Efficacy of Regional Adductor Canal Block using Extended Release Liposomal Bupivacaine in Total Knee Arthroplasty: A Randomized Prospective Study

Background: Exparel (Pacira Pharmaceuticals, Parsippany, NJ, USA) is a long-acting liposomal Bupivacaine extended release compound that can be used as peri-articular injection (PAI) or regional nerve block. The purpose of this study was to compare the post-operative analgesic efficacy of Exparel as a single administration adductor canal block (ACB) varsus PAI.

Methods: From May 2016 to June of 2017, 70 patients with primary knee osteoarthritis undergoing unilateral knee replacement were prospectively randomized into two cohorts: 1) PAI (Exparel 266 mg (20 ml vial) with 20 ml of 0.5% bupivacaine HCl, and normal saline to a total volume of 120 ml); 2) ACB (Subsartorial saphenous nerve using Exparel 266 mg in 20 ml vial). All patents underwent spinal anesthesia with comprehensive pre-emptive and postoperative multimodal pain protocol. All opioids given were converted to morphine equivalents. Pain was recorded at 4 - 12 hrs (day of surgery), post-operative day (POD) 1, 2, and 3 after surgery.

Results: There was no statistical significance between the pain scores during the first 12 hrs (day 0) after surgery. We found a trend towards a significance on POD # 1, as PAI group had less pain (5.3 vs 4.2, p=0.09). The mean pain score in ACB group increased on POD # 3 while in PAI continued a decrease (4.8 vs 1.8, p=0.03). There was no statistical significance between the 2 groups regarding the accumulative daily converted Morphine equivalent consumption or total consumption.

Conclusion: We found similar results between PAI and ACB using Exparel after TKA up to 48 hours.