Voluntary hip dislocation in Down's syndrome: report of two cases.

: Two cases of monolateral voluntary hip dislocation in Down's syndrome are reported. No surgical procedure was permitted by the family in either case, thus showing the natural evolution of the joint morphology. In the case observed a year after the onset of hip dislocation CT Scan already showed an initial smoothing of the posterior acetabular wall. In the other case, after a 9 year follow-up, the voluntary hip dislocation was followed by progressive subluxation and fixed dislocation at the end. This suggests that only early surgical treatment can prevent this outcome.