Patent ID: 8303664

Claim:
A method comprising: distracting a joint that comprises a first bone having a first articular surface and a second bone having a second articular surface; preparing the first bone by: removing the first articular surface of the first bone, thereby creating a cut surface on the first bone; and forming a cavity in the first bone; wherein the cavity opens onto the cut surface; placing a spacer against the cut surface of the first bone, the spacer having: a primary surface sized and shaped to articulate with the second articular surface of the second bone; a secondary surface conforming to the cut surface of the first bone, so that the spacer tends to remain fully seated against the cut surface while remaining free to move on the cut surface; and a bump protruding from the secondary surface at a location such that, when the secondary surface is fully seated against the cut surface, the bump extends into the cavity, without laterally filling the cavity, thereby leaving the spacer free to move in any direction on the cut surface to the extent that the bump can move laterally within the cavity, even when the joint is under load; and reapproximating the joint such that the primary surface of the spacer articulates with the second articular surface of the second bone, and the secondary surface of the spacer fully seats against the cut surface of the first bone.