Adductor Canal Block for Post-Operative Analgesia After Patellar Tension Band Wiring
An adductor canal block (ACB) alone is insufficient for post-operative analgesia after tension band wiring of the patella and must be combined with scheduled multimodal systemic analgesia including paracetamol, NSAIDs, and opioid rescue medications.
Why ACB Alone is Inadequate
The adductor canal block primarily targets the saphenous nerve and portions of the obturator nerve, providing analgesia to the medial and anterior aspects of the knee 1. However, patellar fracture surgery involves significant anterior knee pain from periosteal disruption, hardware placement, and soft tissue trauma that extends beyond the distribution of nerves blocked by ACB alone 2.
- Limited nerve coverage: ACB does not adequately cover the entire anterior knee compartment where patellar fracture pain originates 1
- Peripheral nerve blocks for fractures are effective but require multimodal support: While peripheral nerve blocks are medically necessary for fracture pain management, they work best as part of a comprehensive analgesic strategy 3
Recommended Multimodal Analgesic Protocol
Baseline Scheduled Medications (Non-Negotiable)
- Paracetamol (acetaminophen): Administer on a scheduled basis, not as-needed, throughout the postoperative period 2
- NSAIDs or COX-2 selective inhibitors: Add conventional NSAIDs or COX-2 inhibitors unless contraindicated (renal impairment, bleeding risk, cardiovascular disease) 2
- Single intraoperative dexamethasone: Give 8-10 mg IV intraoperatively for analgesic and anti-emetic effects 2
Regional Anesthesia Component
- Continuous ACB preferred over single-shot: For extended analgesia, use a continuous adductor canal catheter with 0.2% ropivacaine infusion (8 mL/h basal rate) rather than single-shot injection 2, 4
- Catheter placement location matters: Position the catheter at the midpoint between the anterior superior iliac spine and superior border of the patella (proximal location) for superior analgesia compared to distal placement near the adductor hiatus 5
Rescue Analgesia Protocol
- Strong opioids for high-intensity pain: Use IV morphine, fentanyl, or hydromorphone titrated to effect for breakthrough pain 2
- Weak opioids for moderate pain: Tramadol can be used for moderate-intensity breakthrough pain 2
- IV ketorolac as adjunct: Consider ketorolac 0.5-1 mg/kg (max 30 mg) for immediate rescue, which significantly reduces morphine requirements 2
Evidence Supporting Multimodal Approach
The continuous ACB provides superior analgesia compared to IV opioid-based PCA with single-shot ACB, with significantly lower pain scores at 30 minutes, 4 hours, 24 hours, and 48 hours postoperatively 4. However, even in total knee arthroplasty (a less traumatic procedure than open patellar fracture fixation), ACB alone required supplementation with systemic analgesics 4, 6.
Critical distinction: Patellar tension band wiring involves more anterior soft tissue trauma than knee arthroplasty, making isolated ACB even less adequate 7.
Common Pitfalls to Avoid
- Do not rely on ACB as sole analgesic: This will result in inadequate pain control and excessive opioid rescue requirements 4
- Do not use single-shot ACB: Continuous infusion provides significantly better analgesia for orthopedic procedures 2, 4
- Do not skip scheduled non-opioid analgesics: Paracetamol and NSAIDs must be given regularly, not as-needed, to prevent rebound pain when the block wears off 2
- Avoid epidural analgesia: This carries increased risk of serious adverse events without superior benefits compared to peripheral nerve blocks 2
Practical Implementation
Start the continuous ACB infusion before skin incision and maintain it for 48 hours postoperatively 4. Layer this with scheduled paracetamol and NSAIDs beginning in the recovery room 2. Keep strong opioids immediately available for breakthrough pain, as even optimal regional techniques require supplementation in the first 24-48 hours after patellar fracture surgery 2, 4.