A bone screw (1) is provided having first (5) and second (7) threaded portions of different diameter separated by a middle portion (6) that is unthreaded so that the bone screw may be inserted into a pair of adjacent bone fragments and used to compress the fragments together by driving the screw into a hole drilled in the fragments. An installation tool (15) is also disclosed for threadably engaging one end of the bone screw and is used to initially drive the screw into the bone hole. Thereafter, a screwdriver (16) is inserted through the tool and into engagement with a recess (11) in the bone screw and may be used to drive the screw fully into the bone and to separate the bone screw from the installation tool.本發明提供一種接骨螺釘,其具有由一無螺紋之中間部分分離的不同直徑之第一及第二螺紋部分,使得該接骨螺釘可插入一對鄰近骨片中,並用於藉由將該螺釘釘入該等骨片內所鑽製之孔中而將該等骨片壓迫在一起。亦揭示一種安裝工具,其用於螺紋嚙合該接骨螺釘之一端,且用於初始地將該螺釘釘入該骨孔中。此後,一螺絲起子可插入該工具並與該接骨螺釘中之凹座嚙合,並可用於將該螺釘完全釘入骨中及用於自該安裝工具分離該接骨螺釘。進一步提供一種安裝方法。1...接骨螺釘/螺釘2...縱向軸3...前端4...後端5...前部螺紋段6...中間無螺紋段7...後部螺紋段8、9...外螺紋10...中心鑽孔11...構件12...切邊23...壓痕DHS、DMS、DVS...外徑DKH、DKV...根徑L...後部螺紋段之長度
