Dimensionally adjustable spinal prostheses are adjustable in an axial or superior to inferior dimension such that spinal prostheses may assume variations in height. The height adjustable spinal prostheses are characterized by first and second portions that are configured for adjustable 
coupling with one another. Spatial adjustment between the first and second portions is provided by an adjustment 
assembly. The adjustment mechanism preferably, but not necessarily, provides infinite adjustment over a minimum 
prosthesis height to a maximum 
prosthesis height. In one form, first and second ends of the height adjustable spinal prostheses are configured to receive an endplate. The endplates aid in attachment and / or anchoring of the spinal 
prosthesis within the spine. The endplates may be fashioned in various configurations such as circular or anatomical. In one form, the adjustment 
assembly utilizes rotational motion for varying the axial position of one prosthetic portion relative to the other prosthetic portion. Rotational movement of an adjustment mechanism of the adjustment 
assembly is translated into axial movement of one prosthetic portion relative to the other prosthetic portion. In another form, the adjustment mechanism is a screw and gearing assembly. In yet another form, the adjustment mechanism is a 
rack and pinion assembly.