Impact of Intra-Articular Local Anesthesia Infiltration versus Femoral Nerve Block for Postoperative Pain Management in Total Knee Arthroplasty.

Background: Postoperative pain relief after total knee arthroplasty (TKA) can be attained by using several techniques such as intravenous analgesia, epidural analgesia, and peripheral nerve blocks that include femoral nerve and saphenous nerve. Several authors recommended intra-articular injection of local anesthetic (IALA) as a part of multimodal analgesia regimens for TKA instead of other techniques. Aims: The present study compares IALA technique efficacy with single-shot femoral nerve block (FNB) as part of multimodal analgesia regimen in TKA patients for postoperative pain management. Setting and Design: Perioperative care, randomized double-blind comparative study. Subjects and
Methods: We recruited a total of 60 patients scheduled for unilateral total knee replacement under spinal anesthesia. Subjects were allocated randomly into two groups FNB and IALA receiving ultrasound-guided FNB and Intra-articular local anesthesia and morphine mix infiltration, respectively. Twenty-four hour postoperative morphine consumption through patient-controlled analgesia was the primary outcome measure in our study. Secondary outcome measures were pain scores, nausea and vomiting. Statistical Analysis: Chi-square test, Mann-Whitney test.
Results: The amount of morphine consumed at the end of 24 h was noted to be higher in IALA group as compared to FNB (FNB - 16.03 ± 9.37 mgs; IALA - 23.60 ± 13.73 mgs P = 0.03). Visual analog score at 24 h with knee flexion was better in FNB group (FNB - 1.27 ± 1.43; IALA 2.42 ± 2.54, P = 0.04).
Conclusion: FNB technique provides better analgesia in comparison to IALA for postoperative pain management in terms of PCA morphine consumption. Copyright:

INTRODUCTION

Total knee arthroplasty (TKA) is one of the common elective orthopedic procedures done in elderly individuals. Fast track recovery approach has been employed in few centers with good success.[1] The essence of early recovery revolves around the postoperative management that includes good pain control, and early ambulation.[123] The preferred anesthesia for TKA should provide stable intraoperative conditions and rapid recuperation. Postoperative pain is often severe and inadequate pain relief after TKA may prevent early rehabilitation, delayed discharge from hospital[3] and these factors may adversely affect functional outcomes. Conventionally, various analgesic techniques have been used to reduce postoperative pain following TKA that includes patient-controlled analgesia (PCA) using opioids, epidural analgesia, local infiltration analgesia, single-shot or continuous femoral nerve block (FNB), and adductor canal block. Our study compared the postoperative analgesic efficacy of FNB in comparison to intra-articular injection of local anesthetic (IALA) mixture in terms of the amount of PCA morphine consumption in first 24 h, reduction in pain intensity assessed by visual analog scale (VAS) score, opioid-related side effects and time to ambulation after TKA.

SUBJECTS AND METHODS

This single-blinded, prospective, randomized comparative study was conducted in our tertiary hospital after the approval by Institutional Review Board (No. 146/2016). This study was prospectively registered with ANZTCR (ACTRN12616001380482). A total of 60 patients were recruited for the study after explaining them the procedure and obtained informed and written consent as per Helsinki declaration. Figure 1 represents the CONSORT flow chart of the study sample. Randomization was done among the two groups using computer-generated random table. The inclusion criteria were patient undergoing primary TKR, age 40–80 years of either sex, the American Society of Anesthesiologists (ASA) Physical status classes I and II. The exclusion criteria were ASA physical status classes > III, history of allergy/contraindications to morphine, local anesthetics, nonsteroidal anti-inflammatory drugs, paracetamol, central neuraxial block and peripheral nerve blocks and patients who are receiving regular opioids.

Figure 1

CONSORT 2010 flow diagram

All patients received standardized spinal anesthesia using 25G spinal needle in the L4-L5 interspace with a combination of 2.2 mL of 0.5% hyperbaric bupivacaine along with 25 mcg of fentanyl. At the end of the procedure, FNB group received an ultrasound-guided FNB from a consultant anesthesiologist, while the IALA group received local anesthetic along with opioid/saline mixture as described below by the operating surgeon. Postoperative study parameters were observed by the qualified nursing staff in the ward at specified intervals who was blinded about the study groups. In order to reduce the inter-individual technical bias, the same consultant level surgeon and anesthetist did the intervention for all the study cases.

Ultrasound (SonoSite®)-guided FNB was performed by the following technique-the patient in the supine position, a high frequency ultrasound probe was placed in the transverse plane at the midpoint of the inguinal crease to identify femoral vessels. The femoral nerve was identified lateral to the femoral artery as triangular-shaped opaque structure. After obtaining the optimum image of the nerve, a 22-guage 50 mm needle (Insulated sonoPlex A Pajunk®) was inserted with an in-plane approach until the tip of the needle was in close proximity to the femoral nerve. Direct visualization of needle tip maintained by ultrasound while inserting the needle until the needle reaches close to the femoral nerve. The site of injection was confirmed by nerve stimulator (Stimuplex® HNS12) after getting the ipsilateral quadriceps contraction (patellar movement) at 0.5 mA, (stimulator frequency at 2 Hz and pulse width of 0.1 s). A total of 25 mL 0.5% bupivacaine (125 mgs) was injected around the femoral nerve.

In IALA group, a 150 mL solution was prepared that contains 50 mL of 0.25% Bupivacaine (125 mgs), 10 mg of morphine (1 mL) and 99 mL of normal saline. The surgeon injected this exact amount of solution at the posterior capsule, anterior capsule, patellar tendon, quadriceps tendon, and the subcutaneous tissue at the incision line. The patients were transferred to the post anesthesia care unit after completion of the surgical procedure and block. All patients received multi-modal analgesia as paracetamol intravenous (i.v.) 1 g 6 hourly and diclofenac per oral 50 mg 8 hourly, with the first dose being administered through i.v. route at the start of the skin closure intraoperatively. PCA morphine (bolus dose 1 mg, lockout interval 5 min, 4 h max dose 30 mg) was prescribed for the first 24 h. The primary outcome measure in our study was 24 h postoperative morphine consumption through PCA. The following secondary outcome measures: pain scores, nausea and vomiting and ambulation time were recorded at specified intervals in postoperative. Pain assessment was done using the VAS score. One patient in FNB group refused PCA morphine in the postoperative period hence excluded from the analysis.

Sample size calculation

The sample size was derived based on the 24 h PCA morphine consumption in our initial pilot study of 10 patients. The mean PCA morphine consumption in FNB (10.2 mg ± 4.81 mg) and IALA (14.4 mg ± 5.17 mg) with mean difference of 4.2 mgs. A total of 60 patients were required in order to get mean difference of 30% with confidence interval 95%, effect size 0.8 and power of study 90%.

Statistical software

The statistical software namely SPSS 18.0, and R environment ver. 3.2.2 of IBM® were used for the analysis of the data.

RESULTS

Table 1 shows that the two groups have remarkably similar demographics. There was no statistical difference among groups. Table 2 illustrates the PCA morphine consumption in the first 24 h. FNB group has low morphine consumption (P = 0.03) in comparison to IALA group. Table 3 represents the VAS score, and with flexion, VAS score is significantly less in FNB group. Table 4 depicts the ambulation by 24 h all patients were mobilized except one in group FNB, with no statistical or clinical significance (P = 0.186). Table 5 shows no difference in the nausea vomiting incidence in the study population.

Table 1

Demographic parameters of the study group

Baseline variables	Group FNB (n=29)	Group IALA (n=30)	P
Age (years)	65.31±6.51	61.70±6.34	0.051
Gender (female/male)	19/10	20/10	0.99

FNB: Femoral nerve block, IALA: Intra-articular infiltration of local anesthetics

Table 2

24 h patient-controlled analgesia morphine consumption (Mann-Whitney test)

Time frame (h)	Group FNB (n=29)	Group IALA (n=30)	P
4	5.68±6.18	6.60±4.97	0.24
8	9.10±6.53	11.66±5.73	0.09
12	11.20±6.65	15.63±8.97	0.09
16	13.13±7.55	18.40±11.01	0.07
20	14.75±8.21	20.53±12.54	0.08
24	16.03±9.37	23.60±13.73	0.03

FNB: Femoral nerve block, IALA: Intra-articular injection of local anesthetic

Table 3

Visual Analog Scale score

VAS (h)	Group FNB	Group IALA	P
At rest
4	1.00±1.55	1.34±2.00	0.77
8	0.96±0.94	1.31±1.58	0.71
12	0.79±1.01	1.17±1.49	0.55
16	0.75±0.91	0.66±0.90	0.58
20	0.75±1.12	0.64±0.82	0.88
24	0.58±1.11	0.92±1.51	0.23
Flexion
4	1.13±2.15	1.21±1.54	0.47
8	1.21±1.54	1.35±1.59	0.63
12	0.82±0.86	1.28±1.60	0.57
16	1.03±0.98	1.17±1.31	0.85
20	1.37±1.47	1.53±1.20	0.33
24	1.27±1.43	2.42±2.54	0.04

FNB: Femoral nerve block, IALA: Intra-articular infiltration of local anesthetics, VAS: Visual Analog Scale

Table 4

Ambulation in study groups (Fischer’s exact test, P=0.180)

Ambulation	Group FNB, n (%)	Group IALA, n (%)
16	4 (14.3)	1 (3.4)
20	10 (35.7)	17 (56.6)
24	28 (96.5)	30 (100)

FNB: Femoral nerve block, IALA: Intra-articular infiltration of local anesthetics

Table 5

Nausea and vomiting (opioid side effects) Fischer’s exact test

	Group FNB (n=29), n (%)	Group IALA (n=30), n (%)	P
Nausea	5 (17.2)	5 (20.0)	1.00
Vomiting	4 (13.8)	5 (16.7)	1.00

FNB: Femoral nerve block, IALA: Intra-articular infiltration of local anesthetics

DISCUSSION

Our study demonstrated that FNB is effective in reducing the total postoperative morphine PCA consumption for the first 24 h (P = 0.03). The VAS score was not showing any difference between the two study group at rest; however, with flexion VAS score was less in FNB group at 24 h (P = 0.04). Garg et al.[4] concluded similar findings that FNB is superior to IALA; however, they used different drug mix for FNB. Wang et al.[2] studied the effect of single-injection of FNB on patients undergoing TKA and concluded that it provides effective analgesia and facilitated early ambulation as well. Chan et al.[5] in their Cochrane systematic review concluded that FNB provides superior analgesia following TKA in comparison to PCA. Moreover, they noted that data is insufficient to compare efficacy of IALA over FNB. In a study done by Sahin, et al.[6] FNB was compared with placebo and they concluded FNB is superior to placebo in terms of patient satisfaction and PCA morphine consumption. Ng et al.[7] in their study demonstrated that single shot FNB is effective in reducing morphine PCA in comparison to IALA. However, there was no significant difference in other parameters studied. In one of the early meta-analysis of FNB for TKA done by Paul et al.[8] showed that either single shot or continuous FNB provides superior analgesia in comparison to PCA.

Periarticular and intraarticular infiltration of cocktail medications has been tested by many researchers to improve the patient satisfaction, early ambulation, and reduced hospital stay.[39] Kerr and Kohan,[9] Toftdahl et al.,[10] Fu et al.[11] advocated the beneficiary effects of IALA with different mix of medications in achieving early ambulation and fast recovery. Rosen et al.[12] contradicted that IALA with ropivacaine did not show significant difference in comparison to placebo either with VAS score or morphine consumption. Kao et al.[13] in their retrospective study recommended that IALA is superior to single shot FNB contradicting our study findings. The drug composition in their study was different from ours. Najfeld et al.[14] also recommended the IALA as good alternative to regional blocks. Karpetas et al.[15] in their study concluded that IALA and FNB has similar analgesic effect, but IALA group has shown early ambulation, and the duration of hospital stay did not differ in both the groups. We did not find significant difference in ambulation between the groups in our study. Affas et al.[16] recommended IALA for TKA pain relief due to cost effectiveness when compared with FNB. Zinkus et al.[17] compared continuous FNB with continuous IALA and found that IALA provides superior analgesia and less motor block and preserved knee function. Andersen and Kehlet[18] did systemic review of local infiltration technique for analgesia in hip and knee surgery. In total hip arthroplasty, the authors did not find additional advantage of IALA in comparison to placebo in trials with minimal bias. However, the authors noted an interesting finding with knee procedures, where many researchers have reported beneficiary effects of IALA over other modalities of analgesia. They noted increased bias due to nonstandardization of systemic analgesia between the groups studied. This review also noted that IALA improves analgesic efficacy when combined with multimodal analgesia especially in the initial postoperative period. Due to nonstandardized methodology and many different systemic medications used, IALA efficacy cannot be concluded despite several authors claiming its superiority. Our study has the following limitation - the spinal anesthesia effect can lead to bias in assessment during the first few initial hours. Furthermore, our drug composition is fixed dose and compared to studies where IALA efficacy is proven our composition is different.

CONCLUSION

Our study demonstrated that single shot FNB is superior to IALA in terms of PCA morphine consumption, VAS score at flexion. However, the debate surrounding IALA efficacy continues to be a topic for further research, until a definitive consensus is not built based on the available literature.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.