An interbody fusion device in one embodiment includes a tapered body defining a hollow interior or chamber for receiving bone graft or bone substitute material. The body defines exterior threads which are interrupted over portions of the outer surface of the device. The fusion device includes truncated side walls so that on end view the body takes on a cylindrical form. In another embodiment, the tapered body is solid and formed of a porous biocompatible material having sufficient structural integrity to maintain the intradiscal space and normal curvature. The material is preferably a porous tantalum composite having fully interconnected pores to facilitate complete bone tissue ingrowth into the implant. In further embodiments, the fusion devices are provided with osteogenic material to facilitate bone ingrowth. A cap is also provided to block the opening of hollow fusion devices. The cap includes an occlusion body and an elongated anchor. In some embodiments the anchor includes a lip which is engageable to openings in the body wall. Tools are also provided for manipulating caps for interbody fusion devices. In one embodiment the tool includes a pair of prongs each having facing engagement surfaces for engaging the fusion device, and a shaft slidably disposed between the prongs. The shaft has a first end defining a cap-engaging tip for engaging a tool hole in the cap. In one embodiment the cap engaging tip defines threads. In another embodiment the prongs include a pair of releasing members on each of the facing engagement surfaces. The releasing members have a height and a width for being insertable into apertures in a body wall in the fusion device to disengage the elongate anchors from the apertures.