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Avascular Necrosis (AVN) of the Hip

    Avascular Necrosis (AVN) of the Hip

    Avascular necrosis, also know as osteonecrosis, is a rare but serious disease that can destroy the hip joint and necessitate hip replacement surgery.  The hip is a ball and socket joint, and AVN is a disease affecting the blood supply to the ball.  It is easy to forget that bone is living tissue, and like all other living tissues, it requires a steady stream of blood to supply it with the oxygen and nutrients it needs to survive.  The disease of avascular necrosis clogs or blocks the small and delicate arteries that deliver blood to the ball of the hip joint, causing the bone in the center of the ball to die and decay. AVN can result from trauma and injury to the blood vessels that nourish the ball, or it can result from the use of certain medications, like prednisone.  As the pocket of decay grows inside the ball, the thinning layer of normal bone above it can fracture and collapse, changing the shape of the ball so that it is no longer round.  Once the ball (known as the femoral head) has collapsed, the proper fit between the ball and socket is lost and the joint, now stiff and painful, wears out quickly.  In its early stages, the goal of treatment is to arrest the disease before the femoral head has collapsed.  It is not clear what the single best method of treatment is for this early form of AVN.  Options vary from simple solutions such as electrical stimulation and protected weight bearing with crutches to surgical procedures like core decompression or even bone grafting with a vascularized section of the fibula from the patient’s leg.  In the late stages of the disease (after femoral head collapse) hip replacement may be necessary to eliminate pain and restore function.