Management of Grade 2 Avascular Necrosis of the Femoral Head
Core decompression with or without bone grafting is the recommended surgical intervention for Grade 2 (pre-collapse) AVN of the femoral head, as it can arrest disease progression and preserve the native femoral head in carefully selected patients. 1, 2
Risk Stratification and Prognostic Assessment
Before proceeding with treatment, assess the following critical prognostic factors that determine likelihood of progression:
- Necrotic volume: Lesions involving <30% of the femoral head have <5% risk of collapse, while lesions >30% have 46-83% risk of progression to collapse 3, 1
- Patient age >40 years and BMI >24 kg/m² are associated with increased risk of femoral head collapse 3, 1
- Presence of joint effusion or bone marrow edema on MRI indicates higher risk of progression 3, 1
- Bilateral involvement occurs in 70-80% of nontraumatic cases, requiring evaluation of both hips 1
Surgical Management: Core Decompression
Core decompression is the primary surgical intervention for Grade 2 AVN, with the goal of preventing articular collapse and delaying or avoiding total hip replacement 3, 1:
- Success rates are highest in early stages: 92.3% for Stage I and 88% for Stage II disease when patients comply with postoperative protocols 4, 2
- Bone grafting should be added to core decompression, using cancellous autograft from the iliac crest or non-vascularized fibular graft 2
- Supplementation options include autologous bone marrow cells, vascular fibular grafting, or electric stimulation, though overall efficacy remains controversial 3, 1
Critical Postoperative Requirements
- Strict non-weight bearing is mandatory following the procedure to prevent fracture and optimize outcomes 5, 2
- Studies show that non-compliance with weight-bearing restrictions dramatically reduces success rates (from 92.3% to lower rates in Stage I disease) 2
- Regular radiographic follow-up is essential to monitor for disease progression or femoral head collapse 5
Role of Conservative/Noninvasive Therapies
The American College of Radiology acknowledges that noninvasive therapies have limited supporting data but may be considered 3, 1:
- Pharmacological options include statins, bisphosphonates, and anticoagulants 3, 1
- Other modalities include extracorporeal shock wave therapy and hyperbaric oxygen 3, 1
- Bisphosphonates have controversial efficacy in reducing femoral head collapse rates 6
- These should not replace surgical intervention in appropriate candidates but may serve as adjuncts 7
When to Proceed Directly to Arthroplasty
Do not perform core decompression if articular collapse has already occurred (late-stage disease), as success rates drop dramatically 3, 1:
- Resurfacing hemiarthroplasty is indicated for late-stage osteonecrosis with articular collapse 3, 1
- Total hip arthroplasty is performed for severe secondary osteoarthritis 3, 1
- AVN accounts for 10% of total hip replacements in the United States 3
Critical Pitfalls to Avoid
- Failure to evaluate the contralateral hip: 70-80% of nontraumatic cases are bilateral 1
- Screening for multifocal involvement: Check knee (44%), ankle (17%), and shoulder (15%) as these sites are commonly involved 3
- Delaying surgical intervention: Early diagnosis and treatment before collapse is crucial, as outcomes deteriorate significantly once collapse occurs 1, 2
- Poor patient selection: Success rates decline from 92.3% in Stage I to 50% in Stage IIB, emphasizing the importance of early intervention 2
- Inadequate postoperative compliance: Non-compliance with weight-bearing restrictions significantly compromises outcomes 2