Block of the Articular Branches of the Femoral Nerve improves Early Pain Control Following Total Hip Arthroplasty

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1 /jp-journals Michael Tanzer et al ORIGINAL ARTICLE Block of the Articular Branches of the Femoral Nerve improves Early Pain Control Following Total Hip Arthroplasty Michael Tanzer, Riccardo Taddei, Erik Arbeid, Cedrick Zaouter, Thomas M Hemmerling ABSTRACT We assessed the effectiveness of a continuous local anaesthesia block of the articular branches of the femoral nerve (ABFN) for the treatment of early postoperative pain in 74 patients undergoing total hip anthroplasty (THA). Postoperative analgesia was provided by patient-controlled analgesia (PCA) in 20 patients (PCA group), or by continuous block of ABFN in addition to PCA in 54 patients (PCA + ABFN group). Combining standard PCA morphine and ABFN block decreased the morphine consumption in the postanaesthesia care unit (PACU) by 56% and reduced the time in the PACU by 31%. Twenty-four hours after surgery, continuous block of the ABFN decreased morphine consumption by 44% and pain scores by 32% at rest and 19% with activities. The addition of a block of the ABFN is an effective method of pain treatment immediately following THA because it provides excellent pain control while enabling early mobilisation without impairing motor function. Keywords: Hip arthroplasty, Pain, Anaesthesia, Nerve block. How to cite this article: Tanzer M, Taddei R, Arbeid E, Zaouter C, Hemmerling TM. Block of the Articular Branches of the Femoral Nerve improves Early Pain Control Following Total Hip Arthroplasty. Int J Periop Ultrasound Appl Technol 2012; 1(3): Source of support: Nil Conflict of interest: None declared INTRODUCTION In the United States alone, 16% of the US population will be 65 years of age or older. 1 In a general population with increased demands on mobility at old age, total hip arthroplasty (THA) has become a common surgery in the elderly with low-risk of mortality. 1 Almost 300,000 patients undergo hip replacement per year in the United States. 2 Hip arthroplasty can be associated with significant postoperative pain. 21 Whereas intraoperative anaesthesia using spinal anaesthesia is preferred in the elderly and patients with comorbidities, analgesia following THA is commonly based on opioids in various forms of administration, such as patient-controlled analgesia (PCA), or epidural analgesia. Unfortunately, both techniques are prone to significant side effects. 8 Opioid-based analgesia is associated with the risk of sedation, vomiting, nausea or constipation impairing postoperative recovery and mobilisation. The use of epidural analgesia is limited by increasingly aggressive thromboprophylaxis protocols and its negative effect on early mobilisation Pain after THA comes from superficial and deep structures. Whereas the superficial pain can easily be treated using local infiltration with local anaesthetics, blockage of deep pain, particularly from the hip capsule, is more difficult. Isolated nerve blocks, such as the femoral nerve or combined blocks, such as femoral, obturator and lateral cutaneous nerve, might theoretically provide pain relief, but they also limit muscular force in the respective motor areas, thus limiting early mobilisation and increasing the risk of patients falling. In a cadaveric anatomic study, Birnbaum et al determined that the sensory innervation of the anterior hip capsule was mainly articular branches from the femoral nerve (ABFN). 4 We previously reported on a technique to block the ABFN and our preliminary clinical results suggested further evaluation was warranted. 13 The aim of this study was to update our understanding of the effectiveness of the ABFN block on early pain control following THA by comparing post-operative pain and morphine consumption in the first 24 hours following THA in patients using either standard opioid-based analgesia (PCA) or PCA with the addition of a continuous block of the ABFN. MATERIALS AND METHODS Seventy-four patients were included in this prospective audit after having obtained approval by the institutional review board. All patients underwent a cementless THA by a single orthopaedic surgeon using a posterior approach to the hip. There were no changes in surgical technique or THA patient care protocols during the study period. All postoperative nerve blocks were carried out by a single anaesthesiologist, with extensive experience in peripheral nerve block techniques using ultrasound guidance. Routine anaesthetic monitoring was conducted in the operating room using noninvasive blood pressure, peripheral oxygen saturation and continuous 5-lead electrocardiography. All patients received spinal anaesthesia performed in standard fashion (L2-L3) using 10 to 15 mg of isobaric bupivacaine 0.5%. In the postanaesthesia care unit (PACU), pain management was provided either using PCA, using morphine (bolus: 1 mg; lockout: 7 minutes) (PCA group) or PCA and a continuous block of the ABFN (PCA + ABFN group). The PCA group consisted of 20 consecutive patients that underwent THA immediately prior to July 2009 and the PCA + ABFN

2 IJPUT Block of the Articular Branches of the Femoral Nerve improves Early Pain Control Following Total Hip Arthroplasty group consisted of 54 consecutive patients that had their THA after July 2009, when the technique for ABFN was developed. For those patients in the PCA + ABFN group, imaging of the inguinal region was performed by using a linear 10 to 5 MHz ultrasound probe (SonoSite Inc, Seattle, USA). First, the femoral artery was visualized in short axis, the probe was then moved laterally for 3 to 4 cm along the sartorius muscle, 3 to 4 cm inferior to the inguinal ligament. The ABFN was then identified as a white triangular to ovalshaped area, usually an area of 0.5 to 1 cm between the sartorius muscle and the rectus femoris muscle (Figs 1A and B). After sterile preparation, a 4 cm long 18 gauge Tuohy needle was placed under ultrasound guidance (outof-plane technique) targeting the nerve and 10 ml of lidocaine 2% injected through the needle visualising the ABFN surrounded by the local anaesthetic and lifting the sartorius muscle. A 20 G catheter was placed, inserting 2 to 3 cm within the nerve sheath, tunneled and secured via transparent adhesive tape. Ropivacaine 2% was continuously administered at 6 to 8 ml/h for 24 hours. On average, the ABFN was found to be located 3 ± 0.6 cm deep to the skin surface, 3.6 ± 0.7 cm lateral to the femoral artery and 3.5 ± 0.7 cm distal to the lower border of the inguinal ligament. Fig. 1A: Schematic of the proximal thigh demonstrating the location of the ABFN relative to the surrounding muscles and femoral neurovascular structures Fig. 1B: Ultrasound image of the ABFN and adjacent muscles After the placement of the catheter, the patients were monitored in the PACU until complete return of motor and sensory function in the upper thigh. Pain scores were assessed using a visual pain score (VAS) (0 to 10, with 0 being no pain at all and 10 being the worst imaginable pain) and recorded at the time of discharge from the PACU, and at 24 hours after surgery. Morphine consumption was recorded at 2 hour intervals until 24 hours after surgery. Discharge criteria from the PACU were a return of normal motor and sensory function and VAS < 4. Patient data including gender, age, weight, height and the pre-operative classification of the American Society of Anaesthesiologists were compared using Mann-Whitney rank sum test for continuous and Fisher test for categorical data. Pain assessment using visual analogue score (VAS, 0 = no pain, 10 = maximum imaginable pain) was evaluated at rest at the time of discharge from the PACU and at rest and at mobilisation 24 hours after surgery and compared via Mann- Whitney rank sum test. The total morphine consumption within 12 and 24 hours were compared using Mann-Whitney rank sum test. A value p < 0.05 was considered as showing a statistically significant difference between the two groups. RESULTS Patient characteristics were not different between the two groups (Table 1). At the time of discharge from PACU, motor and sensory functions were completely restored in all patients. There was a significant difference in the time patients required to stay in the PACU with the PCA + ABFN group requiring on average 97 minutes less time meeting the discharge criteria than the PCA group (Table 2). While in the PACU, the PCA group required significantly more morphine to control their pain than the patients with an ABFN block (Table 2). The PCA patients used an average of 4.9 mg of morphine more than the PCA + ABFN group. Morphine consumption 12 and 24 hours after the surgery was significantly lower in the PCA + ABFN group than in the patients who only had a PCA (Graph 1). The PCA patients used an average of 15 mg of morphine more than the PCA + ABFN group at 24 hours postoperatively. When tested 24 hours after surgery, all patients could mobilise the leg of the surgical site, with evidence of sensory or motor impairment from the ABFN block was noted. The patients in the PCA + ABFN group were found to have significantly less pain both at rest and with movement than the patients who had only a PCA (Graph 2). DISCUSSION Patients undergoing hip arthroplasty are pre-dominantly elderly patients and post-operative analgesia is based on intravenous opioids or epidural analgesia. 22,23 Although patient controlled administration of opioids produces better International Journal of Perioperative Ultrasound and Applied Technologies, September-December 2012;1(3):

3 Michael Tanzer et al pain relief than conventional intramuscular opioid therapy, 16,24 it is less efficient for pain due to movement and ineffective in preventing reflex spasms of the quadriceps muscle, which are frequent after hip arthroplasty. 5 Epidural analgesia decreases pain with very little sedation but is associated with a greater incidence of urinary retention, pruritus and hypotension. 8 A common problem of lower lumbar epidural analgesia is also the significant concomitant motor blockade and the significant risk of epidural haematoma. 6 The aim of this study was to compare postoperative pain control and morphine consumption in the first 24 hours following THA in patients using either standard opioid-based analgesia (PCA) or PCA with the addition of a continuous block of the ABFN. Blocking the sensory innervation of the anterior hip capsule, by blocking the ABFN is an effective method of pain treatment Table 1: Patient data and preoperative risk assessment according to classification by the American Society of Anaesthesiologists (ASA) PCA group PCA + ABFN p- (n = 20) group (n = 54) value Gender (female/male) 12/8 26/28 NS Age (years) 63 (14) 69 (11) NS Weight (kg) 81 (15) 78 (11) NS Height (cm) 168 (10) 165 (10) NS ASA I/II/III 6/10/04 14/23/17 NS NS: Nonsignificant; Data as mean (standard deviation) immediately following THA. We found that combining standard PCA morphine and ABFN block decreased the morphine consumption in the PACU by 56% and reduced the time in the PACU by 31%. Continuous block of the ABFN resulted in a decrease in pain scores of 32% at rest, 19% with activities and morphine consumption by 44% at 24 hours after THA surgery. The ABFN block combines excellent pain control without impairment of motor function enabling early mobilisation. There are some limitations to this study, none of which have substantive impact on the results or conclusions. Firstly, this is a cohort study with only time-related randomisation. However, there was no change in operating technique or technique in spinal analgesia throughout the study period. The pain assessment and assessment of morphine consumption relied on standard chart review. However, the nurses who took care of pain assessment and morphine administration in the PACU were not involved in this study but performed their routine duties. Whether or not these small but significant decrease in the visual analogue assessment of pain at 24 hours is clinically relevant is unknown. Several authors have advocated that the use of lumbar plexus block with or without sciatic nerve block, 7,14 femoral lateral nerve block 18 and fascia iliaca block 25 following hip Graph 1: The morphine consumption used by the PCA group (black) and the ABFN and PCA group (grey) during their stay in the PACU, and at 12 and 24 hours after surgery. Data presented as means with standard deviation (bars) Graph 2: The VAS in the PCA group (black) and the ABFN and PCA group (grey) 24 hours postoperatively, both at rest and with movement Table 2: Time, morphine consumption and pain scores VAS in post-operative care unit (PACU) PCA group (n = 20) PCA + ABFN group (n = 54) p-value Time in PACU (min) 315 (250) 218 (87) 0.014* First VAS score (before the block) 1.6 (2.7) 1.0 (2.0) NS Maximum VAS 5.3 (2.4) 4.6 (2.8) NS VAS score at discharge 2.7 (2.1) 2.1 (1.5) NS Morphine consumption (mg) 9.0 (6.8) 4.1 (6.0) 0.004* p < 0.05 showing significant difference; Data presented as means (standard deviation); NS: Nonsignificant 96

4 IJPUT Block of the Articular Branches of the Femoral Nerve improves Early Pain Control Following Total Hip Arthroplasty arthroplasty. Two studies showed that posterior lumbar plexus block did cause significantly better analgesia than placebo, 3,26 whereas femoral nerve block was not able to provide any significant pain relief. 3,10 Despite these advantages, the placement of lumbar plexus or sciatic nerve blocks requires advanced regional anaesthesia skills. They can have serious potential side effects, including patients falls and injury, 15 nerve injury, 21 neuraxial block, systemic absorption of local anaesthetic and retroperitoneal haematoma. 19,20 The combination of spinal local anaesthetic and spinal opioid is also used 2,9,11,12,17 to improve pain treatment after hip arthroplasty. However, the administration of opioids, especially morphine, is associated with the significant risk for complications in the increasingly elderly patient population, such as pruritus, vomiting, failure to void or respiratory depression. It was long believed that the ventral hip joint was innervated by articular branches of the obturator nerve. However, Birnbaum et al showed 4 that the anterior hip joint capsule is mainly innervated by articular branches of the femoral nerve. It is therefore appropriate to search for local anaesthesia treatment of these articular branches, the reasoning behind our approach. The ABFN can be located between the sartorius muscle and the rectus femoris muscle; its localisation via ultrasound can be regarded as of similar difficulty as locating the sciatic nerve in the gluteal area. This study clearly demonstrates the effectiveness of a continuous block of the ABFN following THA. 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5 Michael Tanzer et al 25. Stevens M, Harrison G, McGrail M. A modified fascia iliaca compartment block has significant morphine-sparing effect after total hip arthroplasty. Anaesth Intensive Care 2007;35: Stevens RD, Van Gessel E, Flory N, Fournier R, Gamulin Z. Lumbar plexus block reduces pain and blood loss associated with total hip arthroplasty. Anesthesiology 2000 Jul;93: ABOUT THE AUTHORS Michael Tanzer Department of Surgery, Division of Orthopaedic Surgery, McGill University, Montreal, Canada Correspondence Address: McGill University Health Centre, 1650 Cedar, Avenue No. B5159, Montreal, Quebec, H3G 1A4, Canada michael.tanzer@mcgill.ca Riccardo Taddei Erik Arbeid Department of Anaesthesiology, McGill University, Montreal Canada Cedrick Zaouter Thomas M Hemmerling 98