A bone screw includes: a shaft and a sleeve. The shaft has a first male thread and a second male thread at two ends thereof. The sleeve is fitted over the shaft, and a first end and a second end opposite to the first end. On an inner wall of the first end is a female thread engaged with the first male thread, on an outer wall of the first end is a third male thread, on an outer wall of the second end is a forth male thread, a pitch of the forth male thread is greater than that of the third male thread, and the inner wall of the second end communicates with that of the first end so that the shaft optionally penetrates to the second end after penetrating to the first end.一種骨釘,其包含:一桿體、以及一套管。桿體具有一第一公螺紋以及一第二公螺紋於其二端。套管為套接桿體且具有一第一端以及一相對於第一端的第二端,第一端內壁設有一嚙合第一公螺紋的母螺紋,第一端外壁設有一第三公螺紋,第二端外壁設有一第四公螺紋,第四公螺紋的螺距大於第三公螺紋的螺距,且第二端內壁與第一端內壁連通,使桿體自套管第一端穿入後,可選擇地穿至第二端。(1)‧‧‧桿體(11)‧‧‧第一公螺紋(12)‧‧‧第二公螺紋(13)‧‧‧攻螺牙(2)‧‧‧套管(21)‧‧‧母螺紋(22)‧‧‧第三公螺紋(23)‧‧‧第四公螺紋(24)‧‧‧頭部(25)‧‧‧凹孔
