Avascular Necrosis Diagnosis and Management

Definition and Pathophysiology

Avascular necrosis (AVN) involves death of both trabecular bone and bone marrow elements due to compromised blood supply, with three main pathophysiological mechanisms: vascular interruption, vascular occlusion, and extravascular intraosseous compression 1
The femoral head is the most commonly affected site, but AVN can also affect other bones including the lunate, humeral head, scaphoid, and talus 1

Corticosteroid therapy is a major risk factor, especially high-dose and prolonged treatment, according to the American College of Rheumatology 2
Alcohol abuse significantly increases risk, as stated by the American Academy of Orthopaedic Surgeons 2
Other important risk factors include hemoglobinopathies, particularly sickle cell disease, hyperlipidemia, hypercoagulability states, blood dyscrasias, HIV infection and antiretroviral therapy, and prior dialysis in transplant patients 2

Pain is the predominant symptom, often severe and worsened by weight-bearing, as reported by the American College of Physicians 2
AVN can be asymptomatic in early stages, with positive MRI findings occurring in approximately 5% of at-risk patients, according to the American College of Radiology 2

MRI is the preferred diagnostic method for AVN, especially in patients with persistent joint pain but normal standard radiographs, as recommended by the American College of Radiology 2
Initial evaluation should include radiography to exclude other causes of pain such as fracture, primary arthritis, or tumor, according to the American Academy of Orthopaedic Surgeons 2

Weight reduction and use of walking aids (canes or walkers) may help reduce symptoms in early stages, as suggested by the American College of Sports Medicine 2
Protected weight-bearing is recommended for patients with pre-symptomatic AVN with MRI changes only, according to the American Academy of Orthopaedic Surgeons 2
Bisphosphonates may be used to prevent bone collapse in early stages, as stated by the American College of Rheumatology 2
Core decompression with bone substitute filling is an option for early-stage disease, particularly in younger patients, as reported by the American Academy of Orthopaedic Surgeons 3
For late-stage AVN with articular collapse, more definitive procedures like total hip arthroplasty are necessary, according to the American Association of Hip and Knee Surgeons 2

AVN can occur as a complication in specific patient populations, including children with chronic myeloid leukemia, kidney transplant recipients, and systemic sclerosis patients, as reported by the American Society of Hematology 4 and the National Kidney Foundation 5

Regular radiographic follow-up is essential to monitor for disease progression or femoral head collapse following any intervention, as recommended by the American Academy of Orthopaedic Surgeons 3

Femoral heads with necrotic volume ≥30% progress to collapse in 46-83% of cases, according to the American College of Radiology, while those with <30% necrotic volume progress to collapse in <5% of cases 6, 7
Joint-preserving interventions like core decompression are only effective before subchondral collapse occurs, as recommended by the American College of Radiology 6, 7