What is the recommended treatment for a patient with cystic changes in the femoral head, likely due to osteonecrosis or osteoarthritis?

Treatment of Cystic Changes in the Femoral Head

For patients with cystic changes in the femoral head, treatment selection depends critically on lesion size and stage: lesions <2 cm² without collapse should undergo microfracture or core decompression; lesions 2-6 cm² require osteochondral allograft transplantation; and lesions >8 cm² or those with advanced collapse necessitate total hip arthroplasty. 1, 2

Understanding the Clinical Significance

Cystic changes in the femoral head indicate structural instability and are strongly associated with disease progression. Femoral heads with cystic lesions are significantly more likely to develop microfracture, collapse, and crescent sign compared to those without cysts (P < 0.001 for all parameters). 3 These cystic lesions typically form near the sclerosis rim through an osteoarthritis-like mechanism driven by peak stress concentration, and they play an important role in aggravating femoral head collapse. 3

The necrotic volume is the most critical prognostic factor: lesions involving <30% of the femoral head have <5% risk of progression to collapse, while lesions >30% carry a 46-83% risk of progression. 2, 4

Treatment Algorithm by Lesion Size

Small Lesions (<2 cm²)

First-line treatment: Microfracture 1

• Indicated for patients age <45 years with no evidence of osteoarthritis and focal full-thickness lesions 1
• The technique involves creating multiple drill holes that penetrate subchondral bone while maintaining stable bone bridges between holes 1
• Provides immediate structural support and stimulates fibrocartilage formation 1

Alternative: Core decompression 2

• Success rates of 94% for Stage I and 88% for Stage II disease 4
• Protected weight-bearing is mandatory postoperatively to prevent fracture 2
• Should NOT be performed on Stage IV disease with collapse (success rate only 14%) 4

Medium Lesions (2-6 cm²)

First-line treatment: Osteochondral allograft transplantation (OAT) 1

• Indicated for patients aged ≤50 years without evidence of osteoarthritis 1
• Particularly appropriate when substantial subchondral bone loss is present 1
• Provides immediate mechanically functioning hyaline cartilage surface with superior properties compared to fibrocartilage 1
• Historical data shows 80% success rate in non-steroid-induced osteonecrosis, though only 50% success in steroid-induced cases 1

Alternative: Mosaicplasty 1

• Autologous osteochondral graft transplantation from lateral trochlea 1
• Eliminates need for second procedure and allows immediate weight-bearing 1
• Avoids donor tissue scarcity issues associated with allografts 1

Second-line: Matrix-assisted autologous chondrocyte implantation (MACI) 1

• For lesions >2 cm² with Outerbridge grade 3 or 4 defects 1
• Superior outcomes compared to simple debridement: mean Harris Hip Score of 87.4 vs 56.3 at 74-month follow-up (P < 0.05) 1
• Can be performed arthroscopically, avoiding surgical dislocation risks 1
• Critical limitation: Not FDA-approved in the United States (currently only available in Europe) 1

Large Lesions (6-8 cm²)

Definitive treatment: Osteochondral allograft transplantation 1

• Larger defects that cannot be adequately addressed with other joint-preserving techniques 1
• Important caveat: Chondrocyte viability decreases substantially after 28 days of allograft storage 1

Very Large Lesions (>8 cm²) or Advanced Collapse

Definitive treatment: Total hip arthroplasty 1, 2

• Indicated when there is significant joint surface collapse or degenerative arthritis 5
• Joint preservation techniques are rarely successful after significant subchondral collapse 5
• For late-stage osteonecrosis with articular collapse, hemiarthroplasty or total joint arthroplasty is necessary 2

Critical Diagnostic Requirements

CT imaging is essential for surgical planning to determine precise location, extent of necrotic lesion, and degree of collapse. 2, 6 Plain radiographs typically show cystic and sclerotic changes as the first radiographic findings, but MRI is the gold standard for early detection before radiographic changes appear. 4, 7

Common Pitfalls to Avoid

• Do not delay diagnosis: Early intervention prior to collapse is critical to successful outcomes in joint-preserving procedures 7, 8
• Do not perform core decompression on collapsed lesions: Stage IV disease has only 14% success rate with core decompression; arthroplasty is indicated 4
• Do not ignore bilateral disease: Screen the contralateral hip, as 70-80% of nontraumatic cases are bilateral 4
• Do not use excessive pressurization during cemented arthroplasty: This increases risk of bone cement implantation syndrome, particularly in elderly patients with cardiopulmonary disease 1

Postoperative Management

All joint-preserving procedures require protected weight-bearing and regular radiographic follow-up to monitor for disease progression or femoral head collapse. 2, 6 The goal is to prevent further structural deterioration while the repair tissue matures.