Avascular Necrosis

Overview

Avascular necrosis (AVN), sometimes called osteonecrosis or bone infarction, is loss of bone tissue due to interruption of the blood supply. There may be no symptoms at first. Joint discomfort may gradually develop, limiting your ability to move. Complications may include bone or joint surface collapse.

Bone fractures, joint dislocations, alcoholism, and the use of high-dose steroids are all risk factors. The condition might sometimes emerge for no obvious cause. The femur is the most usually afflicted bone. Other typical locations are the upper arm bone, knee, shoulder, and ankle. X-rays, CT scans, and MRIs are commonly used to diagnose patients. Biopsies are only utilized in rare cases.

Medication, not walking on the affected limb, stretching, and surgery are all possible treatments. Most of the time surgery is eventually necessary and may include core decompression, osteotomy, bone transplants, or joint replacement. In the United States, around 15,000 cases occur each year. People aged 30 to 50 are the most typically impacted. Males are more likely to be affected than females.

What is Avascular Necrosis?

Every year, between 10,000 and 20,000 Americans develop avascular necrosis. It can affect people of all ages and genders, although it is more common among adults in their 30s and 40s.

Avascular necrosis occurs when anything prevents blood from flowing to your bone tissue. Your bones are continually changing as your skeletal system produces new bone tissue to replace aged bone tissue, which eventually deteriorates and dies.

Consider this process as a cycle in which your body produces new tissue to replace old, deteriorating, and dying tissue. This routine must be followed correctly in order to maintain your bones healthy and powerful. Blood transports the nutrients and oxygen that bones require to stay healthy and regenerate. Without blood flow, your skeletal system can't make new bone tissue fast enough. The dying bone begins to crumble and eventually collapses.

Causes & Risk Factors for Avascular Necrosis

Things that can make avascular necrosis more likely include:

• Alcohol. Several drinks a day can cause fat deposits to form in your blood, which lower the blood supply to your bones.
• Bisphosphonates. These bone-density-boosting drugs may cause jaw osteonecrosis. If you're taking them for multiple myeloma or metastatic breast cancer, this is more likely.
• Medical treatments. Radiation therapy for cancer can weaken bones. Other conditions linked to AVN include organ transplants, like kidney transplants.
• Steroid drugs. Long-term use of these anti-inflammatory drugs, either orally or intravenously, causes 35% of all instances of non-traumatic AVN. Doctors are unsure why, although long-term use of drugs such as prednisone can result in AVN. They believe the medications will cause your blood fat levels to rise, resulting in decreased blood flow.
• Trauma. Breaking or dislocating a hip can damage nearby blood vessels and cut the blood supply to your bones. AVN may affect 20% or more of people who dislocate a hip.

Other conditions associated with non-traumatic AVN include:

• Decompression sickness, which causes gas bubbles in your blood.
• Diabetes.
• Gaucher disease, in which a fatty substance collects in the organs.
• HIV. 
• Long-term use of drugs called bisphosphonates to treat cancers like multiple myeloma or breast cancer, which can lead to AVN of the jaw.
• Pancreatitis, inflammation of the pancreas.
• Radiation therapy or chemotherapy.
• Autoimmune diseases such as lupus and arthritis.
• Sickle cell disease.

What are the Stages of Avascular Necrosis?

Avascular necrosis can be classified into five different stages: 

• Stage 1: Radiographic changes are absent or show minor osteopenia. An MRI scan is required for identification (can show oedema). The onset of this disease is asymptomatic.
• Stage 2: First stage with radiographic changes. This stage is characterized by sclerosis of the superior central portion of the joint head and/or osteopenia and/or subchondral cysts.
• Stage 3: In this stage, the articular surface is depressed so that the round contour is compromised, without being significantly deformed. This leads to a joint space narrowing. A plain radiograph shows a crescent sign.
• Stage 4: This stage is characterized by a wide collapse of the subchondral bone and destruction of the underlying trabecular pattern. This can lead to secondary arthritis.
• Stage 5: The final stage where both articular surfaces are affected, which leads to a dysfunctional joint.

Avascular Necrosis Signs & Symptoms

Non-traumatic patients will often present with mechanical pain of varying onset and severity, which is frequently difficult to locate. The physical examination is frequently normal in early condition, which causes a delay in diagnosis. Recent trauma, steroid usage, autoimmune illness, sickle cell, alcoholism, cigarette use, manual labour, change in gait, connective tissue diseases, insidious onset pain, and restricted range of motion should all be included in a focused history.

• Hip osteonecrosis. The early stages are frequently asymptomatic. The most common presenting symptoms are hip and groin discomfort, which generally signal late-stage development. Associated symptoms may include buttock and thigh discomfort. The majority of individuals experience pain even while they are at rest. Other symptoms include stiffness and gait abnormalities.
• Osteonecrosis of the Knee. It is most commonly presents as acute onset knee pain that occurs while weight-bearing and at night. History of osteoporosis or osteopenia and no recent trauma are typical responses. On physical exam, pain with palpation over the medial femoral condyle and decreased range of motion are observed.
• Osteonecrosis of the Shoulder. This condition involving the proximal humerus is often associated with trauma and osteonecrosis elsewhere in the body. Pain is characterized as pulsating with radiation to the elbow and a decreased active range of motion.
• Osteonecrosis of the Talus. It is associated with polyarticular disease and trauma. Patients will often complain of pain and difficulty ambulating well beyond the expected recovery time following a traumatic event.
• Osteonecrosis of the Lunate and Scaphoid. It often present without a history of trauma. Patients are usually skilled labourers and complain of unilateral pain on the wrist's dorsal and radial aspects. Decreased range of motion, wrist swelling, and weakened grip strength are other common findings.

How is Avascular Necrosis Diagnosed?

Along with a complete medical history and physical exam, you may have one or more of the following tests:

• X-ray. This test uses invisible electromagnetic energy beams to make images of internal tissues, bones, and organs onto film.
• Computed tomography scan (also called a CT or CAT scan). This is an imaging test that makes detailed images of the body using X-rays and a computer. A CT scan provides information on the bones, muscles, fat, and organs. CT scans provide more information than standard X-rays.
• Magnetic resonance imaging (MRI).  This test uses large magnets, radiofrequencies, and a computer to make detailed images of organs and structures within the body.
• Radionuclide bone scan. A very little quantity of radioactive material is injected into the blood to be detected by a scanner in this nuclear imaging technique. This test demonstrates blood flow to the bone as well as cell activity within the bone.
• Biopsy. A procedure in which tissue samples are removed (with a needle or during surgery) from the body for exam under a microscope. It’s done to find cancer or other abnormal cells or remove tissue from the affected bone.
• Functional evaluation of bone. Tests that usually involve surgery to measure the pressure inside the bone.

Avascular Necrosis Management

Osteonecrosis of the Hip

1. Core Decompression and Grafting

This technique entails drilling one large hole or several smaller holes into the femoral head to alleviate pressure in the bone and provide pathways for new blood vessels to supply the affected parts of the hip.

When hip osteonecrosis is detected early, core decompression can help avoid femoral head collapse and the development of arthritis.

Core decompression is frequently paired with bone and cartilage grafting to help grow healthy bone and support cartilage at the hip joint. A bone graft is healthy bone tissue that is transferred to an area of the body that need it. The tissue may be obtained from a donor (allograft) or from another bone in your body (autograft).

There are also several synthetic bone grafts available today. Sometimes, your own bone marrow cells may be mixed together with the graft substitute to help in the bone regeneration process. It is important to speak with your surgeon about the available options that may be used for your procedure.

2. Vascularized Fibula Graft

A vascularized fibula graft is another surgical option. In this procedure, a segment of bone (fibula) and its blood supply are removed from your leg (an artery and vein). This graft is inserted into a hole in the femoral neck and head, and the artery and vein are reattached to aid in the healing of the osteonecrosis.

3. Total Hip Replacement

Total hip replacement involves the replacement of both the femoral head and the socket with an artificial device.

If osteonecrosis has progressed to the point that the femoral head has collapsed, total hip replacement is the most effective therapy. Your doctor will remove the damaged bone and cartilage, then position new metal or plastic joint surfaces to restore hip function.

Spontaneous Osteonecrosis of the Knee (SONK)

Following a trial of protected weight-bearing and rehabilitation, the majority of cases resolve. Due to the increased prevalence of SONK in the elderly, a unicompartmental knee replacement delivers a satisfactory functional result with a relatively short recovery period. In larger lesions, however, a total knee replacement may be more appropriate. Smaller lesions after intraosseous decompression have had excellent surgical outcomes.

Osteonecrosis of the Shoulder

Staging is used to categorize operational processes. Core decompression is the best therapy for early condition. In mild condition, humeral head resurfacing or hemiarthroplasty is suggested, with complete shoulder replacement reserved for severe disease.

Osteonecrosis of the Talus

The incidence of osteonecrosis of the talus in talar neck fractures is reduced utilizing a procedure to achieve operative anatomic reduction and stable fixation.

Keinbock’s Disease

Early-stage disease treatment tries to revascularize the lunate, either directly with bone grafts or indirectly by procedures to offload the lunate. In stage 1 and 2 disease, immobilization, including external fixation, is frequently attempted. In stage 3, surgical methods address carpal collapse, but advanced disease may necessitate joint-sacrificing procedures such as wrist arthrodesis.

Preiser Disease

Immobilization, cortisone injections, radial wedge osteotomy, and bone transplant are among early-stage therapeutic possibilities. In advanced stages, arthroscopic debridement, scaphoid excision, proximal row carpectomy, or even arthrodesis may be required. Typically, surgical intervention is unavoidable in most cases.

Complications/Risks

Surgical site infections, prosthesis malfunctions, and neurovascular impairment are all common postoperative consequences for osteonecrosis. High failure rates occur when the disease progresses despite surgical intervention. In 90% of individuals treated for AVN of the hip, for example, core decompression failed to halt disease progression. When conducting an osteotomy of the radius in Kienbock's illness, failure to account for the patient's specific anatomy might result in excessive positive ulnar variance and ulnar pain postoperatively.

Complication rates are also strongly influenced by patient comorbidities. Patients with sickle cell disease, for example, who underwent total joint replacement for AVN had longer hospital admissions, a greater risk of acute kidney injury, implant failure, pulmonary embolism, deep vein thrombosis, myocardial infarction, and an overall higher death rate.

Physical Therapy Management

Appropriate therapy for avascular necrosis is required to avoid additional joint degeneration. If left untreated, most individuals would have significant pain and mobility limitations within two years. Although physical therapy cannot cure avascular necrosis, it can slow the disease's course and reduce discomfort. A physical therapy program may aid individuals with Stage 1 and 2 osteonecrosis, according to research. Most patients will require surgical therapy, such as core decompression or arthroplasty, at some point.

Non-operative treatment involves three main goals:

• Relief of symptoms.
• Prevention of disease progression.
• Improvement of functionality.

Non-surgical therapy starts with patient education and addressing identified risk factors including smoking and alcohol abuse. Corticosteroids should also be avoided.

Crutches or other gait aids might be provided to help the patient restore function and reduce uncomfortable symptoms. The physical therapist should show the patient how to utilize these gadgets effectively.

The stress on the hip joint will be reduced by utilizing crutches. This weight-bearing limitation is a crucial preventative measure. Weight-bearing restriction is thought to be ineffective as a stand-alone therapy in avoiding disease development, but it is a viable treatment option when paired with pharmacological medications or surgery.

Physical therapy treatment focuses on exercises to maintain joint mobility and strengthen the muscles around the affected joint.  During physical therapy, excessive compressive and shear forces on the joint should be avoided. The outcome depends on the lesion’s size and stage at the initiation of the treatment.

Both passive and active workouts should be started to preserve joint mobility. Passive workouts include hip passive motions and stretching exercises. Active exercises are 3D motions of the hip joint that may be performed while standing, sitting in a chair, or lying down. Strengthening exercises are introduced in the next stage. These exercises will primarily target the muscles of the hip and thigh, but they will also include exercises for the core, which play an important supporting role.

In order to increase functioning, endurance and coordination training should be performed at a later stage of therapy. Walking on a treadmill or cycling on a home trainer might help you improve your endurance. Walking activities with increasing complexity and balance exercises can be used in physical therapy sessions to enhance coordination.

Physical therapy following surgery is also an important part of the rehabilitation process. It begins the day following surgery. They prepare patients for release by instructing them how to do daily tasks such as getting in and out of bed and walking with a walker or crutches.

In a later stage of therapy, the therapist advises the patient on exercises to strengthen their muscles, enhance range of motion, and focus on balance and gait speed. The patient explicitly learns how to move while taking hip precautions. The rehabilitation approach is supplemented with a home workout program. An example of a training regimen at the advanced stage of recovery is shown below.

When Should I Call My Healthcare Provider?

Avascular necrosis is a progressive condition that gets worse over time. If you have avascular necrosis, you should monitor your symptoms, such as pain and mobility.

You should call your healthcare provider if you have:

• Pain that doesn't improve with rest or pain relievers.
• Pain that makes walking or movement difficult.
• Unexplained limping.

How Can I Prevent Avascular Necrosis?

You might not be able to prevent avascular necrosis, but there are steps you can take to reduce your risk:

• Quit smoking.
• Cut back on your alcohol intake.
• Watch your cholesterol levels.

If you take corticosteroids for a chronic medical condition, talk to your healthcare provider about reducing your dosage.

Outcome

Regardless of the initial management strategy, the prognosis for osteonecrosis is frequently poor. The disease's progression involves continuous pain, disability, and joint degeneration beyond repair. According to the study, 59% of asymptomatic lesions led to symptoms or collapse. AVN of the humeral head, in particular, can be worse, with up to 81% of patients progressing to complete failure necessitating arthroplasty. As a result, if the patient experiences the start of osteonecrosis, the condition is likely to worsen.

Core decompression and bone grafting can slow the progression of hip osteonecrosis. Total hip arthroplasty is required with severe disease or failure of joint-preserving therapies, however it is linked with greater complication rates.

In the early phases of AVN, core decompression and hemiarthroplasty of the shoulder have favourable results. However, total shoulder arthroplasty has higher complication rates. Total shoulder arthroplasties are suggested for end-stage AVN, although they increase the patient's risk of postoperative problems.

In Preiser and Kienbock's disease, the initial stages of AVN are treated with immobilization, but eventual surgical intervention is usually indicated. Surgical repair of the talus in AVN management tends to have significantly better outcomes in younger patients.

Conclusion

The blood supply to the hip joint is cut off in teenagers and young adults with avascular necrosis (AVN), and the bone begins to perish. AVN, also known as osteonecrosis, can cause microscopic breaches in the bone and eventually collapse of the ball of the hip joint (femoral head). Although no one understands why AVN arises, we do know that it is frequently related with a number of underlying diseases, including prior chemotherapy, steroid usage, and sickle cell disease, among others.

AVN can cause hip, thigh, or knee discomfort. The hip joint commonly stiffens, and discomfort might begin suddenly or gradually over weeks or months.

Non-surgical therapy should always be sought first for addressing hip pain. Conservative therapies such as rest, activity limitation, physical therapy, and/or pain medication can help relieve pain and swelling in some cases.

If non-operative therapy does not relieve the hip pain or discomfort caused by avascular necrosis, or if your doctor is worried about additional collapse of the ball and worsening of your condition, surgery for AVN may be advised.