A family with primary protrusio acetabuli.

The family of a child who developed symptoms and flexion contractures with protrusio acetabuli rapidly between the age of 8 and 11 was examined. The mother and one sib showed limitation of hip movements, while radiological criteria for protrusio were found in the mother and 4 of the proband's 8 sibs; only one had complained of pain. At the age of 16 the proband underwent bilateral total replacement arthroplasty; histologically the changes were those of fibrocartilaginous replacement and osteophyte formation.