Dislocation of the semilunar bone, designated by some as backward displacement of the os magnum, by others as perilunar dislocation of the carpus,1 and by still others as subtotal retrolunar subluxation,2 is the third most frequent injury to the wrist bones. It is much more rare than Colles' fracture or fracture of the scaphoid, but its importance is second to neither if the possibility of serious permanent disability is to be considered. Grave results occur from failure to diagnose the condition and from neglect to apply proper early treatment.
At present, information in textbooks is meager and indefinite. Many contributions to the literature fail to emphasize fully the serious possibilities of permanent disability, and surgeons do not consider it as an injury of major importance.
Since the advent of workman's compensation insurance laws, and the consequent more frequent exposure of unfavorable results, this injury can no longer be