What is total hip replacement?

Total Hip Replacement: A Comprehensive Guide

Total hip replacement is a highly effective surgical procedure for patients with end-stage hip osteoarthritis that provides superior pain relief and functional improvement compared to non-surgical treatments. 1

Definition and Indications

Total hip replacement (THR) involves the complete replacement of a damaged hip joint with an artificial prosthesis. The primary indications include:

• Refractory pain or disability with radiographic evidence of structural damage 2
• End-stage osteoarthritis (most common indication) 3
• Severe hip pain that has failed conservative management 1

Surgical Procedure

The procedure involves:

1. Components:

   • Femoral component: Replaces the femoral head and neck
   • Acetabular component: Replaces the socket portion of the hip joint
   • Bearing surfaces: Interface between components

2. Fixation Methods:

   • Cemented: Uses bone cement (polymethylmethacrylate) to secure components
   • Uncemented: Relies on bone ingrowth into porous surfaces
   • Hybrid: Typically cemented femoral component with uncemented acetabular component

3. Bearing Surface Options:

   • Metal-on-polyethylene
   • Ceramic-on-polyethylene
   • Ceramic-on-ceramic
   • Metal-on-metal (less common now due to concerns)

Evidence for Effectiveness

The evidence supporting THR is strong, particularly when compared to non-surgical alternatives:

• A 2024 randomized controlled trial demonstrated that THR resulted in significantly greater improvement in pain and function compared to resistance training in patients with severe hip osteoarthritis (15.9 vs 4.5 point improvement on the Oxford Hip Score) 1

• Despite the widespread use of THR, there have been surprisingly few randomized controlled trials comparing it to non-operative care 2

• Prospective cohort studies show good pain relief and functional improvement with surgery 2

Clinical Outcomes

THR provides excellent outcomes for most patients:

• Pain Relief: Significant reduction in hip pain is typically achieved
• Functional Improvement: Improved mobility and quality of life
• Durability: Modern implants have excellent long-term survival rates
• Patient Satisfaction: High rates of satisfaction reported

Perioperative Management

Anesthesia Options

Both spinal and general anesthesia are recommended options 2, with some evidence suggesting regional anesthesia may reduce postoperative confusion 2.

Pain Management

The PROSPECT guidelines recommend 2:

1. Basic Analgesic Regimen:

   • Paracetamol combined with NSAIDs/COX-2 inhibitors started pre/intra-operatively and continued postoperatively
   • Intravenous dexamethasone 8-10mg intraoperatively for analgesic and anti-emetic effects

2. Regional Techniques:

   • Fascia iliaca block or local infiltration analgesia
   • Intrathecal morphine 0.1mg may be considered if spinal anesthesia is used (though risks must be weighed)

3. Rescue Medication:

   • Opioids reserved for rescue analgesia

Complications and Risks

Potential complications include:

• Infection (both early and late)
• Dislocation
• Periprosthetic fracture
• Heterotopic ossification
• Implant loosening or failure
• Leg length discrepancy
• Venous thromboembolism

Special Considerations

Age Factors

• THR is appropriate regardless of age when indicated by pain and disability 2
• Younger patients generally receive uncemented prostheses to facilitate potential future revisions 2

Component Selection

• Cemented components with polyethylene-on-ceramic articulation may offer cost-effectiveness advantages 4
• Larger femoral head sizes may provide benefits in stability 4

Painful THR

When evaluating a painful THR, consider 5:

• Temporal onset and character of pain
• Physical examination to reproduce symptoms
• Selective laboratory and radiographic evaluation

Future Directions

Areas of ongoing development include:

• Advanced bearing surfaces with improved wear characteristics
• Surface engineering modifications to enhance implant integration
• Modular and custom designs for complex cases 6
• Improved regulatory frameworks for implant safety 3

Pitfalls to Avoid

• Underestimating Rehabilitation Needs: Proper rehabilitation is essential for optimal outcomes
• Ignoring Patient-Specific Factors: Implant selection should consider activity level, bone quality, and anatomical factors
• Overlooking Potential Complications: Early recognition and management of complications improves outcomes
• Inadequate Pain Management: Poor pain control can delay recovery and rehabilitation

Despite the widespread use and success of THR, there remains a need for more high-quality randomized controlled trials with long-term follow-up to better guide clinical practice and implant selection 2, 4.