Is knee replacement surgery safe in patients with an aortic (abdominal aorta) aneurysm?

Safety of Knee Replacement Surgery with Abdominal Aortic Aneurysm

Knee replacement surgery is generally safe in patients with stable abdominal aortic aneurysms (AAA) that are under surveillance, but requires careful preoperative evaluation and risk assessment by a multidisciplinary team.

Risk Assessment for Patients with AAA Requiring Knee Surgery

AAA Size and Stability Considerations

• For small AAAs (30-55 mm):

  • Generally safe to proceed with knee replacement if the aneurysm is stable 1
  • Regular surveillance of the AAA should be maintained according to guidelines:
    • 30-39 mm: Every 3 years
    • 40-44 mm: Every 2 years
    • 45-49 mm: Every year (men)
    • 40-45 mm: Every year (women) 1

• For larger AAAs (≥55 mm in men, ≥50 mm in women):

  • AAA repair is recommended before elective knee surgery 1, 2
  • Elective knee surgery should be postponed until after AAA repair and appropriate recovery period

Preoperative Evaluation

• Comprehensive cardiovascular assessment is essential as patients with AAA often have concurrent cardiovascular disease
• Imaging to confirm current AAA size and stability before proceeding with knee surgery
• Consider the growth rate of AAA - surgery may be contraindicated if growth rate is ≥0.3 cm/year in 2 consecutive years or ≥0.5 cm in 1 year 1

Decision-Making Algorithm

1. Measure and assess AAA size:

   • If <55 mm in men or <50 mm in women and stable → Proceed with knee surgery with appropriate perioperative monitoring
   • If ≥55 mm in men or ≥50 mm in women → Address AAA first, then consider knee surgery

2. Evaluate AAA growth rate:

   • If growth rate is ≥0.3 cm/year or ≥0.5 cm in 1 year → Address AAA first
   • If growth rate is stable → Proceed with knee surgery

3. Consider surgical urgency:

   • Emergency knee surgery with AAA present carries significantly higher risk (2-5 times higher complications) 1
   • For elective knee surgery, timing can be optimized based on AAA status

Important Considerations and Caveats

• Age impact: Each year of delay in addressing either condition increases operative mortality by approximately 5% due to advancing age 3

• Perioperative management:

  • Careful blood pressure control is crucial to prevent stress on the aortic wall
  • Avoid extreme hemodynamic fluctuations during surgery
  • Consider invasive arterial monitoring during knee surgery for patients with AAA
  • Maintain adequate postoperative pain control to prevent hypertensive episodes

• Long-term outcomes: Patients with AAA who undergo successful surgery can expect good long-term survival and quality of life, though slightly reduced compared to age-matched populations 4

• Facility selection: Treatment at specialized centers with both vascular and orthopedic expertise is recommended to ensure optimal outcomes 2

Pitfalls to Avoid

• Underestimating cardiac risk: Patients with AAA often have concurrent coronary artery disease requiring thorough preoperative cardiac evaluation
• Neglecting AAA surveillance: Continuing appropriate AAA monitoring during the perioperative period is essential
• Inappropriate surgical timing: Rushing knee surgery in patients with large or rapidly growing AAAs significantly increases mortality risk
• Inadequate blood pressure control: Poor perioperative hemodynamic management can increase risk of AAA-related complications

By following this approach, knee replacement surgery can be performed safely in patients with appropriately managed abdominal aortic aneurysms, with outcomes similar to those without AAA.