What is the intervention for a smaller left hip head due to conditions like hip dysplasia or avascular necrosis?

Management of Smaller Left Femoral Head on Hip X-ray

For a smaller left femoral head identified on hip x-ray, the intervention should be determined based on the underlying cause, with core decompression recommended for early avascular necrosis and joint-preserving surgical techniques for hip dysplasia with intact cartilage. 1

Diagnostic Considerations

When a hip x-ray reveals a smaller femoral head on one side, the primary differential diagnoses include:

1. Avascular Necrosis (AVN) - Characterized by bone death due to compromised blood supply
2. Developmental Dysplasia of the Hip (DDH) - Abnormal hip development from birth
3. Early osteoarthritis - Degenerative changes affecting the femoral head

Initial Evaluation

• Radiography is the appropriate initial imaging study, but has limited sensitivity for early AVN 1
• MRI is the gold standard for early detection of AVN and should be performed when suspected 1
• Measure the necrotic volume of the femoral head:
  • <30% necrotic volume: <5% risk of collapse

  • 30% necrotic volume: 46-83% risk of collapse 1

Treatment Algorithm Based on Underlying Cause

For Avascular Necrosis

Treatment depends on staging:

1. Early AVN (pre-collapse):

   • Core decompression to prevent articular collapse 1
   • Can be supplemented with:
     • Autologous bone marrow cell injection
     • Vascular fibular grafting
     • Electric stimulation

2. Late AVN (with collapse):

   • Resurfacing hemiarthroplasty for moderate collapse 1
   • Total hip arthroplasty for severe secondary osteoarthritis 1

For Developmental Dysplasia of the Hip

Treatment depends on age and severity:

1. In infants and young children:

   • Pavlik harness for infants up to 6 months with a success rate of 67-83% 2
   • Closed reduction and spica casting (caution: higher AVN risk at 14.3%) 3

2. In older children and adults with residual dysplasia:

   • Joint-preserving surgical options for intact cartilage 1
   • Osteotomy for younger patients with painful hip dysplasia 1

Cartilage Management Strategies

For cases with cartilage damage:

1. Small delaminated cartilage lesions (<3 cm²):

   • Repair with sutures or fibrin adhesive 1
   • Significant improvements in pain scores reported (MHHS pain subscale from 21.8 to 35.8) 1

2. Focal osteochondral defects:

   • Mosaicplasty (autologous osteochondral graft transplantation) for patients <45 years with focal lesions <3 cm² 1

Risk Factors and Monitoring

• Monitor for AVN, which occurs in 6-48% of DDH treatment cases 3
• Risk factors for AVN include:
  • Higher degree of initial dislocation (Tönnis classification) 4
  • Age at onset of treatment 4
  • Treatment method (closed reduction has lower AVN risk than open reduction) 5

Follow-up Protocol

• Regular radiographic assessment to monitor for:

  • Progressive femoral head collapse in AVN
  • Residual dysplasia in DDH
  • Development of secondary osteoarthritis

• MRI follow-up to evaluate:

  • Bone marrow edema
  • Joint effusion
  • Necrotic volume changes

Cautions and Pitfalls

• Avoid delayed treatment of AVN as femoral head collapse significantly worsens outcomes 1
• Be aware that 52.6% of patients with AVN following DDH treatment have poor outcomes 6
• Consider that open reduction alone has the highest probability (94.4%) of causing AVN in children with DDH under 3 years 5
• Recognize that specific morphological characteristics on pelvis radiographs can predict poor outcomes at a very young age 6