When is bilateral total knee arthroplasty (TKA) preferred over unilateral total knee arthroplasty?

Bilateral vs. Unilateral Total Knee Arthroplasty: When to Choose Each Approach

Bilateral total knee arthroplasty (TKA) should only be performed simultaneously in patients younger than 70 years with American Society of Anesthesiologists (ASA) status 1-2, as these patients have no increased rate of complications compared to unilateral procedures.

Patient Selection for Simultaneous Bilateral TKA

Simultaneous bilateral TKA (performing both knees under a single anesthetic) should be limited to:

• Patients younger than 70 years of age 1
• ASA physical status classification 1-2 (healthy patients or with mild systemic disease) 1
• Patients without significant comorbidities
• Patients with bilateral symptomatic knee osteoarthritis affecting quality of life

Contraindications for Simultaneous Bilateral TKA

Staged bilateral TKA (performing each knee in separate surgical sessions) is preferred when patients have:

• Age ≥70 years
• ASA status ≥3
• Significant cardiovascular disease
• Pulmonary disease
• Poorly controlled diabetes mellitus (should be optimized before surgery) 1
• Nicotine dependence (cessation recommended before surgery) 1
• BMI ≥40 (higher complication risk, though not an absolute contraindication) 1

Benefits of Simultaneous Bilateral TKA

When appropriate patient selection criteria are met, simultaneous bilateral TKA offers several advantages:

• Single anesthetic exposure
• Shorter total hospital stay compared to two separate admissions 2
• Lower total cost of care 2
• Shorter total rehabilitation period
• Faster return to baseline function and work

Risks of Simultaneous Bilateral TKA

Despite careful patient selection, simultaneous bilateral TKA carries some increased risks:

• Higher overall complication rate compared to staged procedures 2
• Increased blood loss and transfusion requirements
• Greater physiological stress
• Potentially more challenging rehabilitation initially

Optimal Timing for Staged Bilateral TKA

When simultaneous bilateral TKA is not appropriate, the optimal staging interval is:

• At least 3 months between procedures 2
• This timing minimizes the cumulative risk of complications

Anesthetic Considerations

The choice of anesthesia impacts outcomes in TKA:

• Neuraxial anesthesia (spinal or epidural) is preferred over general anesthesia for TKA when possible 1
• Neuraxial anesthesia is associated with:
  • Decreased pulmonary complications
  • Decreased thromboembolic events
  • Lower mortality
  • Less blood loss

Postoperative Considerations

Regardless of unilateral or bilateral approach:

• Early mobilization on the day of surgery reduces hospital length of stay 1
• Supervised exercise programs during the first 2 months improve physical function 1
• Continuous passive motion devices are not recommended as they do not improve outcomes 1

Common Pitfalls to Avoid

1. Underestimating recovery challenges: Bilateral TKA requires more intensive rehabilitation support and home assistance
2. Inappropriate patient selection: Performing simultaneous bilateral TKA in older patients (≥70) or those with significant comorbidities increases complication risk
3. Inadequate pain management: Bilateral procedures may require more aggressive multimodal pain control
4. Insufficient preoperative optimization: Medical conditions like diabetes should be optimized before surgery 1
5. Ignoring patient preferences: Some patients may prefer staged procedures despite meeting criteria for simultaneous surgery

In summary, while simultaneous bilateral TKA offers efficiency benefits, it should be reserved for carefully selected younger, healthier patients. For most patients with bilateral knee arthritis, especially those over 70 or with significant comorbidities, staged bilateral TKA with at least 3 months between procedures provides the safest approach with the lowest risk of complications.