The Learning Curve Associated with the Administration of Intra-Articular Liposomal Bupivacaine for Total Knee Arthroplasty: A Pilot Study.

INTRODUCTION: Liposomal bupivacaine is a long-acting, local, injectable anesthetic that is used to potentially mitigate post-operative pain after total knee arthroplasty (TKA). In addition, it may reduce opioid use in the post-operative period and shorten lengths-of-stay (LOS). There have been mixed results in the literature with regards to its efficacy, which raises questions regarding the injection technique used. Therefore, we evaluated the learning curve associated with injection techniques prior to, and after, formal teaching. Specifically, we compared differences in: 1) opioid use; 2) LOS; 3) pain intensity; and 4) discharge disposition in patients who did not receive liposomal bupivacaine (no infiltration cohort), received liposomal bupivacaine with less optimal technique (subpar infiltration), and received liposomal bupivacaine with appropriate technique (optimal infiltration) during their primary TKA.

MATERIALS AND METHODS: A 1:1:1 ratio of 54 consecutive cases of patients who had no liposomal bupivacaine infiltration, those who had subpar infiltration, and those who had optimal infiltration were included. To evaluate opioid use, the dosages were obtained and converted to their respective morphine milliequivalents (mEq). The total mEq usage was obtained for the day of surgery through post-operative day (POD) 3. LOS was recorded in days. Pain scores were calculated using the visual analogue scale (VAS), obtained from the first post-operative physical therapy note. Discharge status was recorded as discharged to home or rehabilitation. We used an ANOVA test for continuous and X2-square test for categorical variables.

RESULTS: When compared to patients who had no infiltration, patients who had subpar infiltration had significantly lower opioid use on day 0, while patients who had optimal infiltration had lower opioid use on post-operative day (POD) 0 and 3. When comparing techniques, opioid use was lower on day 3 for patients who had optimal, as compared to subpar technique. However, LOS and VAS were not significantly different among the three groups. The rehab discharge rate was lower for patients who had optimal as compared to subpar technique.

CONCLUSION: There is a learning curve associated with liposomal bupivacaine use, and incorporating an appropriate technique can markedly affect post-operative outcomes. This should be taken into account when evaluating the potential benefits of this peri-articular injection. It appears that liposomal bupivacaine may decrease opioid use and pain scores when optimal infiltration techniques are used.