Abstract
Introduction
Pain control following total knee arthroplasty (TKA) heavily influences timing of mobilization and rehabilitation postoperatively as well as length of hospital stay. Recently, periarticular injection of liposomal bupivacaine (EXPAREL®; Pacira Pharmaceuticals, Inc., San Diego, California) has demonstrated pain relief comparable to femoral nerve block for postoperative analgesia in TKA with earlier mobilization and shortened hospital stay. In order to better explore the use of EXPAREL® in TKA, we standardized the postoperative analgesia to intraoperative periarticular injection of multimodal pain management, which is a recommended postoperative method of pain control in TKA. We studied the effectiveness of periarticular EXPAREL® in TKA postoperative pain control, including impact on early mobilization and length of hospital stay, compared to another local analgesic (Ropivacaine) when both are used as part of a multimodal pain management approach.
Methods
We performed a double blind, randomized, controlled, prospective, IRB-approved study that enrolled 96 participants who underwent a unilateral TKA by one surgeon between May 2014 and March 2015. The two randomized groups were as follows: group 1 (control group) was given the standard intra-articular “pain cocktail” injection, consisting of ropivacaine, ketorolac, morphine, and epinephrine mixed with saline into a 100cc preparation and group 2 (study group) was given a similar intra-articular injection consisting of bupivacaine, ketorolac, morphine, and epinephrine mixed with saline into an 80cc preparation as well as an injection of EXPAREL®, 20cc of 1.3% EXPAREL®, to total 100cc. All patients included in the study were determined to be opioid naïve as described by the Food and Drug Administration criteria. Patients were treated with the same postoperative pain management protocol as well as the same post-operative physical therapy program. The consumption of oral and intravenous narcotics at specific time points as well as total use was recorded during hospital stay. We recorded Visual Analog Pain scores, hours to ambulate 100 feet and length of hospital stay (hours). Both the investigator and the patient were blinded as to which group the patient was randomized, making this a double blind study.
Results
On a per hour basis, the mean use of narcotics of the two groups differed by only 0.1mg. For total narcotic use during hospital stay, the weighted sum used by patients in the EXPAREL® group, 97.7mg of hydrocodone ±42.84 mg, exceeded the weighted sum, 89.6 mg of hydrocodone ± 58.57 mg, used by patients in the control group. The difference between the two groups was not significant. The means for length of stay differed by only 26 minutes and the difference was not significant. Similarly insignificant, the means for the time to ambulate 100 feet differed by 53 minutes, with the EXPAREL® group actually taking the longer time. The two groups did not differ for Visual Analog Score for pain on day 1 or day 2 post-operatively.
Conclusion
When comparing the use of EXPAREL® to another multimodal pain management approach using ropivacaine, there is no difference in post-operative opioid consumption, Visual Analong Scores for pain, amount of time to ambulate or length of hospital stay.
