The Knee 20 (2013) 324–327
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The Knee
Pain control after primary total knee replacement. A prospective randomised controlled trial of local infiltration versus single shot femoral nerve block Anam Ashraf a, Videsh V. Raut b, Stephen J. Canty b, George J. McLauchlan b,⁎ a b
Manchester Medical School, The University of Manchester, Stopford Building, Oxford Road, Manchester, M13 9PT, UK Lancashire Teaching Hospitals NHS Trust, Sharoe Green Lane, Fulwood, Preston, Lancs, PR4 0ND, UK
a r t i c l e
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Article history: Received 3 January 2013 Received in revised form 29 March 2013 Accepted 8 April 2013 Keywords: Knee arthroplasty RCT Pain Local infiltration Nerve block
a b s t r a c t Background: We report a prospective blinded randomised trial of local infiltration versus femoral nerve block in patients undergoing primary total knee replacement (TKR), in accordance with the CONSORT statement 2010. Methods: Fifty patients in a teaching hospital were consented for the study. The study arms were intraoperative local anaesthesia (150 ml 0.2% ropivacaine/1 ml 1:1000 adrenaline/30 mg ketolorac) and femoral nerve block (30 ml 0.2% ropivacaine) with a primary outcome of pain score at 4 h post operatively. Secondary outcomes were pain at 2 h, pain scores before and after physiotherapy on day one, total opiate administered, time to physiotherapy goals and length of stay. Randomisation was by sealed envelope. The assessor was blinded and the patients partially blinded to the intervention. Results: Ten patients were excluded, eight before randomisation. The trial is complete. Forty patients were analysed for the primary outcome measure. The local infiltration group had significantly lower pain scores at 4 h post-operatively; mean [SD] score 2.1 [2.6] versus 6.8 [3.2], p b 0.00001 and on post-operative day one prior to physiotherapy; mean score 2.4 [2.3] versus 4.4 [2.3], p b 0.05. Total opiate use was also significantly lower in the local infiltration group; mean total 115 [50.3] mg versus 176.5 [103.5] mg, p b 0.01. There was no difference in any other outcome. There were no harms as a result of either intervention. Conclusion: Intraoperative local infiltration gives superior pain relief compared to single shot femoral nerve block over the first 24 h following primary TKR and minimises post-operative opiate use. © 2013 Elsevier B.V. All rights reserved.
1. Introduction TKR is a painful procedure. Studies have shown that reducing postoperative pain reduces length of stay [2,3]. However there are a large variety of modalities employed and a limited evidence base upon which to base any conclusions as to the optimum [1]. Femoral nerve block (FNB) has been described as an effective method for managing pain following TKR [3] and has been standard practice at our institution for the past five years. FNB leads to an improvement in pain control on the day of surgery as well as a reduction in opioid analgesia and antiemetic use post operatively [4]. FNB has been found to facilitate early ambulation and range of knee movement post-operatively and has been hypothesised to lead to a decrease in the incidence of deep vein thrombosis and pulmonary emboli in patients who have undergone TKR. Further to this, administration of FNB has led to a reduced hospital stay when compared with patients in a placebo group injected with saline [3].
⁎ Corresponding author. Tel.: +44 1772 522479; fax: +44 1772 522333. E-mail address:
[email protected] (G.J. McLauchlan). 0968-0160/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.knee.2013.04.009
However, the use of FNB has its own costs, with regards to equipment and training, particularly if an ultrasound machine is used to ensure correct placement of the infiltrate. The procedure also prolongs the time spent in the anaesthetic room. An unpleasant numbness of a large portion of the lower extremity is a common experience following femoral nerve block administration [5]. Other adverse events include decreased quadriceps function in the early post-operative period, which can result in incidents of falls. A study of 1018 patients reported 12 incidents of falls following FNB for TKR, with three patients being re-operated on as a result of this. A further consequence of weakened quadriceps is the hindrance to attempts of early rehabilitative physiotherapy. Cases of post-operative femoral neuritis which could be secondary to an FNB have also been documented, as well as, rarely, femoral nerve palsy [6]. A paper looking at major complications from regional anaesthesia in France documented that more than half of patients documented to sustain nerve injury, reported residual symptoms six months following the anaesthetic incident [7]. In recent years there has been more use of intra-articular infiltration using a variety of constituents in controlling post-operative pain. A number of studies have found this technique to be safe and effective in comparison to a placebo [8–11] and a number of authors suggest that it is superior to other interventions [5,12]. A recent meta-analysis
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summarised the evidence [1]. To our knowledge the technique of LIA has never been directly compared to single shot FNB. The present study was designed to compare these two interventions. 2. Patients and methods The study was approved by the regional ethics committee on 15 March 2012 (ref: 12/NW/0153). It was registered with controlledtrials.com, identifier: ISRCTN42045594. All patients scheduled to undergo primary TKR under the care of three consultants were approached and asked to take part in the study. All implants were a cemented Nexgen CR. The inclusion criterion was any patient undergoing a primary TKR. Exclusion criteria included patients that lacked capacity to consent to the study, patients who were unwilling to consent and patients who had a known allergy, intolerance or previous reaction to any of the drugs being administered. Patients who were unable to have a standardised spinal anaesthetic were also excluded. Randomisation was conducted using a series of consecutively numbered sealed envelopes. The primary investigator who recorded the various outcomes was blinded. The patients were partially blinded in that although they could know in the anaesthetic room whether or not they had a femoral block, they were also sedated and in practice had little recollection of events. The ward staff caring for them had no knowledge of which intervention was performed. All patients in the study were given a standard spinal anaesthesia which consisted of heavy bupivacaine 0.5% without any opiate. Sedation with a propofol infusion was administered. Dexamethasone and ondansetron were administered as anti-emetics. Post-operative antiemetics prescribed were ondansetron and cyclizine as per the patients' requirements. Once spinal anaesthesia was confirmed and the propofol infusion started the envelope was opened by the operating surgeon who confirmed whether the patient was to have an ultrasound guided femoral nerve block in the anaesthetic room or local anaesthesia in theatre. Statistical advice was that to show a difference of one point on a 10 cm VAS with a power of 80%, 20 patients would need to be recruited to each group. Previous studies have suggested that a change in pain score of 1 to 1.3 points is clinically significant [5,13]. As the data from this study were thought likely not to be normally distributed the Mann–Whitney U test was used for analysis. Tests were performed using Stats Direct statistical software licensed to our institution. The study arms were as follows: Group 1 (FNB): Ultrasound guided FNB was administered in the anaesthetic room. This single shot femoral nerve block contained 30 ml of 0.2% ropivacaine. Group 2 (LIA): The protocol for administration was placed in the operating theatre for all surgeons to follow and gave instructions to infiltrate into all layers of the knee joint. The drugs infiltrated into the joint comprised: ➢ 150 ml 0.2% ropivacaine ➢ 1 ml 1:1000 adrenaline ➢ 30 mg ketolorac Prior to implantation of the components, the posterior capsule was infiltrated with the mixture. The synovium over the posterior cruciate ligament (PCL) in the notch as well as the medial and lateral collateral areas were infiltrated. Following implantation of the new joint further injection into the capsule and over the anterior aspect was conducted. The fat pad, which is richly innervated was also injected. Further infiltration was carried out subcutaneously prior to skin closure, and was followed by injection into the joint as a bolus of any residual mixture, after application of the dressing but prior to putting on the bandages. Fifty sealed envelopes were prepared. The
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study was stopped when 42 patients had been randomised as the primary investigator was no longer attached to the unit. There were 22 patients in group one (FNB) and 20 patients in group two (LIA). Two patients were not analysed as the study protocol was broken following randomisation. One patient randomised to receive intraoperative infiltration was given a FNB and one patient randomised to intraoperative infiltration had the surgery postponed when an instrument tray was found to be contaminated. The primary outcome measure was post operative pain, measured on a 10 cm VAS at 4 h post-operatively. Secondary outcome measures were pain at 2 h, pain at rest and after physiotherapy on post operative day one, time to achieve physiotherapy goals (flexion to 70 degrees and safe stair climbing), total opiate use and length of stay. All patients were prescribed analgesia as required by their pain level. This included PCA as well as oxycodone, IV paracetomol and non-steroidal anti inflammatory drugs (NSAIDs), if tolerated and not contraindicated. The total amount of opiate analgesia consumed by each of the patients during their stay in hospital post operatively was calculated. Oral oxycodone was converted to IV oxycodone by dividing by 1.5. The ratio for conversion of IV oxycodone to IV morphine is 1:1 and thus a total dose of IV morphine was calculated. A CONSORT flowchart is shown in Fig. 1. 3. Results Fifty patients were initially consented for the study. Two patients were excluded after randomisation as described above. Eight patients were excluded before randomisation. Four required a general anaesthetic, two changed their mind, one had diamorphine put into the spinal and one anaesthetist refused to take part. The primary outcome measure analysed was pain score at 4 h post operatively. The mean (SD) pain score was 6.8 (3.2) for the FNB group and 2.1 (2.6) for the LIA group. This difference of 4.7 points was statistically significant, p b 0.01 (95% CI 2.8–7.5). The mean 2 h pain scores were 3.6 (3.2) in the FNB group and 1.6 (2.4) in the LIA group. This difference of 1.6 points did not reach statistical significance, p = 0.08 (95% CI 0 to 3.9). The mean (SD) pain score before physiotherapy on day one post operatively was 2.9 (2.3) in the LIA group compared to 4.4 (2.3) in the FNB group, p b 0.05 (95% CI 0.2–3.2). The mean pain scores following physiotherapy were not statistically significant between the two groups, p = 0.07 (95% CI −0.1 to 3.3). The mean equivalent total IV morphine dose consumed was 115 (50.3) mg in the LIA group and 176.5 (103.2) mg in the FNB group. This difference was statistically significant, p = 0.01 (95% CI 15–120). The mean (SD) time taken to achieve knee flexion to 70° was 3.1 (1.3) days in the LIA group and 2.6 (1.0) days in the FNB group. This difference did not reach statistical significance, p = 0.18 (95% CI 0 to 1). The second physiotherapy goal assessed was number of days to achieve safety on stairs with crutches. As a number of patients live in single storey accommodation, this is not always objectively measured and patients are deemed fit for discharge without safety on stairs being assessed. There was no statistical difference between the means for the two groups; however, the sample size was considerably reduced due to data being unavailable for a number of patients not requiring the ability to climb stairs with crutches. There was no statistical difference between mean (SD) length of stay between the two groups; 5.4 (1.2) in the LIA group and 5.7 (1.3) in the FNB group, p = 0.52 (95% CI −1 to 1).
4. Discussion Optimising control of post-operative pain after TKR allows early mobilisation and reduces hospital stay [2,3]. A variety of means are used, often in combination. A recent meta-analysis has shown the benefit of local infiltration of anaesthetic in conjunction with femoral nerve block [1]. We are not aware of a study that has directly compared single shot femoral nerve block with local infiltration. Our local policy was to give a single shot femoral nerve block at induction followed by PCA, oxycontin, NSAID and paracetamol as required. We have as a unit preferred not to have prolonged indwelling catheters because of concerns about quadriceps weakness limiting rehabilitation. Similarly we prefer not to leave catheters within the joint for a prolonged period as an infection risk.
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Enrollment
Assessed for eligibility (n= 50)
Excluded (n= 8) Required GA (n= 4) Declined to participate (n= 2) Other reasons (n= 2)
Randomized (n= 42)
Allocation Allocated to FNB (n= 22)
Allocated to local infiltration (n=20 ) Received allocated intervention (n= 19 )
Received allocated intervention (n= 21)
Did not receive allocated intervention (n= 1 )
Did not receive allocated intervention (n= 1)
Follow-Up Lost to follow-up (give reasons) (n= 0 )
Lost to follow-up (give reasons) (n= 0)
Discontinued intervention (give reasons) (n= 0)
Discontinued intervention (give reasons) (n= 0)
Analysis Analysed (n= 19) Excluded from analysis (n= 1)
Analysed (n= 21) Excluded from analysis (n= 1 )
Fig. 1. CONSORT 2010 flow diagram for pain after TKR study.
Our primary outcome measure was pain at 4 h post operation. We felt that this was a reasonable time period after which the effects of the spinal anaesthetic would have sufficiently worn off. The fact that the pain scores changed markedly between the 2 and 4 h stage would support this hypothesis. This study found a significant difference in the pain scores taken at 4 h, the pain scores before physiotherapy on the first post-operative day, as well as the overall opiate use. No differences were observed in the pain after physiotherapy or the time to achieve physiotherapy goals. The median length of stay in the LIA group was one day shorter but this did not reach statistical significance. Others have examined pain in the immediate post-operative period, albeit with continuous methods of analgesia. Toftdahl et al. [12] studied continuous femoral nerve block versus peri- and intraarticular infiltration via a catheter. The authors found significantly lower pain scores during activity on post-operative day one in the LIA group. However, Affas et al. [5] found contradictory results when looking at continuous femoral nerve block versus LIA. Pain assessments were conducted on an hourly basis over the first 24 h post-operatively. The mean pain at rest was found to be marginally lower in the local infiltration analgesia group (1.6) compared to the femoral nerve block (2.2). Additional analysis of the results concluded that one of 20 patients in the local infiltration analgesia group reported a pain intensity of more than seven upon movement, compared to seven out of 19 patients in the femoral block group (p = 0.04). The authors tentatively concluded that local infiltration analgesia could possibly be considered superior to femoral block owing to the fact that it is cheaper and easier to perform but stated that both LIA and femoral block provide good analgesia after TKA. Our study found that LIA led to a significant reduction in total opiate usage compared to single shot femoral nerve block. Kerr and
Kohan [9] found that two-thirds of the 325 patients who received LIA did not require any morphine for post-operative pain relief. Further to this Essving et al. [10] also found lower median morphine usage in patients administered LIA in their study. Toftdahl et al. [12] stated that the patients who received local infiltration analgesia had a reduced demand for opioids on the first day post operatively. However, Affas et al. [5] reported total morphine demand per kg of body weight to be similar between the two groups in their study. The speed with which patients regain mobility has been looked at in a number of studies. Kerr and Kohan [9] reported that the majority of patients could mobilise with assistance and walk 5 to 6 h post-surgery. Furthermore, they regained independent mobility fully 13–22 h after surgery. Toftdahl et al. [12] found no difference in pain scores and opiate consumption but did have positive findings with regards to rehabilitation of patients. The findings from their study concluded that a greater number of patients could walk 3 m on the first post-operative in the local infiltration group. This was the case for 29 of 39 patients who underwent local infiltration, in comparison to seven of 37 patients who were randomised to continuous femoral nerve block. Our study looked specifically at time to achieve 70° of knee flexion and safety on stairs with crutches. Although important locally as a measure of progress these were not monitored in the above studies. Neither of these outcomes were significantly different between the two groups in this study. The current study did not find any significant difference in the mean or median hospital stay between the two study groups. Kerr and Kohan [9] measured length of hospital stay as a primary outcome measure and found that 71% of the 325 patients in the study were discharged following a single overnight stay in hospital when given local infiltration analgesia. Essving et al. [10] concluded that the
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time taken to fulfil discharge criteria was shorter in the LIA group than the placebo group. A recent paper from the Oxford group suggests that 20 ml bolus of 0.5% bupivacaine given on the first post operative day was sufficient to have this effect in patients undergoing primary unicompartmental knee replacement [14]. In summary our study has demonstrated that if surgeons prefer to use a single shot modality of peri-operative analgesia then local infiltration of an anaesthetic mixture gives better early pain relief and use of opiate analgesia is lower, compared to a femoral nerve block. Time to achieve physiotherapy discharge goals was not reduced and on the numbers involved in this study length of stay was not affected, although the study was almost certainly underpowered in this regard. Conflict of interest statement None of the authors nor their institutions have any conflicts of interest in relation to the above study. Acknowledgements The authors acknowledge the statistical advice of Dr Anna Hart of the University of Lancaster. References [1] Gibbs DMR, Green TP, Esler CN. The local infiltration of analgesia following total knee replacement: a review of the current literature. JBJS Br 2012;94-B:1154–9. [2] Duellnan TJ, Gaffigan C, Milbrandt JC, Allan DG. Multi-modal pre-emptive analgesia decreases the length of hospital stay following total joint arthroplasty. Orthopaedics 2009;32(3):167.
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[3] Wang H, Boctor B, Verner J. The effect of single-injection femoral nerve block on rehabilitation and length of hospital stay after total knee replacement. Reg Anesth Pain Med 2002;27:139–44. [4] Duarte VM, Fallis WM, Slonowsky D, Kwarteng K, Yeung CKL. Effectiveness of femoral nerve blockade for pain control after total knee arthroplasty. J Perianesth Nurs 2006;21(5):311–6. [5] Affas F, Nygards EB, Stiller CO, Wretenberg P, Olofsson C. Pain control after total knee arthroplasty: a randomized trial comparing local infiltration anesthesia and continuous femoral block. Acta Orthop 2011;82(4):441–7. [6] Sharma S, Iorio R, Specht LM, Davies-Lepie S, Healy WL. Complications of femoral nerve block for total knee arthroplasty. Clin Orthop Relat Res 2010;468(1): 135–40. [7] Auroy Y, Benhamou D, Bargues L, Ecoffey C, Falissard B, Mercier FJ, et al. Major complications of regional anesthesia in France: the SOS Regional Anesthesia Hotline Service. Anesthesiology 2002;97:1274–80. [8] Andersen LO, Husted H, Otte KS, Kristensen BB, Kehlet H. High-volume infiltration analgesia in total knee arthroplasty: a randomized, double-blind, placebo-controlled trial. Acta Anaesthesiol Scand 2008;52(10):1331–5. [9] Kerr DR, Kohan L. Local infiltration analgesia: a technique for the control of acute postoperative pain following knee and hip surgery: a case study of 325 patients. Acta Orthop 2008;79(2):174–83. [10] Essving P, Axelsson K, Kjellberg J, Wallgren O, Gupta A, Lundin A. Reduced morphine consumption and pain intensity with local infiltration analgesia (LIA) following total knee arthroplasty. Acta Orthop 2010;81(3):354–60. [11] Lombardi AV, Berend KR, Mallory TH, Dodds KL, Adams JB. Soft tissue and intraarticular injection of bupivacaine, epinephrine, and morphine has a beneficial effect after total knee arthroplasty. Clin Orthop 2004;428:125–30. [12] Toftdahl K, Nikolajsen L, Haraldsted V, Madsen F, Tonnesen EK, Soballe K. Comparison of peri- and intraarticular analgesia with femoral nerve block after total knee arthroplasty: a randomized clinical trial. Acta Orthop 2007;78(2):172–9. [13] Gallagher EJ, Liebman M, Bijur PE. Prospective validation of clinically important changes in pain severity measured on a visual analog scale. Emerg Med 2001;38(6): 633–8. [14] Weston-Simons JS, Pandit H, Haliker V, Dodd CAF, Popat MT, Murray DW. Intra-articular local anaesthetic on the day after surgery improves pain and patient satisfaction after UKR. Knee 2012;19(4):352–5.