At our conferences and workshops focused on regional anesthesiology and acute pain medicine, we present and discuss the latest and greatest advances in nerve block techniques for patients having surgery. As physicians and scientists, we are very familiar with the evidence supporting the use of nerve blocks for postoperative pain management. We know they are extremely effective in preventing and treating pain, decreasing the need for opioid medications, and even avoiding the common side effects of general anesthesia such as nausea and vomiting and confusion.
We believe in them.
We are passionate about them.
We want all patients to have access to them.
Within the meeting sessions and sometimes in the common spaces outside the lecture halls, regional anesthesiologists often vigorously debate various things like: the best sites and techniques for nerve block injections, needle and catheter equipment, ultrasound transducers and machines, and local anesthetic selection and use of adjuvants among other things.
For knee replacement patients in particular, we want to provide the best form of pain management while maximizing their postoperative function. Since 2011, dozens of research articles have studied the more distal adductor canal block for pain management in patients who undergo knee replacement as a replacement for the long-standing incumbent, the femoral nerve block. In reality, these sites of nerve block placement are mere centimeters apart and represent different sites of injection along the same set of nerves. Anesthesiologists and surgeons continue to debate this issue in person, in social media, and in publications.
It’s time for a reality check.
I had the opportunity to do a big data study with my friend and colleague, Dr. Stavros Memtsoudis. In this study of over 191,000 knee replacement patients who had surgery across over 400 hospitals in the United States, only 12.1% of all patients had a peripheral nerve block of any kind! Over 76% of patients had general anesthesia alone with no other regional analgesic technique.
A more recent study published this month in the Journal of Arthroplasty evaluated over 219,000 patients who underwent knee replacement, and only 27.3% of patients received a peripheral nerve block. The database used for this study was NACOR, operated by the Anesthesia Quality Institute and the American Society of Anesthesiologists. This was brought to my attention through a Tweet sent by My Knee Guide (@mykneeguide).
Where is the disconnect? The efficacy of peripheral nerve blocks for pain control in patients having knee arthroplasty was first published more than 25 years ago. It is easy to assume that such well-established evidence is being applied daily in clinical practice for the hundreds of thousands of patients who receive this surgery every year, but it’s not. Today, there is more awareness than ever about the risks of opioids, and nerve blocks offer proven opioid-sparing pain relief. Perhaps this is just another example of the gap separating the “ivory tower” of academics and real life.
Knee replacement is one of the most commonly performed operations in the United States with over 700,000 procedures performed annually (1). Besides providing anesthesia care in the operating room, anesthesiologists are dedicated to providing the best perioperative pain management in order to improve patients’ function and facilitate rehabilitation after surgery. In the past, pain management was limited to the use of opioids (narcotics). Opioids only attack pain in one way, and just adding more opioids does not usually lead to better pain control.
In 2012, the American Society of Anesthesiologists (ASA) published its guidelines for acute pain management in the perioperative setting (2). This document recommends “multimodal analgesia” which means that two or more classes of pain medications or therapies, working with different mechanisms of action, should be used in the treatment of acute pain.
While opioids are still important pain medications, they should be combined with other classes of medications known to help relieve postoperative pain unless contraindicated. These include:
Non-steroidal anti-inflammatory drugs (NSAIDs): Examples include ibuprofen, diclofenac, ketorolac, celecoxib. NSAIDs act on the prostaglandin system peripherally and work to decrease inflammation.
Acetaminophen: Acetaminophen acts on central prostaglandin synthesis and provides pain relief through multiple mechanisms.
Gabapentinoids: Examples include gabapentin and pregabalin. These medications are membrane stabilizers that essentially decrease nerve firing.
The ASA also strongly recommends the use of regional analgesic techniques as part of the multimodal analgesic protocol when indicated.
When compared to opioids alone, epidural analgesia produces lower pain scores and shorter time to achieve physical therapy goals (3). However, higher dose of local anesthetic (numbing medicine) may lead to muscle weakness that can limit activity (4). In addition, epidural analgesia can lead to common side effects (urinary retention, dizziness, itchiness) and is not selective for the operative leg, meaning that the non-operative leg may also become numb.
The saphenous nerve is the largest sensory branch of the femoral nerve and can be blocked within the adductor canal to provide postoperative pain relief and facilitate rehabilitation (8, 9). In healthy volunteers, quadriceps strength is better preserved when subjects receive an adductor canal block compared to a femoral nerve block (10).
In actual knee replacement patients, quadriceps function decreases regardless of nerve block type after surgery but to a lesser degree with adductor canal blocks (11). Recently there have been reports of quadriceps weakness resulting from adductor canal blocks and catheters that have affected clinical care (12, 13).
According to a large retrospective study of almost 200,000 cases, the incidence of inpatient falls for patients after TKA is 1.6%, and perioperative use of nerve blocks is not associated with increased risk (14). Patient factors that increase the risk of falls include higher age, male sex, sleep apnea, delirium, anemia requiring blood transfusion, and intraoperative use of general anesthesia (14). The bottom line is that all knee replacement patients are at increased risk for falling due to multiple risk factors, and any clinical pathway should include fall prevention strategies and an emphasis on patient safety.
Other Local Anesthetic Techniques
In addition to a femoral nerve or adductor canal block, a sciatic nerve block is sometimes offered to provide a “complete” block of the leg. There are studies for and against this practice. Arguably, the benefit of a sciatic nerve block does not last beyond the first postoperative day (15). Surgeon-administered local anesthetic around the knee joint (local infiltration analgesia) can be combined with nerve block techniques to provide additional postoperative pain relief for the first few hours after surgery (16, 17).
For more information about anesthetic options for knee replacement, please see my post on My Knee Guide.
American Society of Anesthesiologists Task Force on Acute Pain M: Practice guidelines for acute pain management in the perioperative setting: an updated report by the American Society of Anesthesiologists Task Force on Acute Pain Management. Anesthesiology 2012, 116(2):248-273.
Mahoney OM, Noble PC, Davidson J, Tullos HS: The effect of continuous epidural analgesia on postoperative pain, rehabilitation, and duration of hospitalization in total knee arthroplasty. Clin Orthop Relat Res 1990(260):30-37.
Raj PP, Knarr DC, Vigdorth E, Denson DD, Pither CE, Hartrick CT, Hopson CN, Edstrom HH: Comparison of continuous epidural infusion of a local anesthetic and administration of systemic narcotics in the management of pain after total knee replacement surgery. Anesth Analg 1987, 66(5):401-406.
Chan EY, Fransen M, Parker DA, Assam PN, Chua N: Femoral nerve blocks for acute postoperative pain after knee replacement surgery. Cochrane Database Syst Rev 2014, 5:CD009941.
Barrington MJ, Olive D, Low K, Scott DA, Brittain J, Choong P: Continuous femoral nerve blockade or epidural analgesia after total knee replacement: a prospective randomized controlled trial. Anesth Analg 2005, 101(6):1824-1829.
Jenstrup MT, Jaeger P, Lund J, Fomsgaard JS, Bache S, Mathiesen O, Larsen TK, Dahl JB: Effects of adductor-canal-blockade on pain and ambulation after total knee arthroplasty: a randomized study. Acta Anaesthesiol Scand 2012, 56(3):357-364.
Hanson NA, Allen CJ, Hostetter LS, Nagy R, Derby RE, Slee AE, Arslan A, Auyong DB: Continuous ultrasound-guided adductor canal block for total knee arthroplasty: a randomized, double-blind trial. Anesth Analg 2014, 118(6):1370-1377.
Kwofie MK, Shastri UD, Gadsden JC, Sinha SK, Abrams JH, Xu D, Salviz EA: The effects of ultrasound-guided adductor canal block versus femoral nerve block on quadriceps strength and fall risk: a blinded, randomized trial of volunteers. Reg Anesth Pain Med 2013, 38(4):321-325.
Jaeger P, Zaric D, Fomsgaard JS, Hilsted KL, Bjerregaard J, Gyrn J, Mathiesen O, Larsen TK, Dahl JB: Adductor canal block versus femoral nerve block for analgesia after total knee arthroplasty: a randomized, double-blind study. Reg Anesth Pain Med 2013, 38(6):526-532.
Chen J, Lesser JB, Hadzic A, Reiss W, Resta-Flarer F: Adductor canal block can result in motor block of the quadriceps muscle. Reg Anesth Pain Med 2014, 39(2):170-171.
Veal C, Auyong DB, Hanson NA, Allen CJ, Strodtbeck W: Delayed quadriceps weakness after continuous adductor canal block for total knee arthroplasty: a case report. Acta Anaesthesiol Scand 2014, 58(3):362-364.
Abdallah FW, Brull R: Is sciatic nerve block advantageous when combined with femoral nerve block for postoperative analgesia following total knee arthroplasty? A systematic review. Reg Anesth Pain Med 2011, 36(5):493-498.
Edward R. Mariano, MD, MAS, is a physician specializing in anesthesiology, professor, husband, and father working to improve pain control, outcomes, and the overall experience for patients having surgery