| 摘要 |
An apparatus includes a bone fastener, a bone fixation device and a bone fastener retainer device. The head of the fastener has a convex lower surface with a first arcuate contour, and has a convex upper surface with a second arcuate contour. The fixation device is configured to receive the fastener in an installed position in which the convex lower surface of the fastener head rests on a concave surface of the bone fixation device that also has the first arcuate contour. Additionally, the retainer device is configured to be mounted on the fixation device in a position in which a concave surface of the retainer device overlies the convex upper surface of the fastener head. The concave surface of the retainer device also has the second arcuate contour. The bone fastener retainer device may be receivable over the fixation device in a mechanical interlock with the fixation device.
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