How should avascular necrosis of the hip be diagnosed and treated in a 45‑year‑old male with prolonged high‑dose corticosteroid use and hip pain?

Avascular Necrosis of the Hip in a 45-Year-Old Male with Prolonged High-Dose Corticosteroid Use

Immediate Diagnostic Approach

Obtain plain radiographs of both hips (AP and lateral views) immediately, followed by MRI without IV contrast if radiographs are normal or equivocal, as MRI is the gold standard with sensitivity and specificity approaching 100%. 1

Initial Imaging

• Start with plain radiographs in two planes despite limited sensitivity in early disease, as this excludes other causes like fracture, primary arthritis, or tumor 1, 2
• If radiographs show normal or only suspicious findings, proceed immediately to MRI without IV contrast 1
• MRI detects AVN with 93% sensitivity and 91% specificity in early stages when radiographs remain normal 1

MRI Protocol Specifics

• A coronal STIR sequence alone demonstrates 100% sensitivity for detecting AVN 1
• Add a coronal T1-weighted sequence to increase diagnostic confidence and specificity 1
• MRI characterizes necrotic volume, location, presence of bone marrow edema, and joint effusion—all critical for prognosis 1
• Evaluate both hips on MRI even if symptoms are unilateral, as 70-80% of nontraumatic AVN cases are bilateral 1, 3

Avoid These Imaging Pitfalls

• Do not order CT as first-line imaging; it is less sensitive than MRI for early osteonecrosis 1
• Do not order bone scintigraphy; it has poor spatial resolution, low specificity, and cannot quantify lesion size 1
• Do not order MRI with IV contrast for diagnosis; it adds no value for AVN detection itself 1

Risk Stratification Based on Corticosteroid Exposure

This patient's prolonged high-dose corticosteroid use places him at markedly elevated risk, particularly if daily prednisolone doses reached ≥30 mg with rapid escalation. 1

• High-dose glucocorticoids increase AVN risk at least 1.5-fold compared to low-dose regimens 4
• Meta-analysis demonstrates significantly more AVN cases with high-dose versus low-dose corticosteroids (P<0.001, odds ratio 2.74) 4
• Even very low physiological replacement doses can rarely cause AVN, though this is exceptional 5

Prognostic Assessment After Diagnosis

Measure the necrotic angle on MRI to determine collapse risk and guide treatment urgency. 1, 2

Size-Based Prognosis

• Lesions involving <30% of femoral head volume progress to collapse in <5% of cases 1, 2, 3
• Lesions involving ≥30% of femoral head volume progress to collapse in 46-83% of cases 1, 2, 3

Additional Poor Prognostic Factors

• Age >40 years worsens outcomes (this patient is 45 years old) 1
• BMI >24 kg/m² worsens outcomes 1
• Presence of joint effusion on MRI indicates worse prognosis 1
• Increased bone marrow edema on MRI predicts worse outcomes 1

Treatment Algorithm Based on Disease Stage

Pre-Collapse Disease (Radiographs Normal, MRI Positive Only)

Implement protected weight-bearing with walking aids immediately and consider core decompression with bone marrow aspirate concentrate (BMAC) for lesions ≥30%. 2, 6, 7

• Weight reduction and use of canes or walkers reduce symptoms in early stages 2
• Protected weight-bearing is specifically recommended for pre-symptomatic AVN with MRI changes only 2
• Core decompression with bone substitute filling or BMAC is effective only before subchondral collapse occurs 2, 6, 7
• Bisphosphonates may prevent bone collapse in early stages 2
• Joint-preserving interventions lose effectiveness once collapse begins 2

Post-Collapse Disease (Articular Surface Compromised)

Total hip arthroplasty becomes necessary once articular collapse occurs, as joint-preserving procedures are no longer effective. 2

• More definitive procedures like total hip arthroplasty are required for late-stage AVN with articular collapse 2
• CT imaging becomes useful at this stage for depicting collapse extent and preoperative planning 1

Critical Clinical Considerations

Bilateral Evaluation is Mandatory

• Always image both hips even with unilateral symptoms, as 70-80% of nontraumatic AVN is bilateral 1, 3
• Multifocal joint involvement is common: knee affected in ~44% of cases, ankle in ~17%, shoulder in ~15% 3

Timing is Everything

• Early diagnosis allows possible surgical prevention of articular collapse and delays or avoids joint replacement 1
• Symptoms indicate disease is already underway; approximately 5% of at-risk patients have asymptomatic disease detectable only on MRI 1, 2
• Pain characteristically increases with activity and weight-bearing, not relieved by activity 1

Address Modifiable Risk Factors

• Discontinue or minimize corticosteroid dose if medically feasible 4, 1
• If corticosteroids cannot be stopped, switch to the most physiological preparation (hydrocortisone) at the lowest possible dose 5
• Screen for and treat hyperlipidemia, as it contributes to AVN risk 1, 3, 8
• Evaluate for hypercoagulable states and other metabolic disorders 1, 3

Post-Treatment Monitoring

Perform regular radiographic follow-up to monitor for disease progression or femoral head collapse following any intervention. 2