It is essential to obtain a full, detailed history pertaining to the symptomatology including onset, location of the pain, duration of symptoms, the characteristics of the pain, alleviating and aggravating symptoms, radiation of symptoms, and timing of symptoms. It is equally important to obtain a detailed medical and surgical history to identify any of the risk factors associated with AVN.

Patients with AVN of the femoral head will present with symptoms of hip pain with insidious onset. Typically, the pain will be associated with standing from a seated position, stairs, inclines, and impact loading. The pain will tend to be more noticeable in the anterior hip or groin as opposed to the buttock or greater trochanter. 

There is no single diagnostic test that is 100% reliable. Proper evaluation of a patient with suspected AVN of the femoral head is similar to the patient that presents with hip pain. The physical exam includes inspection of the hip, including the skin, the position of the lower extremity, and gait evaluation as well as palpation of the surrounding bony structures such as the greater trochanter. The range of motion testing includes flexion, extension, abduction, adduction, and internal and external rotation. A thorough neurovascular exam in needed to evaluate for sensory and motor function. There are helpful special hip tests including the log roll and the Stinchfield test to help determine intra-articular pathology.

Standard imaging includes radiographs of the pelvis and hip, including an anteroposterior view of the pelvis, an anteroposterior, and a frog-leg lateral view of the affected hip. The frog-leg lateral view is the radiographic test to confirm subchondral collapse and make decisions regarding patient management.

If there is a high index of suspicion for AVN of the femoral head despite negative radiographs, an MRI of the hip is indicated. MRI has been shown to be approximately 98% sensitive and specific. Findings consistent with AVN of the femoral head include a “double density” appearance which appears dark on the T1 sequence and bright on the T2 sequence. The presence of a bright signal on the T2 sequence indicates bone marrow edema and is predictive of worsening pain and progression of the disease. 

Treatment of AVN of the femoral head is dependent on symptomatology as well as radiographic findings such as evidence of the collapse of the femoral head, size of the necrotic lesion in the femoral head, and involvement of the acetabulum. Treatment options can be broken down into nonoperative and operative categories.

Nonoperative Treatment (Stages 0-2)

• Bisphosphonates

This is largely limited to small lesions, less than 10% involvement of the femoral head, without evidence of collapse. The evidence is inconclusive on whether or not bisphosphonates prevent femoral head collapse.

Operative Treatment[8][5][9][10][11]

• Core decompression of the femoral head with or without stem cell injection
• Vascularized free-fibula grafting
• Total hip resurfacing
• Total hip arthroplasty

Core decompression has traditionally been the treatment of choice during precollapse stages, although the evidence is mixed. The idea behind core decompression is to relieve the increase in pressure within the femoral head thus allowing a return in blood flow and healing. There has been some success demonstrated with the injection of stem cells into the necrotic area. Vascularized free-fibula grafting can be performed in patients with or without collapse in stages 0 to 3. The goal of this particular surgery is to remove the necrotic area and use a free-fibular graft to act as a strut to prevent collapse or to tamp up the collapsed area. The long-term results of this surgery have shown consistent and successful results in regards to functional recovery and pain relief. Total hip resurfacing is indicated in select patients with AVN with careful evaluation of the size of the lesion, its location, and the quality of the bone. The resurfacing procedure requires adequate bone stock to support the resurfacing component. The component design of total hip resurfacing is a metal-on-metal articulation, and its use in young patients, female patients, or patients with a history of the renal disease is not suggested. Furthermore, studies have shown that the outcomes for total hip resurfacing in AVN are worse than in patients with osteoarthritis. Total hip arthroplasty provides the most reliable pain relief and good early clinic results for patients with advanced stages of AVN. It is indicated in younger patients with a crescent sign or more advanced femoral head collapse and patients older than 40 years old with large lesions. 

• Lumbar radiculopathy
• Spinal stenosis
• Sacroiliac degenerative joint disease
• Neuropathy
• Meralgia paresthetica
• Osteoarthritis
• Fracture
• Femoroacetabular impingement
• Labral tear
• Trochanteric bursitis
• Iliopsoas bursitis
• Snapping hip syndrome
• Tendinopathy of the gluteus medius or minimus
• Primary bone tumor
• Metastasis
• Infection

Steinberg Classification for staging AVN of the femoral head (modification of the Ficat classification)[12][13]

• Stage 0 – Normal or nondiagnostic radiograph and MRI
• Stage 1 – Normal radiograph, abnormal MRI
• Stage 2 – Abnormal radiograph showing cystic and sclerotic changes in the femoral head, abnormal MRI
• Stage 3 – Abnormal radiograph showing subchondral collapse, producing a crescent sign, abnormal MRI
• Stage 4 – Abnormal radiograph showing flattening of the femoral head, abnormal MRI
• Stage 5 – Abnormal radiograph showing joint narrowing with or without acetabular involvement, abnormal MRI
• Stage 6 – abnormal radiograph showing advanced degenerative changes, abnormal MRI

The risk of femoral head collapse with AVN can be stratified into three groups based on the modified Kerboul combined necrotic angle. This is calculated by the summation of the arc of femoral head necrosis on mid-sagittal and midcoronal MR image.[14]

• Low-risk group: combined necrotic angle less than 190 degrees
• Moderate-risk group: combined necrotic angle between 190 and 240 degrees
• High-risk group: combined necrotic angle greater than 240 degrees

Mnemonic to help remember the most common causes of AVN

ASEPTIC

• A – Alcohol/AIDS
• S – Steroids, sickle cell disease, SLE
• E – Erlenmeyer flask (Gaucher disease)
• P – Pancreatitis
• T – Trauma
• I – Idiopathic, infection
• C – Caisson’s disease

Hip osteonecrosis is associated with very high morbidity if the diagnosis is missed. Thus, the condition is best managed by an interprofessional team that includes a radiologist, orthopedic surgeon, rheumatologist, internist, nurse practitioner and a pharmacist. There is no one single test that can make the diagnosis of this disorder and hence, communication and discussion with other healthcare workers is vital. The offending drug must be discontinued right away. The patients are managed medically and surgically but a complete recovery is not always guaranteed. Some patients are left with a permanent gait alteration and this can significantly affect the quality of life.[15][16]