headless cannulated screws 

The most important feature of the Cannulated Screws is that it has no nut and the distal pitch is greater than the proximal pitch.  Therefore,with each rotation of the screw,the distance of the orthopedic bone screw in the distal bone segment is greater than that in the proximal bone segment, resulting in pressure effect.After fixation with conventional hollow screws,the nut is exposed outside the calcaneus, resulting in mobility impairment and pain,ultimately requiring screw removal.In order to retain the stability of screw fixation and overcome the disadvantages of traditional Orthopedic Screw,Herbert et al.developed a cannulated counterbore screw to solve the corresponding problems caused by the nut being exposed to the outside of bone,namely Herbert screw. According to comparative clinical studies,Herbert screw percutaneous internal fixation provides higher fixation strength and stability,better fatigue resistance,and better fracture reducti…