ORIGINAL ARTICLE

Continuous Versus Single-Injection Sciatic Nerve Block Added to Continuous Femoral Nerve Block for Analgesia After Total Knee Arthroplasty A Prospective, Randomized, Double-Blind Study Keita Sato, MD,* Takehiko Adachi, MD, PhD,† Naoto Shirai, MD,† and Noriko Naoi, MD† Background and Objectives: The benefit of adding sciatic nerve block (SNB) to femoral nerve block to improve analgesia after total knee arthroplasty (TKA) is uncertain. We hypothesized that the effective duration of single-injection SNB is too short to improve postoperative analgesia and that this contributes to conflicting results on the efficacy of SNB after TKA. We evaluated this hypothesis in a prospective doubleblind randomized controlled trial. Methods: Sixty patients undergoing TKA were randomly allocated to a continuous SNB group or a single-injection SNB group. All patients received femoral nerve block (0.5% ropivacaine 20 mL) and SNB (0.2% ropivacaine 20 mL) and catheters were inserted into both peripheral nerve block sites before surgery. Both groups received continuous femoral nerve block and patient-controlled intravenous analgesia with morphine. Continuous SNB (0.2% ropivacaine 5 mL/h; continuous SNB group) or sham continuous SNB (0.9% normal saline 5 mL/h; singleinjection SNB group) was provided after surgery. The primary outcome was total morphine consumption for 48 hours after surgery. Results: Total morphine consumption in the 48-hour period after surgery was significantly lower in the continuous SNB group compared with the single-injection SNB group [4.9 (5.9) vs 9.7 (9.5) mg, P = 0.002]. Visual analog scale pain scores at rest were also significantly lower in the continuous SNB group (P = 0.035). Conclusions: The combination of continuous femoral and SNB provides a superior opioid sparing effect and improves analgesia after TKA. (Reg Anesth Pain Med 2014;39: 225–229)

T

he number of total knee arthroplasty (TKA) procedures has increased markedly due to an expansion of indications, increased prevalence of obesity, and aging of the population.1 Severe pain often occurs after TKA2 and effective pain relief can promote earlier ambulation and rehabilitation, indicating the importance of improvement of pain control.3–5 Femoral nerve block has a proven opioid sparing effect and superior suppression of pain on motion, and thus plays a central role in analgesia after TKA.6 However, femoral nerve block does not provide complete analgesia of the knee joint. Thus, use of another analgesic method with femoral nerve block may help to attenuate postoperative pain.

From the *Department of Anesthesiology, Tokyo Women’s Medical University, Tokyo; and †Department of Anesthesiology, Kitano Hospital, Osaka, Japan. Accepted for publication October 6, 2013. Address correspondence to: Keita Sato, MD, Department of Anesthesiology, Tokyo Women’s Medical University, 8-1, Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan (e‐mail: [email protected]). The authors declare no conflict of interest. Presented at the Anesthesiology 2013, October 12–16, 2013, San Francisco, California. Copyright © 2014 by American Society of Regional Anesthesia and Pain Medicine ISSN: 1098-7339 DOI: 10.1097/AAP.0000000000000076

The addition of sciatic nerve block (SNB) to femoral nerve block may improve analgesia after TKA, but the benefits of this approach are uncertain. The addition of single-injection SNB to femoral nerve block was found to have no benefit,7 but other studies have shown that continuous SNB and femoral nerve block improves postoperative analgesia, compared with continuous femoral nerve block alone.8,9 These conflicting results may be due to the effective duration of single-injection SNB being too short to improve analgesia after TKA. Cappelleri et al10 showed that continuous SNB improved postoperative pain relief and early rehabilitation compared with single-injection SNB when added to continuous lumbar plexus block. However, a doubleblind randomized controlled trial comparing continuous SNB with single-injection SNB when added to continuous femoral nerve block has not been performed. Thus, this comparison was the aim of the present study.

METHODS This study was performed as a prospective, single-center, double-blind, randomized, controlled trial. The protocol was approved by the institutional review board of Kitano Hospital (Osaka, Japan) and the study is registered at a registry accepted by the International Committee of Medical Journal Editors (UMIN000005789). Written informed consent was obtained from each patient in the study. Patients undergoing unilateral TKA under general anesthesia at our institution were eligible for the study. Exclusion criteria were age younger than 18 or older than 85 years, an American Society of Anesthesiologists physical status greater than 3, fixed flexion and valgus deformity of the knee, revision surgery, cognitive dysfunction, neuromuscular diseases, impaired vascular perfusion of the lower extremities, type 1 diabetes mellitus, morbid obesity (body mass index, >35 kg/m2), renal dysfunction (serum creatinine, >1.5 mg/dL), coagulation dysfunction, infection at the puncture site of peripheral nerve blocks, allergy to local anesthetics or nonsteroidal anti-inflammatory drugs, gastric ulcer, pregnancy, and lactation. Subjects were randomly allocated to a continuous SNB group or a single-injection SNB group using a computer-generated random sequence. Subjects, anesthesiologists, care providers, and those assessing outcomes were all blinded to the group allocation. Patients in both groups received femoral nerve block and SNB with ultrasound guidance (S Nerve; Fujifilm SonoSite, Inc, Bothell, Washington) in an aseptic fashion in the operation room before induction of general anesthesia. Intravenous midazolam 1 to 2 mg and fentanyl 25 to 50 μg were administered for mild sedation, and supplemental oxygen (face mask at 4 L/min) was given. Femoral nerve block was performed with a linear array 6to 13-MHz ultrasound transducer using an 18-gauge 5-cm Tuohy needle (Contiplex Tuohy; B. Braun Melsungen AG, Melsungen, Germany). A 0.5% ropivacaine (20 mL) was injected to create a perineural fluid space. A 20-gauge catheter was then inserted

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Regional Anesthesia and Pain Medicine • Volume 39, Number 3, May-June 2014

perpendicularly to the femoral nerve 5 cm beyond the tip of the Tuohy needle and the position was confirmed with an injection of a small amount of saline by ultrasound. An anterior approach was adopted for SNB. Patients were placed in a supine position with the hip and knee on the operated side flexed and the leg externally rotated. A convex array 2- to 5-MHz ultrasound transducer was first positioned approximately 8 cm distal to the inguinal crease. A clear transverse image of the hyperechoic sciatic nerve located posterior and medial to the lesser trochanter was then scanned by adjusting the position of the transducer. An 18-gauge 10-cm Tuohy needle (Contiplex Tuohy; B. Braun, Bethlehem, Pennsylvania) was inserted in-plane with the transducer from the anteromedial to posterolateral side of the thigh. A 0.2% ropivacaine (20 mL) was injected to create a perineural fluid space. A 20-gauge catheter was then inserted perpendicularly into the sciatic nerve 5 cm beyond the tip of the Tuohy needle. General anesthesia was induced with propofol 1.5 to 2 mg/kg, remifentanil 0.2 to 0.4 μg/kg/min, and rocuronium 0.6 to 0.8 mg/kg, and patients were intubated. Sevoflurane 1% to 1.5%, remifentanil 0.05 to 0.5 μg/kg/min, and an intermittent bolus of rocuronium were administered for maintenance of general anesthesia. Flurbiprofen 50 mg and droperidol 0.5 mg were given intravenously 30 to 60 minutes before completion of surgery. Patients were extubated using sugammadex 2 to 4 mg/kg. Pain evaluated as greater than 40 mm on a visual analog scale (VAS) (0–100 mm) just after surgery was treated with intravenous morphine 1 mg, which was administered repeatedly in the operation room at the anesthesiologist’s discretion. A 0.2% ropivacaine was administered at 5 mL/h through the femoral nerve catheter in both groups after surgery. In the continuous SNB group, 0.2% ropivacaine was also administered at 5 mL/h through the sciatic nerve catheter. In the single-injection SNB group, 0.9% normal saline was similarly administered at 5 mL/h through the sciatic nerve catheter as sham continuous SNB. All continuous infusions were performed using elastomeric pumps (Coopdech Balloonjector 300; Daiken Medical Corporation, Tokyo, Japan). If dorsal or plantar flexion of the foot on the operated side was impaired, drug administration via the sciatic nerve catheter was stopped. After restoration of dorsal or plantar flexion, administration was restarted at 3 mL/h. If flexion was not restored within 12 hours, the sciatic nerve catheter was removed. All patients were managed with an intravenous patient-controlled analgesia (IVPCA) system with morphine (i-Fusor; Debiotech, Lausanne, Switzerland), which was set to deliver morphine at 1 mg every 10 minutes as needed. Oral loxoprofen 60 mg was provided 3 times a day for the first 2 postoperative days (PODs). In cases in which oral intake was not possible, intravenous flurbiprofen 50 mg was given instead of oral loxoprofen. Postoperative VAS pain scores at rest were assessed by a blinded evaluator just after surgery, at 6 hours after surgery, in the morning and evening on POD 1, and in the morning and evening on POD 2. The success rate of femoral nerve block and SNB were assessed by pinprick tests just after surgery and at 6 hours after surgery. An 18-gauge needle was used at the anterior aspect of the thigh and the medial aspect of the lower leg for evaluation of femoral nerve block, and at the dorsal aspects of the foot and the lateral calf for SNB. The primary outcome was total morphine consumption for 48 hours after surgery (morphine administered just after surgery plus morphine delivered by the IVPCA system). The secondary outcomes were VAS pain scores at rest for 48 hours after surgery, incidence of postoperative nausea and vomiting, the maximum angle of continuous passive motion on POD 7, and the length of hospital stay.

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Statistical Analysis Total morphine consumption for 48 hours was predicted to be 13 mg in the single-injection SNB group based on a previous observational study.11 Thus, an equally divided sample of 50 was deemed sufficient for detection of a 50% reduction in morphine usage, with a 2-sided type 1 error of 5% and a power of at least 80%. A target sample size of 60 was established to increase the power. Analysis was performed on an intention-to-treat basis. Continuous variables were expressed as means with standard deviations, and compared by Student t test. Categorical variables were compared by χ2 test. Cumulative morphine consumption and VAS pain scores at rest were analyzed with a linear mixed model of repeated-measure design. Cumulative morphine consumption was analyzed from 5 fixed time points (0, 12, 24, 36, and 48 hours after surgery) and VAS pain score at rest from the 6 fixed time points as stated previously mentioned. Group factors, time factors, and the interaction of group factors and time factors were included in the analysis as fixed effects. Patient factors were included as random effects. Because the interaction effect of group and time factors was significant in the analysis of cumulative morphine consumption, a simple main effect test with Bonferroni correction was performed for comparison of cumulative morphine consumption between the 2 groups at each time point. All statistical analyses were conducted using SPSS ver.17.0 (IBM, Armonk, New York). P < 0.05 was considered to be significant.

RESULTS From September 2011 through March 2013, a total of 95 eligible patients were enrolled and 60 patients underwent randomization. A CONSORT flow diagram is shown in Figure 1.12 One patient in the single-injection SNB group did not receive the intervention because the sciatic nerve was not visible on ultrasound and we could not perform SNB and cannulation. In 1 patient in the continuous SNB group, accidental removal of the femoral nerve catheter occurred on POD 1. All 60 patients were included in the analysis, including these 2 patients. After the predetermined numbers of subjects was obtained, recruitment into the trial was ended. The baseline characteristics of the 2 groups were similar, except for the operated side in TKA (Table 1). The surgical and anesthetic properties of the groups were also similar (Table 2). In pinprick tests, the success rate of femoral nerve block was 100% in both groups and the success rate of SNB did not differ significantly between the 2 groups (70% in the continuous SNB, 80% in the single-injection SNB, P = 0.37). Total morphine consumption in the 48-hour period after surgery was significantly lower in the continuous SNB group than in the single-injection SNB group [4.9 (5.9) vs 9.7 (9.5) mg, P = 0.002] (Fig. 2). A trend toward decreased cumulative morphine consumption in the continuous SNB group emerged at 24 hours after surgery and the difference became significant at 36 hours. Visual analog scale pain scores at rest after surgery were also significantly lower in the continuous SNB group (P = 0.035) (Fig. 3). This was especially apparent on the morning and evening of POD 1. There were no differences between the groups in any other secondary outcomes (Table 3). Dorsal and planter flexion of the foot on the operated side was impaired after surgery in 12 (40%) patients in the continuous SNB group and in 2 (7%) in the single-injection SNB group. Of the 12 patients in the continuous SNB group, sciatic motor blockage resolved within 12 hours in 7 patients after stopping continuous SNB without the removal of the sciatic nerve catheter. In the other 5 patients, sciatic motor function © 2014 American Society of Regional Anesthesia and Pain Medicine

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Regional Anesthesia and Pain Medicine • Volume 39, Number 3, May-June 2014

Continuous Sciatic Nerve Block for TKA

FIGURE 1. Enrollment, randomization, and follow-up of the subjects.

was restored 24 to 48 hours after surgery with removal of the sciatic nerve catheter. For the 2 patients in the single-injection SNB group, motor blockage of the sciatic nerve was mild and resolved within 12 hours after surgery. Thus, none of the 60 patients

in the study had neurological sequelae that persisted beyond the 48-hour period after surgery. Any other complications related to the nerve blocks were not noted.

TABLE 1. Characteristics of the Subjects in the Continuous SNB and Single-Injection SNB Groups

The results of the study demonstrate that continuous SNB significantly reduces postoperative 48-hour morphine consumption after TKA and results in lower VAS pain scores at rest compared with single-injection SNB when added to continuous femoral nerve block. Wegener et al13 found that continuous SNB with continuous femoral nerve block reduced pain on

Continuous SNB Single-Injection SNB (n = 30) (n = 30) Age, y Female sex—no. (%) Body weight, kg Body mass index, kg/m2 Operated side—no. (%) Left Right ASA-PS—no. (%) 1 2 3 Serum creatinine, mg/dL Primary disease—no. (%) Osteoarthritis Rheumatoid arthritis

75 (6) 24 (80) 59 (9) 25.8 (3.7) 11 (37) 19 (63) 2 (7) 23 (77) 5 (17) 0.68 (0.19) 28 (93) 2 (7)

74 25 59 25.3

(6) (83) (10) (4.0)

DISCUSSION

TABLE 2. Procedural and Intraoperative Information in the Continuous SNB and Single-Injection SNB Groups

22 (73) 8 (27) 1 26 3 0.70

(3) (87) (10) (0.20)

26 (87) 4 (13)

Data are expressed as number (%) or mean (SD). ASA-PS indicates American Society of Anesthesiologists physical status.

© 2014 American Society of Regional Anesthesia and Pain Medicine

Operative duration, min Midazolam, mg Fentanyl, μg Blood loss, mL Crystalloid and autologous blood infusion, mL Urinary output, mL Total duration of tourniquet, min

Continuous SNB

Single-Injection SNB

161 (16) 1 (0) 45 (12) 254 (173) 1848 (421)

163 (19) 1 (0) 43 (12) 235 (139) 1793 (193)

350 (212) 92 (38)

287 (244) 96 (42)

Data are expressed as mean (SD).

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TABLE 3. Postoperative Outcome in the Continuous SNB and Single-Injection SNB Groups

PONV—no. (%) Maximum CPM angle on POD 7, degrees Hospital length of stay, d

Continuous SNB

Single-Injection SNB

P

5 (17) 82 (12)

6 (20) 86 (14)

0.73 0.30

25 (7)

23 (5)

0.19

Data are expressed as mean (SD) or number (%). CPM indicates continuous passive motion; PONV, postoperative nausea and vomiting.

FIGURE 2. Cumulative morphine consumption. Box plots and whiskers represent mean and standard deviation, respectively. Data were analyzed from 5 fixed points (0, 12, 24, 36, and 48 hours after surgery) using a linear mixed effects model. Because the interaction between group factors and time factors was significant, a simple main effect test with Bonferroni correction was used for comparison between the 2 groups at each time point. *Significant.

POD 1 compared with single-injection SNB with continuous femoral nerve block in a nonblinded trial, but failed to demonstrate a positive impact of SNB on the time to discharge readiness. Our results are consistent with these findings. In our study, differences between the continuous SNB and singleinjection SNB groups were apparent at 12 to 36 hours after surgery, which indicates that sciatic-related pain after TKA lasts for approximately 36 hours. Thus, addition of single-injection SNB with local anesthetics of low concentration may not have much effect after the patient returns to the ward. Considering the difference of total morphine consumption between the 2 groups was 5 mg, benefits of continuous SNB may seem modest. However, pain control itself was superior in the continuous SNB group. So, the difference of morphine consumption might be more if the same analgesic level could be accomplished by the opioid IVPCA system between the 2 groups.

FIGURE 3. VAS pain scores at rest after surgery. Box plots and whiskers represent mean and standard deviation, respectively. Data were analyzed from 6 time points (at just after surgery, 6 hours after surgery, on the morning and evening of POD 1, and on the morning and evening of POD 2) using a linear mixed effects model. The main effect of group factors was significant (P = 0.035), with an insignificant effect of interaction between group factors and time factors.

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Two concerns of performing SNB in TKA are often discussed.14,15 First, normal sciatic motor function may be required just after surgery to avoid masking of surgical injury to the common peroneal nerve. Peroneal nerve injury is a rare and potentially devastating complication of TKA, with an incidence of 0.3% to 4% after primary TKA.16 Sciatic nerve block, even with a local anesthetic at low concentration, often prevents dorsal and planter flexion of the foot, which makes it difficult to diagnose peroneal nerve injury. The other concern is that impaired sciatic motor function due to SNB may influence early aggressive rehabilitation. In this study, 40% of patients in the continuous SNB group and 7% in the single-injection SNB group presented with transient sciatic motor blockage. This high rate of sciatic motor blockage in continuous SNB group is a major disadvantage, which can make early ambulation difficult. Administration of continuous SNB at a rate of 5 mL/h of 0.2% ropivacaine was too high for maintenance of sciatic motor function. In the 7 patients who presented sciatic motor blockage but restored sciatic function after stopping continuous SNB without the removal of the sciatic nerve catheter, continuous SNB was restarted with a rate of 3 mL/h of 0.2% ropivacaine. None of them had a recurrence of impaired sciatic motor function at this rate. Although the need to perform SNB should be judged based on the individual case and each institution’s policy, we consider continuous SNB is worthwhile especially in the population whom the pain control by opioid IVPCA system is expected to be difficult. Those who have cognitive dysfunction or morbid obesity are examples of such patients. The total success rate of ultrasound-guided SNB evaluated by pinprick test in this study was 75%, which was lower than expected. Most of the patients were elderly women and an anterior approach was relatively difficult to perform without a nerve stimulator. Other approaches such as subgluteal or popliteal approach will be able to perform easier in this population. We also note that the significant difference in VAS pain scores at rest between the continuous SNB and single-injection SNB groups could be viewed as clinically insignificant because the mean scores in the single-injection SNB group were below 40. However, the distribution of VAS pain scores indicates that many patients in the single-injection SNB group experienced moderate pain. Although we planned to provide same analgesic level with patients in both groups by IVPCA system, we failed. This may be either because the loading dose of morphine lacked or because opioid IVPCA is not as effective as continuous SNB for analgesia after TKA. Our study has several limitations. First, it was performed as a single-center trial, which has significant inherent limitations in terms of external validity. Second, the mean hospital stay © 2014 American Society of Regional Anesthesia and Pain Medicine

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Regional Anesthesia and Pain Medicine • Volume 39, Number 3, May-June 2014

was much longer than that in other studies conducted in western countries, due to differences in health insurance systems and medical circumstances. Continuous SNB may have more impact on early rehabilitation in societies in which shorter hospital stays are promoted. Third, in assessing postoperative pain, we did not assess the origins of pain.17 Postoperative pain after TKA is associated with femoral, sciatic, obturator, and lateral femoral cutaneous nerves, and we chose to avoid this complexity in the study design. Fourth, we did not confirm the tip of sciatic nerve catheters by ultrasound because anterior approach of SNB was very deep and that is not practical. We believe the catheter was inserted into the compartment surrounding sciatic nerve, but the tip may be located at an inappropriate position. Within these limitations, we conclude that continuous SNB decreases morphine consumption and reduces VAS pain scores at rest in the 48-hour period after TKA compared with singleinjection SNB when added to continuous femoral nerve block. ACKNOWLEDGMENT The authors thank Prof T. Katayama, MT, PhD, Faculty of Health Sciences, Department of Medical Engineering, Himeji Dokkyo University, Hyogo, Japan, for statistical consultation. REFERENCES 1. Cram P, Lu X, Kates SL, Singh JA, Li Y, Wolf BR. Total knee arthroplasty volume, utilization, and outcomes among Medicare beneficiaries, 1991–2010. JAMA. 2012;308:1227–1236. 2. Gerbershagen HJ, Aduckathil S, van Wijck AJ, Peelen LM, Kalkman CJ, Meissner W. Pain intensity on the first day after surgery: a prospective cohort study comparing 179 surgical procedures. Anesthesiology. 2013;118:934–944. 3. Capdevila X, Barthelet Y, Biboulet P, Ryckwaert Y, Rubenovitch J, d’Athis F. Effects of perioperative analgesic technique on the surgical outcome and duration of rehabilitation after major knee surgery. Anesthesiology. 1999;91:8–15. 4. Chelly JE, Greger J, Gebhard R, et al. Continuous femoral blocks improve recovery and outcome of patients undergoing total knee arthroplasty. J Arthroplasty. 2001;16:436–445. 5. Singelyn FJ, Deyaert M, Joris D, Pendeville E, Gouverneur JM. Effects of intravenous patient-controlled analgesia with morphine, continuous epidural analgesia, and continuous three-in-one block on postoperative pain and knee rehabilitation after unilateral total knee arthroplasty. Anesth Analg. 1998;87:88–92.

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Continuous Sciatic Nerve Block for TKA

6. Paul JE, Arya A, Hurlburt L, et al. Femoral nerve block improves analgesia outcomes after total knee arthroplasty: a meta-analysis of randomized controlled trials. Anesthesiology. 2010;113:1144–1162. 7. Allen HW, Liu SS, Ware PD, Nairn CS, Owens BD. Peripheral nerve blocks improve analgesia after total knee replacement surgery. Anesth Analg. 1998;87:93–97. 8. Morin A, Kratz C, Eberhart L, et al. Postoperative analgesia and functional recovery after total-knee replacement: comparison of a continuous posterior lumbar plexus (psoas compartment) block, a continuous femoral nerve block, and the combination of a continuous femoral and sciatic nerve block. Reg Anesth Pain Med. 2005;30:434–445. 9. Pham Dang C, Gautheron E, Guilley J, et al. The value of adding sciatic block to continuous femoral block for analgesia after total knee replacement. Reg Anesth Pain Med. 2005;30:128–133. 10. Cappelleri G, Ghisi D, Fanelli A, Albertin A, Somalvico F, Aldegheri G. Does continuous sciatic nerve block improve postoperative analgesia and early rehabilitation after total knee arthroplasty? A prospective, randomized, double-blinded study. Reg Anesth Pain Med. 2011;36:489–492. 11. Sato K, Sai S, Shirai N, Adachi T. Ultrasound guided obturator versus sciatic nerve block in addition to continuous femoral nerve block for analgesia after total knee arthroplasty. Jpn Clin Med. 2011;2:29–34. 12. Schulz KF, Altman DG, Moher D, CONSORT Group. CONSORT 2010 statement: updated guidelines for reporting parallel group randomized trials. Ann Intern Med. 2010;152:726–732. 13. Wegener JT, van Ooij B, van Dijk CN, Hollmann MW, Preckel B, Stevens MF. Value of single-injection or continuous sciatic nerve block in addition to a continuous femoral nerve block in patients undergoing total knee arthroplasty: a prospective, randomized, controlled trial. Reg Anesth Pain Med. 2011;36:481–488. 14. Levesque S, Delbos A. Sciatic nerve block for total-knee replacement: is it really necessary in all patients?Reg Anesth Pain Med. 2005;30:410–411. 15. Ilfeld BM, Madison SJ. The sciatic nerve and knee arthroplasty: to block, or not to block—that is the question. Reg Anesth Pain Med. 2011;36:421–423. 16. Zywiel MG, Mont MA, McGrath MS, Ulrich SD, Bonutti PM, Bhave A. Peroneal nerve dysfunction after total knee arthroplasty: characterization and treatment. J Arthroplasty. 2011;26:379–385. 17. Abdallah FW, Brull R. Sciatic nerve block for analgesia after total knee arthroplasty: the jury is still out. Reg Anesth Pain Med. 2012;37:122–123; author reply 123–124.

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Continuous versus single-injection sciatic nerve block added to continuous femoral nerve block for analgesia after total knee arthroplasty: a prospective, randomized, double-blind study.

The benefit of adding sciatic nerve block (SNB) to femoral nerve block to improve analgesia after total knee arthroplasty (TKA) is uncertain. We hypot...
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