Postoperative Pain After Primary Total Knee Arthroplasty: Comparison of Local Injection Analgesic Cocktails and the Role of Demographic and Surgical Factors

BackgroundIt has been reported that pain-related outcomes after total knee arthroplasty (TKA) may vary with different analgesic techniques and with patient demographics. The purposes of this study were to compare local infiltration of regular bupivacaine (periarticular infiltration [PAI] group) vs liposomal bupivacaine (LBUP group) and to examine the effect of patient characteristics on postoperative pain after TKA.MethodsThe study sample included 665 consecutive TKA cases performed between December 2011 and August 2013. The primary outcome measures were the average visual analog scale (VAS) pain score and the percent of VAS pain scores that indicated no pain. Multivariable regression analyses investigated the effect of age, race, ethnicity, body mass index, gender, surgeon, and analgesic protocol on outcomes. For the analgesic groups, the “PAI” group received injections of a cocktail including bupivacaine, ketorolac, and morphine, whereas the “LBUP” group received injections of LBUP.ResultsThe regression analysis demonstrated that postoperative pain was higher in females (P < .001) and younger patients (P < .001). Although overall average VAS pain scores were not significantly different, when specific postoperative days were evaluated, the LBUP group had lower pain scores from day 1 to 5 (P < .014). There were no differences in VAS scores based on patient body mass index (P = .250), race (P = .205), or ethnicity (P = .961) in this sample.ConclusionThis multivariate regression analysis study showed that in patients undergoing primary TKA, postoperative pain was lower in males, older patients, and those treated with LBUP. Awareness of these factors may assist in developing patient-specific multimodal postoperative pain and education protocols that reduce opioid reliance and related adverse events.