PROBLEM TO BE SOLVED: To provide a lug screw which can be assembled in one of screwing-in directions, and ensures stable and non-loosening joining to the bone and removal from the bone with a relatively small force.SOLUTION: A lug screw 3 and a master screw 2 which is provided with a lead similar to the one at a tip male screw part of the lug screw 3 are assembled to a nail 1 as an integral set. The lug screw 3 also includes a double threaded-screw with high static stability at the tip end thereof, a double sided-edge for screwing and unscrewing, and a hexagonal concave surface groove for a screwing tool on a rear end surface. The lug screw 3 further includes a mechanism of double-threaded trapezoidal screw engaging with the nail 1 and the master screw 2, which provides a smooth initial biting of the joined bone at pressing-in by a rotating tool to ensure a permanent secure-engaging non-loosening structure by an engaging mechanism of a serration tooth shape of a tightening nut 6 which screw-engages the lug screw 3 after the initial biting completes.COPYRIGHT: (C)2015,JPO&INPIT【課題】ねじ込み方向の一方向だけで組付けでき、比較的小さい力で、緩みなく安定的に骨の接合と脱着ができるラグスクリュウを提供する。【解決手段】ラグスクリュウ3の先端おねじ部と同様リードを備えるラグスクリュウ3とマスタースクリュウ2の一体を組としてネイル1に組付けると共に、ラグスクリュウ3が先端に静止安定性の高い二条ねじと、ねじ込みと巻き戻しのための両面刃先および後端面にねじ込み工具のための六角形の凹面溝を備える。さらに回し工具による押し込み時に接合骨への滑らかな初期食付きを提供する、ネイル1とマスタースクリュウ2に二条台形ねじ係合する機構を備え、食付き完了後にラグスクリュウ3とねじ係合する締めナット6のセレーション歯形の噛み込み機構により固く係合し、恒久的に緩まない構造を備える。【選択図】図1-1
