Mortality Risk in Bilateral vs. Unilateral Total Knee Arthroplasty
Bilateral total knee arthroplasty carries a significantly higher mortality risk compared to unilateral TKA, with studies showing a 2-3 times increased risk of major complications including death, even in the healthiest patients.
Comparative Mortality Risk Data
Recent evidence from high-quality studies demonstrates concerning mortality differences:
The most recent comprehensive matched analysis (2023) shows bilateral TKA is associated with:
- Significantly increased risk of pulmonary embolism (adjusted OR 2.13)
- Higher stroke risk (adjusted OR 2.21)
- Greater risk of 90-day readmission (adjusted OR 1.35) 1
A 2021 study using the National Surgical Quality Improvement Program database found that bilateral TKA had:
- Increased risk for all complications regardless of health status
- Greater than threefold increase in complications for even the healthiest patients
- Greater than twofold increase in major complications for healthier patients 2
Risk Factors for Adverse Outcomes
The risk of mortality and major complications in bilateral TKA is particularly elevated in patients with:
- Advanced age (especially >75 years)
- Odds ratios for age groups 65-74 and >75 years were 1.88 and 2.66 respectively compared to younger patients 3
- Male gender (OR: 1.54)
- Cardiovascular comorbidities:
- Congestive heart failure (OR: 5.55)
- Pulmonary hypertension (OR: 4.10) 3
Current Guidelines on Bilateral TKA
The American Academy of Orthopaedic Surgeons (AAOS) guidelines state:
- "Limited evidence supports simultaneous bilateral TKA in patients aged <70 years or American Society of Anesthesiologists status 1-2, because there is no increased rate of complications." 4
- This recommendation has a "Limited" strength rating, indicating relatively weak evidence
Special Considerations for Older Patients
For patients ≥75 years old:
- Sequential bilateral TKA under one anesthetic results in significantly more postoperative complications compared to unilateral TKA (46 vs. 27, p=0.003)
- Postoperative cardiovascular complications are significantly greater in bilateral TKA patients 5
Staged vs. Simultaneous Approach
When bilateral TKA is necessary, staging the procedures may be safer:
- No significant difference in complication rates or functional outcomes has been identified between different staging intervals (31-90 days, 91-180 days, 181-270 days, or 271-365 days) 6
- This suggests flexibility in timing the second procedure based on patient recovery
Conclusion
The mortality risk for bilateral TKA is substantially higher than unilateral TKA, with recent evidence suggesting a 2-3 fold increase in major complications including death. This increased risk persists even in otherwise healthy patients, contradicting previous assumptions that bilateral procedures could be safely performed in select low-risk populations.