, comfort and ventilation. Three prototypes were fabricated via fused filament fabrication (FFF) horizontal printing, FFF vertical printing, and powder bed fusion (PBF). Finite element analysis was used to simulate the displacements of splints under the maximum loading provided by patients, with the results validated by physical tests. The stiffness and functionality of splints fabricated by different techniques were evaluated and compared. The results demonstrate that the developed splint is compatible with patients' functional and biomechanical needs, limiting 95.7% sagittal movement, 89.8% coronal movement, and 18.7% maximum grip strength. Moreover, among the three manufacturing methods, FFF vertical printing is recommended for general clinical use considering the safety, functionality, surface quality and cost.