Comparison between Local Infiltration Analgesia and Ultrasound Guided Single Shot Adductor Canal Block Post Total Knee Replacement Surgery - A Randomized Controlled Trial.

CONTEXT: Good quality analgesia posttotal knee arthroplasty (TKA) contributes majorly to early mobilization and shorter hospital stay. AIM: To compare adductor canal block (ACB) versus local infiltration analgesia (LIA) for postoperative pain relief in patients undergoing TKA. SETTINGS AND
DESIGN: This prospective, single-blind, randomized controlled trial was undertaken at a tertiary care university hospital.
MATERIALS AND METHODS: Sixty patients of American Society of Anesthesiologists physical status Classes I, II, and III, who received spinal anesthesia for TKA were randomly allocated to two groups. Group A patients had LIA of the knee joint using a mixture of 50 mL of 0.25% bupivacaine, 10 mg morphine (1 mL) and 99 mL of normal saline. Group B patients received ACB using 25 mL of 0.5% bupivacaine under ultrasound guidance. All patients received multimodal analgesia comprising of paracetamol, diclofenac, and patient controlled analgesia with morphine in the first 24 h' postoperative period. The primary outcome measures were first 24 h' morphine consumption and pain scores at 4, 6, 8, 12, and 24 h. The secondary outcome measures were nausea/vomiting, sedation, and patient satisfaction scores. STATISTICAL ANALYSIS: Statistical analysis was performed using the Student's t-test, Mann-Whitney test, and Chi-square test.
RESULTS: The 24 h morphine consumption was 11.97 ± 7.97 and 10.83 ± 6.41 mg in the LIA group and ACB group, respectively (P = 0.54). No significant differences were noted either in the pain scores at rest and flexion or secondary outcome measures between both groups in the first 24 h.
CONCLUSION: Single-shot ACB is equally effective as LIA as postoperative analgesia for TKA. Copyright:

INTRODUCTION

Popular analgesic options for total knee arthroplasty (TKA) include intrathecal morphine (ITM), femoral nerve block (FNB), and local infiltration analgesia (LIA). ITM risks respiratory depression, pruritus, nausea, and vomiting. FNB although effective[1] can cause quadriceps motor block, delayed mobilization, and increased injury and fall risk.[2] A meta-analysis has shown that adductor canal block (ACB) offers similar pain control as FNB with quadriceps strength preservation and improved mobilization.[3] The main nerves blocked in the adductor canal are saphenous nerve, nerve to vastus medialis, medial cutaneous nerve, and anterior and posterior branches of the obturator nerve.[4] All except the nerve to vastus medialis are purely sensory supplying the anteromedial aspect of the knee.

LIA as an effective analgesia for hip and knee replacement surgery was popularized by Kerr and Kohan in 2008.[5] Several studies indicate that FNB provide similar analgesia to LIA for post-TKA pain relief.[67] We hypothesized that ACB will also provide similar pain relief as LIA. If so ACB with its quadriceps sparing advantage may be preferred to FNB.

MATERIALS AND METHODS

After institution review committee approval in accordance with the Helsinki Declaration of 1975 (as revised in 2013), our trial was registered with Australia New Zealand Clinical trials registry, ACTRN12618001771246.

Our study was a prospective, single-blinded, randomized controlled trial (RCT). The study included 60 adult patients (18–75 years) belonging to the American Society of Anesthesiologist (ASA) physical status Classes I to III, who were admitted for unilateral TKA and had consented for spinal anesthesia along with either LIA or ACB. The exclusion criteria applied were patients with contraindication to spinal anesthesia/nerve block, patients with allergy to local anesthetics/morphine/paracetamol or nonsteroidal anti-inflammatory drugs (NSAIDs), patients on regular opioid use, ASA physical status Class IV patients, and patient refusal to spinal or block. These 60 patients were divided into two groups: Group A and Group B based on a simple randomization table created by the computer software.

All 60 patients enrolled for the study received spinal anesthesia with a combination of 0.5% bupivacaine heavy, 2.8 mL with 20 mcg fentanyl prior to surgery. Group A patients were given LIA at the end of surgery which was injected at the posterior capsule, anterior capsule, patellar tendon, quadriceps tendon, and subcutaneous tissue at incision line. The LIA was prepared using a mixture of 50 mL of 0.25% bupivacaine (B. Braun), 10 mg (1 mL) morphine (Mundipharma) and 99 mL normal saline to make a volume of 150 mL. Group B patients were given ACB under ultrasound guidance with 25 mL 0.5% bupivacaine (B. Braun) at the mid-thigh level at the end of surgery. With the patient in the supine position, a linear transducer probe was placed centrally at the mid-thigh level to identify the femur. The probe was then slid medially to identify the femoral artery which lies in the adductor canal. The adductor canal is an anatomical intermuscular space in the medial side of the thigh. It extends proximally from the apex of the femoral triangle to the adductor hiatus distally. It is bounded anteromedially (roof) by the sartorius, laterally by the vastus medialis and posteriorly by adductor longus and adductor magnus. In addition to the femoral artery, it contains femoral vein, saphenous nerve, nerve to vastus medialis, and branches of obturator nerve. Using a 22 G stimuplex needle in an in-plane approach, the needle was advanced from lateral to medial side to lie just lateral or superficial to femoral artery beneath the sartorius in the adductor canal. After negative aspiration for blood, a test dose of local anesthetic was injected to observe spread around the nerve. If no nerve was visible, then injection was made to observe spread around femoral artery. After ensuring correct spread, a total of 25 mL of 0.5% bupivacaine was injected with frequent aspiration ensuring that there was no intravascular injection. All patients at the time of surgical wound closure received 1 g of paracetamol intravenous (i.v.) and 50 mg of diclofenac i.v. Postsurgery, all patients received multimodal analgesia comprising of 1 g oral paracetamol q 6 h, oral diclofenac 50 mg q 8 h and i.v. Patient controlled analgesia (PCA) morphine. The PCA morphine was prepared at concentration of 2 mg.mL− 1 programmed to a bolus dose of 1 mg, lockout interval of 5 min with a maximum 4 h limit of 30 mg.

An investigator blinded to the group allocation assessed the morphine consumption, severity of pain, nausea/vomiting, and sedation at 4, 6, 8, 12, and 24 h from the time of arrival to the postanesthesia care unit. Pain scores were assessed using the Numerical Rating Scale (NRS), with 0 being no pain and 10 being worst imaginable pain. Sedation scores were assessed using the Pasero Sedation Scale.[8] Nausea/vomiting was assessed at above-mentioned time intervals on a yes/no basis. Overall, patient satisfaction scores with respect to pain relief were assessed at the end of 24 h' postsurgery on a five-point Likert scale where the patients were asked if they were satisfied with the analgesia provided. They were asked to rate their satisfaction as 1 for strongly disagree, 2 for disagree, 3 for neither agree nor disagree, 4 agree and 5 strongly agree. Primary outcome measures in our study were total morphine consumption and pain scores in the first 24 h' postsurgery. Secondary outcome measures were nausea/vomiting, sedation, and patient satisfaction scores.

The anesthesiologist and surgeon involved in administering the ACB or LIA were aware but the investigators assessing the outcome or analyzing the results were blinded. All surgeries were performed by the same surgeon and the ACB was performed by the same anesthesiologist.

Sample size calculation

A pilot study with 5 in each group was performed with morphine consumption at 24 h as the primary end point. The results of the pilot study revealed approximately 30% reduction in morphine consumption (Group A: 13.7 ± 3.9 and Group B: 9.8 ± 3.8) in the Group B. At 95% confidence interval 80% power, a sample size of 30 in each group was calculated using OpenEpi online calculator.

RESULTS

Patients were allocated as shown in CONSORT diagram [Figure 1]. Table 1 depicts age and physical characteristics. The patients in both groups were comparable with no statistical significance in terms of age, height, weight, or body mass index [Table 1]. One of our primary endpoints was i.v. PCA morphine consumption in the first 24 h, as described in Table 2. The mean morphine consumption was 11.97 ± 7.97 and 10.83 ± 6.41 mg in Groups A and B, respectively. While the patients who underwent ACB (Group B) had a slightly lower intake of morphine, the difference was not significant (P = 0.54). The other primary endpoint was a comparison of first 24 h' postoperative pain scores at rest and flexion using the NRS in both groups, as illustrated in Table 3. Overall, there was no statistical difference between the two groups as compared in our study with regard to pain score at rest and at flexion. The pain score at rest at 24 h was 0–3 NRS in 93.3% and 100% in Groups A and B, respectively (P = 0.314). The pain score at flexion of knee at 24 h was 0–3 NRS in 83.3% and 93.3% in Groups A and B, respectively (P = 0.09). Table 4 illustrates sedation scores in the first 24 h. There was no significant difference among the groups compared. Table 5 illustrates the satisfaction survey at the end of first 24 h postsurgery. Patients in both groups were equally satisfied with regard to pain relief in the first 24 h (P = 0.68). Four patients in Group A and three patients in Group B had nausea and/or vomiting in the first 24 h' postoperative period, as demonstrated in Table 6 (P = 0.68).

Figure 1

CONSORT flow diagram

Table 1

Age and physical characteristics

Baseline variables	Group A (LIA) (n=30)	Group B (block) (n=30)	P
Age (years)	63.00±5.77	64.06±4.76	0.438
Weight (kg)	88.62±15.19	86.23±20.09	0.606
Height (cm)	155.93±7.32	158.40±8.28	0.227
BMI	36.35±6.16	34.20±7.84	0.243

Student’s t-test used, P

Table 2

Morphine consumption

Time frame (h)	Group A (LIA) (n=30)	Group B (block) (n=30)	P
4	3.47±3.64	2.10±2.92	0.11
6	5.57±5.07	4.23±3.42	0.23
8	6.70±5.60	5.90±4.18	0.53
12	8.27±6.50	7.23±4.73	0.48
24	11.97±7.97	10.83±6.41	0.54

Student t-test used, P

Table 3

Pain score at rest and flexion

Time frame	At rest		P	At flexion		P
	Group A (LIA) (n=30), n (%)	Group B (block) (n=30), n (%)		Group A (LIA) (n=30), n (%)	Group B (block) (n=30), n (%)
4 h
0-3	29 (96.6)	30 (100)	0.051	24 (80.0)	25 (83.3)	0.06
4-10	1 (3.3)	0	6 (20.0)	5 (16.7)
6 h
0-3	29 (96.6)	29 (96.6)	0.784	25 (83.3)	26 (86.7)	0.38
4-10	1 (3.3)	1 (3.3)	5 (16.7)	4 (13.3)
8 h
0-3	29 (96.6)	28 (93.3)	0.742	27 (90.0)	25 (83.3)	0.90
4-10	1 (3.3)	2 (6.7)	3 (10.0)	5 (16.6)
12 h
0-3	28 (93.3)	28 (93.3)	0.974	24 (80.0)	29 (96.6)	0.80
4-10	2 (6.7)	2 (6.7)	6 (20.0)	1 (3.3)
24 h
0-3	28 (93.3)	30 (100)	0.314	25 (83.3)	28 (93.3)	0.09
4-10	2 (6.7)	0	5 (16.7)	2 (6.7)

Mann-Whitney U-test used, P

Table 4

Sedation score

Time frame	Group A (LIA) (n=30), n (%)	Group B (Block) (n=30), n (%)	P
4 h
S	1 (3.3)	0	0.085
1	29 (96.7)	28 (93.3)
2	0	2 (6.7)
6 h
S	0	0	0.085
1	28 (93.3)	29 (96.7)
2	2 (6.7)	1 (3.3)
8 h
S	2 (6.7)	0	0.085
1	28 (93.3)	29 (96.7)
2	0	1 (3.3)
12 h
S	4 (13.3)	5 (16.7)	0.83
1	26 (86.7)	25 (83.3)
2	0	0
24 h
S	0	1 (3.3)	1
1	30 (100)	28 (86.7)
2	0	1 (3.3)

Mann-Whitney U-test used, P

Table 5

Mean score patient satisfaction

Group A (LIA) (n=30)	Group B (block) (n=30)	P
4.36±1.09	4.46±0.77	0.68

Student’s t-test used, P

Table 6

Incidence of postoperative nausea and vomiting

Group A (LIA) (n=30)	Group B (block) (n=30)	P
4	3	0.68

Chi-square test used, P

DISCUSSION

The primary objective was to compare the first 24 h' morphine consumption and pain scores at 4, 6, 8, 12, and 24 h between both the groups. Our study depicted that the 24-h morphine consumption (Group A: 11.97 ± 7.97, Group B: 10.83 ± 6.41, P = 0.54) was similar in both groups. The pain scores at rest and flexion were also similar between both groups in the first 24 h. The secondary end points namely sedation score, incidence of nausea and vomiting showed no clinical or statistical differences between the study groups. Furthermore, the patient satisfaction survey at the end of first 24 h after surgery also did not differ between the groups.

Our study had similar results to the meta-analysis conducted by Zhao et al.[9] which included 8 RCTs with 675 patients undergoing TKA. They found no difference in pain scores or morphine consumption at 24 or 48 h between ACB and LIA groups post-TKA. However, the LIA group demonstrated better ambulation ability. This differed from Kampitak et al.[10] as well as Tong et al.[11] who compared ACB versus LIA for postoperative analgesia after TKA and they found the ACB group to have a lower morphine consumption in the first 24 and 48 h as compared to the LIA group. Hence, more studies definitely need to be done before arriving at firm conclusion to recommend one over other.

An important issue worth considering is the variability in the composition of the infiltration used in LIA at different centers. Most local infiltrations have ketorolac, an NSAID which in addition to analgesia prevents heterotopic ossification and promotes soft-tissue healing.[12] Andersen et al.[13] demonstrated superior pain relief in first 48 h facilitating early discharge by including ketorolac and local anesthetic combination compared to just local anesthetic for intra-articular infiltration. Kelley et al.[14] demonstrated that the inclusion of ketorolac in the analgesic mixture for peri articular infiltration provided better pain relief post-TKA as compared to analgesic mixtures without ketorolac. Similar results were demonstrated by Kim et al.[15] advocating a combination of local anesthetic, morphine, and ketorolac. Our study did not use ketorolac in the local infiltration as it is not available in the country. If ketorolac had been included in the local infiltrate, possibly a difference between the two groups in favor of LIA could have been demonstrated.

The optimal dose for local infiltration also will have an impact. Our study has different results to Sawhney et al.[16] who demonstrated that LIA group had lower pain scores on rest and movement as compared to ACB group. However, the difference was probably due to the fact that they used double the dose of ropivacaine for LIA as compared to ACB. Hence, standardization of dose is also important.

Another factor that deserves consideration is that a single injection of LIA may have a short duration of action. Andersen and Kehlet[17] reviewed 27 clinical trials to evaluate the analgesic efficacy of LIA in total hip arthroplasty and TKA. As far as TKA was concerned they concluded that LIA provided effective analgesia both in terms of reduced pain scores as well as opioid consumption in the first 48 h. However, most of these trials had wound infiltration catheters placed through which multiple postoperative analgesic injections were done as boluses or continuous infusion. Hence, it was difficult to interpret the duration of action of the intraoperative LIA. Although repeated boluses or continuous infusion of LIA through an intra-articular catheter is an option to extend the analgesia, it is limited by concerns of intra-articular infection. Perhaps, then combining LIA with single-shot ACB may be a good option to improve the quality as well as extend the duration of analgesia. In this regard, we note with particular interest the meta-analysis done by Zuo et al.[18] where they looked at TKA patients receiving postoperative analgesia with ACB or a combination of ACB plus LIA. They found that the latter group of patients had a lower Visual Analog Scale (VAS) score and morphine consumption on day 0 and day 1 as well as better range of motion. Lan et al.[19] studied patients undergoing medial unicondylar knee arthroplasty. All patients received LIA. One arm of patients received continuous ACB in addition to LIA and another arm was the placebo group who received saline instead of local anesthetic through the adductor canal catheter. They found better pain scores at rest and movement in patients receiving ACB with LIA. The quadriceps strength was comparable in both groups; however, ambulation was significantly better in the ACB + LIA group. Andersen et al.[20] also did a similar study where they compared patients receiving LIA versus patients receiving LIA plus twice a day adductor canal bolus of local anesthetic. They found significantly better pain scores and better ambulation in the combination group versus just LIA. Hence, a combination may be better and needs further research in this aspect.

An interesting option maybe the use of liposomal bupivacaine for LIA. The Pillar study[21] demonstrated a 78% reduction in opioid consumption, 13.6% reduction in VAS scores in first 48 h with liposomal bupivacaine as compared to bupivacaine. Furthermore, 10% of patients receiving liposomal bupivacaine for infiltration remained opioid free at 72 h as compared to 0% receiving bupivacaine.

The area that needs to be further explored in future would be the role of various additives to the local anaesthetic in ACB. Goyal et al.[22] demonstrated that addition of dexmeditomidine to the local anesthetic in ACB resulted in a longer duration of analgesia as compared to just local anesthetic for ACB.

One of the limitations in our study was we tested only pain at rest and on flexion. We did not evaluate motor strength or ambulation. The other limitation was our study was powered to only 30 patients in each limb. Had our study included a larger sample size, a difference between the two groups may have been a probability.

CONCLUSION

Both ACB and LIA may be used as equally effective alternative modes of analgesia post-TKA. There is still a lot of heterogeneity with regard to LIA combinations and dose used. Further studies are needed to arrive an ideal combination for infiltration and feasibility of using liposomal bupivacaine to provide longer duration of analgesia needs to be explored. ACB requires the use of ultrasound and an experienced anesthesiologist familiar with the technique which may prove to be a stumbling block in low-resource settings where LIA may be the preferred option. In well-equipped centers with the necessary expertise LIA combined with single shot or continuous ACB presents an exciting alternative which requires further research.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.