Protrusio Acetabulum Protrusio acetabuli is a rare anatomic pattern of the hip in which the femoral head protrudes into the true pelvis. Protrusio acetabuli (arthrokatadysis or Otto pelvis) is a relatively rare condition associated with secondary osteoarthritis of the hip. Radiographically, protrusio acetabuli is present when the medial aspect of the femoral head projects medial […]