A Prospective, Randomized Trial of Liposomal Bupivacaine Compared to Conventional Bupivacaine on Pain Control and Post-Operative Opioid Use in Receiving Adductor Canal Blocks for Total Knee Arthroplasty

BACKGROUND The femoral nerve block and the adductor canal nerve block are two regional anesthesia techniques used to manage pain control following TKA Femoral nerve blocks were the first peripheral nerve block employed for post-surgical analgesia, however they are now less frequently used due to significant drawbacks that influence recovery. The femoral nerve provides motor and sensory innervation to the quadriceps muscle. Blockade of the motor branches of this nerve leads to quadriceps weakness and increased risk of falling after surgery. Additionally, for similar reasons, ambulation after surgery can be significantly delayed. In contrast, the adductor canal block does not affect the quadriceps muscle, as it avoids the motor branches of the femoral nerve. The location of the block, located in the mid-thigh, mainly affects the sensory neuronal branches of the saphenous nerve. It has been found as a superior method for post-surgical analgesia since motor weakness is spared.

The adductor canal block is an interfascial plane block that can be performed as a single injection, or as a continuous infusion via insertion of a catheter. Continuous peripheral nerve blocks can provide prolonged post-operative analgesia, however, they are associated with several complications including catheter infection, obstructions, and fluid leakage Catheter placement takes a significant amount of time to perform and can consume valuable clinical resources. Additionally, catheter displacement can be frequent with ACBs, since the aponeurosis where the saphenous nerve lies is superficial, leading to easy dislodgement and block failure. In comparison, a single injection of local anesthetic in the adductor canal space is much simpler to place, is more cost effective, and has a lower infection risk. However, risk of rebound pain is much higher in single injection nerve blocks due to their shorter duration of action.

Liposomal bupivacaine (LB) is an extended-release local anesthetic that combines the benefits of a single injection nerve block with the long-lasting effects of continuous catheter infusions. LB received Food and Drug Administration approval in October 2011 for post-surgical anesthesia via local infiltration and, in April 2018, for interscalene brachial plexus blocks. LB has been reported to provide analgesia for up to 72 hours, making it the longest lasting local anesthetic currently available.

There have been several studies evaluating the effectiveness of perineural LB in improving peripheral nerve block analgesia compared to non-liposomal anesthetics for total knee arthroplasty but the evidence is not definitive. A meta-analysis performed found that LB was associated with higher pain relief compared to traditional bupivacaine and reduced opioid related complications in TKA patients. Another study found decreased opioid consumption and improved pain scores within the early post-operative period following TKA, but there was no significant difference in length of hospital stay, patient satisfaction, or adverse postoperative events. Another study found patients receiving LB for TKA had no improvement in narcotic use, length of stay, patient reported pain, or functional ability compared to those who received a single shot short acting ropivacaine nerve block. A recent meta-analysis concluded that perineural infiltration of LB in various, distinct peripheral nerve block locations was not superior to non-liposomal bupivacaine.

There is an institutional desire to improve postoperative pain outcomes and shorten length of stay in patients undergoing TKA. It is possible that liposomal bupivacaine may help improve these measures, however, current evidence is inconclusive. The purpose of this study is to investigate the analgesic efficacy of liposomal bupivacaine comparative to conventional bupivacaine in ACBs for individuals undergoing TKA.