Jæger, P.*
Rigshospitalet - Copenhagen University Hospital, Department of Anaesthesia, Copenhagen, Denmark
ESRA Academy. Jæger P. Sep 16, 2017; 195882
Dr. Pia Jæger
Dr. Pia Jæger

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Learning Objectives
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After viewing this presentation the participant will be able to:

- Recognize the importance of patient mobilization post-TKA surgery when comparing efficacy of different types of blocks
- Evaluate studies comparing opioid consumption and pain scores with different blocks, including the adductor canal block

Along with the development of enhanced recovery after surgery protocols, there has been an increased focus on early rehabilitation and a need to avoid impaired mobilization after surgery. To meet the challenge of providing adequate pain relief without compromising muscle strength the motor-sparing adductor canal block (ACB) was introduced as an alternative to the femoral nerve block (FNB). The only motor fibers traversing the adductor canal are those of the nerve to the vastus medialis, making the ACB a predominately, sensory nerve block. 

The ACB has been shown to provide efficient postoperative pain relief in patients undergoing total knee arthroplasty (TKA). Pain and opioid consumption is reduced with reference to placebo,1  and the pain-relieving effect seems to be similar to that of the mainstay treatment – the FNB.2-3

Besides providing efficient analgesia, the ACB furthermore preserves muscle strength both in healthy volunteers4-5 and in patients.2, 6-7 Most importantly, the ACBs affection on quadriceps strength is less than 10%,4-5 and thus less than the side-to-side difference that is normal in healthy individuals. In the surgical setting, the ACB significantly preserves quadriceps strength compared with the FNB. The ACB has even been shown to almost double postoperative strength compared with placebo, probably through pain-inhibiting reflexes.8-9 Preserved muscle strength translated into improved mobility in healthy volunteers,4 but even though a well-functioning quadriceps muscle is essential for walking, the results of the clinical studies are conflicting.4 Despite a seemingly potential of the ACB to improve mobility in the clinical setting, other factors as confounding motor block from additional regional anesthesia techniques, provision of walking aids, and dizziness hindering mobilization may limit how this translates into clinical practice.

The ACB is not yet a fully developed technique and the name of the block has been eagerly discussed. Naturally, the name of the block does not affect the results of the published reports: showing effective and motor sparing analgesia following subsartorial injections of local anesthetics at the midthigh level. More importantly, the efficacy of an ACB may be related to volume. Although the optimal volume for an ACB remains to be established in a clinical setting, previous studies suggest that injection of 20–30 ml will ensure spread of local anesthetic throughout the adductor canal10 and affection of the nerve to the vastus medialis,11 without a negative impact on quadriceps strength.12

A recently published network meta-analysis recommended a combination of femoral and sciatic nerve blocks for pain treatment after TKA.13 Although interesting, the network meta-analysis has several limitations. First, the analysis is based on studies published between 1987–2016, failing to adjust for advancements in study methodology and the inclusion of supplemental analgesic regimens developed over time. For example, the more dated studies were not as frequently blinded and did not often provide supplemental analgesia. This may explain why the network meta-analysis found the FNB to provide the most efficient pain relief, while the more recent and direct comparisons between ACB and FNB do not find any difference between the two blocks in terms of analgesia. Furthermore, the network analysis did not include analyses of muscle strength and ambulation, important aspects of modern pain regimens for TKA.

The best block, or the best combination of blocks may not yet hae been established, but at present, the ACB is a relevant alternative, and the only block providing efficient analgesia without muscle impairment.

1. Jiang X, Wang QQ, Wu CA, Tian W. Analgesic Efficacy of Adductor Canal Block in Total Knee Arthroplasty: A Meta-analysis and Systematic Review. Orthop Surg 2016; 8: 294-300

2. Jaeger P, Zaric D, Fomsgaard JS, et al. Adductor canal block versus femoral nerve block for analgesia after total knee arthroplasty: a randomized, double-blind study. Reg Anesth Pain Med 2013; 38: 526-32

3. Kim DH, Lin Y, Goytizolo EA, et al. Adductor canal block versus femoral nerve block for total knee arthroplasty: a prospective, randomized, controlled trial. Anesthesiology 2014; 120: 540-50

4. Li D, Ma GG. Analgesic efficacy and quadriceps strength of adductor canal block versus femoral nerve block following total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 2016; 24: 2614-9

5. Wang D, Yang Y, Li Q, et al. Adductor canal block versus femoral nerve block for total knee arthroplasty: a meta-analysis of randomized controlled trials. Sci Rep 2017; 7: 40721

6. Jaeger P, Nielsen ZJ, Henningsen MH, Hilsted KL, Mathiesen O, Dahl JB. Adductor canal block versus femoral nerve block and quadriceps strength: a randomized, double-blind, placebo- controlled, crossover study in healthy volunteers. Anesthesiology 2013; 118: 409-15

7. Kwofie MK, Shastri UD, Gadsden JC, et al. 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: 321-5

8. Grevstad U, Mathiesen O, Lind T, Dahl JB. Effect of adductor canal block on pain in patients with severe pain after total knee arthroplasty: a randomized study with individual patient analysis. Br J Anaesth 2014; 112: 912-9

9. Sorensen JK, Jaeger P, Dahl JB, Gottschau B, Stephensen SL, Grevstad U. The Isolated Effect of Adductor Canal Block on Quadriceps Femoris Muscle Strength After Total Knee Arthroplasty: A Triple-Blinded, Randomized, Placebo-Controlled Trial with Individual Patient Analysis. Anesth Analg 2016; 122: 553-8

10. Jaeger P, Jenstrup MT, Lund J, et al. Optimal volume of local anaesthetic for adductor canal block: using the continual reassessment method to estimate ED95. Br J Anaesth 2015; 115: 920-6

11. Grevstad U, Jaeger P, Sorensen JK, et al. The Effect of Local Anesthetic Volume Within the Adductor Canal on Quadriceps Femoris Function Evaluated by Electromyography: A Randomized, Observer- and Subject-Blinded, Placebo-Controlled Study in Volunteers. Anesth Analg 2016; 123: 493-500

12. Jaeger P, Koscielniak-Nielsen ZJ, Hilsted KL, Fabritius ML, Dahl JB. Adductor Canal Block With 10 mL Versus 30 mL Local Anesthetics and Quadriceps Strength: A Paired, Blinded, Randomized Study in Healthy Volunteers. Reg Anesth Pain Med 2015; 40: 553-8

13. Terkawi AS, Mavridis D, Sessler DI, et al. Pain Management Modalities after Total Knee Arthroplasty: A Network Meta-analysis of 170 Randomized Controlled Trials. Anesthesiology 2017; 126: 923-937

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