Abstract: Embodiments of devices for connecting a spinal rod to a vertebra or to two vertebrae are disclosed. In one embodiment, there is provided a first hook having a threaded protrusion for fitting a connector in which the spinal rod is inserted, a second hook, a rod for connecting the two hooks, and structure for immobilizing the ends of the hook-connecting rod on the heads of the hooks. The end of the hook-connecting rod in contact with the first hook may have an oblong aperture, and the structure for immobilizing this end on the head of the first hook may include a nut intended to cooperate with the connector. Also disclosed are embodiments of a spinal osteosynthesis system including such devices.