ABSTRACT
Objective To develop a new type fusion apparatus for scaphoid-trapezium-trapezoid (STT) arthrodesis.Methods The apparatus was designed on the basis of the anatomic data of STT measured from Chinese cadaveric wrists.Simulated arthrodeses of STT joints were conducted to test the fixation performance of the apparatus made of titanium alloy on the STT joint specimens.Several modifications were made before the apparatus was made into a finished product.Results The fusion apparatus consists of a plate and screws.The fusion plate for STT arthrodesis is made into a taper one connected to a cylinder.On the plate are three screw holes through which the three carpal bones (STT) are fixed by three screws respectively.The hollow cylinder is designed for bone grafting,and its outer threads ensure a very tight contact between the fusion plate and the carpal bones.Auxiliary tools are also made.Conclusions As the novel design of the fusion apparatus improves the mechanical strength of fixation of STT and prevents the possible rotation and collapse of fused STT,the apparatus is a reliable internal fixation device for the limited intercarpal arthrodesis.