Why all this talk about an adductor canal block (ACB)?
For years, femoral nerve blocks (FNB) have been the gold standard for pain control in more invasive knee/lower leg surgeries (total knees, ACLs, etc.). More recently, adductor canal blocks have been gaining in popularity over femoral nerve blocks because there seems to be less motor blockade from ACB than FNB. This is important because it decreases fall risk and allows earlier patient ambulation while also providing adequate analgesia.
Anesthesiology Mar 2014. Kim et al. Adductor Canal Block versus Femoral Nerve Block for Total Knee Arthroplasty: A Prospective, Randomized, Controlled Trial.
From the ASA 2017:
Virtual Anatomy lab for regional:
Femoral nb: fem art, Top of iliacus muscle, within fasc iliaca. Flat nerve. Want local anesthesia (LA) spread going under femoral artery (FA). Does hip joint capsule > Adductor CB (hip fractures, not THA). Catheters to POD3. Fascia iliaca more cranial than inguinal crease to get hip jt nerves. Do inplane to avoid bowel.
Adductor Canal block: nerve sits on lateral side of FA. Want FA when dives under Sartorius muscle. Aim for bottom of FA to get under membrane. Block the Nerve to Vastus medialis nerve also (not effect motor). Nerve bt vastus med and sartorius. Looks like it’s in the membrane bt muscles. Want proximimal sartorius (pain and strength better)
Comparison of two different volumes of 0.5%, ropivacaine used in ultrasound-guided adductor canal block after knee arthroplasty: A randomized, blinded, controlled noninferiority trial. J Anaesthesiol Clin Pharmacol. 2022 Jan-Mar; 38(1): 84–90.
-mepivacaine 1.5% (3.5 ml, 52.5 mg), hyperbaric bupivacaine 0.75% (1.5 ml, 11.25 mg) or isobaric bupivacaine 0.5% (2.5 ml, 12.5 mg). Early ambulation predicts successful same-day discharge,6 which is consistent with our results. The earlier return of motor function likely allowed patients who received mepivacaine to meet physical therapy milestones sooner, contributing to a faster discharge.
No additives (fentanyl, epinephrine) were added to any spinal dose.
aPatients under 4′10″ were excluded from the study (none were encountered).
All patients were compliant with a standardized multimodal perioperative pain and nausea protocol. Patients were given sustained-release morphine 15 mg, meloxicam 15 mg, and gabapentin 300 mg. Dexamethasone 8 mg was given intravenously after anesthetic induction for nausea and pain control. Patients were asked to urinate prior to transfer to the operating room and Foley catheters were not utilized. Intraoperatively, a periarticular injection of 120 mL of diluted ropivacaine 300 mg with epinephrine 1 mg and ketorolac 30 mg was used for local administration. Intraoperative surgeon-delivered adductor canal blockade with 20 mL of the cocktail was added as previously described . The postoperative pain regimen consisted of sustained-release morphine 15 mg every 8 hours for 24 hours, meloxicam 15 mg daily, gabapentin 300 mg twice daily, scheduled oral acetaminophen 975 mg every 8 hours, scheduled tramadol 50 mg every 6 hours, and oxycodone 5-10 mg as needed with morphine 1-2 mg intravenously for breakthrough pain. A repeat dose of dexamethasone 8 mg intravenously was also given the morning after surgery. All patients were mobilized immediately after surgery when physical therapy was available and neurologic function was sufficient.