improves quality of life , and reduces the likelihood of developing chronic pain syndromes

Femoral Nerve Block Versus Long-Acting Wound Infiltration in Total Knee Arthroplasty RogeR H. emeRson JR, mD; JoHn W. BaRRington, mD; oluseun olugBoDe, ms; scott lovalD, PHD, mBa; HeatHeR Watson, PHD; Kevin ong, PHD The introduction of less invasive surgical techniques to the practice of total joint replacement has led to a new focus on pain management. Effective pain control improves satisfaction, promotes earlier mobility and physiotherapy, results in fewer cardiac and pulmonary complications, enhances recovery, Multimodal wound infiltration analgesic techniques have attracted growing interest for applications in total knee arthroplasty (TKA). A benefit of using wound infiltration instead of femoral nerve block (FNB) in a multimodal pain control regimen is the limitation of muscle strength impairment to the surgical area, which will focus the pain control effort and may provide the opportunity for easier rehabilitation and earlier discharge from the hospital. The current study directly compares patients undergoing TKA who are given a continuous FNB with those who were administered an injection of liposomal bupivacaine infiltration. The study cohort included 36 patients with osteoarthritis who were treated with a continuous FNB (OnQ pump; I-Flow, Lake Forest, California), and 36 patients who were administered an injection for liposome bupivacaine infiltration (EXPAREL; Pacira Pharmaceuticals, Inc, Parsippany, New Jersey) for postoperative pain analgesia. The average number of narcotic doses and the total number of narcotics consumed was greater in the FNB group (P<.001). Average visual analog scale pain scores trended higher for patients in the FNB group (2.29 vs 1.93) overall and for each day postoperatively up to day 5, although the overall difference was not significant in this study sample (P=.115). The results of the current study support the conclusion that long-acting liposome bupivacaine infiltration gives comparable postoperative analgesia compared with a continuous FNB, but with significantly less narcotic medication. [Orthopedics. 2016; 39(3):e449-e455.] The authors are from the Texas Center for Joint Replacement (RHE, OO) and the Plano Orthopedic Sports Medicine and Spine Center (JWB), Plano, Texas; Exponent, Inc (SL, HW), Menlo Park, California; and Exponent, Inc (KO), Philadelphia, Pennsylvania. Mr Olugbode has no relevant financial relationships to disclose. Dr Emerson is on the speaker’s bureau of Pacira, Inc. Dr Barrington is a paid consultant for Biomet, Pacira, Inc, Smith & Nephew, United Surgical Partners, and Orthosensor; is on the speaker’s bureau of Pacira, Inc, and Biomet; and receives royalties from Biomet. Dr Lovald’s institution has received consulting fees from Stryker, Biomet, and Pacira, Inc, and payment for manuscript writing and review from Pacira, Inc. Dr Watson’s institution has received consulting fees and payment for manuscript writing and review from Pacira, Inc. Dr Ong’s institution has received consulting fees from Stryker, Biomet, Paradigm Spine, Medtronic, MAKO Surgical, and Pacira, Inc; provided expert testimony for Ethicon and Zimmer; received payment for manuscript writing and review from Pacira, Inc; and received payment for manuscript preparation from Stryker, Biomet, Paradigm Spine, Medtronic, MAKO Surgical, and Pacira, Inc. Support for statistical analysis and associated manuscript preparation was provided by Pacira, Inc. Correspondence should be addressed to: Scott Lovald, PhD, MBA, Exponent, Inc, 149 Commonwealth Dr, Menlo Park, CA 94025 (slovald@ exponent.com). Received: February 13, 2015; Accepted: September 9, 2015. doi: 10.3928/01477447-20160315-03 MAY/JUNE 2016 | Volume 39 • Number 3 e449 Copyright © SLACK inCorporAted n Feature Article improves quality of life, and reduces the likelihood of developing chronic pain syndromes.1-3 Given the importance of the pain experience, the Agency for Healthcare Quality and Research and the Joint Commission recommend that adequacy of pain management and patient satisfaction serve as metrics for hospital performance.4,5 To date, there are no prevailing best practices for pain management following total knee arthroplasty (TKA).2 Common pain management techniques for TKA are still heavily opioid dependent, despite the observance that opiate analgesics on their own are a suboptimal modality.5 Opioidrelated adverse events, including constipation, nausea, vomiting, and ileus, are common early complications that, along with difficulties in pain control, may delay patient rehabilitation and discharge.3 Multimodal analgesia regimens have been designed to combine oral medications (eg, nonopiate analgesics, opiate analgesics, anti-inflammatory medication) with regional techniques, either wound infiltration with local anesthetics or femoral nerve block (FNB), to decrease opiate consumption.2 Femoral nerve blocking is a commonly used regional technique and has been shown to be highly effective for pain relief after TKA. However, quadriceps weakness due to the block can delay rehabilitation and is a known contributing factor for patient falls inside and outside of the hospital.5 It is estimated that quadriceps strength can be reduced by at least 50% of baseline with nerve blocks, even with low infusion rates.6 Given the muscle strength impairment inherent in femoral nerve blocking, the dosage must be balanced to allow early physical therapy, and thus more opioids may be necessary to supplement pain control. Wound infiltration analgesic techniques have attracted growing interest for applications in large joint arthroplasty. In relation to FNB, a major benefit of using wound infiltration in a multimodal pain control regimen is the limitation of muscle strength impairment to the surgical area, which will focus the pain control effort and may provide the opportunity for easier rehabilitation and earlier discharge from the hospital.7 In terms of pain control, there is no current consensus on the effectiveness of local infiltration compared with peripheral nerve blocks.8 Traditionally, the effectiveness of local wound infiltration with bupivacaine-based injections has been limited by the duration of its effectiveness, having a half-life of 2.7 hours. Recently, a single-dose local analgesic was introduced that uses bupivacaine in combination with a liposomal time-released product delivery platform (EXPAREL; Pacira Pharmaceuticals, Inc, Parsippany, New Jersey). It has been proposed that the time release mechanism can improve the duration of effectiveness for wound infiltration analgesia, and thus could potentially reduce the amount of opioid medications required for effective pain control. The current study directly compared patients undergoing TKA who were given a continuous FNB supplementing local surgical-site bupivacaine hydrochloride infiltration with those who were administered liposomal bupivacaine infiltration supplementing the same local surgical-site bupivacaine hydrochloride infiltration. The purpose of this study was to compare the pain scores and opiate consumption for patients undergoing primary TKA with these differing pain management techniques. The hypothesis was that the liposomal bupivacaine could provide equivalent pain relief to a continuous FNB while requiring a lower supplemental opioid dosage. Materials and Methods The study cohort included 72 patients with osteoarthritis treated with primary TKA by a single surgeon (R.H.E.) between December 2011 and August 2013. The treatment course for all patients was identical aside from the analgesic regimen. Anesthesia for all patients included preemptive medications (75 mg of pregabalin, 10 mg of oxycodone, and 200 mg of nonsteroidal anti-inflammatory drugs [NSAIDs]), along with general anesthesia. In addition, all patients received local infiltration with 0.5% bupivacaine hydrochloride with epinephrine and ketorolac (30 mg) if medical status permitted. For postoperative pain analgesia, 36 patients (from December 2011 to September 2012) were treated with a continuous FNB using 0.5% bupivacaine administered with a pump device (OnQ pump; I-Flow, Lake Forest, California) to achieve longer effectiveness, and 36 patients (from October 2012 to August 2013) were administered liposome bupivacaine infiltration (EXPAREL) to achieve similar extended analgesia. For all analgesic infiltration, the posterior injections were done just prior to placing the implant components, and all other anatomic layers were injected while the cement was setting up prior to closure at the end of the surgery. Additional medications were administered on a scheduled basis as shown in Table 1. Opiate medications were available on a scheduled basis and for rescue at the discretion of the patient. The number of opiate doses given and requested and the total amount of opiates (converted to hydrocodone equivalents) were tabulated. Patients from each group were selected randomly from a prospectively collected database to minimize unforeseen biases. The wound infiltration for both groups was done with a 21-gauge, 1.5-inch needle. A moving injection technique was used on all tissue layers, inserting the needle and injecting on the way out to prevent a large volume of medication placed into one location. The back of the knee was injected prior to placing the components due to ease of access, aspirating before injecting and avoiding the midline vascular structures. The synovium, suprapatellar pouch, medial and lateral capsule, and subcutaneous layers were injected while the cement was setting. A total volume of injected solution was adjusted with normal saline to be between 60 and 100 cc, depending on