Adductor Canal Block for Total Knee Arthroplasty
Adductor canal block (ACB) is strongly recommended as the preferred regional anesthetic technique for total knee arthroplasty (TKA) due to its superior preservation of quadriceps strength while providing effective pain control comparable to femoral nerve block. 1
Primary Anesthetic Approach
- General anesthesia combined with ACB is recommended as the primary technique for surgery and postoperative analgesia 2
- Alternatively, spinal anesthesia with local anesthetic plus spinal morphine can be effectively used 2
- ACB provides better preservation of quadriceps muscle strength and improved mobilization ability compared to femoral nerve block, leading to enhanced functional recovery without compromising pain control 1
Optimal ACB Technique
- For extended analgesia, continuous ACB catheter technique is preferred over single-shot injection 2, 3
- Continuous ACB provides superior analgesia and fewer side effects without significant motor deficit compared to IV-PCA with single-shot ACB 3
- Use 0.5% ropivacaine 20cc for initial block, followed by 0.2% ropivacaine continuous infusion for optimal results 3
- If using single-shot technique, 10mL of bupivacaine 0.25% with epinephrine 1:300,000 effectively reduces pain and opioid requirements 4
Multimodal Analgesic Protocol
- Scheduled administration of paracetamol (acetaminophen) should be included as a baseline analgesic 2, 5
- Add conventional NSAIDs or COX-2 selective inhibitors unless contraindicated 6, 5
- For high-intensity pain, supplement with intravenous strong opioids 6, 5
- For moderate to low-intensity pain, use weak opioids 6, 5
- Implement cooling and compression techniques to reduce local inflammation and pain 5
Bilateral ACB Considerations
- When performing bilateral ACB for bilateral TKA, reduce the total dose of local anesthetic to minimize risk of systemic toxicity 5
- Be particularly cautious with bilateral blocks in elderly patients or those with significant comorbidities 5
Duration of ACB
- While 48-hour continuous ACB shows marginal benefits in reducing the number of patients with moderate pain compared to 24-hour or single-shot ACB, all three approaches demonstrate similar opioid usage and functional outcomes 7
- The decision between continuous (24-48 hour) versus single-shot ACB should be based on institutional resources and patient factors 7
Comparative Efficacy
- ACB is superior to local infiltration analgesia (LIA) for TKA, with patients receiving ACB requiring less postoperative opioids and demonstrating better performance-based activities 8
- When comparing ACB to femoral nerve block, ACB provides similar pain control but better preserves quadriceps muscle strength and improves mobilization ability 1
Common Pitfalls and Caveats
- Avoid bilateral blocks with full doses in elderly patients or those with significant comorbidities due to increased risk of local anesthetic systemic toxicity 5
- Avoid epidural analgesia due to increased risk of serious adverse events without superior benefits compared to peripheral nerve blocks 5
- A combination of femoral and sciatic nerve blocks is not recommended over ACB due to limited and inconsistent evidence 5
- Ensure proper timing of ACB administration to provide adequate analgesic effect in the immediate postoperative period 6