A 55-year-old patient undergoes total knee replacement with spinal anaesthesia plus adductor canal block (ACB). Compared to femoral nerve block (FNB) for the same procedure, the primary advantage of ACB is:

• A Superior pain control for posterior knee pain
• B Avoidance of local anaesthetic systemic toxicity
• C Preservation of quadriceps strength facilitating early mobilisation ✓
• D Longer duration of action due to deeper tissue deposition

Explanation

The adductor canal contains the saphenous nerve (sensory to medial knee), nerve to vastus medialis, and medial femoral cutaneous nerve — it does NOT contain the main femoral motor branches to the rectus femoris and vastus lateralis. A femoral nerve block provides excellent analgesia but blocks the quadriceps motor branches, causing quadriceps weakness and high fall risk. ACB provides comparable analgesia for anterior knee pain while preserving quadriceps strength (>80% of FNB analgesia in trials), enabling earlier physiotherapy and mobilisation — a critical advantage in enhanced recovery after surgery (ERAS) protocols. ACB does not provide posterior knee coverage; the sciatic/popliteal nerve block is needed for that.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.