Avascular necrosis of the femoral head: Dead bone tissue and damage to the hip joint caused by impaired blood flow to the femoral head

Avascular necrosis of the femoral head is the partial death of the femoral head. The femoral head is the uppermost part of the thigh bone that fits into the hip socket. When the tiny blood vessels that supply this bone become blocked or rupture, blood flow is impaired. Without oxygen and nutrients, the bone tissue becomes necrotic—in other words, it dies.

In orthopedics and trauma surgery, physicians distinguish between two main types:

1. Idiopathic femoral head necrosis: In this case, the exact cause remains unknown. Femoral head necrosis in adults appears to occur more frequently in men than in women.

2. Secondary femoral head necrosis: This form has a clear cause or a known risk factor.

The causes of avascular necrosis of the femoral head are varied. The main triggers are considered to be the use of cortisone (glucocorticoids) and excessive alcohol consumption, as both disrupt fat metabolism and can contribute to vascular occlusion. Accidents (such as a femoral neck fracture) can also contribute to avascular necrosis of the femoral head. Additionally, metabolic disorders or chemotherapy can increase the risk of avascular necrosis of the femoral head.

Since avascular necrosis of the femoral head can develop gradually, the initial signs are often overlooked. In the early stages, the patient is often still asymptomatic. However, as the disease progresses, specific symptoms begin to appear.

Certain symptoms indicate avascular necrosis of the femoral head:

• Pain in the groin: A typical pulling sensation in the groin that can occur during physical activity but also at rest.

• Hip pain: This often radiates into the thigh or down to the knee.

• Limited range of motion: In particular, internal rotation and abduction of the leg are restricted.

If the necrosis is far advanced and the bone collapses (head collapse), sudden, severe pain and loss of function in the hip joint occur. Since these symptoms also occur with osteoarthritis, a differential diagnosis must be made to determine whether the condition is avascular necrosis of the femoral head.

The structure of the pelvis © Henrie | AdobeStock

Diagnosis is crucial for preserving the joint. If avascular necrosis of the femoral head is suspected, the patient undergoes a clinical examination and imaging studies.

Diagnosis Using X-rays and MRI An X-ray only reveals avascular necrosis of the femoral head in advanced stages, when the bone structure is already damaged or the joint surface has collapsed. MRI (magnetic resonance imaging) is essential for the early detection of avascular necrosis of the femoral head. On an MRI, avascular necrosis of the femoral head is visible even in the early stages, before any changes appear in the bone on an X-ray. Once avascular necrosis of the femoral head is diagnosed, it is classified into stages.

Stages of avascular necrosis of the femoral head (ARCO classification) The severity of the condition is divided into different stages. The widely used ARCO classification (Association for Research on Circulation in Bone) helps doctors choose the appropriate treatment. According to ARCO, avascular necrosis of the femoral head is classified into four different stages:

• Stage 0–1: MRI shows changes (edema); X-ray is unremarkable.

• Stage 2: Sclerosis and cysts are visible, but the femoral head is still round.

• Stage 3: The femoral head collapses (crescent sign), and its round shape is lost.

• Stage 4: Severe osteoarthritis; the joint is destroyed.

Treatment for avascular necrosis of the femoral head depends on the stage of the disease, the patient’s age, and the extent of the necrosis. As a general rule, the earlier avascular necrosis of the femoral head is diagnosed, the better the chances of preserving the patient’s own joint.

Conservative Therapy and Weight-Bearing Relief In very early stages, conservative therapy may be attempted. This includes using crutches to relieve weight-bearing on the leg in order to minimize pressure on the bone. Medications (such as bisphosphonates or agents that promote blood flow) can be helpful. However, conservative treatment alone is often no longer sufficient to permanently halt the progression of avascular necrosis of the femoral head. Spontaneous healing of avascular necrosis of the femoral head is extremely rare in adults.

Surgical Treatment in the Early Stages As long as the femoral head has not yet collapsed, joint-preserving surgery is recommended. The standard procedure is core decompression. In this procedure, the necrotic area within the femoral head is drilled. This reduces pressure within the bone, improves blood flow, and can relieve pain. It is often combined with bone marrow grafts. If avascular necrosis of the femoral head is treated before the bone fractures, the prognosis is good.

Treatment in Advanced Stages In later stages (ARCO 3 and 4), when the articular surface has fractured and the bone has collapsed, joint preservation is usually no longer possible. At this point, avascular necrosis of the femoral head inevitably leads to osteoarthritis. In these advanced stages, the use of a total hip replacement may be considered. Artificial hip joints replace the destroyed bone and restore pain relief and mobility to the patient. Avascular necrosis of the femoral head is one of the most common indications for total hip replacement in younger patients.

You can find more information about surgical options in our article on hip surgery.

The prognosis depends heavily on the stage of avascular necrosis of the femoral head at the time of presentation to a doctor. In the early stages (ARCO 1–2), the joint can be preserved in up to 70% of patients through a drilling procedure. If avascular necrosis of the femoral head is detected late, joint replacement is often unavoidable.

Since both hips can often be affected by avascular necrosis of the femoral head, regular monitoring of the unaffected side via MRI is important. Risk factors such as smoking or alcohol consumption should be stopped immediately to positively influence the disease’s progression.

What are the causes of avascular necrosis of the femoral head?

The causes of avascular necrosis of the femoral head are often circulatory disorders. The most common triggers include corticosteroid use, excessive alcohol consumption, traumatic injuries (femoral neck fracture), or metabolic disorders. In the idiopathic form, the cause is unknown.

What symptoms indicate avascular necrosis of the femoral head?

Typical signs of avascular necrosis of the femoral head include pain in the groin that radiates into the thigh. Initially, the pain occurs during physical activity; later, it may also be felt at rest. Limited hip mobility (especially internal rotation) is also characteristic.

Can avascular necrosis of the femoral head heal on its own?

Spontaneous healing of avascular necrosis of the femoral head is extremely rare and unlikely in adults. Without treatment, bone destruction usually progresses until the femoral head collapses.

How is avascular necrosis of the femoral head treated?

Treatment for avascular necrosis of the femoral head depends on the stage of the disease. In early stages, core decompression is often performed to relieve pressure on the bone. In later stages, a hip replacement (prosthesis) is usually necessary.

How quickly does avascular necrosis of the femoral head progress?

The course of the disease varies from person to person, but it can progress rapidly. It can take anywhere from a few months to two years from the onset of pain until the femoral head collapses. If left untreated, the condition almost always leads to severe osteoarthritis.

When does avascular necrosis of the femoral head become visible on an X-ray?

Avascular necrosis of the femoral head is only visible on an X-ray once the bone has already sustained structural damage (usually starting in stage 2 or 3). In the early stages, the X-ray is often unremarkable, which is why an MRI is necessary for diagnosis.

Is it possible to participate in sports with avascular necrosis of the femoral head?

In the acute stage, high-impact activities (jogging, jumping) should be avoided to prevent the weakened bone from fracturing. Sports that are gentle on the joints, such as swimming or cycling, are permitted and help maintain mobility.

What does the ARCO classification mean?

According to ARCO, avascular necrosis of the femoral head is classified into four stages. This classification helps the doctor assess the extent of the damage and select the appropriate treatment. Stages 1 and 2 are early stages, while stages 3 and 4 are late stages involving bone collapse.