Open intervertebral spacer

Open chambered spacers, implanting tools and methods are provided. The spacers ′ include a body ′ having a wall ′ which defines a chamber ′ and an opening ′ in communication with the chamber ′. In one embodiment the wall ′ includes a pair of arms ′, ′ facing one another and forming a mouth ′ to the chamber ′. Preferably, one of the arms ′ is truncated relative to the other, forming a channel . In one aspect the body ′ is a bone dowel comprising an off-center plug from the diaphysis of a long bone. The tools include spacer engaging means for engaging a spacer and occlusion means for blocking an opening defined in the spacer. In some embodiments, the occlusion means includes a plate extendable from the housing . In one specific embodiment the plate defines a groove which is disposed around a fastener attached to the housing so that the plate is slideable relative to the housing