| 摘要 |
<p>A drill head assembly (100) for drilling holes in bony structure is disclosed. The assembly has an inner drill (102) and an outer drill (104) which rotate together as a unit. The leading portions (169) of the outer drill are contiguous with the peripheral portions of the inner drill (116) and the inner and outer drills are adapted to form a bore-countersink opening in the bone, whereby the drill head assembly may be used to safely drill through relatively thin bone.</p> |
