SolutionsAs for bone screw 1, that core 15 is cone the basic end of the screw thread attachment where that core 11 and screw thread 12 has fixed diameter the basic end of the screw thread attachment to 2, to a central part 3 of 2 and the screw thread attachment, at the same time, it possesses the diameter which is increased gradually from end to the basic edge, it has with the central part 3 of the screw thread attachment. Screw thread 16 of the screw thread equipped central part 3 the screw thread equipped basic end is smaller than diameter of screw thread 12 of 2, it possesses fixed diameter. Pitch of screw thread 16 of the central part 3 of the screw thread attachment gradually becomes small from end facing toward the basic edge. The pitch in the basic edge of the central part 3 of the screw thread attachment the screw thread equipped basic end is larger than pitch of screw thread 12 of 2. Bone screw 1, furthermore, has the screw thread equipped terminal part 4. Core 17 of the screw thread equipped terminal part 4 and screw thread 18 has fixed diameter. Screw thread 18 has the diameter which is smaller than diameter of screw thread 16. As for pitch of screw thread 18 of the terminal part 4 of the screw thread attachment, it is larger than pitch of the screw thread 16 in the end of the central part 3 of the screw thread attachment.【解決手段】骨ねじ1は、ねじ山付きの基端部分2にして、そのコア11及びねじ山12が一定の直径を有するねじ山付きの基端部分2と、ねじ山付きの中央部分3にして、そのコア15が円錐形であり、且つ、末端から基端まで徐々に増大する直径を有する、ねじ山付きの中央部分3とを備える。ねじ山付き中央部分3のねじ山16は、ねじ山付き基端部分2のねじ山12の直径よりも小さい、一定の直径を有する。ねじ山付きの中央部分3のねじ山16のピッチは、末端から基端に向かって徐々に小さくなる。ねじ山付きの中央部分3の基端におけるピッチは、ねじ山付き基端部分2のねじ山12のピッチよりも大きい。骨ねじ1は、さらに、ねじ山付き末端部分4を備える。ねじ山付き末端部分4のコア17及びねじ山18は一定の直径を有する。ねじ山18は、ねじ山16の直径よりも小さい直径を有する。ねじ山付きの末端部分4のねじ山18のピッチは、ねじ山付きの中央部分3の末端におけるねじ山16のピッチよりも大きい。
