The presently disclosed technology is directed towards an adjustable prosthesis for replacing a mandible along with the ramus with a mandibular condyle. The prosthesis articulates to the skull at the temporal bone region. The prosthesis, of embodiments of the disclosed technology, has a horizontal/sagittal (or generally horizontal) and/or vertical (or generally vertical) adjustment screw which is accessible after implantation. In one embodiment, the adjustment screw is accessible by way of using a tool and rotating an adjustment rod. The adjustment rod is accessed via a sub-periosteal intra-oral incision, through points in the oral cavity post-surgical placement. The adjustment rod allows the length of the device, both a horizontal portion and vertical portion, to be adjusted post-placement.