Whilst avascular necrosis (AVN) can affect many areas of the skeleton, its consequences are perhaps most serious when it affects the head of the femur: the ball of the ball and socket joint. Usually no cause is identified but it may follow severe fractures round the hip, prolonged treatment with steroids often in the context of kidney disease or chemotherapy, alcohol abuse and various metabolic disorders. Sickle cell disease is the commonest cause of AVN in Mr Bankes’ practice and he has extensive experience treating the condition in this patient group.
The condition is characterised by disruption to the blood supply of the femoral head making the bone extremely painful. Pain in the groin and upper thigh that tends to particularly present at night in the presence of a normal range of motion are the hallmarks of early disease. Intervention at this early stage to decompress bone by drilling (core decompression) can relieve pain and stimulate healing of the bone, provided not too much bone is affected.
Bisphosphonate therapy may also be helpful in the early stages. As well as being painful, dead bone is also soft and so the affected area may collapse leading to flattening of the femoral head. In addition the cartilage no longer adheres to the dead bone. These two factors combine to produce secondary osteoarthritis. In this circumstance total hip replacement may be necessary when there are significant progressive symptoms.
Given the improvement in results of hip replacements in younger patients, there has been a move away from femoral osteotomy and vascularised fibular bone graft procedures.