Hip Osteonecrosis

Hip Osteonecrosis

What Is Hip Osteonecrosis?

Hip osteonecrosis is a progressive condition in which the bone tissue of the femoral head is damaged because its blood supply is disrupted. Without an adequate blood supply the bone cells cannot stay healthy; over time the femoral head weakens, collapses and the joint surface breaks down, leading to hip arthritis. It is also called avascular necrosis (AVN) or aseptic necrosis.

It is most common in adults between 40 and 65, and in a proportion of patients both hips are affected. Recognising and treating it in an early stage improves the chance of delaying or preventing collapse of the femoral head. For other hip problems you can review the hip page.

What Causes It? Risk Factors

Osteonecrosis develops when the blood supply to the femoral head is reduced or cut off. In some cases no clear cause is found, but many conditions markedly increase the risk.

• Hip injuries: a hip fracture or dislocation can directly disrupt the vessels supplying the femoral head.
• Long-term or high-dose corticosteroid use and excessive alcohol intake.
• Systemic diseases: conditions such as sickle cell anaemia, systemic lupus, clotting disorders and vasculitis.
• Other causes such as radiotherapy, chemotherapy and decompression (diving) sickness.

Symptoms

Osteonecrosis can be silent in the early stage; symptoms usually appear as the bone weakens and collapse begins.

• The first and most common symptom is pain in the groin; the pain can spread to the thigh and hip.
• Pain that increases with weight-bearing and walking and eases somewhat with rest; night pain in advanced stages.
• Restricted movement, a limp and joint stiffness as the disease progresses.

Stages

Osteonecrosis progresses roughly through four stages; the stage directly determines the choice of treatment. In early stages the aim is to preserve the joint, and in later stages to relieve pain and restore function.

1. Stage I: the X-ray is normal and changes are seen only on MRI.
2. Stage II: early changes in the femoral head visible on X-ray, without collapse yet.
3. Stage III: collapse of the femoral head has begun; the joint surface breaks down.
4. Stage IV: advanced arthritis in which the joint cartilage is also affected.

Conditions That Can Be Confused With It

There are other hip problems that cause groin pain, and early osteonecrosis can be confused with them. Hip arthritis causes similar pain and stiffness; but in early osteonecrosis the X-ray can be normal while MRI shows a clear change. Femoroacetabular impingement and a labral tear cause more mechanical pain that increases with rotation.

The importance of this distinction is that early diagnosis in osteonecrosis allows joint-preserving treatment. For this reason, in a patient with risk factors and persistent groin pain, MRI is considered even if the X-ray is normal.

Diagnosis: Examination and Imaging

The diagnosis is made from the history, examination and imaging. Risk factors (corticosteroids, alcohol, injury, systemic disease) are asked about; the range of motion of the hip and pain are assessed.

• X-ray: shows collapse and deformity in advanced stages but can be normal in an early stage.
• MRI: the most sensitive method; it can show early osteonecrosis even when the X-ray is normal and can assess the other hip.
• Relevant blood tests may be requested if an underlying systemic cause is suspected.

Non-Surgical Treatment

Non-surgical treatment is mostly used in the early stage and to manage symptoms. It can reduce pain and slow the process somewhat, but it does not reverse a collapse that has already begun.

• Activity modification and reducing load with crutches where needed.
• Anti-inflammatory medication under medical advice and physiotherapy for pain management.
• Addressing the underlying cause: reviewing the corticosteroid dose where possible and stopping alcohol.

Surgical Treatment

The surgical method is chosen according to the stage of the disease and whether the femoral head has collapsed. The aim is to preserve the patient's own joint in early stages and to achieve a pain-free, functional hip in later stages.

• Core decompression: in the early stage before collapse; channels drilled into the femoral head reduce pressure and stimulate healing, supported with a graft where needed.
• Bone graft (including a vascularised graft in selected cases): can be used to support the femoral head in advanced but non-collapsed cases.
• Total hip replacement: the most effective method when the femoral head has collapsed and the joint is damaged; the damaged surfaces are replaced with an artificial joint.

Recovery and Follow-up

Recovery time varies with the method used. After joint-preserving surgery, weight-bearing is restricted for a period and physiotherapy is used; after a replacement, early movement is the aim.

Because osteonecrosis can be bilateral in a proportion of patients, the other hip may be followed even if it has no symptoms. Managing the underlying risk factors and monitoring for any hip arthritis that may develop are important for the course of the condition.

When Should You See a Doctor?

In osteonecrosis, early diagnosis increases the chance that joint-preserving treatment will work, so hip pain should not be ignored in people at risk.

• Your groin or hip pain has lasted for several weeks and affects your walking.
• You have a history of long-term corticosteroid use, excessive alcohol or a hip injury and hip pain has started.
• You have been diagnosed with osteonecrosis in one hip and pain has now appeared in the other.

For the assessment of hip symptoms you can contact Assoc. Prof. Serkan Sürücü, and you can also review the other conditions covered within hip surgery.