Hip Osteonecrosis

What is Hip Osteonecrosis?

Hip osteonecrosis occurs due to disruption of the blood supply to the highest part of the thigh bone (femoral head). Due to lack of nourishment, the bone tissue of the femoral head dies and gradually collapses, which may further lead to degeneration of the underlying cartilage.

The hip joint is a ‘ball and socket’ joint. The ‘ball’ is the head of the femur or thighbone, and the 'socket' is the cup-shaped acetabulum. The joint surface is covered by a smooth articular surface (cartilage) that allows pain-free movement in the joint. Hip osteonecrosis can ultimately cause severe arthritis.

Risk factors of Hip Osteonecrosis

The common risk factors include:

• Trauma or injury to the blood vessels supplying the femur
• Excess use of steroid medications
• Excess alcohol consumption
• Certain viral infections (AIDS)
• Medical conditions such as sickle cell anemia, Gaucher’s disease, Caisson disease, pancreatitis, rheumatoid arthritis, etc.

Symptoms of Hip Osteonecrosis

The time taken for the initial onset of symptoms to the final stage can range between a few months to more than a year. Many people have no symptoms in the early stages but as it worsens, the symptoms can gradually progress from difficulty bearing weight to pain in the hip area even when lying down, to throbbing pain in the groin area. Untreated hip osteonecrosis may progress to difficulty with standing and walking.

Diagnosis of Hip Osteonecrosis

Your doctor will assess your symptoms and order imaging tests such as X-ray’s or MRI, the results of which vary at different stages of osteonecrosis.

• Stage 1: X-ray is normal but MRI reveals the dead bone.
• Stage 2: At this stage, there is no collapse of the femoral bone; X-ray and MRI reveal the dead bone.
• Stage 3: A crescent sign on X-ray and MRI indicates the collapse of the femoral bone.
• Stage 4: Collapse of femoral bone and sign of osteoarthritis on X-ray and MRI.

Treatment of Hip Osteonecrosis

Treatment depends on the stage of hip osteonecrosis. Your doctor initially prescribes medication to manage pain, inflammation and progressive collapse of bone tissue. You will be advised to minimize weight-bearing activities. Physical therapy may be suggested.

Surgery

Surgery is recommended by your doctor if conservative methods fail. The surgical procedure may be either of the following:

• Core decompression: It is a surgical procedure that involves surgical drilling into the dead bone area. This reduces pressure within the bone and increases blood flow allowing more blood vessels to form. 
• Osteotomy: It involves cutting or removing the damaged end of the femur bone and alignment of the bone.
• Arthroplasty: The damaged cartilage and bone are removed from the hip joint and replaced with artificial components.
• Bone grafting: This method involves taking a small piece of healthy bone from the patient’s leg and grafting it to the area of dead bone (femur).

Prevention

Hip osteonecrosis can be prevented by lowering the risk factors and following a healthy lifestyle.