| 摘要 |
PROBLEM TO BE SOLVED: To provide a screw which can reduce damage delivered to an object to be screwed together when its rotation force is applied thereto, and is difficult to loosen.SOLUTION: An intramedullary nail lug screw 11 to be threaded into a bone tissue includes: a screw body 12; and a threaded part 15 having thread grooves 13 formed spirally in the circumference surface of the screw body 12, and screw threads 14 formed along the thread grooves 13. In the threaded part 15, the diameter of the screw thread 14 is reduced with distance from the intermediate portion in the axial direction of the threaded part 15 toward the front end and the base end. The diameter of a screw thread 14a in the intermediate portion in the axial direction is larger than that of a screw thread 14b on the front end side and a screw thread 14c on the base end side. |
