a spinal cage device for fusion of spinal vertebrae comprising a cage body having a cavity defined by upper , lower , and side walls ; a piston selectively insertable into the cavity through a side wall , the piston having at least one angled surface ; at least one channel extending through at least one of the upper wall and the lower wall ; at least one fastening member moveable within the at least one channel between a first disengaged position and a second engaged position ; and wherein in second engaged position the at least one fastening member is held substantially stationary relative to the cage body by contact with the piston . according to one aspect of the invention , the device includes a locking means for supplementing fixation of the piston to the cage body .