spacer 200 a l has a predetermined depth denoted by the preferred dimension identified adjacent each spacer provided in that while each spacer 200 a l shares the same annular groove dimensions as the other spacers each spacer 200 a l has a different flange thickness dimension for example the flanges 204 l 206 l are thicker than the flanges 204 a 206 a with regard to the instrument for the insertion and removal of the trial spacer elements a first embodiment particularly useful for inserting constant thickness trial spacers of a spacer insertion tool includes an elongated shaft and a handle at one end of the shaft the distal end of the shaft includes semi circular hook that is adapted to hold a trial spacer within an enclosure formed by the hook the angle swept out by the hook is slightly greater than 180 degrees but the inner diameter of the hook is only slightly larger than the central trunk of the trial spacer therefore the trial spacer may be snapped into the enclosure but maintains complete rotational freedom within its grasp a loading tool may be provided to assist in the loading and unloading of the trial spacer from the trial spacer insertion instrument of this embodiment this loading tool comprises a forked hook having two tines separated by a notch that engages the shaft of the insertion tool as the tines engage the flanges of the trial spacer to force the trial spacer into the enclosure alternatively and or additionally the same device may be utilized to remove the spacer from the enclosure by reversing the position of.