A cage or spacer device for harvesting bone graft material for use in bone fusion surgery, e.g., spinal fusion. The device is inserted between facing surfaces of the bones to be fused, and a chamber is formed in the device for containing a slurry of morselized bone and blood to be effused from the bones. In one embodiment, a bone cutter assembly including a cannula having a bend at a distal end is inserted in the chamber for operation. A wire having a cutting tip is passed inside the cannula so that the tip projects a determined distance from the distal end of the cannula. Accordingly, the cutting tip strikes and cuts grooves in the facing surfaces of the bones when the cannula is rotationally driven about its axis. The mentioned slurry effuses from the grooved surfaces and remains in the chamber to promote a solid and healthy fusion.
