What is the recommended anesthesia plan, including peripheral nerve block, for a patient undergoing tension band wiring of the patella, considering their overall health, medical history, and potential risks for complications?

Peripheral Nerve Block for Tension Band Wiring of Patella

Recommended Anesthesia Approach

Peripheral nerve blocks combined with general anesthesia should be the preferred technique for tension band wiring of the patella, providing superior postoperative analgesia while maintaining a secure airway during the procedure. 1

Block Selection and Technical Approach

Required Nerve Blocks

For complete surgical anesthesia and postoperative analgesia of the patella, a combination of blocks is necessary:

• Femoral nerve block for anterior thigh and knee coverage (including the patella) 2
• Sciatic nerve block (popliteal approach) for posterior knee coverage 2
• Obturator nerve block may be considered for complete analgesia, though less critical for isolated patellar surgery 2

Risk Classification

All three blocks fall into the low-risk category for hemorrhagic complications, as bleeding would be easily controllable and the areas are compressible 3. This makes them suitable even in patients with mild coagulation concerns, provided the benefit-risk ratio is favorable 3.

Technical Execution

• Ultrasound guidance is mandatory to reduce local anesthetic systemic toxicity, improve needle placement accuracy, and allow for reduced volumes of local anesthetic 2, 4
• Use in-plane needling along the visual axis for improved speed and accuracy 2, 4
• Calculate safe local anesthetic dose based on patient weight to prevent systemic toxicity 2, 4
• Position the ultrasound machine in front of the operator rather than perpendicular for improved accuracy 2, 4
• Apply standard aseptic technique similar to neuraxial procedures 2, 4

Advantages Over Alternative Approaches

Why Combine with General Anesthesia

• Reduces total opioid consumption and decreases respiratory depression compared to general anesthesia alone 1
• Provides extended postoperative analgesia (12-24 hours for single-injection blocks) beyond the surgical period 5
• Fewer physiological and hemodynamic side effects compared to neuraxial techniques—most peripheral blocks do not cause sympathectomy leading to hypotension 2
• Avoids complications associated with neuraxial anesthesia (spinal hematoma, urinary retention) 6

Why Not Neuraxial Alone

While neuraxial anesthesia (spinal/epidural) is effective for lower extremity surgery 3, peripheral nerve blocks offer:

• Reduced risk of urinary retention and hemodynamic instability 6
• No contraindication in patients on antiplatelet therapy (aspirin), whereas neuraxial techniques require more caution 3
• Selective analgesia without motor blockade of uninvolved areas 6

Special Considerations for Anticoagulated Patients

Antiplatelet Therapy

• Aspirin is NOT a contraindication to these low-risk peripheral blocks if the benefit-risk ratio is favorable 3
• P2Y12 inhibitors (clopidogrel, ticagrelor, prasugrel) require careful assessment; low-risk blocks may be performed if justified, but ideally should be discontinued 5-7 days prior 3

Anticoagulant Therapy

• Low-risk peripheral blocks may be performed under dabigatran if the benefit-risk ratio is favorable 3
• For patients on therapeutic anticoagulation, ensure ultrasound guidance by an experienced operator 3
• If dabigatran concentration is >30 ng/mL and blocks are essential, consider idarucizumab administration 3

Critical Safety Measures

Immediate Precautions

• Have resuscitation equipment immediately available at the bedside 2, 1
• Monitor blood pressure and electrocardiogram continuously, especially in patients with cardiovascular risk 2, 4, 1
• Thoroughly test for block success before proceeding with surgery to avoid inadequate anesthesia 2, 4, 1

Positioning Considerations

• Position the patient with the leg slightly abducted for optimal access 2, 4
• Avoid compression near the fibular head during positioning to prevent peroneal neuropathy 4
• Use proper padding and positioning checks to prevent positioning-related nerve injury 1

Common Pitfalls and How to Avoid Them

Performing Blocks Under General Anesthesia

It is acceptable to perform peripheral nerve blocks after induction of general anesthesia in adults, contrary to older teaching 7. There is no scientific evidence that performing blocks under general anesthesia increases the risk of nerve injury compared to awake patients 7. This approach is particularly useful for anxious patients or when patient cooperation is limited 7.

Inadequate Block Assessment

The most common error is failing to test block success before surgical incision 2, 4, 1. Always verify sensory blockade in all relevant dermatomes before proceeding.

Local Anesthetic Systemic Toxicity

• Calculate maximum safe dose based on patient weight before beginning 2, 4
• Use ultrasound to minimize required volumes 2
• Aspirate frequently during injection to avoid intravascular injection 5

Duration Limitations

Single-injection blocks provide only 12-24 hours of analgesia 5. For prolonged pain control, consider:

• Continuous peripheral nerve block catheters for procedures with expected severe postoperative pain >24 hours 5, 8
• However, for tension band wiring of the patella, single-injection blocks are typically sufficient 9

Postoperative Management

• Peripheral nerve blocks are highly effective for postoperative analgesia, with 96.3% of patients achieving adequate pain control 8
• Minor incidents (hypoesthesia, numbness) occur in approximately 3-5% of cases but typically resolve without intervention 8
• Major neurologic complications are rare (0.21%) and usually resolve within days to weeks 8
• Multimodal analgesia with scheduled acetaminophen and NSAIDs (if not contraindicated) should supplement the block 3