Avascular Necrosis (AVN)
Avascular necrosis (AVN) is a pathologic condition characterized by death of bone tissue due to inadequate blood supply, which leads to bone collapse and eventual degenerative joint disease if left untreated. 1, 2
Definition and Pathophysiology
- AVN, also called osteonecrosis or aseptic necrosis, involves death of both trabecular bone and bone marrow elements due to compromised blood supply 2, 3
- Three main pathophysiological mechanisms have been identified:
- The femoral head is the most commonly affected site, but AVN can also affect other bones including the lunate, humeral head, scaphoid, and talus 3, 2
Risk Factors
- Corticosteroid therapy is a major risk factor, especially high-dose and prolonged treatment 1, 3, 5
- Alcohol abuse significantly increases risk 1, 4
- Other important risk factors include:
Clinical Presentation
- Pain is the predominant symptom, often severe and worsened by weight-bearing 1, 5
- Restricted joint motion develops as the disease progresses 5
- AVN can be asymptomatic in early stages, with positive MRI findings occurring in approximately 5% of at-risk patients 1
- Late presentation is a major negative prognostic factor 1
Diagnosis
- MRI is the preferred diagnostic method for AVN, especially in patients with persistent joint pain but normal standard radiographs 1, 2
- Initial evaluation should include radiography to exclude other causes of pain such as fracture, primary arthritis, or tumor 1
- CT imaging is valuable for determining the extent of necrosis and for surgical planning 1, 7
- Bone scintigraphy has largely been replaced by MRI due to poor spatial resolution and low specificity 1
Complications and Prognosis
- Untreated AVN inevitably leads to early degenerative joint disease 1
- AVN is estimated to cause up to one-third of all total hip arthroplasties performed in patients under 60 years of age 1
- The necrotic volume is a critical prognostic factor - lesions involving <30% of the femoral head have <5% progression to collapse 7
Management
Non-Surgical Approaches
- Weight reduction and use of walking aids (canes or walkers) may help reduce symptoms in early stages 1
- Protected weight-bearing is recommended for patients with pre-symptomatic AVN with MRI changes only 1
- NSAIDs and analgesics can provide symptomatic pain relief but do not alter disease progression 1
- Bisphosphonates may be used to prevent bone collapse in early stages 1
Surgical Management
- Core decompression with bone substitute filling is an option for early-stage disease, particularly in younger patients 7, 5
- For young adults with symptomatic hip AVN, especially with dysplasia or varus/valgus deformity, joint-preserving procedures such as osteotomy may be considered 1
- For late-stage AVN with articular collapse, more definitive procedures like total hip arthroplasty are necessary 1, 7
- For elderly patients with poor bone quality, cemented femoral fixation should be considered to reduce periprosthetic fracture risk 1
Special Considerations
- AVN can occur as a complication in specific patient populations:
- In children with chronic myeloid leukemia, AVN usually affects the femoral head and hip pain may precede the diagnosis by several months 8
- In kidney transplant recipients, AVN is a well-recognized complication, with glucocorticoid dosage and prior dialysis being important risk factors 8
- In systemic sclerosis patients, multifocal AVN (affecting multiple anatomic sites) has been reported but is rare 9