| 摘要 |
A nested fastener and set screw combination for securing a spinal fixation rod to a bone screw includes a fastener base receivable into an open channel of a bone screw. The fastener base has a central threaded bore to receive a threaded set screw. The set screw is provided with projecting structure, such as a ring, point or dome-shaped structure, for positive engagement with the surface of a rod. Uploaded and downloaded set screw embodiments are disclosed. In an uploaded set screw embodiment, the fastener base is provided with a radially inwardly extending abutment shoulder to engage and abut the set screw, prohibiting advancement of the set screw out of a top of the fastener and allowing for simultaneous removal of the set screw and the fastener. In an embodiment, the fastener includes a break-off head that separates from the fastener when a pre-selected installation torque is exceeded. |
