Higher incidence of manipulation under anesthesia following TKA associated with the periarticular infiltration of a liposomal bupivacaine cocktail compared to a modified Ranawat cocktail

Background: The purpose of this study was to compare the frequency of postoperative stiffness requiring manipulation under anesthesia (MUA) before and after switching from the intraoperative use of liposomal bupivacaine (LB). Methods: This was an institutional review board (IRB)-exempt retrospective cohort study (IRB#71733) on all patients who underwent primary total knee arthroplasty (TKA) by a single surgeon between April 2016 and December 2017. We compared 169 knees that received LB group to 167 knees that received a modified Ranawat cocktail (MR group). Perioperative care pathways remained consistent during the study period, as were requirements for MUA which included flexion range of motion below approximately 90 at 6–12 weeks. To compare the incidence of MUA between the groups, a population-averaged Poisson regression analysis was used. Results: The two groups were similar, with mean age of 63 (range 31–91) in the LB group and 64 (range 42–84) in the MR group, a preponderance of females in both groups ( p = 0.866), similar preoperative knee flexion between groups ( p = 0.162), and similar Patient-Reported Outcomes Measurement Information System scores. The frequency of MUA, however, was significantly lower in the MR group (LB: 7.7% [95% CI 3.7–12%] vs. MR: 2.4% [95% CI <1–4.7%] [IRR 3.2, 95% CI 1.08–9.76, p . 0.037]). Conclusions: In summary, this is a novel report of a potentially previously unrecognized increased incidence of MUA associated with the use of LB compared with a MR cocktail. Given no other notable changes to the perioperative care or MUA thresholds following TKA, the reasons for these findings are unclear but deserve additional investigation.