| 摘要 |
A surgical implant, typically a cervical plate assembly, comprises a plate having at least two apertures and two screw threaded fastening devices for securing the plate to bone. Each aperture in the plate has an annular groove intermediate opposite ends of the aperture and each fastening device comprises an outer screw and an inner plug. The screw has a head at one end, a tip at the other end, an externally threaded shank between the head and the tip and an internal bore extending axially through the head and at least part way into the shank for receiving the inner plug. The head comprises a plurality of resiliently deformable fingers separated by one another by axially extending slits. Each finger has an outwardly projecting rib extending circumferentially of the head intermediate opposite ends of the finger for snap fit engagement in the annular groove of a respective plate aperture. The inner plug is arranged so that when it is inserted into the internal bore of the screw it will prevent contraction of the head of the screw thereby preventing the ribs disengaging from the groove.
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