Osteosynthesis systems useful in the fusion of cervical vertebrae are described. An osteosynthesis system includes a plate, a set of anchors, a set of locking members, and a set of pins. The plate defines anchor passageways that receive the anchors, locking member passageways that receive the locking member passageways; and pin passageways that receive the pins. Each of the locking member passageways partially intersects one of the anchor passageways and each of the pin passageways provides a passageway extending from a side of the plate to one of the locking member passageways. Each of the locking members is rotatable within the respective one of the locking member passageways and is adapted to engage an adjacent anchor from the side.