What are the mortality differences between unilateral and bilateral total knee arthroplasty (TKA) procedures?

Mortality Differences Between Unilateral and Bilateral Total Knee Arthroplasty

Bilateral total knee arthroplasty (BTKA) is associated with significantly higher mortality risk compared to unilateral TKA, particularly when performed simultaneously under a single anesthetic setting.

Risk Comparison Between Unilateral and Bilateral TKA

Mortality Risk

• Simultaneous bilateral TKA is associated with increased risk of serious complications that can lead to higher mortality compared to unilateral procedures 1
• The most recent evidence (2023) demonstrates that simultaneous bilateral TKA has significantly increased risk of:
  • Pulmonary embolism (adjusted odds ratio 2.13)
  • Stroke (adjusted odds ratio 2.21)
  • Acute blood loss anemia (adjusted odds ratio 2.06)
  • Blood transfusion requirements (adjusted odds ratio 7.84)
  • 90-day hospital readmission (adjusted odds ratio 1.35) 1

Specific Mortality Risk Factors

• Advanced age is a major risk factor for adverse outcomes in bilateral TKA:
  • Age 65-74: 1.88 times higher risk
  • Age >75: 2.66 times higher risk compared to patients aged 45-65 2
• Male gender increases risk (odds ratio 1.54) 2
• Cardiovascular comorbidities dramatically increase mortality risk:
  • Congestive heart failure (odds ratio 5.55)
  • Pulmonary hypertension (odds ratio 4.10) 2

Staging Considerations

Simultaneous vs. Staged Bilateral TKA

• Current evidence indicates that complication risks are minimized when bilateral TKA procedures are staged at least 3 months apart 3, 4
• Limited evidence supports simultaneous bilateral TKA only in:
  • Patients aged <70 years
  • American Society of Anesthesiologists (ASA) status 1-2 (healthy patients)
  • Patients without significant comorbidities 5

Risk Mitigation Strategies

• When simultaneous bilateral TKA is pursued, the following measures should be implemented:
  • Regional anesthesia and analgesia
  • Invasive hemodynamic monitoring
  • Postoperative observation in intensive care setting
  • Aggressive management of hemodynamic changes 6
  • Antifibrinolytic therapy to reduce transfusion requirements 4

Patient Selection Algorithm

1. High-Risk Patients (should avoid simultaneous bilateral TKA):

   • Age >70 years
   • ASA status 3 or higher
   • Presence of cardiovascular disease, especially CHF or pulmonary hypertension
   • Multiple comorbidities

2. Moderate-Risk Patients (consider staged bilateral TKA with 3+ months between procedures):

   • Age 65-70 years
   • ASA status 2
   • Controlled comorbidities
   • Male gender

3. Lower-Risk Patients (may consider simultaneous bilateral TKA):

   • Age <65 years
   • ASA status 1-2
   • No significant comorbidities
   • Female gender
   • Good functional capacity

Clinical Implications

The significantly higher risk of serious complications with simultaneous bilateral TKA warrants careful patient selection and thorough preoperative optimization. For most patients requiring bilateral knee replacement, the staged approach (with procedures separated by at least 3 months) offers the safest option with mortality rates closer to those of unilateral procedures 3, 4.

While simultaneous bilateral TKA may be economically advantageous due to shorter total operative time and hospital stay 3, this benefit must be carefully weighed against the substantially increased risk of serious complications and mortality, particularly in older patients and those with comorbidities.