In total knee arthroplasty, regional anesthesia provides effective analgesia, reduces opioid consumption, and facilitates early mobilization. However, the limited duration of single-shot peripheral nerve blocks can pose issues for some surgeries, particularly in the context of enhanced recovery protocols. Strategies to extend the duration of nerve blocks have therefore become an important focus in perioperative pain management for total knee surgeries. Approaches include the use of adjuvants, optimization of multimodal analgesia, and catheter-based techniques.
Among pharmacologic adjuncts, dexamethasone can consistently extend the duration of nerve blocks for total knee arthroplasty. As a corticosteroid with anti-inflammatory and membrane-stabilizing properties, it has demonstrated a reliable capacity to prolong femoral nerve block duration. In a randomized controlled trial, dexamethasone added to bupivacaine significantly increased block longevity and improved postoperative pain control without additional adverse effects (1).
Other agents have been investigated with more variable results. Buprenorphine, a partial μ-opioid receptor agonist, has shown mixed evidence. One prospective randomized trial reported that buprenorphine prolonged femoral nerve block duration and enhanced analgesia (2). However, a subsequent placebo-controlled study in a fast-track TKA cohort did not demonstrate meaningful clinical benefit, indicating inconsistency in outcomes (3). Similarly, naloxone has recently been examined as an additive to ropivacaine. A randomized trial suggested that low-dose naloxone significantly extended block duration, possibly through peripheral modulation of opioid receptors (4). While encouraging, such findings are preliminary, and the evidence for opioid-based adjuvants remains limited. These results highlight the importance of continued exploration not only of novel opioid-related agents but also of alternative adjuvant classes that may offer more predictable efficacy.
Multimodal analgesia can influence how patients experience the duration of nerve blocks by reducing rebound pain as the block wears off and supporting analgesia during the transition period. Periarticular infiltration (PAI), in which the surgeon injects local anesthetics and adjuncts into the tissues around the knee joint capsule, provides site-specific pain relief that complements but is distinct from peripheral nerve blockade. Because PAI targets the joint rather than the nerve, it can help cover pain once the block begins to fade. However, evidence suggests that the combination is not always additive. In one large analysis, outcomes with PAI plus a nerve block were not superior to PAI alone, indicating that the design of multimodal regimens should focus on complementarity rather than the simple layering of techniques (5).
Continuous catheter techniques represent the most direct method to extend peripheral nerve block duration, often maintaining analgesia for 48 to 72 hours, which is beneficial in major surgeries like total knee surgery. Randomized trials have shown that continuous adductor canal blocks improve postoperative pain control and functional recovery compared with single-injection techniques (Nelson et al., 2019). However, their use introduces logistical challenges, including the need for infusion pumps, additional nursing resources, and the risk of catheter dislodgement or infection. Continuous femoral catheters in particular may also reduce quadriceps strength, which can hinder early ambulation and delay discharge.
References
Sherif AA, Elsersy HE. Dexamethasone as adjuvant for femoral nerve block following knee arthroplasty: a randomized, controlled study. Acta Anaesthesiol Scand. 2016;60(7):977-987. doi:10.1111/aas.12750
- Kosel J, Bobik P, Siemiątkowski A. Buprenorphine added to bupivacaine prolongs femoral nerve block duration and improves analgesia in patients undergoing primary total knee arthroplasty-a randomised prospective double-blind study. J Arthroplasty. 2015;30(2):320-324. doi:10.1016/j.arth.2014.07.016
- van Beek R, Zonneveldt HJ, van der Ploeg T, Steens J, Lirk P, Hollmann MW. In patients undergoing fast track total knee arthroplasty, addition of buprenorphine to a femoral nerve block has no clinical advantage: A prospective, double-blinded, randomized, placebo controlled trial. Medicine (Baltimore). 2017;96(27):e7393. doi:10.1097/MD.0000000000007393
- Lee SC, Kim JH, Choi SR, Park SY. A Low Dose of Naloxone Added to Ropivacaine Prolongs Femoral Nerve Blockade: A Randomized Clinical Trial. Pain Res Manag. 2021;2021:6639009. Published 2021 Jan 31. doi:10.1155/2021/6639009
- Laoruengthana A, Jarusriwanna A, Rattanaprichavej P, Eiamjumras W, Kositanurit I, Pongpirul K. Additional Peripheral Nerve Block to Periarticular Injection Has No Benefit for Patients Undergoing TKA: A Factorial Propensity Score-Matched Analysis Comparing Four Multimodal Analgesic Techniques. J Arthroplasty. 2022;37(1):39-44. doi:10.1016/j.arth.2021.09.011
- Elkassabany NM, Cai LF, Badiola I, et al. A prospective randomized open-label study of single injection versus continuous adductor canal block for postoperative analgesia after total knee arthroplasty. Bone Joint J. 2019;101-B(3):340-347. doi:10.1302/0301-620X.101B3.BJJ-2018-0852.R2
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