What Is Avascular Necrosis of the Femoral Head?

Femoral head ischemic necrosis (AVN), also known as femoral head necrosis (ONFH), is the interruption or damage of the blood supply to the femoral head, causing the death of bone cells and bone marrow components and subsequent repair, which in turn leads to structural changes in the femoral head, collapse of the femoral head, Diseases of joint dysfunction are common refractory diseases in the field of orthopedics. The disease can be divided into two categories, traumatic and non-traumatic. The former is mainly caused by hip injuries such as femoral neck fractures and hip dislocations. The main causes of the latter in China are the application of corticosteroids and alcohol abuse.

Basic Information

nickname: Femoral head necrosis
Common locations: Hip

Common causes: Trauma, corticosteroid use, and alcoholism
Common symptoms: Hip pain
Contagious: no

Causes of Femoral Head Ischemic Necrosis

The disease can be divided into two categories, traumatic and non-traumatic. The former is mainly caused by hip injuries such as femoral neck fractures and hip dislocations. The main causes of the latter in China are the application of corticosteroids and alcohol abuse.

Clinical manifestations of avascular necrosis of the femoral head

Early clinical symptoms of femoral head necrosis are not typical. Pain induced by internal rotation is the most common symptom. After the femoral head collapses, there may be limited range of motion of the hip joint. Deep local tenderness, adductor tenderness, and some patients with axillary pain may be positive. In the early stage, it was positive because of hip pain, Thomas sign, and 4 character test; in the later stage, it was positive because of femoral head collapse, hip dislocation, Allis sign, and single leg independent test sign. Other signs include abduction, limited external rotation, or limited internal rotation. The affected limb can shorten, muscle atrophy, and even subluxation. Patients with hip dislocation can also move on the Nelaton line, the bottom of the Bryant triangle is less than 5cm, and the Shenton line is discontinuous.

Avascular necrosis of the femoral head

Clinical examination

A medical history should be carefully examined, including hip trauma, corticosteroid use, drinking or history of anemia. For clinical symptoms, it is necessary to clarify the pain site, nature, and relationship with weight bearing. Examination should include hip rotation activity.

2.X-ray film

It is difficult to diagnose early (stage 0, ), and it can show positive changes for lesions above stage , such as sclerotic bands, X-ray cystic changes, spotted sclerosis, subchondral fractures, and femoral head collapse. It is recommended to take X-rays of the posterior anterior (orthopedic) position of the hips and the frog lateral position, the latter can more clearly show the changes in the necrotic area of the femoral head.

3.MRI scan

The T ₁ weighted image of a typical AVN is changed to a residual epiphyseal line of the femoral head, a meandering band-shaped low-signal region near or crossing the epiphyseal line, and a low-signal band surrounding the high-signal region or mixed-signal region. T ₂ weighted images may show double signs. The recommended scanning sequence is T ₁ and T ₂ weighted images. For suspicious lesions, T ₂ lipid suppression or short T ₁ reverse recovery (STIR) sequence can be added. Coronal and cross-sectional scans are generally used. In order to estimate the necrotic volume more accurately and to show the lesion more clearly, a sagittal scan can be added. Roll-enhanced MRI is particularly effective for early AVN detection.

4. Nuclide scanning

Early diagnosis of AVN has high sensitivity and low specificity. A ^99m scan of diphosphate scan can confirm the diagnosis if there is a cold zone in the hot zone. However, pure nuclide concentration (hot zone) should be distinguished from other hip joint diseases. This test can be used to screen for lesions and look for multiple sites of necrosis. Single-photon emitter tomography (SPECT) can increase sensitivity, but the specificity is still not high.

5.CT inspection

For stage and lesions, the boundary, area, sclerotic zone, self-repair of the lesion and subchondral bone can be clearly displayed. CT shows that the clarity and positive rate of subchondral fractures are better than MRI and X-ray films. The addition of two-dimensional reconstruction can show the overall situation of the coronal position of the femoral head. A CT scan can help identify the lesion and select a treatment.

Diagnosis of Avascular Necrosis of the Femoral Head

Main criteria

(1) Clinical symptoms, signs and medical history: the groin, buttocks and thighs are the main joint pains, the hip internal rotation is limited, and there is a history of hip trauma, a history of corticosteroid use, and a history of alcohol abuse.

(2) The X-ray film changes the collapse of the femoral head without narrowing the joint space; there is a hardened zone within the femoral head; there is an X-ray zone under the cartilage (Crescent sign, subchondral fracture).

(3) A nuclide scan showed a cold zone in the hot zone in the femoral head.

(4) The T ₁ weighted image of the MRI of the femoral head is a band low signal (band type) or the T ₂ weighted image has a double sign.

(5) Bone biopsy showed that more than 50% of osteocyte pits in the trabeculae were involved, and adjacent trabeculae were involved, with bone marrow necrosis.

2. Minor criteria

(1) X-ray film shows the collapse of the femoral head with narrowing of the joint space, cystic or spotted sclerosis in the femoral head, and flattening of the outer and upper part of the femoral head.

(2) The nuclide bone scan shows cold or hot areas.

(3) MRI shows a band-like type with low or high signal intensity without T ₁ image.

A diagnosis is confirmed by meeting two or more major criteria. A diagnosis is possible if it meets a primary criterion, or a secondary criterion with a positive number of 4 (including at least one X-ray positive change).

3. Other

Diagnosis of femoral head necrosis can be performed by asking medical history, clinical examination, X-rays, magnetic resonance imaging (MRI), radionuclide scanning, and computed tomography (CT).

Differential diagnosis of ischemic necrosis of the femoral head

For lesions with similar X-ray changes or MRI changes, attention should be paid to identification.

1. Differential diagnosis of diseases with similar X-ray changes

(1) Intermediate and advanced osteoarthritis may be confused when the joint space is narrowed and subchondral cystic changes occur, but the CT manifestations are sclerosis and cystic deformation, and MRI changes are mainly low-signal, which can be identified based on this.

(2) Secondary osteoarthritis due to dysplasia of the acetabulum. Incomplete encapsulation of the femoral head. The acetabular line is on the outer and upper part of the femoral head. The joint space narrows and disappears. Bone sclerosis and cystic changes. The disease is easy to identify.

(3) Ankylosing spondylitis involves the hip joint in adolescent males, mostly bilateral sacroiliac joints. It is characterized by HLA-B27 positive, the femoral head remains round, but the joint space becomes narrow, disappears, or even fuses. Difficult to identify. In some patients, long-term use of corticosteroids can be combined with AVN, and the femoral head can collapse, but it is often not severe.

(4) Rheumatoid arthritis is more common in women. The femoral head remains round, but the joint space narrows and disappears. Common femoral head articular surface and acetabular invasion are common, and identification is not difficult.

2. Differential diagnosis of diseases with similar MRI changes

(1) Temporary osteoporosis (ITOH) can be seen in middle-aged men and women, and is a temporary painful bone marrow edema. X-rays showed a decrease in bone mass in the femoral head, neck, and even trochanter. MRI shows that the T ₁ weighted image has a uniform low signal and the T ₂ weighted image has a high signal, ranging from the femoral neck and the trochanter. There is no band-shaped low signal, which can be distinguished from the disease. The disease can be cured within 3 to 6 months.

(2) Infrachondral fractures are more common in elderly patients over 60 years of age, with no obvious history of trauma, showing sudden hip pain, inability to walk, and limited joint movements. The X-ray film showed a slight flattening of the outer and upper part of the femoral head. The T ₁ and T ₂ weighted images of MRI showed low signal lines under the cartilage, and the surrounding bone marrow edema.

(3) Pigmented villous nodular synovitis is more common in the knee joint, and hip joint involvement is rare. Hip joint involvement is characterized by: adolescent onset, mild and moderate hip pain with claudication, and early and mid-term joint movements are mildly restricted. CT and X-rays can show femoral head, neck or acetabular cortical bone invasion, light and moderate narrowing of joint space. MRI showed extensive synovial hypertrophy, with low or moderate signals evenly distributed.

(4) Femoral head contusion is more common in middle-aged patients with a history of hip trauma, which manifests as hip pain and lameness. MRI is located in the femoral head of T ₁ weighted image with medium intensity signal and T ₂ weighted image with high signal intensity, which is more medial.

(5) Synovial hernia This is a benign lesion of synovial tissue invasion into the femoral neck cortex. MRI shows small round lesions with low signal of T ₁ weighted image and high signal of T ₂ weighted image, which mostly invades the upper cortex of femoral neck. Asymptomatic.

Femoral head ischemic necrosis treatment

At present, there is no method to cure AVN of different types, different stages and different necrotic volumes. The formulation of a reasonable treatment plan should comprehensively consider staging, necrotic volume, joint function, and patient age and occupation.

Non-surgical treatment of femoral head necrosis should pay attention to the curative effect of non-surgical treatment of this disease is unpredictable.

Protective load

Academia is still debating whether this method can reduce femoral head collapse. The use of crutches can effectively reduce pain, but wheelchair use is not recommended.

2. Drug treatment

It is suitable for early (stages 0, , ) AVN. Non-steroidal anti-inflammatory and analgesics can be used. For high-coagulation and low-fibrinolytic conditions, low-molecular-weight heparin and corresponding Chinese medicine can be used for treatment. Alendronate can prevent femoral head collapse and expand blood vessels Drugs also have some effect.

3. Physical therapy

Including extracorporeal shock waves, high-frequency electric fields, hyperbaric oxygen, and magnetic therapy, etc., are beneficial to relieve pain and promote bone repair.

4. Surgery

Most patients will be treated with surgery, including surgery to retain the patient's own femoral head surgery and artificial hip replacement. Femoral head-sparing surgery includes core decompression, bone grafting, osteotomy, etc. It is suitable for patients with ARCOI, stage II and early stage III with necrosis volume of more than 15%. If appropriate, artificial joint replacement can be avoided or postponed.

(1) Decompression of the femoral head pith core. It is recommended to use a thin needle with a diameter of about 3mm, and drill multiple holes under the guidance of the perspective. It can be used for autologous bone marrow cell transplantation and bone morphogenetic protein (BMP) implantation. This therapy should not be used in advanced stages (stages III and IV).

(2) Autogenous bone grafts with blood vessels Fibula grafts with blood vessels, iliac bone grafts with blood vessels, etc., are applicable to stage II and III AVN. If the application is appropriate, the effect is better. However, such surgery may cause complications in the donor site, and the operation is traumatic, the operation time is long, and the effect varies greatly.

(3) Bone transplantation without blood vessels The most commonly used bone grafts include decompression of the femoral trochanter, and bulb-like decompression of the femoral head and neck. Bone grafting methods include compacting and supporting bone grafts. Applied bone graft materials include autogenous cancellous bone, allogeneic bone, and bone replacement materials. This type of surgery is applicable to stage II and early stage III AVNs. If applied properly, the mid-term effect is better.

(4) Osteotomy Remove the necrotic area from the femoral head weight-bearing area and the unnecrotic area from the weight-bearing area. Clinical osteotomy includes varus or valgus osteotomy, femoral rotator osteotomy, etc. This method is suitable for stage II or stage III early and middle stage AVN with medium necrosis volume. This technique will bring greater technical difficulties for future artificial joint replacement.

(5) Artificial joint replacement. Once the femoral head collapses severely (stage III, IV, ), and joint function or pain is severe, artificial joint replacement should be selected. For patients under 50 years of age, surface replacement can be used. This type of surgery can retain more bone for future revision surgery, but each has its own indications, technical requirements and complications, and should be selected carefully.

Artificial joint replacement has a positive effect on advanced AVN. It is generally believed that the non-cemented or mixed type prosthesis is superior to the cemented prosthesis in the medium and long term. Femoral head necrosis of artificial joint replacement is different from arthroplasty for other diseases. Some related issues should be paid attention to: The patient has been receiving corticosteroids for a long time, or the underlying disease needs to be treated, so the infection rate is increased; Prosthesis is easy to penetrate into the acetabulum due to osteoporosis and other reasons; femoral head preservation surgery has been performed, which will bring various technical difficulties. In addition: dead bone removal and bone cement filling femoral head reconstruction

In addition, there is controversy in the academia about asymptomatic AVN treatment. Some studies believe that AVNs with large necrosis volume (> 30%) and necrosis in the weight-bearing area should be actively treated without waiting for symptoms to appear.

5. Treatment options for different stages of femoral head necrosis

For stage 0 non-traumatic AVN, if diagnosis is made on one side and stage 0 is highly suspected on the contralateral side, close observation is recommended. MRI follow-up is recommended every 6 months. If the stage and AVNs are asymptomatic, non-weight-bearing areas, and 15% of the lesion area, they should be actively treated with joint-sparing surgery or drugs. Stage IIIA and IIIB AVN can be treated with various bone implants, osteotomy and limited surface replacement, and patients with mild symptoms can also be treated conservatively. In patients with stage IIIC and IV AVN, if the symptoms are mild and young, joint surgery can be reserved. Other patients can choose surface replacement and total hip replacement.