Table of Contents  
Year : 2015  |  Volume : 8  |  Issue : 4  |  Page : 644-647

Femoral nerve block versus local infiltration analgesia for postoperative pain after total knee arthroplasty

1 Department of Anesthesiology, Intensive Care and Pain Management, Faculty of Medicine, Ain Shams University, Cairo, Egypt
2 Free Lance Orthopedic Surgeon, Johns Hopkins Aramco Healthcare, Dhahran, Saudi Arabia

Date of Submission06-Feb-2015
Date of Acceptance05-Jun-2015
Date of Web Publication29-Dec-2015

Correspondence Address:
Amr Sobhy
Department of Anesthesiology, Intensive Care and Pain Management, Faculty of Medicine, Ain Shams University, 11566 Cairo
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1687-7934.172759

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This prospective study compares the pain control after total knee replacement using a single-shot femoral nerve block (FNB) against local infiltration analgesia (LIA).
Patients and methods
Sixty-four patients were included the study. A total of 29 patients received single-shot ultrasound-guided FNB at the end of the procedure, whereas 35 patients received LIA. Both groups were compared as regards pain at 2 and 4 h after surgery, pain before and after physical therapy on the first postoperative day, early flexion of the knee to 90°, total opiate use, and length of stay in the hospital.
All patients completed the study. The group that received LIA showed significantly less pain at 4 h postoperatively, on the first postoperative day, and after physical therapy. The LIA group also showed significantly better rehabilitation and less hospital stay. Patients who received FNB used significantly more opiate compared with the LIA group.
LIA gives better pain control compared with single-shot FNB after total knee replacement.

Keywords: femoral nerve block, infiltrative analgesia, pain, total knee

How to cite this article:
Rizk H, Hosni Y, Sobhy A, Hamdy AN. Femoral nerve block versus local infiltration analgesia for postoperative pain after total knee arthroplasty . Ain-Shams J Anaesthesiol 2015;8:644-7

How to cite this URL:
Rizk H, Hosni Y, Sobhy A, Hamdy AN. Femoral nerve block versus local infiltration analgesia for postoperative pain after total knee arthroplasty . Ain-Shams J Anaesthesiol [serial online] 2015 [cited 2021 Oct 23];8:644-7. Available from:

  Introduction Top

Acute postoperative pain after total knee replacement (TKR) can be severe even at rest [1],[2] . This pain interferes significantly with general activity and walking ability of patients [2],[3] . Inadequate pain relief can cause delayed mobilization, greater risk of developing venous thrombosis, coronary ischemia, poor wound healing, longer length of hospital stay, unnecessary psychological distress, and decreased patient satisfaction [4],[5],[6],[7] .

Different modalities have been used to control pain after TKR. These include regional analgesia by means of femoral and sciatic nerve block, epidural analgesia, intravenous patient controlled analgesia (PCA), multimodal analgesia, and local infiltration analgesia (LIA) [8] .

Nerve supply to the knee is a variable one, derived from a combination of the femoral, obturator, and sciatic nerves. The saphenous nerve runs down the anterolateral edge of the sartorius and gives the main supply at the medial aspect of the knee. The common peroneal nerve and the tibial nerve, branches of the sciatic nerve, give supply to articular structures of the knee. A cutaneous branch of the posterior division of obturator nerve, supplies the medial aspect of the knee. The femoral branches to the vastus medialis and lateralis are distributed to the superoanterior aspect of the articular capsule [8],[9] . Femoral nerve block (FNB) can be performed as single shot or as continuous infusion by means of a catheter, and both provide effective analgesia, facilitate early ambulation, and reduce the length of hospitalization in patients undergoing TKA [10],[11] . Meanwhile, a randomized controlled study by Widmer et al. [12] questioned the value of FNB.

LIA in total knee arthroplasty has been reported in multiple studies to achieve good pain control for the immediate postoperative period [13],[14] . These findings were not constant. Other studies did not find statistically significant difference in lowering pain scores or narcotic usage [15],[16] .

  Patients and methods Top

The study was conducted at Ain-Shams University Hospitals during the period from 1 June 2014 to 30 October 2014, 64 patients candidate for cemented TKR were included in the present study. The study was a controlled randomized prospective study. The protocol of the study was approved by the research ethics committee of Anesthesia and Intensive Care Department at Ain Shams University. Informative consent was obtained from all patients. None of them reported any allergies or contraindications to spinal analgesia or any other medication. All surgeries were performed by the same surgeon and the same anesthetists, and a similar implant was used in every patient.

At the preadmission visit, each patient was asked to choose one of the multiple sealed envelopes. Each envelope contained a choice of either FNB method or LIA method. The envelopes were kept sealed until they were opened intraoperatively.

All patients received spinal analgesia using 0.5% bupivacaine with appropriate dose based on weight, height, and age. No spinal morphia was given. All patients were sedated using propofol infusion at a rate of 2-4 mg/kg/h. Sedation continued throughout the surgery and covered the time of postoperative FNB administration and thus the patients were also blinded to the analgesia given.

After the procedure began, the envelope was opened by the circulating nurse and then either LIA was to be performed by the surgeon or FNB was to be performed by the anesthetist after the wound was dressed.

In case of FNB, ultrasound-guided single shot of 30 ml of ropivacaine 0.2% was administered in the operating room at the end of surgery after the dressing was applied.

Cases in which LIA was used, a mix of 60 ml of ropivacaine 0.2%, 60 mg of ketorolac (2 ml), 5 mg of morphine sulfate (10 ml), and 1 mg of epinephrine 1 : 1000 (1 ml) was used. Injection into the posterior capsule was carried out after the tibia and distal femoral cuts and posterior release were performed, with the knee flexed to 90° for better visualization of the posterior capsule. A volume of 30 ml of the mixture was injected into the posterior capsule. Before closure of the arthrotomy, the fat pad and the medial collateral ligament were injected, and a spinal needle was inserted into the joint and kept until the wound was all closed; thereafter, the remaining mixture was injected into the joint, and the needle was removed. No injection was given at the wound edges for fear of wounded skin necrosis due to epinephrine.

The group that received FNB was named group A, whereas the LAI group was named group B.

Postoperatively, all patients received PCA morphine for pain control. All patients were educated on how to use the PCA on the preadmission visit. The nurses in the ward were not informed about what was given to the patients in the operating room, and they were asked to record pain level in each patient over the 10 cm visual analog scale (VAS) 4 h after the surgery, and every 2 h in the first postoperative day. Patients started physical therapy on the first postoperative day. On the second postoperative day, the pain at rest and pain after physical therapy were also recorded. PCA was stopped on the second postoperative day. Thereafter, pain was controlled using pain relief negligible morphine, oxycodone, paracetamol, and celecoxib if there was no contraindication.

The time the patient achieved 90° of flexion, the length of stay, and the total opioid use were recorded. Oral oxycodone was converted to morphine at a ratio of 1 : 1 [1] .

Statistical data analysis

Results were analyzed using SPSS (16.0 for Windows; SPSS Inc., Chicago, Illinois, USA) software. The nonparametric data were presented as median [interquartile range (IQR)] and the Mann-Whitney U-test was used for analysis, whereas parametric data were presented as mean (SD) and Student's t-test was used for analysis. A P value of less than 0.5 was considered significant. The study included patients selected for surgery over a period of 5 months, ensuring that each group size exceeded 20 patients to account for patients with incomplete data, which we did not encounter. This sample size allows for a power of 80% and a error of 0.05 (two tailed) when 1 point on the VAS is clinically significant.

  Results Top

Group A, the FNB group, included 29 patients, seven male (24.14%) and 22 female patients (75.86%), with a mean age of 68.17 years (7.68). Group B, the LIA group, included 35 patients, nine male (25.7%) and 26 female patients (74.3%), with a mean age of 69.28 years (5.38). There were no significant differences between the two groups as regards personal characteristics.

Operative time was 105.5 min (± 9.39) in group A, whereas it was 104.25 min (± 9.4) in group B, and this was a nonsignificant difference.

The median VAS at 2 h postoperatively was 1 with an IQR of 2 in group A, whereas it was 1 with an IQR of 1 in group B, and this was a nonsignificant difference (P = 0.08). Meanwhile, at 4 h postoperatively, the median VAS was 2 in group A, whereas it was 1 in group B, and this was significantly less (P < 0.05).

The median VAS at rest in group A was 3, whereas it was significantly less in group B with a median VAS of 2 (P < 0.05). Moreover, after physical therapy, group B had significantly lower VAS of 3 versus 6 [Figure 1] in group A (P < 0.05).
Figure 1: Pain level in the two groups at 2 and 4 h postoperatively, and before and after physical therapy (PT) on VAS. Data are presented as median. VAS was signifi cantly less in group B at 4 h postoperatively, at rest on the second postoperative day, and after physical therapy (P < 0.05). FNB, femoral nerve block; LIA, local infiltration analgesia; VAS, visual analog sca le.

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The mean opiate use in group A was 131.44 (± 22.6), whereas in group B it was 101.97 (± 21.9), which was significantly less (P < 0.05) (Figure2). The average length of stay in group A was 4.9 days (± 0.25), whereas in group B it was 4 days, which was significantly less (± 0.7) (P < 0.05) [Figure 2].
Figure 2: Total opiate use in mg (morphine). Data are presented as mean. It was significantly less in group B (P < 0.05). FNB, femoral nerve block; LIA, local infiltration analgesia

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Patients in group B were able to reach 90° of knee flexion significantly earlier (2.2 ± 0.9 days) compared with patients in group A (3.4 ± 1 days) (P < 0.001) [Figure 3]. There were no complications reported in both groups.
Figure 3: Time to achieve 90° of flexion and length of stay in the two groups. Data are presented as mean. Both were significantly less in group B (P < 0.05). FNB, femoral nerve block; LIA, local infiltration analgesia

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  Discussion Top

Total knee arthroplasty is a painful procedure. Besides the humanitarian concerns, pain control is essential for early mobilization, which reduces the risk of complications. Moreover, good pain control reduces the length of stay in hospital and hence the cost. Uncontrolled acute postoperative pain is a risk factor for chronic postoperative pain, which was found to be a source of patient dissatisfaction [1],[2],[7],[17],[18] .

The multiple options for postoperative pain control reflects the fact that until now there is no gold standard established for pain control after TKA.

LIA a simple procedure, which can be performed by the surgeon intraoperatively, does not require instrumentation such as ultrasound machines, does not affect muscle power, and it is not time consuming.

As far as we know, there are not many studies comparing LIA with single-shot FNB for the control of pain after total knee arthroplasty.

Pain score was not significantly different between the two groups at 2 h postoperatively. This can be attributed to the pain relief effect of the spinal anesthesia given to all patients, as the average operative time in both groups was almost similar.

At 4 h postoperatively, when the effect of the spinal analgesia faded, the LAI group showed significantly less pain on VAS. On the first postoperative day, pain before and after physical therapy was, also, significantly less in group B. Similar findings were reported by Ashraf et al. [14] . Moghtadei et al. [19] reported better pain control in the LIA group on the first postoperative day, but pain scores were similar on the next day. This could be attributed to the absorption of the entire mixture that was injected at the soft tissue and lack of mixture in the joint to be slowly absorbed or pushed into the tissues when the patient started to mobilize. Affas et al. [20] found the average pain before ambulation to be less, but this was not significant, and pain after ambulation was similar in both groups. This might be explained by the fact that, in their study, Affas et al. [20] used a continuous femoral nerve infusion and not a single shot. Moreover, their mixture of LIA did not contain morphine and contained 30 mg of ketorolac.

Total opiate consumption was significantly less in group B. This was also noticed by Ashraf et al. [14] , Moghtadei et al. [19] , and Affas et al. [20] , whereas Rosen et al. [16] found no reduction in narcotic use with LIA.

In our study, group B had shorter length of stay in the hospital. Similar results were reported by Antoni et al. [21] , whereas Ashraf et al. [14] and Moghtadei et al. [19] found no significant difference between the two methods.

Flexion to 90° was achieved earlier in the LIA group, which facilitated earlier discharge. This was not reported in the similar study conducted by Ashraf et al. [14] and Moghtadei et al. [19] , but in both studies there was no intra-articular morphine given.

  Conclusion Top

In our study of LIA using a mixture of ropivacaine, ketorolac, morphine, and epinephrine, versus a single-shot FNB, showed better pain control, faster rehabilitation, and earlier discharge from the hospital in LIA patients. This may be due to the motor effect of FNB, which is absent in LIA and to the fact that FNB does not cover the posterior part of the joint. Moreover, the analgesic effect of ketorolac may be better in intra-articular injection [22],[23] .

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2], [Figure 3]

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