The first total knee arthroplasty (TKA) was performed in 1968, and current projections anticipate 1.5 million TKA procedures will be performed annually in the United States by 2050.^[1],[2] Given the prevalence of this procedure, there has been great interest through the years in optimizing the perioperative surgical and anesthetic care for these patients. The evolution of anesthesia and analgesia choices for TKA over four decades creates an interesting historical narrative.

The Primary Anesthetic: General Versus Neuraxial

General anesthesia or neuraxial anesthesia (NA)—including spinal, lumbar epidural, or combined spinal epidural (CSE) have been employed for decades for TKA. Evidence for NA has been conflicting: some systematic reviews demonstrated reduced complications with NA,^[3] whereas others showed only modest or no improvement in various patient-centered outcomes.^[4]

The holy grail of analgesia for TKA would provide opioid-sparing, prolonged analgesia without motor block and be simple and cost-effective with minimal side effects or complications.

More recently, database reviews and outcome studies with large numbers of patients have provided more robust evidence. Although those retrospective studies cannot account for anesthesia selection differences or institution-specific practices, one review combining total hip and knee arthroplasty (including 544,000 TKA) showed reduced risk of major complications and intensive care unit use when NA was employed.^[5] Two studies using data from the American College of Surgeons National Surgical Quality Improvement Program database showed reduced infection, transfusion, and overall complications with NA but no difference in mortality when compared with general anesthesia.^[6],[7]

Despite this, general anesthesia remains a common choice for TKA, with database studies showing that NA is used in only 25.5–45% of cases.^[8] Over time, epidural use has decreased in favor of spinal anesthesia for NA.^[4]

Early Analgesic Considerations: Epidural Analgesia

Historically, the desire to continue epidural analgesia (EA) into the postoperative period influenced the choice of lumbar epidural as the primary anesthetic. Because TKA is expected to produce moderate to severe pain, EA was continued for 2 to 3 days in the 1980s and 1990s.^[9] A number of important developments led to an evolution away from EA, including the release of enoxaparin for venous thromboembolism prophylaxis in the United States in 1993, followed by multiple reports of spinal hematomas and paraplegia after NA in patients receiving enoxaparin. This resulted in the Food and Drug Administration (FDA) issuing a public health advisory and black box warning about the combination in 1997.

At the same time, there was enthusiasm to mobilize patients soon after surgery and reduce hospital length of stay. Two European studies^[10],[11] showed continuous femoral nerve block (cFNB) and EA significantly reduced pain scores when compared with systemic opioids (intravenous patient-controlled anesthesia), but cFNB had a better side-effect profile (less nausea, pruritus, urinary retention) than EA. Both studies also were the earliest to show that cFNB and EA resulted in improved knee flexion and earlier patient mobilization, demonstrating improvement with regional blockade in surgical outcomes and not just analgesia. This led to a shift from EA and epidural as the primary anesthetic for TKA, although some institutions have continued to use CSE with EA for 1 to 2 days postoperatively.

Parenthetically, the earliest CSE (1979) used separate needle insertions, because needle-through-needle was thought to risk catheter damage or metal shaving contamination in the epidural space.^[12] In addition, it was feared that threading an epidural catheter following the dural puncture for the spinal might increase the risk of an inadvertent intrathecal catheter. The latter concern was later disproven with cadaver epiduroscopy,^[13] and matched needle-through-needle kits for CSE became commercially available in the late 1980s. Fenestrated Tuohy needles and a unique double-barreled CSE needle (Eldor) were also available but did not garner widespread interest.

Physicians had a brief interest in postoperative analgesia produced by spinal microcatheters (32G) that could be inserted through a 22–26G spinal needle, but technical difficulties and breakage occurred, and cases of cauda equina syndrome likely because of local anesthesia (LA) maldistribution led to a 1992 FDA safety alert and withdrawal of microcatheters from the United States market after a few years.^[14]

The History of Anterior Analgesic Options

Analgesic approaches for TKA have evolved as well over the past several decades. With EA, both the lumbar plexus and the sciatic nerve distributions are well anesthetized. However, controversy continues as to which nerve distributions need to be blocked for analgesia following TKA and how best to accomplish blockade without causing side effects or interfering with mobilization. The TKA incision is primarily in the femoral nerve distribution, although tibial bone cuts involve the sciatic and likely the obturator distribution medially.

The Rise and Fall of the Three-in-One Block

Alon Winnie developed the concept of the three-in-one block whereby all three nerves of the lumbar plexus (femoral, obturator, and lateral femoral cutaneous nerve) theoretically should be blocked by a single inguinal injection after eliciting a femoral nerve paresthesia.^[15] Although his fascial compartment blocks were revolutionary in promoting simpler, single-injection upper- and lower-extremity block techniques, most experts believe that the obturator nerve is unlikely to be blocked by a single perifemoral nerve injection. In addition, the cutaneous sensory distribution of the obturator nerve is variable or absent, and the success of an obturator nerve block (ONB) could not, therefore, be proven by sensory testing.^[16] In fact, controversy remains over the relative contribution of the obturator nerve to pain after TKA, with a few studies showing improved analgesia with the addition of ONB.^[17],[18] However, researchers in a more recent prospective study found that only 7% of TKA patients with cFNB experienced pain in the postanesthesia care unit, which was then successfully treated with ONB (Sanjay K. Sinha, personal communication).

Alternative inguinal approaches to the lumbar plexus included a more lateral needle entry or fascia iliaca block with tactile perception of needle passage through the fascia lata and then fascia iliaca.^[19] Catheter placement at this site in the inguinal crease was also presumed to produce a three-nerve block and was quicker and less costly than nerve stimulator–guided cFNB.^[20] At one point, inguinal approaches commonly advanced catheters proximal 10–15 cm but sometimes even 20 cm beyond the needle with the thought that they would follow the psoas muscle cephalad to the origin of the lumbar plexus. However, a key study showed radiographically that catheters generally curled and only 23% advanced cephalad toward the lumbar plexus^[21]; in addition, the catheters were at risk for knotting with high threading distances.

Although inguinal block approaches are unlikely to reliably produce ONB, direct blockade of the obturator nerve can be added to cFNB if desired, or a posterior lumbar plexus (PLP, or psoas) approach can be employed. Some institutions favored continuous psoas block over cFNB to ensure obturator coverage,^[22] but quadriceps as well as adductor weakness can occur. In addition, the 1997 concern for the potent and irreversible anticoagulant effect of enoxaparin
coupled with a few case reports of substantial retroperitoneal bleeding after PLP block and anticoagulation made PLP (like EA) less attractive. By ASRA’s third edition of the Regional Anesthesia in the Patient Receiving Antithrombotic or Thrombolytic Therapy guidelines in 2010, which expanded to include deep blocks, PLP began to fall out of favor relative to more distal approaches.^[23] Incidentally, although early continuous nerve block techniques often employed epidural catheters, equipment specific to continuous peripheral nerve block techniques became available in the late 1990s. This included an insulated, stimulating needle with injection port and diaphragm for inserting the catheter through the needle after LA injection.^[24]

The Last Straw: Patient Falls

Although a large study showed that older age and higher comorbidity but not peripheral nerve block, were associated with falls after TKA,^[25] most anesthesiologists continued to have concern for fall risk with PLP and cFNB approaches, as they result in unavoidable quadriceps weakness and delayed mobilization. Although various rates and concentrations of local anesthetics have been compared,^[26] a combination has not been found that provides analgesia without quadriceps weakness. Patient fall risk became, then, the third strike encouraging transition away from PLP and cFNB blocks.

Enter Ultrasound

At the end of the 20th century, portable ultrasound entered regional anesthesia practice, first at the University of Vienna (Drs Marhofer, Kapral, and others), University of Toronto (Dr. V. Chan), and University of Alberta (Dr. B. Tsui). cFNB was readily adapted^[27]; catheter placement with ultrasound guidance was shown to be faster, less painful, and with reduced risk of vascular puncture compared with nerve stimulator guidance.^[28] Most important to the evolution of regional analgesia for TKA, it also provided opportunities for more specific distal block approaches.

Distal Blocks Take Hold

In 2011, groups in Copenhagen reported the evaluation of blockade distal to the inguinal crease in the adductor canal, postulating that saphenous and obturator blockade could provide analgesia after TKA.^[29] Most investigators have shown analgesia from those blocks to be noninferior to FNB following TKA, with an important advantage of a reduced risk of quadriceps weakness. Although some studies have shown dynamic analgesia with cFNB to be superior to continuous adductor canal block (cACB), mobilization milestones were still reached earlier with cACB.^[30]

Controversy has raged as to whether the location in the mid or proximal thigh should be considered within or proximal to the adductor canal and which different nerves are targeted at the various sites. For simplicity, we will call it an ACB, although anatomic purists may argue. Certainly with ACB, the saphenous nerve and some medial and anterior cutaneous branches of the femoral nerve may be blocked. The nerve to the vastus medialis, within its own fascial compartment, may also be blocked by approaches that are mid or proximal thigh level. More distal blocks in the true adductor canal affect some of the posterior obturator fibers, and LA spread through the adductor hiatus to the popliteal plexus may also contribute to analgesia.^[31]

Regardless of which nerves are blocked, cACB has taken hold as the alternative to cFNB with adequate analgesia and reduced risk of quadriceps weakness. Catheters require placement or tunneling to avoid the surgical field, and hence, the exit site is commonly under the tourniquet. Dose-finding and rate studies for cACB continue to refine the technique.^[32] As with any newer technique, complications may occur with more widespread use. Quadriceps myotoxicity, for example, has been reported with cACB.^[33]

Posterior Analgesic Options: The Sciatic Nerve

Although most pain following TKA originates in the lumbar plexus distribution, the sciatic nerve and its innervation to the posterior capsule contribute to postsurgical pain as well. The incremental analgesic benefit of sciatic block offsetting motor weakness and interference with mobilization is controversial. Concern also surrounds the risk of obscuring surgical stretch or injury to the common peroneal nerve, which is reported to have an incidence as high as 0.3–10% following TKA.^[34]

Definitive but relatively short-lived (8 hours) analgesic benefit has been demonstrated from performing a single-shot sciatic nerve block,^[35] but the potential consequences previously mentioned have led to the introduction of other options for analgesia to the posterior knee. This includes selective tibial nerve blocks and posterior infiltration of the knee capsule by the surgeon or anesthesiologist.^[36-39]

The debate continues regarding the addition of the sciatic nerve block versus posterior capsule infiltration by the surgical team.^[40-42] Other innovations include infiltration between the popliteal artery and capsule of the knee (iPACK) block by the anesthesiologist. The iPACK with ACB and modified periarticular infiltration (PAI) showed improved analgesia compared with PAI alone.^[43]

Periarticular Infiltration

Developed in Europe as an alternative to specific anterior and posterior nerve blocks, injection of large volumes of dilute long-acting local anesthetic solutions for PAI has also been used.^[44] PAI, which sometimes combines nonsteroidal anti-inflammatory drugs and opioid adjuvants, can be infiltrated in multiple fascial, muscular, subcutaneous, and cutaneous sites. Substantial literature on the PAI technique, both single shot and continuous, has shown a benefit when combined with a proximal (ACB) nerve block.^[45] More prolonged, single-injection local anesthetics for infiltration are theoretically advantageous because of cost, simplicity, and infection risk. Studies of PAI with liposomal bupivacaine, however, have not shown improved quality or duration of analgesia over standard PAI techniques.^[46] Anesthesiologists may also perform PAI techniques, although PAI outside the highly sterile operating room environment raises a theoretical concern for infection risk; the literature is silent at present on this issue.

Future Directions

Many patients continue to have significant pain for days or weeks after a TKA procedure.^[47] Most of the analgesic approaches under current investigation have limited duration of a few days, and systemic analgesic regimens with multimodal therapy remain the mainstay of recovery pathways. In addition, the opioid epidemic adds pressure to taper rapidly or avoid opioid analgesics as much as possible. Other competing analgesic considerations include rising health care costs, changes to reimbursement, and an interest in shorter lengths of stay. The holy grail of analgesia for TKA would provide opioid-sparing, prolonged analgesia without motor block and be simple and cost-effective with minimal side effects or complications.

Enthusiasm for shorter inpatient stays has led Medicare to add an outpatient procedural code for TKA, and, as a result, some groups now send some patients home on the day of surgery with cACB. Others are using single-shot adductor canal blocks with long-lasting adjuvants off label, which have recently been shown to be clinically noninferior or equivalent when compared with cACB for 24–48 hours postoperatively.^[48],[49]

Future directions include some promising developments. For example, some evidence for peripheral nerve stimulation techniques for TKA is encouraging, but it is still investigational with an accompanying high cost.^[50] Cryoanalgesia and radiofrequency genicular nerve ablation techniques are also under investigation.

The steady growth in TKA procedures worldwide will challenge anesthesiologists and acute pain medicine physicians to continue their creative development and scientific investigation of regional anesthesia techniques over the coming decades, with the goal of enhancing the quality of recovery for patients following this procedure.

References

1. OrthoInfo. Total knee replacement. https://orthoinfo.aaos.org/en/treatment/total-knee-replacement. Accessed June 3, 2019.
2. Inacio MCS, Paxton EW, Graves SE, Namba RS, Nemes S. Projected increase in total knee arthroplasty in the United States—an alternative projection model. Osteoarthritis Cartilage. 2017;25(11):1797–1803. https://doi.org/10.1016/j.joca.2017.07.022
3. Macfarlane AJ, Prasad GA, Chan VW, Brull R. Does regional anesthesia improve outcome after total knee arthroplasty? Clin Orthop Relat Res. 2009;467(9):2379–2402. https://doi.org/10.1007/s11999-008-0666-9
4. Johnson RL, Kopp SL, Burkle CM, et al. Neuraxial vs general anaesthesia for total hip and total knee arthroplasty: a systematic review of comparative-effectiveness research. Br J Anaesth. 2016;116(2):163–176. https://doi.org/10.1093/bja/aev455
5. Memtsoudis SG, Rasul R, Suzuki S, et al. Does the impact of the type of anesthesia on outcomes differ by patient age and comorbidity burden? Reg Anesth Pain Med. 2014;39(2):112–119. https://doi.org/10.1097/AAP.0000000000000055
6. Liu J, Ma C, Elkassabany N, Fleisher LA, Neuman MD. Neuraxial anesthesia decreases postoperative systemic infection risk compared with general anesthesia in knee arthroplasty. Anesth Analg. 2013;117:1010–1016. https://doi.org/10.1213/ANE.0b013e3182a1bf1c
7. Pugely AJ, Martin CT, Gao Y, Mendoza-Lattes S, Callaghan JJ. Differences in short-term complications between spinal and general anesthesia for primary total knee arthroplasty. J Bone Joint Surg Am. 2013;95:193–199. https://doi.org/10.2106/JBJS.K.01682
8. Kopp SL, Børglum J, Buvanendran A, et al. Anesthesia and analgesia practice pathway options for total knee arthroplasty: an evidence-based review by the American and European Societies of Regional Anesthesia and Pain
   Medicine. Reg Anesth Pain Med. 2017;42(6):683–697. https://doi.org/10.1097/AAP.0000000000000673
9. Capdevila X, Barthelet Y, Biboulet P, Ryckwaert Y, Rubenovitch J, d’Athis F. Effects of perioperative analgesic technique on the surgical outcome and duration of rehabilitation after major knee surgery. Anesthesiology. 1999;91(1):8–15.
10. Singelyn FJ, Deyaert M, Joris D, Pendeville E, Gouverneur JM. Effects of intravenous patient-controlled analgesia with morphine, continuous epidural analgesia, and continuous three-in-one block on postoperative pain and knee rehabilitation after unilateral total knee arthroplasty. Anesth Analg. 1998;87:88–92.
11. YaDeau JT, Brummett CM, Mayman DJ, et al. Duloxetine and subacute pain after knee arthroplasty when added to a multimodal analgesic regimen: a randomized, placebo-controlled, triple-blinded trial. Anesthesiology. 2016;125(3):561–572. https://doi.org/10.1097/ALN.0000000000001228
12. Brownridge P. Central neural blockade and caesarian section. Part 1: review and case series. Anaesth Intensive Care. 1979;7(1):33–41.
13. Holmström B, Rawal N, Axelsson K, Nydahl PA. Risk of catheter migration during combined spinal epidural block: percutaneous epiduroscopy study. Anesth Analg. 1995;80(4):747–753.
14. Hurley RJ, Lambert DH. Continuous spinal anesthesia with a microcatheter technique: preliminary experience. Anesth Analg. 1990;70(1):97–102.
15. Winnie AP, Ramamurthy S, Durrani Z. The inguinal paravascular technic of lumbar plexus anesthesia: the “3-in-1 block.” Anesth Analg. 1973;52(6):989–996.
16. Bouaziz H, Vial F, Jochum D, et al. An evaluation of the cutaneous distribution after obturator nerve block. Anesth Analg. 2002;94(2):445–449.
17. McNamee DA, Parks L, Milligan KR. Post-operative analgesia following total knee replacement: an evaluation of the addition of an obturator nerve block to combined femoral and sciatic nerve block. Acta Anaesthesiol Scand. 2002;46(1):95–99.
18. Macalou D, Trueck S, Meuret P, et al. Postoperative analgesia after total knee replacement: the effect of an obturator nerve block added to the femoral 3-in-1 nerve block. Anesth Analg. 2004;99:251–254.
19. Dalens B, Vanneuville G, Tanguy A. Comparison of the fascia iliaca compartment block with the 3-in-1 block in children. Anesth Analg. 1989;69(6):705–713.
20. Morau D, Lopez S, Biboulet P, Bernard N, Amar J, Capdevila X. Comparison of continuous 3-in-1 and fascia iliaca compartment blocks for postoperative analgesia: feasibility, catheter migration, distribution of sensory block, and analgesic efficacy. Reg Anesth Pain Med. 2003;28(4):309–314
21. Capdevila X, Biboulet P, Morau D, Bernard N, Deschodt J, Lopez S, d’Athis F. Continuous three-in-one block for postoperative pain after lower limb orthopedic surgery: where do the catheters go? Anesth Analg. 2002;94(4):1001–1006.
22. Lennon RL, Horlocker TT. Mayo Clinic Analgesic Pathway: Peripheral Nerve Blockade for Major Orthopedic Surgery. Rochester, MN: Mayo Clinic Scientific Press; 2006.
23. Horlocker TT, Wedel DJ, Rowlingson JC, et al. Regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy: American Society of Regional Anesthesia and Pain Medicine evidence-based guidelines (third edition). Reg Anesth Pain Med. 2010;35(1):64–101. https://doi.org/10.1097/AAP.0000000000000763
24. Steele SM, Klein SM, D’Ercole FJ, Greengrass RA, Gleason D. A new continuous catheter delivery system. Anesth Analg. 1998;87(1):228.
25. Memtsoudis SG, Danninger T, Rasul R, et al. Inpatient falls after total knee arthroplasty: the role of anesthesia type and peripheral nerve blocks. Anesthesiology. 2014;120(3):551–563. https://doi.org/10.1097/ALN.0000000000000120
26. Bauer M, Wang L, Onibonoje OK, et al. Continuous femoral nerve blocks: decreasing local anesthetic concentration to minimize quadriceps femoris weakness. Anesthesiology. 2012;116(3):665–772. https://doi.org/10.1097/ALN.0b013e3182475c35
27. Marhofer P, Schrögendorfer K, Koinig H, Kapral S, Weinstabl C, Mayer N. Ultrasonographic guidance improves sensory block and onset time of three-inone blocks. Anesth Analg. 1997;85(4):854–857.
28. Mariano ER, Loland VJ, Sandhu NS, et al. Ultrasound guidance versus electrical stimulation for femoral perineural catheter insertion. ER J Ultrasound Med. 2009;28(11):1453–1460.
29. Lund J, Jenstrup MT, Jaeger P, Sørensen AM, Dahl JB. Continuous adductor-canal-blockade for adjuvant post-operative analgesia after major knee surgery: preliminary results. Acta Anaesthesiol Scand. 2011;55(1):14–19. https://doi.org/10.1111/j.1399-6576.2010.02333.x
30. Machi AT, Sztain JF, Kormylo NJ, et al. Discharge readiness after tricompartment knee arthroplasty: adductor canal versus femoral continuous nerve blocks—a dual-center, randomized trial. Anesthesiology. 2015;123(2):444–456. https://doi.org/10.1097/ALN.0000000000000741
31. Runge C, Moriggl B, Børglum J, Bendtsen TF. The spread of ultrasound-guided injectate from the adductor canal to the genicular branch of the posterior obturator nerve and the popliteal plexus: a cadaveric study. Reg Anesth Pain Med. 2017;42(6):725–730. https://doi.org/10.1097/AAP.0000000000000675
32. Monahan AM, Sztain JF, Khatibi B, et al. Continuous adductor canal blocks: does varying local anesthetic delivery method (automatic repeated bolus doses versus continuous basal infusion) influence cutaneous analgesia and quadriceps femoris strength? A randomized, double-masked, controlled, split-body volunteer study. Anesth Analg. 2016;122(5):1681–1688. https://doi.org/10.1213/ANE.0000000000001182
33. Neal JM, Salinas FV, Choi DS. Local anesthetic-induced myotoxicity after continuous adductor canal block. Reg Anesth Pain Med. 2016;41(6):723–727. http://dx.doi.org/10.1097/AAP.0000000000000466
34. Nercessian OA, Ugwonali OFC, Sangdo P. Peroneal nerve palsy after total knee arthroplasty. J Arthroplasty. 2005;20(8):1068–1073. https://doi.org/10.1016/j.arth.2005.02.010
35. Abdallah FW, Madjdpour C, Brull R. Is sciatic nerve block advantageous when combined with femoral nerve block for postoperative analgesia following total knee arthroplasty? A meta-analysis. Can J Anaesth. 2016;63:552–568. https://doi.org/10.1007/s12630-016-0613-2
36. Mahadevan D, Walter RP, Minto G, Gale TC, McAllen CJ, Oldman M. Combined femoral and sciatic nerve block vs combined femoral and periarticular infiltration in total knee arthroplasty: a randomized controlled trial. J Arthroplasty. 2012;27:1806–1811. https://doi.org/10.1016/j.arth.2012.05.018
37. Sinha SK, Abrams JH, Arumugam S, et al. Femoral nerve block with selective tibial nerve block provides effective analgesia without foot drop after total knee arthroplasty: a prospective, randomized, observer-blinded study. Anesth Analg. 2012;115:202–206. https://doi.org/10.1213/ANE.0b013e3182536193
38. Badner NH, Bourne RB, Rorabeck CH, MacDonald SJ, Doyle JA. Intra-articular injection of bupivacaine in knee-replacement operations. Results of use for analgesia and for preemptive blockade. J Bone Joint Surg Am. 1996;78(5):734–738.
39. Xing Q, Dai W, Zhao D, Wu J, Huang C, Zhao Y. Adductor canal block with local infiltrative analgesia compared with local infiltrate analgesia for pain control after total knee arthroplasty: a meta-analysis of randomized controlled trials. Medicine. 2017;96(38):e8103. https://doi.org/10.1097/MD.0000000000008103
40. Zhang Z, Yang Q, Xin W, Zhang Y. Comparison of local infiltration analgesia and sciatic nerve block as an adjunct to femoral nerve block for pain control after total knee arthroplasty: a systematic review and meta-analysis. Medicine. 2017;96(19):e6829. https://doi.org/10.1097/MD.0000000000006829
41. Kim DH, Beathe JC, Lin Y, et al. Addition of infiltration between the popliteal artery and the capsule of the posterior knee and adductor canal block to periarticular injection enhances postoperative pain control in total knee arthroplasty: a randomized controlled trial. Anesth Analg. 2018. https://doi.org/10.1213/ANE.0000000000003794
42. Elliott CE, Myers TJ, Soberon JR, et al. The adductor canal block combined with iPACK improves physical therapy performance and reduces hospital length of stay. Paper presented at: 40th Annual Regional Anesthesiology and Acute Pain Medicine Meeting; May 2015; Las Vegas, NV.
43. Sinha SK. Addition of iPACK and ACB with PAI enhances analgesia for TKA 6. In: Innovative Regional Techniques for Analgesia After Total Knee Arthroplasty. New York, NY: NYSORA; 2014. 7.
44. Kuang MJ, Du Y, Ma JX, He W, Fu L, Ma XL. The efficacy of liposomal bupivacaine using periarticular injection in total knee arthroplasty: a systematic review and meta-analysis. J Arthroplasty. 2017;32(4):1395–1402. https://doi.org/10.1016/j.arth.2016.12.025
45. Andersen LØ, Gaarn-Larsen L, Kristensen BB, Husted H, Otte KS, Kehlet H. Subacute pain and function after fast-track hip and knee arthroplasty. Anaesthesia. 2009;64(5):508–513. https://doi.org/10.1111/j.1365-2044.2008.05831.x
46. Ilfeld B. Continuous peripheral nerve blocks: an update of the published evidence and comparison with novel, alternative analgesic modalities. Anesth Analg. 2017;124(1):308–335. https://doi.org/10.1213/ANE.0000000000001581
47. Lee S, Rooban N, Vaghadia H, Sawka AN, Tang R. A randomized non-inferiority trial of adductor canal block for analgesia after total knee arthroplasty: single injection versus catheter technique. J Arthroplasty. 2018;33(4):1045–1051. https://doi.org/10.1016/j.arth.2017.11.018
48. Turner JD, Dobson SW, Henshaw DS, et al. Single-injection adductor canal block with multiple adjuvants provides equivalent analgesia when compared with continuous adductor canal blockade for primary total knee arthroplasty:
    a double-blinded, randomized, controlled, equivalency trial. J Arthroplasty. 2018;33(10):3160–3166. https://doi.org/10.1016/j.arth.2018.05.026
49. Abdallah FW, Madjdpour C, Brull R. Is sciatic nerve block advantageous when combined with femoral nerve block for postoperative analgesia following total knee arthroplasty? A meta-analysis. Can J Anaesth. 2016;63(5):552–568. https://doi.org/10.1007/s12630-016-0613-2
50. Tanikawa H, Sato T, Nagafuchi M, Takeda K, Oshida J, Okuma K. Comparison of local infiltration of analgesia and sciatic nerve block in addition to femoral nerve block for total knee arthroplasty. J Arthroplasty. 2014;29(12):2462–2467. https://doi.org/10.1016/j.arth.2014.04.011