US Patent 8128663 Spine distraction implant

A spine distraction implant alleviates pain associated with spinal stenosis and facet arthropathy. The implant may provide a spinal extension stop while allowing freedom of spinal flexion. The implant includes a central portion and first, second, third, and fourth arms that extend away from the central portion to form two generally oppositely facing saddles. For some versions, one arm is longer than the other arms. For some versions, all the arms are of different length, with one of the arms being longer than the other three, and one of the arms being shorter than the other three.