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Effect of combining peri-hamstring injection or anterior obturator nerve block on the analgesic efficacy of adductor canal block for anterior cruciate ligament reconstruction: a randomised controlled trial
British Journal of Anaesthesia, xxx (xxx): xxx (xxxx) doi: 10.1016/j.bja.2019.11.032 Advance Access Publication Date: xxx Clinical Investigation
CLINICAL INVESTIGATION
Effect of combining peri-hamstring injection or anterior obturator nerve block on the analgesic efficacy of adductor canal block for anterior cruciate ligament reconstruction: a randomised controlled trial David F. Johnston1, Rakesh V. Sondekoppam2,*, Vishal Uppal3, Robert Litchfield4, Robert Giffin4 and Sugantha Ganapathy5 1
Department of Anaesthesia and Perioperative Medicine, Royal Victoria Hospital, Belfast Trust, Belfast, UK, 2Department
of Anesthesia, University of Iowa, Iowa City, IA, USA, 3Department of Anesthesia, University of Dalhousie, Halifax, NS, Canada, 4Department of Orthopedic Surgery, London Health Sciences Centre, Western University, London, ON, Canada and 5Department of Anesthesia and Perioperative Medicine, London Health Sciences Centre, Western University, London, ON, Canada *Corresponding author. E-mail: [email protected]
Abstract Background: Pain after anterior cruciate ligament reconstruction (ACLR) with autologous hamstring graft can be attributed to both arthroscopic surgery and the graft donor site. This study investigated whether donor site pain control was superior with the addition of either peri-hamstring injection or anterior division obturator nerve block in comparison with adductor canal block (ACB) alone. Methods: Patients scheduled to undergo knee arthroscopy with ACLR using a graft from the ipsilateral hamstring were randomised to one of three groups. All patients received ACB and multimodal analgesia. Subjects in Group H received peri-hamstring local anaesthetic injection while subjects in Group O received an anterior division of the obturator nerve block, and subjects in Group C served as a control group (ACB alone). Results: In 105 subjects undergoing ACLR, there was no significant difference between groups H, O, and C for the primary outcome of pain on movement as assessed by numerical rating scale (NRS) on knee flexion at 2 h after operation (P¼0.11). There was no difference in NRS at any time point in the first 48 h after operation, nor was there a difference in oxycodone consumption between the three groups at 24 h (P¼0.2). Worst knee pain was initially at the graft donor site in all three groups, which transitioned to anterior knee pain after 12 h. Conclusions: The addition of ultrasound-guided peri-hamstring injection or anterior division of obturator nerve block to ACB did not result in a significant reduction in pain or opioid consumption after ACLR with ipsilateral hamstring graft. Clinical trial registration: NCT 01868282. Keywords: adductor canal block; anterior cruciate ligament reconstruction; hamstring block; nerve blockade; obturator nerve block
Successful discharge after ambulatory arthroscopic knee surgery relies on adequate postoperative analgesia. Poorly controlled pain has been shown to result in increased utilisation of acute care services after hospital discharge.1,2
Anterior cruciate ligament reconstruction (ACLR) is commonly performed via an arthroscopic approach and often utilises ipsilateral hamstring (gracilis-semitendinosus) tendon autograft and hence the source of postoperative pain can
Received: 16 July 2019; Accepted: 2 November 2019 © 2019 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved. For Permissions, please email: [email protected]
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either be from the graft donor site or the arthroscopic surgical site. Regional anaesthetic techniques in knee arthroplasty are known to decrease opioid consumption, reduce opioid-related side-effects, and facilitate earlier hospital discharge while also enhancing patient satisfaction.3,4 While proximal nerve blocks (e.g. femoral and sciatic) provide excellent analgesia, muscle weakness may interfere with early rehabilitative efforts and may also increase the risk of falls.5 Hence, distal techniques are preferred to ensure adequate analgesia while minimising muscle weakness. For ACLR, adductor canal block (ACB) has been shown to be non-inferior to femoral nerve block while still maintaining quadriceps strength.6 While ACB provides analgesic value for surgical site pain, the benefit is less clear for donor site pain,7,8 and infiltration of local anaesthetic may be more practical, yet equally as effective as peripheral nerve blocks, raising the question if performing these techniques is even worthwhile.9 Proposed approaches to treat donor site pain include surgical deposition of local anaesthetic around the hamstring donor site either injected through a tailored suction catheter10 or via an arthroscopic shaver sleeve.11 More recently, a preincision ultrasound-guided peritendinous local anaesthetic injection to the hamstring autograft area has been suggested.12 Another approach is to target the innervation of the donor’s muscles with an anterior division obturator nerve (aON) block in the proximal third of the medial thigh. The obturator nerve (L2eL4) passes through the obturator canal and divides into anterior and posterior branches. The aON descends anterior to the adductor brevis and posterior to the pectineus and adductor longus. The aON consistently provides innervation to the gracilis, adductor brevis, adductor longus, and occasionally to the pectineus muscles.13 It also contributes to the subsartorial plexus along with the anterior cutaneous nerve of the thigh and branches of the saphenous nerve.14 This plexus provides sensation to the anteromedial thigh before contributing a minor component of innervation to the posteromedial knee capsule.15,16 Sakura and colleagues17 have shown that the addition of a single shot obturator nerve block to a femoral nerve block conferred additional analgesia for patients undergoing ACLR with hamstring autograft, but whether the same is true in conjunction with ACB is currently unknown. The extent to which the two ultrasound-guided techniques (aON block vs peritendinous hamstring injection) benefit the patients in terms of overall analgesia and specifically the autograft site analgesia needs evaluation. We hypothesise that the addition of either peritendinous injection or aON block will improve analgesic outcomes when compared with ACB alone for patients undergoing ACLR and hence, our null hypothesis was that there is no difference in early postoperative pain scores with the addition of either aON or hamstring block to that of ACB alone. The aim of this study was to compare the analgesic efficacy of combining ACB and multimodal analgesia with (1) peritendinous hamstring injection, (2) aON block, or (3) sham injections in patients undergoing ACLR with ipsilateral autograft from gracilis and semitendinosus tendon graft.
Methods Ethical approval for this study was obtained from the institutional ethics board (University of Western Ontario HSREB study number 103681) in August 2013. This study was
registered with ClinicalTrials.gov (identifier: NCT01868282, June 4, 2013). This was a single-centre, three parallel-arm, shared control group RCT, with 1:1:1 allocation conducted at the University Hospital, London Health Sciences Centre, London, ON. The consolidated standards of reporting trials diagram is shown in Fig 1.
Patients and design After obtaining written informed consent, 105 patients aged 16e85 yr, with ASA physical status 1e3, who were scheduled to undergo elective day case ACLR under general anaesthesia with ipsilateral autograft were recruited for this study between July 2013 and August 2015. All subjects were given verbal and written education on how to measure and record their pain scores at home. Patients were excluded if they were ASA physical class 4, undergoing revision surgery, having an autograft from the contralateral side or an allograft, or had any opioid use within the previous 3 months. Patients were also excluded if they had chronic pain conditions; significant cardiac, haematological, or respiratory disease; deranged coagulation parameters; psychiatric illnesses; contraindications to the performance of the blocks; unable to give informed consent; an allergy to any of the drugs used in the study or had any preoperative neurological deficits.
Randomisation and blinding Patients were randomised to one of three groups. The first group (Group H) received ultrasound-guided peri-hamstring local anaesthetic injection and an ultrasound-guided sham aON block with normal saline. The second group (Group O) received an ultrasound-guided aON block and a sham perihamstring local anaesthetic injection. The third group was the control group (Group C) which received ultrasound-guided sham injections to both the peri-hamstring site and aON with normal saline. In addition, each subject received an active ACB and perioperative multimodal analgesia. The multimodal analgesia consisted of oral paracetamol 975 mg, naproxen 500 mg, and gabapentin 600 mg and was administered less than 2 h before operation. These medications were continued in the perioperative period and subjects were discharged with a 5-day supply of paracetamol 975 mg four times per day, naproxen 500 mg twice per day, and gabapentin 600 mg twice per day. Individuals were randomised to a study group using a computer-generated random number table, and the allocation concealment was performed using a sealed envelope technique. The sealed opaque envelopes were kept locked in a dedicated research safe and were accessed by a research coordinator only when a patient consented for the study. This coordinator was then responsible for drawing up the local anaesthetic, saline, or both according to group allocation into three separate syringes and applying an adhesive label to each syringe documenting it as the ‘adductor canal’, ‘perihamstring’ or ‘anterior obturator’ syringe. The adductor canal syringe always contained ropivacaine 0.5%, 20 ml. The perihamstring syringe contained either ropivacaine 0.5%, 15 ml or saline 0.9%, 15 ml. The anterior obturator syringe contained either ropivacaine 0.5%, 10 ml or saline 0.9%, 10 ml based on the group allocation. Anaesthetists and block-assistants involved in performing blocks, and research assistants who collected the postoperative data were blinded to group
Hamstring versus obturator block in ACL
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3
Assessed for eligibility (n=136)
FOLLOW-UP
ALLOCATION
Excluded (n=31) Not meeting inclusion criteria (n=4) Declined to participate (n=27)
Randomised (n=105)
Allocated to Group H (n=35)
Allocated to Group C (n=35)
Successful ACB (n=34) Failed ACB (n=1) Lost to follow-up (n=11)
Successful ACB (n=35) Failed ACB (n=0) Lost to follow-up (n=16)
Analysed (n=35) Excluded from analysis (n=0)
Analysed (n=35) Excluded from analysis (n=0)
ANALYSIS
Successful ACB (n=35) Failed ACB (n=0) Lost to follow-up (n=17)
Allocated to Group O (n=35)
Analysed (n=35) Excluded from analysis (n=0)
Fig 1. Consolidated standards of reporting trials diagram of patient enrolment, allocation, follow-up, and final analysis. ACB, adductor canal block.
allocation. Subjects were also blinded to their group allocation (as they each received all three injections).
Interventions All nerve blocks were carried out in a dedicated block room area before operation. On arrival to the block room, study participants had a preoperative motor power assessment in the quadriceps muscles using a hand-held dynamometer (MET900 Lafayette Dynamometer, METEquipmentUS, La Porte, IN, USA) by a blinded study investigator not involved with the drug preparation or the performance of the block. Standard monitoring including noninvasive BP, ECG, and pulse oximeter was applied, and procedural sedation was offered with midazolam 1e2 mg and fentanyl 50e100 mg i.v. titrated to effect. Subjects were placed in the supine position with the operative leg externally rotated. Asepsis was achieved using chlorhexidine 2% in alcohol. The skin at block sites was subsequently infiltrated with lidocaine 2%.
Adductor canal block A pre-procedural scan using a 5 cm (7e13 MHz) highfrequency linear transducer (Sonosite M-Turbo, Sonosite, Bothell, WA, USA) was performed to identify the location of the descending genicular artery arising from the superficial femoral artery (supplementary File 1). The finding of this vascular landmark is known to demark the exit (and subsequent bifurcation) of the saphenous nerve from the adductor
canal just distal to the discontinuation of the vasoadductor membrane.18 The injection point for the ACB was 2 cm proximal to this landmark along the sartorius muscle. A 21-gauge 90 mm Arrow® (Teleflex®, Morrisville, NC, USA) needle was passed in-plane in an anterolateral to posteromedial direction through the sartorius muscle. Once the needle tip location was confirmed (by hydro-location using dextrose 5%, 1e2 ml) to be lateral to the femoral artery but within the adductor canal, ropivacaine 0.5%, 20 ml was injected after negative aspiration for blood.
Peri-hamstring injection After the completion of the ACB, the transducer was moved further posteriorly around the thigh. The same needle was redirected in a steeper posteromedial direction towards the fascial plane between the sartorius and gracilis muscle. Once the needle tip was confirmed to be deep to sartorius but superficial to gracilis, ropivacaine 0.5%, 7.5 ml was injected superficially to the deep fascia of the muscle sheath to achieve free spread around the anterior surface of the muscle contained within the fascial compartment (as the muscle was viewed in short axis on ultrasound). The needle was then advanced further posteriorly towards the fascial planes between the semimembranosus and semitendinosus, and an additional ropivacaine 0.5%, 7.5 ml was similarly injected to achieve spread around the anterior aspect of the semitendinosus muscle superficial to its deep fascia (supplementary File 2a and 2b). While ropivacaine was used in group H
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individuals, the same injections were performed for Group O and Group C, except saline 0.9% was used instead.
Anterior division of obturator nerve block The anterior branch of the obturator nerve was seen in the proximal thigh medial to the femoral vessels between the adductor longus and adductor brevis below the inguinal crease. The same 21-gauge 90 mm needle was directed through the adductor longus in an out of plane technique (supplementary File 3). A small volume of dextrose 5%, (1e2 ml) was injected to ensure the needle tip was positioned between the two muscles. Neurostimulation with a 0.6 mA current was used as an additional aid to confirm the needle position to look for adductor magnus and gracilis muscle contractions. If the desired muscle twitch was not encountered despite ultrasound demonstration of the needle tip placement within the correct muscle plane, the needle was adjusted while the neurostimulation current was slowly increased up to 1.5mA until a muscle twitch was obtained, and this was subsequently lowered to the 0.6 mA threshold. After negative aspiration, ropivacaine 0.5%, 10 ml was injected in this muscle plane to surround the aON (Group O). The same technique was used for Groups H and C except saline 0.9% was used instead of ropivacaine. After the performance of the blocks, the motor strength assessments in the quadriceps muscles were performed by the same investigator performing the preoperative motor assessments at 30 min post-block. After the assessments for block success (confirmed loss of pin-prick sensation over the medial calf) and motor strength in the quadriceps muscles (standardised dynamometry of knee extension), the patient was transferred to theatre for surgery under general anaesthesia. The choice of the airway and ventilation mode was left to the discretion of the anaesthetist (supraglottic airway vs tracheal intubation). Induction of anaesthesia took place using fentanyl 2e3 mg kg1 and propofol 1.5e2.5 mg kg1 followed by maintenance with desflurane in the air-oxygen mixture. Vasopressors, antiemetics, and opioids were administered as needed, and titrated to the clinical effect according to the theatre anaesthetist who was independent to the study and blinded to group allocation. The total dose of opioid used was recorded.
Outcomes The primary outcome was the numerical rating scale (NRS) of postoperative pain scores on knee flexion 2 h after arrival in the PACU. Secondary outcome measures included: NRS pain scores at and 4 h after PACU arrival and self-recorded NRS pain scores (via a pain diary) every 6 h thereafter until 48 h after PACU arrival. Patients were discharged home with a ‘pain diary’ for recording pain scores, pain location, analgesic consumption, and side-effects at various time intervals. In addition, the duration of block performance and success of sensory loss in the saphenous nerve distribution was recorded. The failure rate of saphenous nerve blockade (as defined by an unchanged perception of pin-prick sensation before and after the ACB) was determined by a blinded investigator not involved with the performance of the blocks.
Statistical analysis The sample size was calculated using estimates for the primary outcome measure (NRS at movement in PACU at 2 h after
operation). The mean (standard deviation) NRS pain scores at early postoperative periods are noted to be around 5.50 (1.62) in a study using femoral nerve blocks for ACLR with ipsilateral hamstring graft.11 The sample size estimate (two-tailed) was calculated to show a 30% decrease in pain intensity with the use of regional nerve blocks for controlling graft donor site pain. The required number of subjects in each group was calculated using the formula n¼(zaþzb)2.(2s)2/D2 where s is the standard deviation of the response variable, D is the smallest difference between the mean of the two groups, which is of clinical or scientific interest, and zaþzb¼multiplier which depends on the level of significance a and power 1-b,19 which showed 31 patients per group were required to ensure an adequate sample size with an a of 0.01 and 90% power. Therefore, the sample size for each group was planned to be 35 patients to allow for an estimated 10% attrition rate of cases. The continuous and discrete variables are presented as mean and standard deviation, and the categorical variables presented as frequencies. The normality of distribution was assessed visually using Q-Q plots. Quantitative data such as pain scores and narcotic consumption were compared between groups using analysis of variance. The categorical data were analysed using the c2 test. All statistical calculations were performed using SPSS 20 (trial version, IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Version 20.0. IBM Corp., Armonk, NY, USA) and Stata 15 (Stata/IC 15.1 for Mac, StataCorp, College Station, TX, USA). A P-value <0.025 was considered to be statistically significant to account for multiple group comparisons.
Results Between November 2013 and May 2014, 136 patients were assessed for eligibility. Of these, four did not meet the study inclusion criteria and 27 declined to participate in the study (Fig 1). Of the 105 patients evenly allocated across the three groups, only one patient had block failure with ACB, as noted by normal sensation at the medial calf. All other subjects were included for the analysis of the primary outcome, and the 4 h (day surgery unit stay) secondary outcomes and a subsequent sensitivity analysis performed by including and excluding the patient with failed ACB did not show any disagreements. Sixty-one subjects completed and returned the pain diary, which recorded the 6e48 h postoperative pain scores, the location site of predominant pain, and analgesic consumption. Hence, the datapoints were captured in all subjects for the primary outcome and the secondary outcomes until 4 postoperative hours, while the remaining outcomes had missing values which were handled using pair-wise deletions. There were no significant differences in baseline subject characteristics or block performance time (Table 1). Subject ages (yr) in the three groups were [median (range): Group H, O, and C, 26 (18e61), 28 (18e57), and 29 (18e52), respectively], while the sex (M:F) ratios were: Group H 18:17, Group O 21:14, and Group C 13:22. Subject ASA physical status assignments (1:2:3) in each group were: Group H 26:9:0, Group O 23:10:2, and Group C 25:9:1. The primary outcome of pain score on knee flexion measured at 2 h after operation was not significantly different between the groups, and this trend continued at all other time points of measurement (Fig 2). The decrease in quadriceps motor power 30 min after block completion was statistically significant compared with the pre-block motor power in all the three groups, but did not differ between group comparison. The changes in quadriceps motor power are
Hamstring versus obturator block in ACL
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Table 1 Block performance and analgesic outcome measures after blocks.
Block performance (min) I/O fentanyl (mg) I/O hydromorphone (mg) NRS pain 2 h NRS discharge NRS 24 h 24 h oxycodone consumption (mg)
Group H
Group O
Group C
P-value (sig <0.025)
6.4 (3.8) 118.3 (68.8) 0.47 (0.37) 3.1 (1.8) 2.8 (1.5) 2.9 (1.5) 37.4 (28.8)
7.1 (7.3) 106.25 (56.4) 0.55 (0.36) 2.9 (2.3) 2.5 (2.0) 4.1 (1.9) 40.0 (25.0)
7.23 (3.9) 128.4 (92.5) 0.38 (0.27) 4.0 (2.2) 3.2 (1.6) 4.6 (2.5) 34.2 (20.1)
0.51 0.50 0.37 0.11 0.37 0.07 0.20
I/O, intraoperative; NRS, numerical rating scale; Sig, significance.
Group
Pain score (NRS 1-10)
7
H O C
Group
6
H O C
5
Error bars show 95% CI of
4
mean
3
2
Pain48
Pain24
Pain18
Pain12
Pain6
Pain4
Pain PACUdischarge
Pain2
Pain0
1
Time (h) Fig 2. Dynamic numeric rating pain score on knee flexion at various time points after operation. Group H: peri-hamstring injection, Group O: anterior division of obturator nerve, Group C: control group. CI, confidence interval; NRS, numerical rating scale.
displayed in Table 2. The percentage decrease in motor power for Group H (9.1%), Group O (4.7%), and Group C (7.4%) was considered to be clinically non-significant. The intraoperative opioid requirement was not significantly different between the groups. Among the subjects who completed the pain diary, the postoperative rescue opioid requirement did not differ at any time point up to the 48 h postoperative mark (Fig 3). The predominant site of pain was located at the posterior knee (the donor site) in the majority of patients in all three groups until 18 postoperative hours (Fig 4). After this time point, the predominant site of pain was both the anterior and posterior areas of the knee. There was a trend towards better analgesic cover at the donor site with perihamstring injection (group H), and a greater number of subjects in this group had no pain until 48 postoperative hours
Table 2 Dynamometer quadriceps motor assessment before and 30 min after block completion (motor score measured in Newtons). Group H (n¼32) Baseline pre-block motor score: mean (SD) 30-min post-block motor score: mean (SD) Percentage difference P-value within group P-value between groups SD, standard deviation.
Group O (n¼34)
Group C (n¼33)
47.6 (14.0) 46.4 (15.7) 47.2 (18.2) 38.5 (16.9) 41.7 (15.0) 39.8 (15.1) 9.1 <0.01 0.14
4.7 <0.01
7.4 <0.01
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Group 8
H O C
Opioid consumption
Group 6
H O C
Error bars show 95% CI of
4
mean
2
0 Rescue48
Rescue24
Rescue18
Rescue12
Rescue6
Rescue4
Rescue PACUdischarge
Rescue2
Rescue0
Time (h) Fig 3. Opioid consumption in oral morphine equivalents at various time points after anterior cruciate ligament reconstruction. Group H: peri-hamstring injection, Group O: anterior division of obturator nerve, Group C: control group. CI, confidence interval.
compared with the other two groups. However, firm conclusions cannot be drawn with certainty from these data, as the study was not adequately powered for measuring this secondary outcome. There were no significant differences for other secondary outcomes, such as the incidence of pruritus or nausea/vomiting between the three groups.
Discussion Our study demonstrated a lack of benefit for donor site pain when either a peri-hamstring injection or an aON block was added to an ACB for patients undergoing ACLR using an autologous hamstring muscle graft in terms of reduction in pain scores. Furthermore, there were no differences in the intraoperative opioid requirement, 24-h oxycodone consumption, or opioid-related side-effects observed between the three groups. The reduction in quadriceps strength was also not significantly different between the groups. Wide-ranging techniques have been described in the literature for obtaining analgesia after ACLR. Some examples include intra-articular injection of local anaesthetic20 and opioids,21 lumbar epidural,22 femoral nerve block,23 sciatic nerve block,24 patient-controlled infrapatellar fat-pad bupivacaine infusion,25 and site-specific interventions to target pain at the autologous donor site.5,7 Compared with using a patellar-bone-tendon-bone graft for ACLR (via an anterior longitudinal incision over the medial border of the patellar tendon), harvesting the hamstring tendon allows a smaller skin incision, less donor
site morbidity, and less extensor mechanism dysfunction while still possessing equally successful long-term clinical results.26 It does require an anteromedial longitudinal incision midway between the tibial tubercle and the pes anserinus insertion. In addition, the sartorius fascia is incised to gain surgical access to both gracilis and semitendinosus tendons which are then freed from their fascial attachments and then undergo tendon stripping, before a scalpel is used to elevate the distal tendon from the bone with a flap of periosteum. After the hamstring harvest, the reconstruction via knee arthroscopy takes place. Afferents from the femoral, obturator, and tibial branch of the sciatic nerve are consequently all stimulated via this process. In the current study, the tibial nerve was not blocked by any of the regional anaesthetic interventions. In this study, all patients received multimodal analgesia with paracetamol, an NSAID, and gabapentin. All individuals received a preoperative ACB, which was successful in >99% as evidenced by the loss of pin-prick sensation in the saphenous nerve distribution. In addition, all individuals received intraoperative opioids. It is reassuring that the postoperative and pre-discharge NRS rating scored very low in all groups. This, too, may have been the reason why we failed to demonstrate an analgesic benefit from the addition of either peri-hamstring injection or aON block. A further explanation for the absence of statistical difference in NRS between study groups could be baseline imbalances in the patient characteristics, as group C comprised 63% females compared with 48% in group H and 40% in group O. While pain is known to be reported more
Hamstring versus obturator block in ACL
90 80
Percentage
70
Percentage
7
Predominant pain: both front & back
Predominant pain: back of knee 80 60 50 40 30 20 10
70 60 50 40 30 20 10
0 2
4
6
12
18
24
0
48
2
Postoperative hours
4
6
12
18
24
48
Postoperative hours
(a)
(b)
Predominant pain: front of knee
No postoperative pain
20
Group H
50
Group O 15
40
Percentage
Percentage
-
30 20 10
Group C
10
5
0 2
4
6
12
18
24
48
Postoperative hours
(C)
0 2
4
6
12
18
24
48
Postoperative hours
(d)
Fig 4. Worst site of pain (as a proportion) at various time points after anterior cruciate ligament reconstruction. (a) Back of the knee, (b) both front and back, (c) front of the knee, (d) no pain and the groups are defined as Group H: peri-hamstring injection, Group O: anterior division of obturator nerve, Group C: control group.
frequently in females compared with males,27 the numbers in this study are too low to reliably attribute the absence of reduced pain reporting in group C to the gender imbalances between the groups occurring during randomisation in the absence of the minimisation process. It is interesting to observe the migration of knee pain during the first 48 h after operation. The pain location moved from a predominantly posterior area in the first 6 postoperative hours to a predominantly anterior or posterior-and-anterior area in the latter half of pain recordings (Fig 4). This effect was observed across all three groups, but the extremes of anterior-to-posterior distinction were least marked in Group H. Logically, the increased frequency of anterior or posteriorand-anterior knee pain observed after 12 h would be in keeping with the ACB resolution, and a return of pain signalled via the saphenous nerve. The failure to demonstrate a reduction in pain scores with ACB after ACLR could be attributable to additional pain mediated by the sheering, stripping, and excision forces during the hamstring tendon harvest and the posteromedial thigh incision. The same findings were seen more recently by Stebler and colleagues28 when ACB was compared with local anaesthetic infiltration for ACL surgery. They observed no difference in cumulative morphine at 24 h, dynamic pain scores, and functional outcomes between both groups despite the local anaesthetic infiltration technique involving an injection of ropivacaine 0.5%, 8 ml into the harvest site. This is in contrast to the findings by Faunø and colleagues29 where patients undergoing ACL surgery were randomised to receive bupivacaine 0.25%, 20 ml vs placebo via a surgically placed
catheter tip located in the donor site space. In combination with an active femoral nerve block (FNB in both groups), the bupivacaine group experienced lower NRS and opioid consumption in the first 6 h after surgery. In the present study neither ultrasound-guided perihamstring injection or anterior division of the obturator nerve delivered sufficient analgesia to significantly reduce pain mediated by this component of the surgical procedure. While the outcomes of NRS and opioid consumption were not affected by the addition of either peri-hamstring injection or aON, one can appreciate at 24 and 48 h there were still individuals in group H who observed no pain (unlike groups O and C), and there was a modest trend towards a lower NRS in group H at this time interval also. This is in keeping with the concept that pain mediated from the autograft donor site contributes significantly to overall pain after ACL surgery regardless of the ‘antero-medial’ strategy. The addition of a tibial nerve block would reliably cover the semitendinosus tendon graft (and the gracilis muscle anaesthetised by the anterior obturator nerve block). Anterior femoral cutaneous and posterior cutaneous nerve of thigh blocks would be required in addition, to reduce pain associated with the skin incision. The difficulties of adding numerous blocks for the ambulatory ACLR procedure are the logistical hurdles and time constraints of performing multiple injections, while still maintaining a quick turnover of cases such as would be required in a day surgical procedure unit. Performing tibial nerve blocks is also necessarily associated with leg weakness and would represent a theoretical risk of fall, which many would deem unacceptable for ambulatory
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anaesthetic procedures. In practice, this risk is low as patients are very unlikely to attempt to mobilise by themselves within the first 24 h after ACLR surgery. Runge and colleagues30 have observed the spread of injectate from the very distal adductor canal boundary through the conduit of the adductor hiatus that the femoral vessels traverse from medial to posterior compartments of the thigh. In this cadaveric study, the dye injectate spread to stain both the popliteal plexus and the genicular branch of the posterior obturator nerve. Using this technique would help to alleviate posterior capsule knee pain, but may not contribute to analgesia for the hamstring autograft harvest site. Furthermore, the observation of sciatic nerve staining in 10% of cadavers may represent too high a risk of foot-drop, thus preventing early ambulation for this distal ACB technique to be used routinely in ACL surgery. While discussing motor function, it is reassuring to observe the preservation of motor power on dynamometer assessment of knee extension before and 30 min after adductor canal and either aON or peri-hamstring injection. Our findings were that in all three groups, there was a statistically significant decrease in quadriceps function. The mean percentage reduction ranged from 4.7% in Group O to 9.1% in Group H (Table 2). This reduction was not felt to be clinically significant and did not represent a risk of quadriceps weakness sufficient to cause a fall. Our figures for percentage reduction in quadriceps function in healthy volunteers after ACB fit well in the literature findings of 8% reduction observed by Jæger and colleagues31 and 11% reduction demonstrated by Kwofie and colleagues.32 A limitation of the study design was that objective evidence of successful aON block could not be ascertained. Cutaneous innervation of the medial thigh from the obturator nerve is highly variable, and as such cannot be used as a reliable measure of successful obturator nerve block (akin to how the saphenous nerve blockade was tested). Hip adduction dynamometry was not performed because of the confounding effect of hip adduction caused by the unblocked posterior obturator and sciatic nerves, which would invalidate the use of dynamometry for hip adduction to confirm successful aON block. All individuals had readily recognisable adductor muscle sonoanatomy, and identification of the presence of aON between adductor longus and brevis was observable in all individuals. A less than 30% difference in pain scores compared with ACB alone could have been present with the addition of aON or hamstring block, but our study was underpowered to detect such a change. A further weakness of this study is the completion of the pain diary in only 61/105 (58%) of individuals. While a pair-wise comparison was made to compensate for the short-coming in follow-up, a limited inference can be made from the secondary outcomes up to 48 h, derived from incomplete patient pain diaries. Every effort was made with follow-up calls to encourage individuals with incomplete/missing data. While the pattern of analgesia appeared to transition from posterior to anterior, suggestive of an analgesic component from the ACB, the study was not powered to map the change in analgesia location. Further trials considering the predominant site of pain after ACLR are needed to know the analgesic utility of ACB. In conclusion, the addition of ultrasound-guided perihamstring injection or anterior division of obturator nerve block to an ACB did not reduce NRS or opioid consumption after ACLR.
Authors’ contributions Acquisition of data: DFJ, RVS, VU, RL, RG, SG Drafting the article: DFJ, RVS Analysis and interpretation of data: DFJ, RVS, VU Revising manuscript critically for important intellectual content: DFJ, RVS, VU, SG Final approval of the version to be published; agreement to be accountable for all aspects of the work thereby ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved: all authors Substantial contribution to conception and design: RVS, VU, RL, RG, SG Revising the manuscript critically for important intellectual content pertaining to the surgery: RL, RG
Declaration of interest The authors declare that they have no conflict of interest.
Funding Internal research grant, Department of Anesthesia internal research fund, University of Western Ontario, London, ON, Canada.
Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.bja.2019.11.032.
References 1. Liu J, Kim DH, Maalouf DB, Beathe JC, Allen AA, Memtsoudis SG. Thirty-day acute health care resource utilization following outpatient anterior cruciate ligament surgery. Reg Anesth Pain Med 2018; 43: 849e53 2. Okoroha KR, Keller RA, Jung EK, et al. Pain assessment after anterior cruciate ligament reconstruction: bonepatellar tendon-bone versus hamstring tendon autograft. Orthop J Sports Med 2016; 4. 2325967116674924 3. Terkawi AS, Mavridis D, Sessler DI, et al. Pain management modalities after total knee arthroplasty: a network meta-analysis of 170 randomized controlled trials. Anesthesiology 2017; 126: 923e37 4. Luber MJ, Greengrass R, Vail TP. Patient satisfaction and effectiveness of lumbar plexus and sciatic nerve block for total knee arthroplasty. J Arthroplasty 2001; 16: 17e21 5. 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: 135e40 6. Abdallah FW, Whelan DB, Chan VW, et al. Adductor canal block provides noninferior analgesia and superior quadriceps strength compared with femoral nerve block in anterior cruciate ligament reconstruction. Anesthesiology 2016; 124: 1053e64 7. Sehmbi H, Brull R, Shah UJ, et al. Evidence basis for regional anesthesia in ambulatory arthroscopic knee surgery and anterior cruciate ligament reconstruction: Part II: adductor canal nerve block-a systematic review and meta-analysis. Anesth Analg 2019; 128: 223e38 8. Kejriwal R, Cooper J, Legg A, Stanley J, Rosenfeldt MP, Walsh SJ. Efficacy of the adductor canal approach to saphenous nerve block for anterior cruciate ligament
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reconstruction with hamstring autograft: a randomized controlled trial. Ortho J Sport Med 2018; 6: 1e5 Ramlogan R, Tierney S, McCartney CJL. Anterior cruciate ligament repair and peripheral nerve blocks: time to change our practice? Br J Anaesth 2019; 123: e186e8 Logan JS, Elliott RR, Wilson AJ. A new technique for hamstring donor site blockade in anterior cruciate ligament reconstruction. Ann R Coll Surg Engl 2011; 93: 326 Bushnell BD, Sakryd G, Noonan TJ. Hamstring donor-site block: evaluation of pain control after anterior cruciate ligament reconstruction. Arthroscopy 2010; 26: 894e900 Walter RP, Dhadwal A, Htyn M, Mandalia V. Ultrasonography guided peritendinous anaesthetic infiltration in hamstrings autograft anterior cruciate ligament reconstruction. Ann R Coll Surg Engl 2014; 96: 386e99 Moore KL, Dalley AF. Clinically orientated anatomy. 4th Edn. Philadelphia: Lippincott Williams & Wilkins; 1999 Horner G, Dellon AL. Innervation of the human knee joint and implications for surgery. Clin Orthop Relat Res 1994; 301: 221e6 Snell RS. Clinical anatomy by regions. 9th Edn. Baltimore: Lippincott Williams & Wilkins; 2012 L, Behets C, Kouassi JK, et al. Distribution of Fonkoue sensory nerves supplying the knee joint capsule and implications for genicular blockade and radiofrequency ablation: an anatomical study. Surg Radiol Anat 2019; 41: 1461e71 Sakura S, Hara K, Ota J, Tadenuma S. Ultrasound-guided peripheral nerve blocks for anterior cruciate ligament reconstruction: effect of obturator nerve block during and after surgery. J Anesth 2010; 24: 411e7 Horn JL, Pitsch T, Salinas F, Benninger B. Anatomic basis to the ultrasound-guided approach for saphenous nerve blockade. Reg Anesth Pain Med 2009; 34: 486e9 Eng J. Sample size estimation: how many individuals should be studied? Radiology 2003; 227: 309e13 Tetzlaff JE, Dilger JA, Abate J, Parker RD. Preoperative intra-articular morphine and bupivacaine for pain control after outpatient arthroscopic anterior cruciate ligament reconstruction. Reg Anesth Pain Med 1999; 24: 220e4 Akinci SB, Saricaoglu F, Atay OA, Doral MN, Kanbak M. Analgesic effect of intra-articular tramadol compared with morphine after arthroscopic knee surgery. Arthroscopy 2005; 21: 1060e5 Dauri M, Polzoni M, Fabbi E, et al. Comparison of epidural, continuous femoral block and intraarticular analgesia after anterior cruciate ligament reconstruction. Acta Anaesthesiol Scand 2003; 47: 20e5
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23. Frost S, Grossfeld S, Kirkley A, Litchfield B, Fowler P, Amendola A. The efficacy of femoral nerve block in pain reduction for outpatient hamstring anterior cruciate ligament reconstruction: a double-blind, prospective, randomized trial. Arthroscopy 2000; 16: 243e8 24. Jansen TK, Miller BE, Arretche N, Pellegrini JE. Will the addition of a sciatic nerve block to a femoral nerve block provide better pain control following anterior cruciate ligament repair surgery? J Am Assoc Nurse Anesth 2009; 77: 231e8 25. Chew HF, Evans NA, Stanish WD. Patient-controlled bupivacaine infusion into the infrapatellar fat pad after anterior cruciate ligament reconstruction. Arthroscopy 2003; 19: 500e5 26. Charalambous CP, Kwaees TA. Anatomical considerations in hamstring tendon harvesting for anterior cruciate ligament reconstruction. Muscles Ligaments Tendons J 2012; 2: 253e7 27. Fillingim RB, King CD, Ribeiro-Dasilva MC, RahimWilliams B, Riley JL. Sex, gender, and pain: a review of recent clinical and experimental findings. J Pain 2009; 10: 447e85 28. Stebler K, Martin R, Kirkham KR, Lambert J, De Sede A, Albrecht E. Adductor canal block versus local infiltration analgesia for postoperative pain after anterior cruciate ligament reconstruction: a single centre randomised controlled triple-blinded trial. Br J Anaesth 2019; 123: 343e9 29. Faunø P, Lund B, Christiansen SE, Gjøderum O, Lind M. Analgesic effect of hamstring block after anterior cruciate ligament reconstruction compared with placebo: a prospective randomized trial. Arthroscopy 2015; 31: 63e8 30. Runge C, Moriggl B, Børglum J, Bendtsen TF. The spread of ultrasound-guided injectate from the adductor canal to the genicular branch of the posterior obturator nerve and the popliteal plexus: a cadaveric study. Reg Anaesth Pain Med 2017; 42: 725e30 31. Jæger P, Nielsen ZJ, Henninsen MH, Hilsted KL, Mathiesen O, Dahl JB. Adductor canal block versus femoral nerve block and quadriceps strength: a randomized double-blind placebo-controlled, crossover study in healthy volunteers. Anesthesiology 2013; 118: 409e15 32. Kwofie MK, Shastri UD, Gadsden JC, et al. The effects of ultrasound-guided adductor canal block versus femoral nerve block on quadriceps strength and fall risk: a blinded, randomized trial of volunteers. Reg Anesth Pain Med 2013; 38: 321e5
Handling editor: Jonathan Hardman
CLINICAL INVESTIGATION
Effect of combining peri-hamstring injection or anterior obturator nerve block on the analgesic efficacy of adductor canal block for anterior cruciate ligament reconstruction: a randomised controlled trial David F. Johnston1, Rakesh V. Sondekoppam2,*, Vishal Uppal3, Robert Litchfield4, Robert Giffin4 and Sugantha Ganapathy5 1
Department of Anaesthesia and Perioperative Medicine, Royal Victoria Hospital, Belfast Trust, Belfast, UK, 2Department
of Anesthesia, University of Iowa, Iowa City, IA, USA, 3Department of Anesthesia, University of Dalhousie, Halifax, NS, Canada, 4Department of Orthopedic Surgery, London Health Sciences Centre, Western University, London, ON, Canada and 5Department of Anesthesia and Perioperative Medicine, London Health Sciences Centre, Western University, London, ON, Canada *Corresponding author. E-mail: [email protected]
Abstract Background: Pain after anterior cruciate ligament reconstruction (ACLR) with autologous hamstring graft can be attributed to both arthroscopic surgery and the graft donor site. This study investigated whether donor site pain control was superior with the addition of either peri-hamstring injection or anterior division obturator nerve block in comparison with adductor canal block (ACB) alone. Methods: Patients scheduled to undergo knee arthroscopy with ACLR using a graft from the ipsilateral hamstring were randomised to one of three groups. All patients received ACB and multimodal analgesia. Subjects in Group H received peri-hamstring local anaesthetic injection while subjects in Group O received an anterior division of the obturator nerve block, and subjects in Group C served as a control group (ACB alone). Results: In 105 subjects undergoing ACLR, there was no significant difference between groups H, O, and C for the primary outcome of pain on movement as assessed by numerical rating scale (NRS) on knee flexion at 2 h after operation (P¼0.11). There was no difference in NRS at any time point in the first 48 h after operation, nor was there a difference in oxycodone consumption between the three groups at 24 h (P¼0.2). Worst knee pain was initially at the graft donor site in all three groups, which transitioned to anterior knee pain after 12 h. Conclusions: The addition of ultrasound-guided peri-hamstring injection or anterior division of obturator nerve block to ACB did not result in a significant reduction in pain or opioid consumption after ACLR with ipsilateral hamstring graft. Clinical trial registration: NCT 01868282. Keywords: adductor canal block; anterior cruciate ligament reconstruction; hamstring block; nerve blockade; obturator nerve block
Successful discharge after ambulatory arthroscopic knee surgery relies on adequate postoperative analgesia. Poorly controlled pain has been shown to result in increased utilisation of acute care services after hospital discharge.1,2
Anterior cruciate ligament reconstruction (ACLR) is commonly performed via an arthroscopic approach and often utilises ipsilateral hamstring (gracilis-semitendinosus) tendon autograft and hence the source of postoperative pain can
Received: 16 July 2019; Accepted: 2 November 2019 © 2019 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved. For Permissions, please email: [email protected]
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either be from the graft donor site or the arthroscopic surgical site. Regional anaesthetic techniques in knee arthroplasty are known to decrease opioid consumption, reduce opioid-related side-effects, and facilitate earlier hospital discharge while also enhancing patient satisfaction.3,4 While proximal nerve blocks (e.g. femoral and sciatic) provide excellent analgesia, muscle weakness may interfere with early rehabilitative efforts and may also increase the risk of falls.5 Hence, distal techniques are preferred to ensure adequate analgesia while minimising muscle weakness. For ACLR, adductor canal block (ACB) has been shown to be non-inferior to femoral nerve block while still maintaining quadriceps strength.6 While ACB provides analgesic value for surgical site pain, the benefit is less clear for donor site pain,7,8 and infiltration of local anaesthetic may be more practical, yet equally as effective as peripheral nerve blocks, raising the question if performing these techniques is even worthwhile.9 Proposed approaches to treat donor site pain include surgical deposition of local anaesthetic around the hamstring donor site either injected through a tailored suction catheter10 or via an arthroscopic shaver sleeve.11 More recently, a preincision ultrasound-guided peritendinous local anaesthetic injection to the hamstring autograft area has been suggested.12 Another approach is to target the innervation of the donor’s muscles with an anterior division obturator nerve (aON) block in the proximal third of the medial thigh. The obturator nerve (L2eL4) passes through the obturator canal and divides into anterior and posterior branches. The aON descends anterior to the adductor brevis and posterior to the pectineus and adductor longus. The aON consistently provides innervation to the gracilis, adductor brevis, adductor longus, and occasionally to the pectineus muscles.13 It also contributes to the subsartorial plexus along with the anterior cutaneous nerve of the thigh and branches of the saphenous nerve.14 This plexus provides sensation to the anteromedial thigh before contributing a minor component of innervation to the posteromedial knee capsule.15,16 Sakura and colleagues17 have shown that the addition of a single shot obturator nerve block to a femoral nerve block conferred additional analgesia for patients undergoing ACLR with hamstring autograft, but whether the same is true in conjunction with ACB is currently unknown. The extent to which the two ultrasound-guided techniques (aON block vs peritendinous hamstring injection) benefit the patients in terms of overall analgesia and specifically the autograft site analgesia needs evaluation. We hypothesise that the addition of either peritendinous injection or aON block will improve analgesic outcomes when compared with ACB alone for patients undergoing ACLR and hence, our null hypothesis was that there is no difference in early postoperative pain scores with the addition of either aON or hamstring block to that of ACB alone. The aim of this study was to compare the analgesic efficacy of combining ACB and multimodal analgesia with (1) peritendinous hamstring injection, (2) aON block, or (3) sham injections in patients undergoing ACLR with ipsilateral autograft from gracilis and semitendinosus tendon graft.
Methods Ethical approval for this study was obtained from the institutional ethics board (University of Western Ontario HSREB study number 103681) in August 2013. This study was
registered with ClinicalTrials.gov (identifier: NCT01868282, June 4, 2013). This was a single-centre, three parallel-arm, shared control group RCT, with 1:1:1 allocation conducted at the University Hospital, London Health Sciences Centre, London, ON. The consolidated standards of reporting trials diagram is shown in Fig 1.
Patients and design After obtaining written informed consent, 105 patients aged 16e85 yr, with ASA physical status 1e3, who were scheduled to undergo elective day case ACLR under general anaesthesia with ipsilateral autograft were recruited for this study between July 2013 and August 2015. All subjects were given verbal and written education on how to measure and record their pain scores at home. Patients were excluded if they were ASA physical class 4, undergoing revision surgery, having an autograft from the contralateral side or an allograft, or had any opioid use within the previous 3 months. Patients were also excluded if they had chronic pain conditions; significant cardiac, haematological, or respiratory disease; deranged coagulation parameters; psychiatric illnesses; contraindications to the performance of the blocks; unable to give informed consent; an allergy to any of the drugs used in the study or had any preoperative neurological deficits.
Randomisation and blinding Patients were randomised to one of three groups. The first group (Group H) received ultrasound-guided peri-hamstring local anaesthetic injection and an ultrasound-guided sham aON block with normal saline. The second group (Group O) received an ultrasound-guided aON block and a sham perihamstring local anaesthetic injection. The third group was the control group (Group C) which received ultrasound-guided sham injections to both the peri-hamstring site and aON with normal saline. In addition, each subject received an active ACB and perioperative multimodal analgesia. The multimodal analgesia consisted of oral paracetamol 975 mg, naproxen 500 mg, and gabapentin 600 mg and was administered less than 2 h before operation. These medications were continued in the perioperative period and subjects were discharged with a 5-day supply of paracetamol 975 mg four times per day, naproxen 500 mg twice per day, and gabapentin 600 mg twice per day. Individuals were randomised to a study group using a computer-generated random number table, and the allocation concealment was performed using a sealed envelope technique. The sealed opaque envelopes were kept locked in a dedicated research safe and were accessed by a research coordinator only when a patient consented for the study. This coordinator was then responsible for drawing up the local anaesthetic, saline, or both according to group allocation into three separate syringes and applying an adhesive label to each syringe documenting it as the ‘adductor canal’, ‘perihamstring’ or ‘anterior obturator’ syringe. The adductor canal syringe always contained ropivacaine 0.5%, 20 ml. The perihamstring syringe contained either ropivacaine 0.5%, 15 ml or saline 0.9%, 15 ml. The anterior obturator syringe contained either ropivacaine 0.5%, 10 ml or saline 0.9%, 10 ml based on the group allocation. Anaesthetists and block-assistants involved in performing blocks, and research assistants who collected the postoperative data were blinded to group
Hamstring versus obturator block in ACL
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Assessed for eligibility (n=136)
FOLLOW-UP
ALLOCATION
Excluded (n=31) Not meeting inclusion criteria (n=4) Declined to participate (n=27)
Randomised (n=105)
Allocated to Group H (n=35)
Allocated to Group C (n=35)
Successful ACB (n=34) Failed ACB (n=1) Lost to follow-up (n=11)
Successful ACB (n=35) Failed ACB (n=0) Lost to follow-up (n=16)
Analysed (n=35) Excluded from analysis (n=0)
Analysed (n=35) Excluded from analysis (n=0)
ANALYSIS
Successful ACB (n=35) Failed ACB (n=0) Lost to follow-up (n=17)
Allocated to Group O (n=35)
Analysed (n=35) Excluded from analysis (n=0)
Fig 1. Consolidated standards of reporting trials diagram of patient enrolment, allocation, follow-up, and final analysis. ACB, adductor canal block.
allocation. Subjects were also blinded to their group allocation (as they each received all three injections).
Interventions All nerve blocks were carried out in a dedicated block room area before operation. On arrival to the block room, study participants had a preoperative motor power assessment in the quadriceps muscles using a hand-held dynamometer (MET900 Lafayette Dynamometer, METEquipmentUS, La Porte, IN, USA) by a blinded study investigator not involved with the drug preparation or the performance of the block. Standard monitoring including noninvasive BP, ECG, and pulse oximeter was applied, and procedural sedation was offered with midazolam 1e2 mg and fentanyl 50e100 mg i.v. titrated to effect. Subjects were placed in the supine position with the operative leg externally rotated. Asepsis was achieved using chlorhexidine 2% in alcohol. The skin at block sites was subsequently infiltrated with lidocaine 2%.
Adductor canal block A pre-procedural scan using a 5 cm (7e13 MHz) highfrequency linear transducer (Sonosite M-Turbo, Sonosite, Bothell, WA, USA) was performed to identify the location of the descending genicular artery arising from the superficial femoral artery (supplementary File 1). The finding of this vascular landmark is known to demark the exit (and subsequent bifurcation) of the saphenous nerve from the adductor
canal just distal to the discontinuation of the vasoadductor membrane.18 The injection point for the ACB was 2 cm proximal to this landmark along the sartorius muscle. A 21-gauge 90 mm Arrow® (Teleflex®, Morrisville, NC, USA) needle was passed in-plane in an anterolateral to posteromedial direction through the sartorius muscle. Once the needle tip location was confirmed (by hydro-location using dextrose 5%, 1e2 ml) to be lateral to the femoral artery but within the adductor canal, ropivacaine 0.5%, 20 ml was injected after negative aspiration for blood.
Peri-hamstring injection After the completion of the ACB, the transducer was moved further posteriorly around the thigh. The same needle was redirected in a steeper posteromedial direction towards the fascial plane between the sartorius and gracilis muscle. Once the needle tip was confirmed to be deep to sartorius but superficial to gracilis, ropivacaine 0.5%, 7.5 ml was injected superficially to the deep fascia of the muscle sheath to achieve free spread around the anterior surface of the muscle contained within the fascial compartment (as the muscle was viewed in short axis on ultrasound). The needle was then advanced further posteriorly towards the fascial planes between the semimembranosus and semitendinosus, and an additional ropivacaine 0.5%, 7.5 ml was similarly injected to achieve spread around the anterior aspect of the semitendinosus muscle superficial to its deep fascia (supplementary File 2a and 2b). While ropivacaine was used in group H
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individuals, the same injections were performed for Group O and Group C, except saline 0.9% was used instead.
Anterior division of obturator nerve block The anterior branch of the obturator nerve was seen in the proximal thigh medial to the femoral vessels between the adductor longus and adductor brevis below the inguinal crease. The same 21-gauge 90 mm needle was directed through the adductor longus in an out of plane technique (supplementary File 3). A small volume of dextrose 5%, (1e2 ml) was injected to ensure the needle tip was positioned between the two muscles. Neurostimulation with a 0.6 mA current was used as an additional aid to confirm the needle position to look for adductor magnus and gracilis muscle contractions. If the desired muscle twitch was not encountered despite ultrasound demonstration of the needle tip placement within the correct muscle plane, the needle was adjusted while the neurostimulation current was slowly increased up to 1.5mA until a muscle twitch was obtained, and this was subsequently lowered to the 0.6 mA threshold. After negative aspiration, ropivacaine 0.5%, 10 ml was injected in this muscle plane to surround the aON (Group O). The same technique was used for Groups H and C except saline 0.9% was used instead of ropivacaine. After the performance of the blocks, the motor strength assessments in the quadriceps muscles were performed by the same investigator performing the preoperative motor assessments at 30 min post-block. After the assessments for block success (confirmed loss of pin-prick sensation over the medial calf) and motor strength in the quadriceps muscles (standardised dynamometry of knee extension), the patient was transferred to theatre for surgery under general anaesthesia. The choice of the airway and ventilation mode was left to the discretion of the anaesthetist (supraglottic airway vs tracheal intubation). Induction of anaesthesia took place using fentanyl 2e3 mg kg1 and propofol 1.5e2.5 mg kg1 followed by maintenance with desflurane in the air-oxygen mixture. Vasopressors, antiemetics, and opioids were administered as needed, and titrated to the clinical effect according to the theatre anaesthetist who was independent to the study and blinded to group allocation. The total dose of opioid used was recorded.
Outcomes The primary outcome was the numerical rating scale (NRS) of postoperative pain scores on knee flexion 2 h after arrival in the PACU. Secondary outcome measures included: NRS pain scores at and 4 h after PACU arrival and self-recorded NRS pain scores (via a pain diary) every 6 h thereafter until 48 h after PACU arrival. Patients were discharged home with a ‘pain diary’ for recording pain scores, pain location, analgesic consumption, and side-effects at various time intervals. In addition, the duration of block performance and success of sensory loss in the saphenous nerve distribution was recorded. The failure rate of saphenous nerve blockade (as defined by an unchanged perception of pin-prick sensation before and after the ACB) was determined by a blinded investigator not involved with the performance of the blocks.
Statistical analysis The sample size was calculated using estimates for the primary outcome measure (NRS at movement in PACU at 2 h after
operation). The mean (standard deviation) NRS pain scores at early postoperative periods are noted to be around 5.50 (1.62) in a study using femoral nerve blocks for ACLR with ipsilateral hamstring graft.11 The sample size estimate (two-tailed) was calculated to show a 30% decrease in pain intensity with the use of regional nerve blocks for controlling graft donor site pain. The required number of subjects in each group was calculated using the formula n¼(zaþzb)2.(2s)2/D2 where s is the standard deviation of the response variable, D is the smallest difference between the mean of the two groups, which is of clinical or scientific interest, and zaþzb¼multiplier which depends on the level of significance a and power 1-b,19 which showed 31 patients per group were required to ensure an adequate sample size with an a of 0.01 and 90% power. Therefore, the sample size for each group was planned to be 35 patients to allow for an estimated 10% attrition rate of cases. The continuous and discrete variables are presented as mean and standard deviation, and the categorical variables presented as frequencies. The normality of distribution was assessed visually using Q-Q plots. Quantitative data such as pain scores and narcotic consumption were compared between groups using analysis of variance. The categorical data were analysed using the c2 test. All statistical calculations were performed using SPSS 20 (trial version, IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Version 20.0. IBM Corp., Armonk, NY, USA) and Stata 15 (Stata/IC 15.1 for Mac, StataCorp, College Station, TX, USA). A P-value <0.025 was considered to be statistically significant to account for multiple group comparisons.
Results Between November 2013 and May 2014, 136 patients were assessed for eligibility. Of these, four did not meet the study inclusion criteria and 27 declined to participate in the study (Fig 1). Of the 105 patients evenly allocated across the three groups, only one patient had block failure with ACB, as noted by normal sensation at the medial calf. All other subjects were included for the analysis of the primary outcome, and the 4 h (day surgery unit stay) secondary outcomes and a subsequent sensitivity analysis performed by including and excluding the patient with failed ACB did not show any disagreements. Sixty-one subjects completed and returned the pain diary, which recorded the 6e48 h postoperative pain scores, the location site of predominant pain, and analgesic consumption. Hence, the datapoints were captured in all subjects for the primary outcome and the secondary outcomes until 4 postoperative hours, while the remaining outcomes had missing values which were handled using pair-wise deletions. There were no significant differences in baseline subject characteristics or block performance time (Table 1). Subject ages (yr) in the three groups were [median (range): Group H, O, and C, 26 (18e61), 28 (18e57), and 29 (18e52), respectively], while the sex (M:F) ratios were: Group H 18:17, Group O 21:14, and Group C 13:22. Subject ASA physical status assignments (1:2:3) in each group were: Group H 26:9:0, Group O 23:10:2, and Group C 25:9:1. The primary outcome of pain score on knee flexion measured at 2 h after operation was not significantly different between the groups, and this trend continued at all other time points of measurement (Fig 2). The decrease in quadriceps motor power 30 min after block completion was statistically significant compared with the pre-block motor power in all the three groups, but did not differ between group comparison. The changes in quadriceps motor power are
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Table 1 Block performance and analgesic outcome measures after blocks.
Block performance (min) I/O fentanyl (mg) I/O hydromorphone (mg) NRS pain 2 h NRS discharge NRS 24 h 24 h oxycodone consumption (mg)
Group H
Group O
Group C
P-value (sig <0.025)
6.4 (3.8) 118.3 (68.8) 0.47 (0.37) 3.1 (1.8) 2.8 (1.5) 2.9 (1.5) 37.4 (28.8)
7.1 (7.3) 106.25 (56.4) 0.55 (0.36) 2.9 (2.3) 2.5 (2.0) 4.1 (1.9) 40.0 (25.0)
7.23 (3.9) 128.4 (92.5) 0.38 (0.27) 4.0 (2.2) 3.2 (1.6) 4.6 (2.5) 34.2 (20.1)
0.51 0.50 0.37 0.11 0.37 0.07 0.20
I/O, intraoperative; NRS, numerical rating scale; Sig, significance.
Group
Pain score (NRS 1-10)
7
H O C
Group
6
H O C
5
Error bars show 95% CI of
4
mean
3
2
Pain48
Pain24
Pain18
Pain12
Pain6
Pain4
Pain PACUdischarge
Pain2
Pain0
1
Time (h) Fig 2. Dynamic numeric rating pain score on knee flexion at various time points after operation. Group H: peri-hamstring injection, Group O: anterior division of obturator nerve, Group C: control group. CI, confidence interval; NRS, numerical rating scale.
displayed in Table 2. The percentage decrease in motor power for Group H (9.1%), Group O (4.7%), and Group C (7.4%) was considered to be clinically non-significant. The intraoperative opioid requirement was not significantly different between the groups. Among the subjects who completed the pain diary, the postoperative rescue opioid requirement did not differ at any time point up to the 48 h postoperative mark (Fig 3). The predominant site of pain was located at the posterior knee (the donor site) in the majority of patients in all three groups until 18 postoperative hours (Fig 4). After this time point, the predominant site of pain was both the anterior and posterior areas of the knee. There was a trend towards better analgesic cover at the donor site with perihamstring injection (group H), and a greater number of subjects in this group had no pain until 48 postoperative hours
Table 2 Dynamometer quadriceps motor assessment before and 30 min after block completion (motor score measured in Newtons). Group H (n¼32) Baseline pre-block motor score: mean (SD) 30-min post-block motor score: mean (SD) Percentage difference P-value within group P-value between groups SD, standard deviation.
Group O (n¼34)
Group C (n¼33)
47.6 (14.0) 46.4 (15.7) 47.2 (18.2) 38.5 (16.9) 41.7 (15.0) 39.8 (15.1) 9.1 <0.01 0.14
4.7 <0.01
7.4 <0.01
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Group 8
H O C
Opioid consumption
Group 6
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Time (h) Fig 3. Opioid consumption in oral morphine equivalents at various time points after anterior cruciate ligament reconstruction. Group H: peri-hamstring injection, Group O: anterior division of obturator nerve, Group C: control group. CI, confidence interval.
compared with the other two groups. However, firm conclusions cannot be drawn with certainty from these data, as the study was not adequately powered for measuring this secondary outcome. There were no significant differences for other secondary outcomes, such as the incidence of pruritus or nausea/vomiting between the three groups.
Discussion Our study demonstrated a lack of benefit for donor site pain when either a peri-hamstring injection or an aON block was added to an ACB for patients undergoing ACLR using an autologous hamstring muscle graft in terms of reduction in pain scores. Furthermore, there were no differences in the intraoperative opioid requirement, 24-h oxycodone consumption, or opioid-related side-effects observed between the three groups. The reduction in quadriceps strength was also not significantly different between the groups. Wide-ranging techniques have been described in the literature for obtaining analgesia after ACLR. Some examples include intra-articular injection of local anaesthetic20 and opioids,21 lumbar epidural,22 femoral nerve block,23 sciatic nerve block,24 patient-controlled infrapatellar fat-pad bupivacaine infusion,25 and site-specific interventions to target pain at the autologous donor site.5,7 Compared with using a patellar-bone-tendon-bone graft for ACLR (via an anterior longitudinal incision over the medial border of the patellar tendon), harvesting the hamstring tendon allows a smaller skin incision, less donor
site morbidity, and less extensor mechanism dysfunction while still possessing equally successful long-term clinical results.26 It does require an anteromedial longitudinal incision midway between the tibial tubercle and the pes anserinus insertion. In addition, the sartorius fascia is incised to gain surgical access to both gracilis and semitendinosus tendons which are then freed from their fascial attachments and then undergo tendon stripping, before a scalpel is used to elevate the distal tendon from the bone with a flap of periosteum. After the hamstring harvest, the reconstruction via knee arthroscopy takes place. Afferents from the femoral, obturator, and tibial branch of the sciatic nerve are consequently all stimulated via this process. In the current study, the tibial nerve was not blocked by any of the regional anaesthetic interventions. In this study, all patients received multimodal analgesia with paracetamol, an NSAID, and gabapentin. All individuals received a preoperative ACB, which was successful in >99% as evidenced by the loss of pin-prick sensation in the saphenous nerve distribution. In addition, all individuals received intraoperative opioids. It is reassuring that the postoperative and pre-discharge NRS rating scored very low in all groups. This, too, may have been the reason why we failed to demonstrate an analgesic benefit from the addition of either peri-hamstring injection or aON block. A further explanation for the absence of statistical difference in NRS between study groups could be baseline imbalances in the patient characteristics, as group C comprised 63% females compared with 48% in group H and 40% in group O. While pain is known to be reported more
Hamstring versus obturator block in ACL
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Fig 4. Worst site of pain (as a proportion) at various time points after anterior cruciate ligament reconstruction. (a) Back of the knee, (b) both front and back, (c) front of the knee, (d) no pain and the groups are defined as Group H: peri-hamstring injection, Group O: anterior division of obturator nerve, Group C: control group.
frequently in females compared with males,27 the numbers in this study are too low to reliably attribute the absence of reduced pain reporting in group C to the gender imbalances between the groups occurring during randomisation in the absence of the minimisation process. It is interesting to observe the migration of knee pain during the first 48 h after operation. The pain location moved from a predominantly posterior area in the first 6 postoperative hours to a predominantly anterior or posterior-and-anterior area in the latter half of pain recordings (Fig 4). This effect was observed across all three groups, but the extremes of anterior-to-posterior distinction were least marked in Group H. Logically, the increased frequency of anterior or posteriorand-anterior knee pain observed after 12 h would be in keeping with the ACB resolution, and a return of pain signalled via the saphenous nerve. The failure to demonstrate a reduction in pain scores with ACB after ACLR could be attributable to additional pain mediated by the sheering, stripping, and excision forces during the hamstring tendon harvest and the posteromedial thigh incision. The same findings were seen more recently by Stebler and colleagues28 when ACB was compared with local anaesthetic infiltration for ACL surgery. They observed no difference in cumulative morphine at 24 h, dynamic pain scores, and functional outcomes between both groups despite the local anaesthetic infiltration technique involving an injection of ropivacaine 0.5%, 8 ml into the harvest site. This is in contrast to the findings by Faunø and colleagues29 where patients undergoing ACL surgery were randomised to receive bupivacaine 0.25%, 20 ml vs placebo via a surgically placed
catheter tip located in the donor site space. In combination with an active femoral nerve block (FNB in both groups), the bupivacaine group experienced lower NRS and opioid consumption in the first 6 h after surgery. In the present study neither ultrasound-guided perihamstring injection or anterior division of the obturator nerve delivered sufficient analgesia to significantly reduce pain mediated by this component of the surgical procedure. While the outcomes of NRS and opioid consumption were not affected by the addition of either peri-hamstring injection or aON, one can appreciate at 24 and 48 h there were still individuals in group H who observed no pain (unlike groups O and C), and there was a modest trend towards a lower NRS in group H at this time interval also. This is in keeping with the concept that pain mediated from the autograft donor site contributes significantly to overall pain after ACL surgery regardless of the ‘antero-medial’ strategy. The addition of a tibial nerve block would reliably cover the semitendinosus tendon graft (and the gracilis muscle anaesthetised by the anterior obturator nerve block). Anterior femoral cutaneous and posterior cutaneous nerve of thigh blocks would be required in addition, to reduce pain associated with the skin incision. The difficulties of adding numerous blocks for the ambulatory ACLR procedure are the logistical hurdles and time constraints of performing multiple injections, while still maintaining a quick turnover of cases such as would be required in a day surgical procedure unit. Performing tibial nerve blocks is also necessarily associated with leg weakness and would represent a theoretical risk of fall, which many would deem unacceptable for ambulatory
8
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anaesthetic procedures. In practice, this risk is low as patients are very unlikely to attempt to mobilise by themselves within the first 24 h after ACLR surgery. Runge and colleagues30 have observed the spread of injectate from the very distal adductor canal boundary through the conduit of the adductor hiatus that the femoral vessels traverse from medial to posterior compartments of the thigh. In this cadaveric study, the dye injectate spread to stain both the popliteal plexus and the genicular branch of the posterior obturator nerve. Using this technique would help to alleviate posterior capsule knee pain, but may not contribute to analgesia for the hamstring autograft harvest site. Furthermore, the observation of sciatic nerve staining in 10% of cadavers may represent too high a risk of foot-drop, thus preventing early ambulation for this distal ACB technique to be used routinely in ACL surgery. While discussing motor function, it is reassuring to observe the preservation of motor power on dynamometer assessment of knee extension before and 30 min after adductor canal and either aON or peri-hamstring injection. Our findings were that in all three groups, there was a statistically significant decrease in quadriceps function. The mean percentage reduction ranged from 4.7% in Group O to 9.1% in Group H (Table 2). This reduction was not felt to be clinically significant and did not represent a risk of quadriceps weakness sufficient to cause a fall. Our figures for percentage reduction in quadriceps function in healthy volunteers after ACB fit well in the literature findings of 8% reduction observed by Jæger and colleagues31 and 11% reduction demonstrated by Kwofie and colleagues.32 A limitation of the study design was that objective evidence of successful aON block could not be ascertained. Cutaneous innervation of the medial thigh from the obturator nerve is highly variable, and as such cannot be used as a reliable measure of successful obturator nerve block (akin to how the saphenous nerve blockade was tested). Hip adduction dynamometry was not performed because of the confounding effect of hip adduction caused by the unblocked posterior obturator and sciatic nerves, which would invalidate the use of dynamometry for hip adduction to confirm successful aON block. All individuals had readily recognisable adductor muscle sonoanatomy, and identification of the presence of aON between adductor longus and brevis was observable in all individuals. A less than 30% difference in pain scores compared with ACB alone could have been present with the addition of aON or hamstring block, but our study was underpowered to detect such a change. A further weakness of this study is the completion of the pain diary in only 61/105 (58%) of individuals. While a pair-wise comparison was made to compensate for the short-coming in follow-up, a limited inference can be made from the secondary outcomes up to 48 h, derived from incomplete patient pain diaries. Every effort was made with follow-up calls to encourage individuals with incomplete/missing data. While the pattern of analgesia appeared to transition from posterior to anterior, suggestive of an analgesic component from the ACB, the study was not powered to map the change in analgesia location. Further trials considering the predominant site of pain after ACLR are needed to know the analgesic utility of ACB. In conclusion, the addition of ultrasound-guided perihamstring injection or anterior division of obturator nerve block to an ACB did not reduce NRS or opioid consumption after ACLR.
Authors’ contributions Acquisition of data: DFJ, RVS, VU, RL, RG, SG Drafting the article: DFJ, RVS Analysis and interpretation of data: DFJ, RVS, VU Revising manuscript critically for important intellectual content: DFJ, RVS, VU, SG Final approval of the version to be published; agreement to be accountable for all aspects of the work thereby ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved: all authors Substantial contribution to conception and design: RVS, VU, RL, RG, SG Revising the manuscript critically for important intellectual content pertaining to the surgery: RL, RG
Declaration of interest The authors declare that they have no conflict of interest.
Funding Internal research grant, Department of Anesthesia internal research fund, University of Western Ontario, London, ON, Canada.
Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.bja.2019.11.032.
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Handling editor: Jonathan Hardman