What is the step-by-step procedure for bipolar hemiarthroplasty in a patient with a fracture of the femur?

Step-by-Step Procedure for Bipolar Hemiarthroplasty in Femoral Neck Fracture

Bipolar hemiarthroplasty is the recommended surgical procedure for unstable (displaced) femoral neck fractures, particularly in elderly patients, as it provides better outcomes than internal fixation. 1 The procedure involves replacing the femoral head with a prosthesis that has two articulating surfaces - one between the prosthesis and the acetabulum, and another within the prosthesis itself.

Pre-operative Considerations

1. Timing of Surgery:

   • Surgery should be performed within 24-48 hours of admission for better outcomes 1
   • Avoid unnecessary delays as they increase morbidity and mortality

2. Anesthesia Options:

   • Either spinal or general anesthesia is appropriate (strong recommendation) 1
   • Spinal anesthesia may reduce postoperative confusion 1

3. Pre-operative Medication:

   • Administer tranexamic acid to reduce blood loss and need for transfusion 1
   • Implement multimodal analgesia including preoperative nerve block 1

Surgical Procedure

1. Patient Positioning and Preparation

• Position patient in lateral decubitus position (for posterolateral approach) or supine (for anterolateral approach)
• Prepare and drape the hip region using standard aseptic technique
• Administer prophylactic antibiotics prior to incision

2. Surgical Approach

• An anterolateral or posterolateral approach can be used (no preferred approach per guidelines) 1
• Make skin incision and dissect through subcutaneous tissue
• Identify and protect the tensor fascia lata (anterolateral approach) or gluteus maximus (posterolateral approach)
• Identify and protect the abductor muscles
• Incise the hip capsule and expose the femoral neck fracture

3. Femoral Head Removal

• Identify the fracture site
• Remove the femoral head using a corkscrew or bone hook
• Inspect the acetabulum for any damage or pathology
• Measure the size of the femoral head for appropriate prosthesis sizing

4. Femoral Canal Preparation

• Identify the femoral canal
• Ream the femoral canal progressively to appropriate size
• Trial with broaches of increasing size until proper fit and stability are achieved
• Ensure proper anteversion (10-15 degrees) of the femoral component

5. Prosthesis Implantation

• Cemented femoral stem is strongly recommended over uncemented stems 1

  • Prepare cement (polymethylmethacrylate)
  • Insert cement restrictor in the femoral canal
  • Inject cement in retrograde fashion
  • Insert the femoral stem with proper anteversion
  • Maintain position until cement hardens

• For the bipolar component:

  • Select appropriate size bipolar head
  • Assemble the bipolar prosthesis
  • Attach the bipolar head to the femoral stem
  • Reduce the hip joint

6. Stability Testing

• Test hip stability through range of motion:
  • Flexion, extension, abduction, adduction
  • Internal and external rotation
• Ensure no impingement or dislocation occurs

7. Closure

• Irrigate the wound thoroughly
• Repair the capsule if possible
• Close the fascia, subcutaneous tissue, and skin in layers
• Apply sterile dressing

Post-operative Management

1. Immediate Post-operative Care:

   • Continue multimodal analgesia 1
   • Monitor vital signs and neurovascular status
   • Initiate deep vein thrombosis prophylaxis

2. Mobilization:

   • Begin weight-bearing as tolerated with assistive devices
   • Start physical therapy on post-operative day 1

3. Follow-up:

   • Regular follow-up with radiographic evaluation
   • Assess for complications: dislocation, infection, loosening
   • Evaluate functional outcomes using standardized measures

Clinical Considerations and Pitfalls

• Bipolar vs. Unipolar Hemiarthroplasty: Guidelines indicate that both unipolar and bipolar hemiarthroplasty can be equally beneficial for unstable femoral neck fractures 1, though bipolar components may reduce acetabular erosion 2

• Cementation: Always use cemented femoral stems as they improve hip function and are associated with lower residual pain postoperatively 1

• Complications to Monitor:

  • Dislocation (1.1% of cases) 3
  • Infection (3.1% of cases) 3
  • Hematoma formation (1.7% of cases) 3
  • Acetabular erosion (more common with unipolar prostheses) 2

• Conversion Rate: The conversion rate from bipolar hemiarthroplasty to total hip arthroplasty is very low (0.6% for groin pain), making it a durable solution 4

• Interdisciplinary Care: Implement interdisciplinary care programs to decrease complications and improve outcomes 1

By following this step-by-step procedure and adhering to current guidelines, bipolar hemiarthroplasty provides excellent outcomes for patients with femoral neck fractures, particularly in elderly patients.