Role of Fibular Bone Graft in the
Treatment of Avascular Necrosis

Avascular necrosis (AVN), also known as osteonecrosis, is a debilitating condition that affects the femoral head, leading to bone death due to compromised blood supply. It is most common in young and middle-aged adults, often causing pain, deformity, and limp. Fibular bone grafting is one of the preservation techniques used in the early stages of AVN to delay the need for total hip replacement (THR). Though THR is often recommended in late-stage AVN, fibular grafts provide an option to preserve the femoral head in select patients, especially those who are younger and wish to avoid or delay joint replacement surgery.

Functional Anatomy

The hip joint is a ball-and-socket joint formed by the femoral head (ball) and the acetabulum (socket) in the pelvis. The femoral head is supported by a delicate vascular network that provides essential nutrients to the bone. Avascular necrosis occurs when the blood supply to the femoral head is disrupted, often leading to bone collapse and severe arthritis if untreated. Fibular bone grafting aims to provide structural support and nutritional restoration to the affected bone, potentially slowing the progression of AVN and avoiding the collapse of the femoral head.

MRI in the coronal section showing avascular necrosis lesions in both hips.

Biomechanics or Physiology

In AVN, the loss of blood supply to the femoral head leads to bone death and the collapse of the femoral head. This collapse causes mechanical failure in the hip joint, resulting in pain, stiffness, and functional limitations. Fibular bone grafting works by addressing the bone collapse and restoring blood flow to the affected area. The fibula, a bone from the lower leg, is harvested and inserted into the femoral head to provide structural support and a vascular supply that can promote bone regeneration. The fibula’s bone cells gradually replace the necrotic bone through a process known as creeping substitution, wherein the graft tissue is replaced by new, healthy bone over time.

Common Variants and Anomalies

• Early-stage AVN: When detected early, fibular bone grafting may prevent femoral head collapse and delay the need for total hip replacement.

• Late-stage AVN: If the bone collapse is severe or if there is significant joint damage, total hip replacement is usually indicated.

• Vascularized fibular grafting: This technique involves transferring fibular bone along with its blood vessels, ensuring an enhanced blood supply to the femoral head and improving the chances of bone regeneration.

• Non-vascularized grafts are less effective in restoring bone health and may only provide structural support.

Clinical Relevance

Fibular bone grafting is a valuable treatment option for young patients with early-stage AVN who wish to avoid immediate joint replacement. It can help preserve the femoral head, delay the need for total hip replacement, and potentially restore normal hip function. However, the success of this procedure is not guaranteed, and AVN may progress despite intervention. This highlights the importance of careful patient selection, as well as the consideration of implant replacement surgery as a long-term solution, especially when conservative options fail.

Imaging Overview

• X-rays: The primary imaging modality used to assess the femoral head for signs of AVN. Subchondral sclerosis (hardening of the bone) and joint space narrowing are indicative of advanced AVN.

• MRI: The most sensitive test for detecting early-stage AVN. MRI can identify bone marrow edema (swelling) in the femoral head, which is often the first sign of AVN before bone collapse occurs.

• CT scans: Used to visualize bone collapse and evaluate the extent of damage to the femoral head.

• Bone scans: Can detect early changes in bone metabolism, such as increased uptake in the femoral head, indicating AVN.

Associated Conditions

• Corticosteroid use: Long-term use of glucocorticoids for conditions such as rheumatoid arthritis, systemic lupus erythematosus, or nephrotic syndrome is a major risk factor for developing AVN.

• Trauma: Hip fractures or dislocations can damage blood vessels supplying the femoral head, leading to AVN.

• Alcohol abuse: Chronic alcohol consumption can disrupt blood flow to the femoral head, increasing the risk of AVN.

• Other systemic diseases: Sickle cell disease and vascular disorders can also contribute to AVN by impairing blood supply to the hip.

Surgical or Diagnostic Applications

• Core decompression: A procedure in which a small section of the femoral head is removed to reduce internal pressure and stimulate revascularization.

• Fibular bone grafting: A non-surgical approach in which the fibula is harvested and implanted into the femoral head. The vascularized fibular graft enhances blood supply to the necrotic bone, encouraging healing.

• Total hip replacement (THR): The most common treatment for late-stage AVN or advanced bone collapse, where the femoral head is replaced with an artificial joint.

• Stem cell therapy: An experimental treatment option aimed at regenerating bone tissue using stem cells derived from the patient’s own body.

Prevention and Maintenance

While AVN cannot always be prevented, certain steps may reduce the risk:

• Minimizing corticosteroid use whenever possible or using the lowest effective dose for the shortest period.

• Maintaining bone health through calcium, vitamin D, and weight-bearing exercises.

• Regular monitoring of patients on corticosteroid therapy for early signs of AVN.

• Early diagnosis through MRI or bone scans allows for prompt intervention before femoral head collapse occurs.

Removed head of femur during surgery showing avascular necrotic lesion.

Research Spotlight

A recent study assessed the outcomes of core decompression (CD) with or without nonvascularized fibular grafting in early-stage avascular necrosis (AVN) of the femoral head. The study included 76 hips, with Stage 1 patients undergoing CD alone and Stage 2 patients receiving CD with fibular grafting.

At an average follow-up of 53.5 months, the study found that 72.3% of hips showed no progression of the disease. However, 27.6% of cases demonstrated disease progression, with a higher failure rate in the fibular grafting group (30%) compared to CD alone (25%).

The study concluded that while CD with fibular grafting can delay disease progression and help preserve the femoral head, it does not entirely prevent further collapse or arthritis, emphasizing the importance of early intervention in the disease’s progression. (“Study on core decompression and fibular grafting for AVN – see PubMed“).

Summary and Key Takeaways

• Avascular necrosis (AVN) of the femoral head is a progressive condition that can lead to pain and loss of joint function if untreated.

• Corticosteroid use is the most common cause of AVN, particularly in young, middle-aged adults.

• Early-stage AVN can be managed with core decompression, fibular bone grafting, and stem cell therapy, potentially delaying the need for total hip replacement.

• Total hip replacement is the gold standard for advanced AVN, providing excellent pain relief and joint function.

• Early diagnosis through MRI and bone scans is crucial for preserving the femoral head and preventing further joint damage.

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