Adductor Canal Blockade Following Total Knee Arthroplasty—Continuous or Single Shot Technique? Role in Postoperative Analgesia, Ambulation Ability and Early Functional Recovery: A Randomized Controlled Trial

The Journal of Arthroplasty xxx (2015) xxx–xxx

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Adductor Canal Blockade Following Total Knee Arthroplasty—Continuous or Single Shot Technique? Role in Postoperative Analgesia, Ambulation Ability and Early Functional Recovery: A Randomized Controlled Trial Nilen A. Shah, MS, MCH(orth) a, Nimesh P. Jain, MS(orth.) a,b, Karnav A. Panchal, MS(orth.) a,c a b c

Bombay Hospital and Research Centre, Marine Lines, Mumbai, Maharashtra, India Joint Reconstruction Center, Seoul National University Bundang Hospital, Bundang-gu, Seongnam-si, South Korea Rajasthan Hospital, Shahibaug, Ahmedabad, Gujrat, India

a r t i c l e

i n f o

Article history: Received 19 July 2014 Accepted 10 March 2015 Available online xxxx Keywords: total knee arthroplasty adductor canal block continuous single shot ambulation ability analgesia

a b s t r a c t Total knee arthroplasty (TKA) can be associated with severe pain in early postoperative period. Adductor canal block may provide optimal analgesia following TKA. However, ideal regimen for administration whether continuous or single shot is yet undefined. We prospectively randomized 90 patients in continuous and single shot adductor canal blockade groups. Postoperative VAS (visual analog scale for pain) score was significantly better at all times in continuous than single shot technique (P b 0.001). However, ambulation ability (Timed Up & Go, 10 m walk, 30 s chair) and early functional recovery (active SLR, ambulation with walker, staircase competency, ambulation distance and maximal flexion at discharge) showed no statistical significant difference. Continuous adductor canal blockade was superior to single shot block in terms of pain control but was similar for early functional recovery. Level of evidence: Level III, therapeutic study. © 2015 Elsevier Inc. All rights reserved.

Total knee arthroplasty (TKA) is a frequently performed elective orthopedic intervention for painful arthritic knee. However, TKA is followed by intense pain in postoperative period. Moreover, early mobilization post-TKA can prevent knee stiffness, lessens hospital stay and improves overall patient satisfaction and outcome of TKA [1]. Besides, early knee mobilization is associated with decreased risk of deep vein thrombosis and good long-term functional outcomes [2,3]. Adequate pain relief following TKA may facilitate early mobilization and thus the overall outcomes. However, one of the challenges of treating post-operative pain after TKA with regional anesthetic techniques is to provide sufficient analgesia with preserved muscle function and minimal side effects. Conventional postoperative analgesia is provided by either intravenous patient-controlled analgesia (PCA) or epidural analgesia. Recently several studies reported an upsurge in peripheral nerve block (PNB) use for orthopedic patients [4,5]. Moreover, analgesic efficacy and surgical outcomes of PNB are comparable to PCA or epidural analgesia without the associated side-effects [5,6]. Femoral nerve block (FNB) is often considered as the gold standard for pain alleviation after TKA [4,7–11]. However, FNB reduces quadriceps muscle strength thereby potentially compromising postoperative mobilization [12–16]. Furthermore, the

No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.03.006. Reprint requests: Nilen. A. Shah, MS, MCH (orth), Flat No. 2, Building no. 2, India House, Kemps Corner, Mumbai, 400 026 Maharashtra, India.

FNB is associated with higher risks of fall due to quadriceps weakness following block [17–19]. Therefore, alternative analgesic techniques for effective pain treatment with preserved muscle function need to be evaluated. Adductor canal block (ACB), an alternative form of PNB, is almost a pure sensory nerve block. Several studies, in recent past, had reported the efficacy of ACB in management of analgesia following TKA [20–24]. Moreover, few studies [13,15,21] had demonstrated the superiority of ACB in preserving quadriceps muscle strength and thereby early mobilization compared to FNB. In addition, the administration of ACB may be accomplished either as a single shot injection or as a continuous block using epidural catheter and infusion. Furthermore, no previous study in literature has studied the differences in efficacy of a single shot adductor canal or continuous adductor canal blockade post-TKA. Hence, an ideal regimen for adductor canal blockade to provide optimum pain relief and concomitantly promote early patient mobilization following TKA needs to be defined. The present study aimed to determine and compare the efficacy of continuous adductor canal block (CACB) and single shot adductor canal block (SACB) on (1) postoperative pain control, (2) early patient ambulation and functional recovery and (3) opioid consumption, treatment related side effects and complications post-TKA. As continuous block technique permits the delivery of local anesthetic for prolonged duration, we hypothesized that there will be a significant difference between the CACB group and the SACB group in terms of postoperative analgesia, ambulation ability and early functional recovery after TKA.

http://dx.doi.org/10.1016/j.arth.2015.03.006 0883-5403/© 2015 Elsevier Inc. All rights reserved.

Please cite this article as: Shah NA, et al, Adductor Canal Blockade Following Total Knee Arthroplasty—Continuous or Single Shot Technique? Role in Postoperative Analgesia, Am..., J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.03.006

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N.A. Shah et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx

Patients and Methods Study Design and Subjects After obtaining institutional ethics committee approval, we assessed all 90 consecutive patients scheduled for unilateral primary TKA, from January 2014 to March 2014 for inclusion into the study. Written informed consent was obtained from all subjects prior to enrolment. To determine whether our sample size had sufficient statistical power, we performed a priori power analysis using the two-sided hypothesis test at an alpha level of 0.05 and a power of 80%. Forty-four (22 in each group) were required to detect a 10 mm difference in pain scale, which we considered clinically significant. Accordingly, the study sample size of 85 knees (46 in CACB and 39 in the SACB group) satisfied the priori analysis described earlier and to allow for exclusions and dropouts. Eligibility criteria included were primary, unilateral TKA under spinal anesthesia, and American Society of Anesthesiologists physical status classification of I–III. Exclusion criteria included renal insufficiency, contraindications to adductor canal block (localized infection, sepsis, preexisting lower extremity neurological abnormality), history of arrhythmia or seizures, history of chronic pain unrelated to the knee requiring treatment with long acting opioids, alcohol or drug abuse, allergy to local anesthetics and difficulties in comprehending visual analog scale (VAS) pain scores. Of the 90 patients assessed 3 patients were excluded for the following reasons: two patients with ASA grade 4 or above and one patient with renal insufficiency and raised

creatinine levels. With these exclusions, 87 patients were enrolled for the study and randomized into two groups (SACB or CACB), using computer generated randomization table with a permutation block of six (Fig. 1). Thus, 47 and 40 patients were assigned in CACB and SACB group respectively. Moreover, one patient in each group had a failure of block. Thus a total of 85 (46 CACB, 39 SACB) patients were assessed for analysis. The patients and a clinical investigator (N.P.J.) who prospectively collected all clinical information were unaware of the group identities until the final data analysis. There were no significant differences in the demographic data, preoperative status and operative time among the two groups (Table 1). Anesthesia Technique Spinal anesthesia was induced with 3.0 ml 0.5% hyperbaric bupivacaine at the L3/4 interspaces (alternatively at the L2/3 or L4/5 interspaces). Sedation using propofol and intravenous fluid therapy during surgery was administered at the discretion of the anesthetist. Administration of Adductor Canal Block In all patients, ACB was performed immediately postoperatively. After sterile preparation and draping, at the midthigh level, approximately halfway between the anterior superior iliac spine and the patella, a high-frequency linear ultrasound (US) transducer (S—Nerve Ultrasound, Sonosite Inc., Bothell, WA, USA) was placed transverse to

Enrollment

Assessed for eligibility (n=90)

Excluded (n=3) ♦ Not meeting inclusion criteria (n= 3) ♦ Declined to participate (n=0) ♦ Other reasons (n=0)

Analysis

Follow up

Allocation

Randomized (n= 87)

CACB (n=47) allocated Intervention (n=47) ♦ Did not receive allocated Intervention (n= 0) ♦ Received

SACB (n=40) allocated Intervention (n=40) ♦ Did not receive allocated Intervention (n=0) ♦ Received

Lost to follow-up (n= 0)

Lost to follow-up (n= 0)

Discontinued intervention (n=1)

Discontinued intervention (n=1)

Analysed (n=46) ♦ Excluded

(n=1)

from analysis

Analysed (n= 39) ♦ Excluded

from analysis

(n=1)

Fig. 1. Flow diagram showing patient selection and randomization.

Please cite this article as: Shah NA, et al, Adductor Canal Blockade Following Total Knee Arthroplasty—Continuous or Single Shot Technique? Role in Postoperative Analgesia, Am..., J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.03.006

N.A. Shah et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx Table 1 Demographic Characteristics of Patients in CACB and SACB Groups. Demographic Variables Gender Male Female Age (years) Height (cm) Weight (kg) BMI (kg/m2) ASA grade I II III Patient category A B Preoperative VAS Operative time Catheter placement time

CACB (N = 46)

SACB (N = 39)

13 (28.3)a 33 (71.7)a 68.34 (7.71) 155.28 (8.75) 71.09 (14.24) 29.58 (5.55)

7 (17.9)a 32 (82.1)a 66.30 (6.38) 154.61 (8.19) 72.40 (16.20) 30.27 (5.40)

12 (26.1)a 32 (69.6)a 2 (4.3)a

14 (35.9)a 23 (59.0)a 2 (5.1)a

18 (39.1)a 28 (60.9)a 66.52 (5.85) 69.00 (4.60) 4.95 (0.73)

14 (35.9)a 25 (64.1)a 68.20 (4.93) 67.51 (4.82) 4.82 (0.72)

P Value 0.312

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i.v. was administered in case of moderate to severe nausea or vomiting, if needed. The adductor canal catheter was removed at 8:00 am on postoperative day (POD) 2 and site was inspected daily for signs of localized infection. Outcome Assessment

0.193 0.719 0.692 0.562 0.646

0.824

0.161 0.151 0.391

Data are presented as mean with standard deviation in the parenthesis. CACB, continuous adductor canal block group; SACB, single shot adductor canal block group; BMI, body mass index; ASA, American Society of Anesthesiologists physical status; VAS, visual analog scale. a Data are presented as number of patients with percentage in the parenthesis.

the longitudinal axis of the extremity. Underneath the sartorius muscle the femoral artery was identified, with the vein just inferior and the saphenous nerve just lateral to the artery. From the lateral side of the transducer a 10-cm, 18-gauge Tuohy needle (Braun Medical, Melsungen, Germany) was inserted in plane, through the sartorius muscle. With the tip of the Tuohy needle placed just lateral to the artery and the saphenous nerve, 20 ml of 0.75% Ropivacaine was injected to expand the adductor canal. A 21-gauge catheter was then inserted 5–8 cm through the cannula. To obtain the correct position of the catheter tip, the catheter was slowly retracted during injection of a further 10 ml of Ropivacaine under US guidance, until an expansion between the fascia and the vessels could be visualized. All blocks were performed by a senior anesthesiologist (D.A.C.), with considerable experience in USguided nerve blocks. SACB group patients were given a single shot loading dose of 30 cc inj. ropivacaine 0.75% followed by a bolus of inj. normal saline 30 cc at an interval of 4 hours post-operatively, while CACB group patients were given a loading dose of 30 cc inj. ropivacaine 0.75% followed by repeated boluses of inj. ropivacaine 0.25%, 30 cc at an interval of 4 hours till 8:00 am on the morning of the second day after surgery.

At the time of admission, patients were explained about the visual analog scale pain scale and mobilization ability assessment. Patients were assessed for pain at 4, 8, 12 and 24 hours postoperatively, pain at rest, pain after mobilization on POD1 and POD2, opioid consumption, side effects if any. Ambulation ability was assessed 24 hours after the block, in form of Timed Up & Go (TUG) test, 10 m walk test and 30 s chair stand test [12]. Furthermore, time to active SLR, ambulation with walker, and staircase competency were measured. Also, ambulation distances at discharge, maximal flexion at discharge and length of hospital stay were evaluated. Pain was evaluated on a VAS with 0 = no pain, and 100 = worst imaginable pain. The TUG test measures the time it takes a person to stand up from a chair, walk a distance of 3 m, and return to the chair. The 10-m walk test measures the time it takes to walk a distance of 10 m as quickly as possible. The 30-s Chair Stand test assesses how many times a person is able to rise from a chair and sit down again in 30 s, with the arms kept crossed over the chest. The mobilization tests have been validated in previous studies [25–27]. During the assessment of ambulation ability, use of gait aids was not allowed. The tests were only performed if the subject felt that it was possible without the risk of falling. Statistical Analysis Statistical analyses were performed using SPSS® for Windows® (version 20.0, IBM, Chicago, IL, USA). The nature of the hypothesis testing was 2-tailed and a P value less than 0.05 was considered statistically significant, for all comparisons. The Kolmogorov–Smirnov test was used to determine whether measured and calculated parameters were normally distributed. The multivariate analysis of variance (MANOVA) was done so as to assess multiple outcomes evaluated for each patient. Moreover, a separate analysis of variance (ANOVA) was conducted for each dependent variable with each ANOVA evaluated at an alpha level of 0.05. In addition, the correlation analyses were carried out to investigate the confounding effects of patient factors such as age, weight, height, and BMI. No significant group differences were found for demographic data (Table 1). Results

Surgical Procedure and Perioperative Management All surgeries were done by the senior author (N.A.S.) using minisubvastus approach. All surgeries were performed without the use of a tourniquet. Cruciate retaining implants were used in all cases and patella was resurfaced in selected group of patients. All patients were given intraarticular cocktail infiltration (20 cc 0.25% sensorcaine + 250 mg inj. cefuroxime + 40 mg inj. triamcenolone acetate—not in diabetic patients). Below knee TED stockings for both lower limbs were utilized. Aspirin 75 mg OD for 6 weeks was used as a chemical prophylaxis for DVT. Perioperative intravenous antibiotics were given to all patients. Intravenous patient controlled analgesia was provided with inj. diclofenac sodium 75 mg in 100 cc NS 8 hourly, if pre-operative serum creatinine level was normal, otherwise inj. paracetamol 1000 mg infusion was given 8 hourly. In both groups of patients, inj. tramadol 50 mg was given for breakthrough pain (termed “rescue analgesia”). Additional analgesics consisted of oral acetaminophen 500 mg administered at 6 hours intervals starting 6 hour postoperatively. Ondansetron 4 mg

Postoperative pain scores assessed in the form of VAS scale (Table 2) showed better results in the CACB group than in the SACB group. Accordingly, VAS score at 4, 8, 12, and 24 hours after surgery showed significantly superior results in CACB than in the SACB groups (22.39 ± 4.56 vs. 26.15 ± 4.04, 20.51 ± 4.01 vs. 26.79 ± 4.93, 21.08 ± 5.66 vs. 27.82 ± 5.1 and 20.76 ± 4.29 vs. 26.92 ± 4.38; Hotelling's Trace = 3.737/Wilk's lambda = 0.211, F(8,76) = 35.506, P b 0.001 respectively). Similarly, pain scores at rest and after mobilization were better in the CACB group on POD1 (20.78 ± 4.34 vs. 27.30 ± 4.41 and 26.63 ± 4.22 vs. 36.28 ± 4.54, P b 0.001, respectively) and POD 2 (15.43 ± 2.94 vs. 22.94 ± 2.97 and 22.06 ± 2.9 vs. 30.12 ± 4.5, P b 0.001, respectively), with significant intergroup differences. The ambulation ability (Table 3) assessed by TUG test, 10-m walk test and 30 s chair test showed that patients in the CACB group were faster than those in the SACB group, but without any statistical significance (57.95 vs. 60.33, 67.60 vs. 70.12, 0.68 vs. 0.72 respectively, Hotelling's Trace = 0.957/Wilk's lambda = 0.511, F(8,76) = 9.090, P N 0.05). Moreover, time to active SLR, ambulation with walker, and staircase competency showed similar results with no significant

Please cite this article as: Shah NA, et al, Adductor Canal Blockade Following Total Knee Arthroplasty—Continuous or Single Shot Technique? Role in Postoperative Analgesia, Am..., J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.03.006

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N.A. Shah et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx

Table 2 Group Statistics of Visual Analog Scale for Assessment of Pain, in Patients, in CACB and SACB Groups. VAS Score

DOO 4 hours 8 hours 12 hours 24 hours POD1 at rest POD1 after mobilization POD2 at rest POD2 after mobilization

Block

CACB SACB CACB SACB CACB SACB CACB SACB CACB SACB CACB SACB CACB SACB CACB SACB

No. of Patients

46 39 46 39 46 39 46 39 46 39 46 39 46 39 46 39

Mean

22.39 26.15 20.51 26.79 21.08 27.82 20.76 26.92 20.78 27.3 26.63 36.28 15.43 22.94 22.06 30.12

SD

4.56 4.04 4.01 4.93 5.66 5.1 4.29 4.38 4.34 4.41 4.22 4.54 2.94 2.97 2.9 4.57

SEM

0.64 0.69 0.65 0.71 0.79 0.86 0.63 0.69 0.64 0.71 0.61 0.70 0.43 0.47 0.55 0.60

F Value

Sig. P Value

1.634

b0.001

3.511

b0.001

0.008

b0.001

0.13

b0.001

0.204

b0.001

0.127

b0.001

3.702

b0.001

3.898

b0.001

95% CI of Difference Lower

Upper

21.12 24.77 19.19 25.37 19.49 26.09 19.48 25.54 19.47 25.91 25.34 34.88 14.56 22.01 20.96 28.93

23.66 27.53 21.80 28.21 22.04 29.54 22.03 28.30 22.04 28.70 27.91 37.67 16.30 23.89 23.16 31.32

VAS, visual analog scale; CACB, continuous adductor canal block group; SACB, single shot adductor canal block group; SD, standard deviation; SEM, standard error of mean; sig., significance; CI, confidence interval; DOO, day of operation; POD, postoperative day.

Discussion

intergroup difference (5.32 vs. 5.46, 8.56 vs. 8.60, 23.33 vs. 23.39 respectively, P N 0.05). Also, ambulation distance at discharge, maximum flexion at discharge and length of hospital stay displayed almost identical results with no statistical significance (90.32 vs. 89.23, 106.5 vs. 106.4, 3.08 vs. 3.20, P N 0.05, respectively). The average time for catheter placement was similar in both the groups without any significant difference (4.95 vs. 4.82, P = 0.391). Besides, one patient in each group had a failure of block with a success rate of about 97.8% and 97.4% in the CACB group and SACB group respectively. Two patients in the SACB group required rescue analgesia in the form of inj. tramadol (50 mg) while none of the patient in the CACB group required rescue analgesia. Between the two patients who required rescue analgesia in the SACB group, one patient required only a single injection of 50 mg tramadol at 8 hours post-operatively whereas the other patient required 3 injections at 8 hours, 16 hours and 24 hours post-operatively. One patient in each group had single episode of nausea and vomiting and were treated accordingly. None of the patient in both groups showed any other side effects or treatment related complications.

Total knee arthroplasty can be associated with severe, early postoperative pain. Thus, optimal analgesia after major knee surgery is prerequisite to facilitate early rehabilitation and mobilization, enhance functional recovery and to minimize post-operative morbidity [1]. Femoral nerve block is effective in pain control post-TKA [4,7,8,11]. However, it results in quadriceps weakness [12–16] and thus there is trade-off between the goals of adequate pain relief and muscle strength. Adductor canal block has been found to be an effective modality for postoperative analgesia with minimal quadriceps weakness [15,20–24]. However, the ideal local anesthetic regimen for ACB administration that maintains balance between the analgesia and early mobilization to an optimal level is yet to be determined. Therefore, the present study was conducted to evaluate and compare the efficacy of continuous and single shot adductor canal block with regard to pain control, ambulation ability, early functional recovery, the success rate and treatment related side effects.

Table 3 Group Statistics of Postoperative Ambulation Ability Assessment and Functional Recovery of Patients in CACB and SACB Groups. Outcome Variable

TUG test (s) 10-m walk test (s) 30 s chair test Time for active SLR (hours) Time for ambulation with walker (hours) Time for staircase competency (hours) Ambulation distance at discharge (meters) Maximum flexion at discharge (degrees) Length of hospital stay (days)

Group

CACB SACB CACB SACB CACB SACB CACB SACB CACB SACB CACB SACB CACB SACB CACB SACB CACB SACB

Mean

57.95 60.33 67.6 70.12 5.28 5.01 5.32 5.46 8.56 8.6 23.33 23.39 90.32 89.23 106.5 106.4 3.08 3.2

SD

8.46 3.82 6.11 6.12 0.68 0.72 1.03 0.94 1.97 1.65 1.73 1.67 9.03 9.42 8.74 8.42 0.35 0.4

SEM

1.24 0.61 0.89 0.98 0.11 0.11 0.15 0.15 0.29 0.26 0.25 0.26 1.33 1.51 0.05 0.06 1.29 1.34

F Value

Sig. P Value

1.045

0.094

0.559

0.078

0.416

0.091

0.589

0.532

2.939

0.911

0.06

0.876

0.033

0.586

0.061

0.953

4.714

0.157

95% CI of Difference lower

upper

49.38 59.93 64.82 67.95 5.08 4.30 5.03 5.14 8.07 7.98 22.89 22.79 87.62 86.29 96.23 95.73 2.97 3.08

53.08 63.95 68.83 72.30 5.47 4.72 5.61 5.77 9.14 9.14 23.89 23.87 93.02 92.16 108.2 107.8 3.19 3.32

CACB, continuous adductor canal block group; SACB, single shot adductor canal block group; SD, standard deviation; SEM, standard error of mean; sig., significance; CI, confidence interval; TUG, Timed Up & Go; SLR, straight leg raising.

Please cite this article as: Shah NA, et al, Adductor Canal Blockade Following Total Knee Arthroplasty—Continuous or Single Shot Technique? Role in Postoperative Analgesia, Am..., J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.03.006

N.A. Shah et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx

The findings of the study support our hypothesis that CACB is better than SACB in optimal postoperative analgesia following TKA (Table 2). Postoperative pain evaluated as VAS score showed significantly better results in the CACB group, at 4, 8, 12, 24 hours following surgery, as well as in pain at rest and pain after mobilization on POD1 and POD2. These findings may be intuitively explained by the fact that continuous nerve blockade permits the delivery of local anesthetic for prolonged duration compared to single shot technique [28]. Consequently, the continuous infusion catheters are expected to provide effective analgesia for longer time. Also, the present study is first to report the results of comparison between continuous and single shot adductor canal blockade. Several studies have reported the efficacy of adductor canal block in postoperative analgesia following TKA or arthroscopic procedures [15,20–24,29]. Moreover, few studies reported that duration of analgesic effect from single shot technique is typically 12 to 24 [6,30] hours but may be as long as 48 hours [31], with varying efficacy. And, the severe pain following TKA, particularly during early mobilization and physiotherapy, may persist through the second day after surgery [1,31]. Consequently, several similar studies on comparison of continuous and single shot femoral nerve block showed better results with continuous femoral nerve block [7,10,32,33]. Nevertheless, the ACB in both the groups, was administered immediately after the surgical procedure when the effect of spinal anesthesia was still present and the patients, therefore, remain pain free postoperatively. Furthermore, 2 patients in the SACB group required rescue analgesia in the form of inj. tramadol 50 mg in normal saline whereas none of the patient in the CACB group required the rescue analgesia used in our study, probably due to better analgesia with CACB technique. Our findings concur with multiple studies [7,32,33] on femoral nerve block that CFNB required less opioid analgesics than SFNB. Also, a previous study had showed that unilateral peripheral nerve blocks provide analgesia quality and functional outcomes similar to that of continuous epidural analgesia and superior to that of systemic intravenous opioid analgesia, but with fewer side effects [34]. However, adductor canal blockade following TKA does not provide total analgesia as knee is innervated by the lumbar plexus (femoral and obturator nerve) anterolaterally and the sacral plexus posteriorly (sciatic nerve) [35,36]. In addition, it is important to note that none of the blocks can provide complete analgesia around the knee per se and thus evaluation of different analgesic techniques alone or in combination is warranted. However, every patient, in our study, was given basic regimen including inj. diclofenac sodium 75 mg in 100 cc NS 8 hourly or inj. paracetamol 1000 mg every 8 hours for pain control during the hospitalization period. The findings of present study did not support the hypothesis that CACB provides better results in terms of ambulation ability and early functional recovery, as compared to SACB technique (Table 3). Ambulation ability assessed by TUG test, 10-m walk test and 30-s chair test showed similar results in both the groups with no statistical significance (P N 0.05). Moreover, time to active SLR, ambulation with walker, and staircase competency, ambulation distance at discharge, maximal flexion at discharge and length of hospital stay were almost the same between CACB and SACB groups. ACB is almost a pure sensory nerve block that only affects the motor function of vastus medialis due to its effect on nerve to the muscle as it traverses the adductor canal. Moreover, ACB reduces quadriceps strength by only 8% [12] and spares motor function and balance [14] as reported in human volunteers. Likewise, recent studies [13,15] reported superior motor function preservation and ambulation ability with adductor canal block. However, whether the modality used, either continuous or single shot, has any variable effect on ambulation ability is not yet known. Albeit, the ambulation ability and early functional recovery showed no difference between the two groups, findings in the CACB group were better than those in the SACB group without reaching statistical significance. All blocks were performed by a senior anesthesiologist with considerable experience in US guided peripheral nerve blocks. The success rate of the adductor canal block was 97.8% in the CACB group and 97.4% in the SACB group. The success rate was comparable with results in similar

5

studies using US guided adductor [13,22,23] and saphenous nerve block [37,38]. The success of the block was determined after each bolus injection by assessing the pin prick sensation with similar force on both legs in the saphenous area of distribution; specifically on the medial side of the lower leg and if on the operated side pain was less the block was considered effective. The mean time taken for administration of ACB catheter placement was similar in the CACB and SACB groups (4.95 vs. 4.82, P = 0.391), with no significant intergroup difference. However, the time required for catheter placement did not add significantly to the primary surgical procedure. We used high volume about 30 ml of local anesthetic agent in both the block groups. This large volume of local anesthetic is required to fill the adductor aponeurotic space even in its distal extent where posterior branch of obturator nerve joins the canal as demonstrated by Lund et al [24] in their study on CACB. Moreover, we preferred intermittent boluses of local anesthetic over continuous infusions specifically in CACB to ensure the appropriate spread of drug throughout the adductor canal. Multiple previous studies [39,40] have shown that intermittent boluses provide superior analgesia compared with continuous infusions via an indwelling catheter, even though the mechanism is unknown. Although peripheral nerve blocks have definite advantages over conventional pain controlling techniques there are some reported side effects with its use like catheter site infection [41], prolonged nerve palsies [17] and heel ulcers [42] due to sensory blockade. However, no such complications, in any patient were noted in our study. Several limitations of the study should be noted. First, regarding the study patient population, 76.5% (65/85) of our patients were females. Furthermore, our patients tended to be elderly (mean age N 66 years old). Moreover, because factors, such as, age, gender, and ethnicity probably influence pain perception, these cohort-related characteristics should be considered before foreseeing our findings to patient populations in different parts of the world. Second, in addition to the block, patients in both study groups also received continuous mode IV-PCA in the form of injection diclofenac and oral analgesics for pain control, because we believed that the removal of routine pain control for study purposes would be unethical. Thus evaluation of block role in pain control may not be precisely depicted by our results. Third, the assessment timings for ambulation ability 24 hours after surgery might have differed because surgeries were completed at varied times during the day, and the evaluation was performed at a fixed time point. However, assessment by a single investigator in a ward is considered to be more reliable than assessments performed by different inpatient care providers. Finally, we had not applied any specific monitoring devices to measure the adverse effects of ropivacaine use as anesthetic drug for block; instead, patients were monitored closely for clinical symptoms. Furthermore, no assessments of serum levels of ropivacaine were undertaken, and thus, we failed to determine whether the levels rose beyond the toxic threshold after large volume administration for block in both groups. However, no patients developed a ropivacaine-related toxicity or complication. In conclusion, the adductor canal block, either continuous or single shot, is almost a pure sensory block and can be utilized as an adjunct for postoperative analgesia post-TKA. The continuous adductor canal block showed significantly superior results in terms of pain control than the single shot group. However, the ambulation ability and early functional recovery showed no significant difference among the two groups. Lastly, the adductor canal block, and the type of local anesthetic used, cannot provide complete analgesia around knee. Therefore, the effect of co-administration of other nerve blocks or analgesic methods following knee surgery is a matter of further investigations. Acknowledgments The authors are grateful to Dr. Deepa Chaudhari, the anesthetist who actively showed her interest in assisting us with the execution of the trial. They wish to also specifically thank Dr. Palak Wani, the physiotherapist for her invaluable assistance.

Please cite this article as: Shah NA, et al, Adductor Canal Blockade Following Total Knee Arthroplasty—Continuous or Single Shot Technique? Role in Postoperative Analgesia, Am..., J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.03.006

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Please cite this article as: Shah NA, et al, Adductor Canal Blockade Following Total Knee Arthroplasty—Continuous or Single Shot Technique? Role in Postoperative Analgesia, Am..., J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.03.006