WHAT IS AVASCULAR NECROSIS?
In this condition an area of bone in the femoral head (ball of the hip) looses its blood supply and dies. The dead bone becomes weak and if it cannot support the weight of the body any more the joint surface collapses. Other joints in the body such as the ankle, knee and elbow may be affected too, but the hip is the most common site of this disease.
WHAT ARE THE RISK FACTORS?
Age. It typically occurs between 30-60 but children can be affected too.
Sex. It is more common in men.
Steroids. Longer term and high dose steroid treatment is more likely to cause AVN than short term steroid use.
Sickle cell anaemia.
Radiotherapy near the hip joint.
Decompression disease. This occurs when someone transits from a high pressure environment to a lower pressure one too quickly. This can happen to deep sea divers when they come up to the surface.
Previous injury to the hip. If you had a fracture across the neck of the thigh bone the blood supply to the ball may be compromised.
WHAT ARE THE SYMPTOMS?
Pain. Most people localise the pain in the groin and thigh. At the onset of the disease you may only feel it after a longer walk or strenuous activity, but later it can become constant including at night. If the bone collapses the pain can be very severe.
Stiffness. The first movement to go is rotating the hip inwards then all other movements decrease gradually. This leads to difficulty putting on socks and shoes and getting in and out of the car.
Limited mobility. The usual walks become shorter and shorter and in the end you may only be able to walk a few hundred yards with significant limp. If the bone collapses you may not be able to weight bear at all.
HOW IS AVASCULAR NECROSIS DIAGNOSED?
A history of the predisposing factors and typical symptoms raises the suspicion of this diagnosis.
The clinical examination confirms the painfully limited movement of the hip joint. Examination of the other hip, the spine, knee, walking pattern and leg length gives further information for the planning of your treatment.
X-ray is often inconclusive in the early stages of the disease. Later on it can be visible especially if a large area is affected or the bone has already collapsed.
MRI scan is useful to diagnose avascular necrosis in the early stages and exclude other problems such as a stress fracture, hip impingement or soft tissue problems around the hip.
WHAT TREATMENTS CAN I HAVE?
Depending on the stage of the disease and the area affected you may be able to manage the symptoms conservatively for a while (without an operation). Most adult patients however will need surgery either to try and prevent the collapse of the bone or to replace the hip.
A hip injection can be considered when the affected area is small and the main reason for the pain is inflammation in the joint. This is not cure, just a treatment for the pain.
Core decompression is a procedure designed to remove some of the dead bone and encourage the blood vessels to enter the diseased area of the femoral head.
Bone grafting. Core decompression can be supplemented with packing bone into the defect. The bone graft can be harvested from a different part of the body or taken from a bone bank.
Total hip replacement. Once the bone collapsed the joint cannot be salvaged any more and a hip replacement is necessary to alleviate the severe pain and to restore the mobility of the patient.