Comparison of Intra-articular Analgesia and Femoral Nerve Block for Postoperative Pain Relief in Unilateral Total Knee Arthroplasty: A Randomized Clinical Study.

BACKGROUND AND AIMS: Femoral nerve block (FNB) and intra-articular analgesia (IAA) are used for postoperative analgesia after total knee arthroplasty (TKA). AIMS AND
OBJECTIVES: We aimed to determine the better technique among the two, with regard to duration and quality of postoperative analgesia along with 24-h rescue analgesic consumption. The functional recovery in the early postoperative period was also assessed. SETTINGS AND
DESIGN: This was a prospective double-blind study comprising 40 American Society of Anesthesiologists I-III patients undergoing elective TKA who were randomly assigned to two groups (n = 20).
METHODOLOGY: In Group A, 20 mL ropivacaine 0.5%, containing dexmedetomidine (1 μg.kg - 1), was given by FNB, and in Group B, intra-articular administration of the same drug was done. Analgesic effect was evaluated by measuring the Visual Analog Scale (VAS) and duration of analgesia. Quadriceps muscle strength was noted. STATISTICAL ANALYSIS: Observation data obtained were reported as mean value and analyzed using Student's t-test or Wilcoxon/Mann-Whitney rank test.
RESULTS: The mean VAS on passive movement at the 2nd, 6th, and 16th h postoperatively was 1.75 ± 0.44, 2.90 ± 0.72, and 2.75 ± 0.44 in Group A as compared to 2.25 ± 0.72, 4.30 ± 2.05, and 2.20 ± 0.77 in Group B (P = 0.026, 0.043, and 0.014, respectively). In Group A, the first request for analgesic (rescue analgesic) was at 637 ± 119 min and the total consumption of tramadol was 50.00 mg. In Group B, the first request for analgesic was at 404.44 ± 136 min, with a total dose of 63.89 mg. The Pvalue for the time of rescue analgesic was <0.001, while for total drug consumption, it was 0.018.
CONCLUSION: We concluded that the duration and quality of analgesia (VAS) were significantly superior and rescue analgesic requirement less in patients who received FNB as compared to IAA. Copyright:

INTRODUCTION

Total knee arthroplasty (TKA) is an accepted and effective treatment for advanced, painful degeneration of the knee joint. It has been shown to dramatically decrease pain and improve function in appropriately selected patients.[1] Early postoperative ambulation after knee surgery is important to obtain clinically preferable outcomes. This may, however, exaggerate postoperative pain, and thus, its management is an essential component of perioperative care. Multiple techniques of postoperative pain control such as intravenous analgesics, epidural analgesia, and regional anesthesia in the form of femoral nerve block (FNB) have been used. Compared to systemic analgesia, regional analgesic techniques provide superior pain relief, reduced need for rescue analgesia, and faster postoperative knee rehabilitation.[2] FNB is preferred by many for analgesia after TKA, but associated quadriceps weakness, leading to a delayed ambulation, has reduced its widespread acceptance.[3] As a result, alternative methods of analgesia are being sought, and there has been an increasing support for the inclusion of peri- or intra-articular local anesthetics in the multimodal pain management regimen after TKA. Intra-articular analgesia (IAA) with ropivacaine (0.25%) containing dexmedetomidine in patients undergoing arthroscopic knee surgery has shown to improve the quality and duration of postoperative analgesia.[4] Dexmedetomidine is a highly selective central alpha-2 agonist with sedative, anxiolytic, and analgesic properties. The primary aim of our study was to compare the benefits of using ropivacaine (0.5%) with dexmedetomidine in FNB and in IAA after unilateral TKA in terms of duration and quality of postoperative analgesia along with 24-h rescue analgesic consumption. Till date, no study has been done using dexmedetomidine as an adjuvant to ropivacaine to compare the analgesic effect of FNB and IAA.

METHODOLOGY

The study was conducted in a prospective, double-blind manner in a tertiary level hospital after approval of the institutional ethics committee and written informed consent of patients from February 2014 to June 2015. The study was registered with Clinical Trials Registry-India (CTRI/2014/08/004902). All procedures performed in the study followed the ethical guidelines of the Declaration of Helsinki. The sample size was determined by post hoc power analysis conducted using the software package, G*Power version 3.1.9.2 (Franz Faul, university kiel, Germany). Based on a previous study by Paul et al., with an alpha level of P < 0.05 and beta of 0.20 with 10% chance of error using duration of analgesia as the parameter, a sample size of 20 patients in each of the two groups was required for a power of 80%.[4]

All patients of American Society of Anesthesiologists (ASA) Class I–III of either sex who were admitted for unilateral TKA were screened. Patients with contraindications for regional anesthesia, presence of cognitive dysfunction, myopathies, and severe liver and kidney disease were excluded. Patients were randomized by the use of sequentially numbered, sealed envelopes into two treatment groups of 20 patients each depending on the technique for postoperative analgesia, i.e., FNB or IAA.

Group A: FNB using 20 mL ropivacaine 0.5% containing dexmedetomidine (intravenous preparation neon laboratories) (1 μg.kg − 1) was given, and the same volume of normal saline 0.9% was given intra-articular.

Group B: Intra-articular administration of 20 mL ropivacaine 0.5% containing dexmedetomidine (1 μg.kg − 1) was done, and the same volume of normal saline 0.9% was given for FNB.

The interventional medications were procured by indenting from the hospital pharmacy and thus were identical. A thorough preanesthetic checkup comprising detailed history and general physical and systemic examination was conducted, and routine investigations done with automated technique in the institutional laboratory were obtained before the surgery. During the preanesthesia interview, patients were instructed about using the Visual Analog Scale (VAS)[5] as a tool for measuring postoperative pain, the pain relief plan, and their ability to request rescue analgesic when needed. All the patients were kept nil orally for at least 6 h before the surgery and premedicated with 0.25 mg alprazolam and 150 mg ranitidine orally the night before and on the morning of the surgery.

On arrival in the operation theater, routine monitoring (electrocardiography, heart rate, noninvasive blood pressure, and pulse oximetry) was started and baseline vital parameters were recorded. After preloading with 10 mL.kg −1 of 0.9% saline over 20 min, spinal anesthesia was performed in the lateral position (operative limb dependent) using 10 mg 0.5% (hyperbaric) bupivacaine +25 μg fentanyl (total volume: 2.5 mL) in L2–L3 or L3–L4 interspace.

After completion of the surgery, a multiperforated catheter drain for closed negative pressure drainage was placed in the joint cavity. Depending on the group allocation, syringes labeled as solution I and solution II were handed to the concerned consultant anesthesiologist and orthopedic surgeon who were blinded to the drug solution. Each patient received ultrasound-guided FNB by the consultant anesthesiologist and IAA through intra-articular drain by the orthopedic surgeon. FNB was performed using linear ultrasound probe by in-plane technique between the fascia iliaca and iliopsoas muscle to lift the nerve toward the surface.

Continuous monitoring of vitals was done in the recovery room by an anesthetist who was blinded to the study protocol. Patients' pain relief was assessed in terms of the first request for postoperative analgesia, total amount of rescue analgesia needed in 24 h postoperatively, and quality of postoperative analgesia. Patients were asked to rate their pain at rest and on passive movement using VAS on a scale of 0–10. At arrival in recovery room VAS at rest, VAS on passive movement, quadriceps muscle strength (motor power assessment) scale, and sedation score were recorded at 0 min, 30 min, 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, 16 h, 20 h, and 24 h. As part of multimodal analgesia technique, all patients received injection diclofenac 75 mg 8 hourly and the first dose was given at arrival in the recovery room. VAS ≥4 was considered as inadequate analgesia and treated with tramadol 50 mg as a rescue analgesic. A similar dose was repeated up to a maximum of 100 mg in contiguous 4 h or 400 mg in 24 h. Total rescue analgesic consumption in 24 h postoperatively was also recorded.

In postoperative period, patients were observed for side effects such as nausea, vomiting, bradycardia/tachycardia, hypotension/hypertension, hypoxia (SpO2 ≤ 90%), respiratory depression, excessive sedation, and quadriceps weakness. After completion of 24-h study period, patients were asked to rate their overall pain relief satisfaction as excellent (4), good (3), moderate (2), and poor (1). Sedation was assessed using a five-point sedation score: 1 = alert and wide awake, 2 = arousable to verbal command, 3 = arousable to gentle tactile stimulation, 4 = arousable with vigorous shaking, and 5 = unarousable. Quadriceps weakness was determined by assessing motor power grade as 0 = no movement, 1 = flicker of movement only, 2 = movement possible when assisted by gravity or gravity is eliminated, 3 = movement possible against gravity but without imposed resistance, 4 = weak movement possible against gravity with imposed resistance, and 5 = normal movement against gravity and against imposed resistance.

Statistical analysis

Observation data obtained were reported as mean value, with variability expressed as standard deviation. It was tabulated and analyzed using Student's t-test or Wilcoxon/Mann–Whitney rank test for parametric data. P < 0.05 was taken as statistically significant. Degree of freedom and confidence interval were also calculated. Statistical analysis was performed using the Statistical Package for the Social Sciences 21 (SPSS Inc., Chicago, IL, USA) version statistical program for Microsoft Windows.

RESULTS

The demographic data of the two groups were similar, with no significant differences in sex ratio, age, ASA physical status, and body mass index.

To maintain uniformity, both FNB and IAA were given at the end of the procedure in all patients in both the groups. The mean baseline VAS was comparable in both the groups at rest, and it remained lower in Group A than Group B for the first 8 h postoperatively. The value was significant only at the 6th h, i.e., 1.75 ± 0.55 in Group A versus 2.80 ± 1.67 in Group B (P = 0.03). At the 12th and 16th h postoperatively, VAS was statistically higher in Group A compared to Group B, i.e., 2.80 ± 1.61 versus 1.95 ± 1.85 and 1.70 ± 0.47 versus 1.00 ± 0.65 (P = 0.033 and 0.002, respectively). The mean VAS on passive movement remained high in Group B as compared to Group A for initial 6 h postoperatively, and it was significantly low in Group A at the 2nd, 6th, and 16th h postoperatively as compared to Group B (P = 0.026, 0.043, and 0.014, respectively) [Table 1].

Table 1

Pain score (Visual Analog Scale) comparison of both groups in recovery room (on passive movement)

VA at movement	Group A		Group B		df	Z	P	95% CI
	Mean±SD	Median (IQR)	Mean±SD	Median (IQR)				Lower	Upper
Baseline	0.65±0.88	1 (0-1)	1.05±1.00	1 (0-2)	38	−1.377	0.201	0.116	0.384
30 min	1.05±0.69	1 (0.5-1.5)	1.40±0.88	1 (1-2)	38	−1.297	0.231	0.057	0.293
60 min	1.55±0.60	2 (1-2)	1.70±0.86	2 (1-2.25)	38	−0.428	0.698	0.475	0.775
2 h	1.75±0.44	2 (1.5-2)	2.25±0.72	2 (2-3)	38	−2.450	0.043	0.000	0.072
4 h	2.35±0.75	3 (2-3)	2.65±0.49	3 (2-3)	38	−1.251	0.277	0.096	0.354
6 h	2.90±0.72	3 (3-3)	4.30±2.05	5 (3-6)	38	−2.368	0.026	0.000	0.072
8 h	3.10±1.12	3 (2.5-4)	3.10±1.02	3 (3-3)	38	−0.141	0.904	0.882	1.000
12 h	3.95±1.76	3 (3-6)	3.10±1.86	2.5 (2-3.75)	38	−2.033	0.052	0.000	0.157
16 h	2.75±0.44	3 (3-3)	2.20±0.77	2 (2-3)	38	−2.703	0.014	0.000	0.072
20 h	2.45±0.94	2 (2-3)	2.15±0.81	2 (2-3)	38	−0.880	0.445	0.296	0.604
24 h	2.05±0.51	2 (2-2)	1.90±0.72	2 (1.75-2)	38	−1.106	0.383	0.137	0.413

SD=Standard deviation, IQR=Interquartile range, CI=Confidence interval

The muscle strength was more in Group B as compared to Group A, and in the first 24 h postoperatively, most of the values were statistically significant [Table 2].

Table 2

Quadriceps muscle strength in postoperative period

Quadriceps muscle strength	Group A		Group B		df	Z	P	95% CI
	Mean±SD	Median (IQR)	Mean±SD	Median (IQR)				Lower	Upper
Baseline	0.8±0.41	1 (1-1)	1±0.46	1 (1-1)	38	−1.399	0.341	0.180	0.470
30 min	1.05±0.51	1 (1-1)	1.35±0.59	1 (1-2)	38	−1.574	0.221	0.096	0.354
60 min	1.5±0.61	2 (1-2)	2.05±0.39	2 (2-2)	38	−3.080	0.012	0.000	0.072
2 h	1.9±0.31	2 (2-2)	2.35±0.49	2 (2-3)	38	−3.086	0.024	0.000	0.072
4 h	2.1±0.45	2 (2-2)	2.9±0.45	3 (3-3)	38	−4.363	0.000	0.000	0.072
6 h	2.4±0.5	2 (2-3)	3.3±0.66	3 (3-4)	38	−3.854	0.000	0.000	0.072
8 h	2.95±0.39	3 (3-3)	3.35±0.49	3 (3-4)	38	−2.615	0.049	0.000	0.072
12 h	3.05±0.6	3 (3-3)	3.6±0.5	4 (3-4)	38	−2.973	0.010	0.000	0.072
16 h	3.45±0.69	4 (3-4)	3.9±0.31	4 (4-4)	38	−2.498	0.052	0.000	0.072
20 h	3.7±0.57	4 (3.5-4)	4.1±0.31	4 (4-4)	38	−2.658	0.081	0.000	0.073
24 h	3.8±0.83	4 (4-4)	4.3±0.47	4 (4-5)	38	−2.379	0.086	0.000	0.073

SD=Standard deviation, IQR=Interquartile range, CI=Confidence interval

The sedation score was higher in Group A for the first 6 h postoperatively, but from the 8th to 20 h, it increased and was higher in Group B, with statistical significance being observed only at the 12th and 16th h (P = 0.021 and 0.006, respectively).

The mean time when patient demanded analgesia for the first time or VAS > 4 was 637 ± 119 min. in Group A and 404.44 ± 136 min in Group B (P < 0.001). Total rescue analgesic consumption also was significantly more in Group B (P = 0.018) [Table 3].

Table 3

Duration of analgesia (minutes) and total rescue analgesic consumption among both groups

	Group A		Group B		df	Z	P	95% CI
	Mean±SD	Median (IQR)	Mean±SD	Median (IQR)				Lower	Upper
Time (VAS≥4 or patient demands analgesia for the first time) (min)	637.65±119.19	670 (600-720)	404.44±136.31	360 (360-427.5)	33	−3.750	0.000	0.000	0.072
Total rescue analgesia 24 h (mg)	50±0	50 (50-50)	63.89±23.04	50 (50-100)	33	−2.313	0.018	0.000	0.073

VAS=Visual Analog Scale, SD=Standard deviation, IQR=Interquartile range, CI=Confidence interval

At the end of 24-h period, analgesia quality was assessed from the patients' point of view and graded as excellent, good, moderate, and poor [Figure 1].

Figure 1

Analgesia quality comparison in both groups

DISCUSSION

The primary objective of our study was to compare the two techniques of regional anesthesia for postoperative pain after TKA, i.e., FNB and IAA, and to determine the better one in reducing postoperative pain and analgesic consumption. The secondary outcome was the assessment of functional recovery measured by the strength of quadriceps muscle in the early postoperative period. In our study, FNB and IAA were given immediately after completion of the procedure using dexmedetomidine (1 μg.kg − 1) added to ropivacaine (0.5%), to make a total drug solution of 20 mL. We observed that in Group A where the study drug solution was given by FNB, the duration of analgesia was longer than Group B where the study drug solution was given by intra-articular route and the results were statistically significant. The mean time when patient demanded analgesia for the first time (VAS ≥ 4) was significantly more (637 ± 119 min) in Group A than Group B (404.44 ± 136 min) (P = 0.000).

The duration of analgesia in Group A in our study was longer as compared to a study by Theodosiadis et al. who performed 3-in-1 block following TKA and compared ropivacaine (398 min) with bupivacaine (367 min) (P = 0.62).[6] This difference from our study could be due to the blind technique of block administration (3-in-1 block) versus ultrasound-guided FNB and the use of dexmedetomidine with ropivacaine to prolong the analgesia.

The duration of analgesia in Group B in our study was shorter (404.44 ± 136 min) as compared to a study done by Paul et al. (650.4 ± 156 min).[4] They performed IAA following knee arthroscopy using ropivacaine 0.25% with dexmedetomidine 1 μg.kg − 1 (total volume: 20 mL). This difference could be due to first, in our study, the drug solution was given through intra-articular drain compared to direct administration into the knee joint by arthroscopic ports at the end of the procedure. Dead space of intra-articular drain tubing decreased the actual amount of drug reaching the knee joint. Second, in our study, the procedure is TKA which is more extensive, invasive, and involves more tissue handling.

In a study by Panigrahi et al., patients undergoing knee arthroscopy were given 18 mL ropivacaine 0.2% with dexmedetomidine 1 μg.kg − 1 intra-articular. The duration of analgesia was 433.2 ± 54.3 min which is comparable to our study results of 404.44 ± 136 min.[7] In our study, we used total a drug solution of 20 mL, but the actual volume of drug solution that reached into joint was 1–2 mL less because of dead space of drain tubing (from tip of drain tube to clamp).

The total rescue analgesic consumption was significantly more (P = 0.018) in Group B (63.89 mg of tramadol) as compared to Group A. Kao et al. compared FNB (25 mL 0.25% levobupivacaine) with IAA (60 mL 0.5% bupivacaine) after TKA and found that total rescue analgesic consumption (morphine) in the first 24 h postoperatively in the two groups did not differ significantly.[8] However, Moghtadaei et al. compared a single-shot FNB with peri-articular plus IAA using ropivacaine 10 mg.mL − 1 with 30 mg ketorolac and 0.5 mg epinephrine, and found significantly more opioid consumption in the FNB group as compared to IAA. These differences could be due to the different drug compositions being used.[9]

At 24-h postoperative period, analgesia quality (excellent, good, moderate, or poor) was assessed from patients' point of view, patient satisfaction being higher in Group A as compared to Group B. In a previous study by Toftdhal et al., on comparing the two techniques, the satisfaction of the patients with the measures taken to control pain did not reveal a significant difference between the two groups (P = 0.563), and they described the overall results as satisfactory.[10] In our study, patients in Group A reported: excellent – 7 and good – 13 whereas Group B: 2 patients as excellent, 13 as good, and 5 as moderate quality of analgesia.

The quadriceps muscle strength was more in Group B as compared to Group A in the first 24 h postoperatively, and most of the values were statistically significant. IAA improves ambulation of patients undergoing TKA as compared to FNB which causes motor weakness. The results of our study are supported by Toftdhal et al. where walking distance and quadriceps muscle strength were significantly improved in patients given IAA compared to patients given FNB (P = 0.002).[10] Ropivacaine (10 mg.mL−1) 20 mL was used for FNB, followed by an infusion of 0.2% at 10 mL.h−1, and for IAA, a solution of 150 mL ropivacaine (2 mg.mL−1), 1 mL ketorolac (30 mg.mL−1), and 1 mL epinephrine (0.5 mg.mL−1) was given. The partial motor block of quadriceps femoris muscle by FNB causes delayed ambulation in TKA patients which, in turn, may cause a delayed hospital discharge. The possible advantage of IAA in early ambulation in patients helps in early rehabilitation and early discharge from hospital.

Similar to previous studies where ropivacaine was used for FNB and IAA, no significant side effects and hemodynamic changes were noticed in our study in both the groups.[49]

Based on relative merits and demerits of these two techniques (peri-articular plus IAA with FNB) to provide for postoperative analgesia following TKA, different studies drew different conclusions. Peri-articular plus IAA has been shown to be of greater advantages for early analgesia following TKA.[910] However, Carli et al. concluded that continuous FNB was better for recovery in terms of walking capacity, physical activity, and knee function from TKA.[11] In these studies, peri-articular plus IAA was used, but in our study, we administered the drug intra-articular only. Moghtadaei et al. employed a single injection FNB as in our study, while others employed continuous FNB.[9] Francis observed that a continuous FNB could extend the analgesic effect compared to a single-injection FNB after TKA, but the indwelling catheter has its own complications.[12] We, therefore, preferred a single-injection technique, and to prolong its duration of action, adjuvant (dexmedetomidine) was used with local anesthetic. The successful analgesic effect of FNB and IAA is clinically relevant in patients undergoing TKA. The study holds strength in being a randomized controlled, double-blinded trial comparing two modalities of postoperative analgesia. There are a few limitations. First, the surgeries were done by different surgeons, thus causing varied tissue handling and local anesthetic infiltration. Furthermore, the drug solution delivered intra-articular was done by a catheter drain by the surgeon, so the actual amount of drug that reached in the joint cavity was less because of the dead space.

CONCLUSION

We conclude that the quality of analgesia was significantly superior in patients who received FNB as compared to IAA. The time to the first demand and total rescue analgesic consumption was more in IAA as compared to FNB. The quality of analgesia was significantly superior in patients who received FNB. However, the main benefit of IAA over FNB is that it does not cause significant motor weakness, which improves early ambulation after TKA. Hence, a single-shot IAA with ropivacaine and dexmedetomidine can be recommended as a safe, effective alternative to a single-shot FNB as a part of multimodal analgesia after unilateral TKA. Future studies need to be performed to compare these blocks and different doses of dexmedetomidine.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.