What are the considerations for a total hip replacement (THR) in a patient with a dysplastic hip?

Total Hip Replacement in Dysplastic Hip: Key Considerations

For patients with hip dysplasia requiring total hip replacement (THR), reconstruction at or near the normal anatomic acetabular location is recommended when pelvic bone stock allows, with careful attention to both acetabular and femoral abnormalities to optimize outcomes. 1

Anatomical Challenges in Dysplastic Hips

Acetabular Abnormalities

• Shallow, elongated acetabulum with deficient bone stock
• Superior and lateral migration of the femoral head
• Deficient anterior and superior walls
• Abnormal version of the acetabulum

Femoral Abnormalities

• Femoral hypoplasia
• Excessive femoral neck anteversion (commonly 15-80°)
• Valgus neck-shaft angle
• Metaphyseal-diaphyseal mismatch
• Posteriorly displaced greater trochanter
• Narrowed femoral canal 2, 3

Preoperative Planning

• Thorough radiographic assessment including:
  • AP pelvis
  • Cross-table lateral view
  • CT scan to evaluate acetabular bone stock and femoral version
  • 3D reconstruction when available for complex cases
• Classification of dysplasia severity (Crowe or Hartofilakidis classification)
• Assessment of leg length discrepancy
• Templating for component size and position

Acetabular Reconstruction Options

1. Anatomic Placement (Preferred)

   • Reconstruct socket at or near normal anatomic location
   • Medialization technique (cotyloplasty) to improve coverage
   • Use of smaller acetabular components when appropriate 1, 4

2. Bone Grafting Options

   • Lateral bone grafting for deficient lateral coverage
   • Femoral head autograft for large defects
   • Note: Long-term results show higher failure rates with cemented components in grafted bone (46% loose at 12-year follow-up) 5

3. Component Selection

   • Uncemented porous-coated hemispherical components show superior results
   • None reported loose at 7-year follow-up in one series 5
   • Consider augmented or custom components for severe defects

Femoral Reconstruction Considerations

1. Standard Stem Options

   • Tapered stems to accommodate narrow canals
   • Modular stems to address version and offset independently

2. Femoral Shortening Techniques

   • Required in high dislocation cases (Crowe III and IV)
   • Options include:
     • Metaphyseal resection with greater trochanteric osteotomy and advancement
     • Subtrochanteric shortening osteotomy to avoid nerve injury and facilitate reduction 1, 2, 3

3. Version Control

   • Critical to address excessive anteversion
   • May require derotational osteotomy in severe cases

Technical Pearls

• Place acetabular component at true anatomic hip center when possible
• Avoid oversizing the acetabular component
• Consider dual mobility or constrained liners in high-risk instability cases
• Careful soft tissue balancing and release
• Intraoperative assessment of stability and leg length
• Meticulous attention to component positioning to prevent impingement 6, 2

Postoperative Management

• Early mobilization with physical therapy starting postoperative day 0-1
• Multimodal pain management including paracetamol, NSAIDs/COX-2 inhibitors
• Special attention to hip abductor strengthening
• Modified weight-bearing protocol may be needed with bone grafting or osteotomies 6

Potential Complications

• Higher risk of:
  • Nerve injury (particularly sciatic) due to lengthening
  • Dislocation due to abductor insufficiency
  • Aseptic loosening
  • Periprosthetic fracture
  • Leg length discrepancy 6, 2

Outcomes

• High rate of pain relief and functional improvement
• Long-term durability of cemented THR is inferior compared to standard primary THR
• Uncemented implants show promising results, though long-term data is still developing
• Revision rates are higher than in primary osteoarthritis cases 1, 4

THR in dysplastic hips presents significant technical challenges but offers excellent pain relief and functional improvement when performed with careful attention to the unique anatomical considerations of these patients.