|Year : 2014 | Volume
| Issue : 3 | Page : 376-380
Efficacy and safety of ankle block versus sciatic-saphenous nerve block for hallux valgus surgery
Ayman I Tharwat1, Ossama El Shazly2
1 Department of Anesthesiology, Intensive Care, and Pain Management, Faculty of Medicine, Cairo, Egypt
2 Department of Orthopedics, Ain-Shams University, Cairo, Egypt
|Date of Web Publication||27-Aug-2014|
Ayman I Tharwat
Department of Anesthesiology, Intensive Care, and Pain Management, Faculty of Medicine, Ain-Shams University, Cairo
Source of Support: None, Conflict of Interest: None
Various nerve block techniques had been used in foot surgery.
The aim of this study was to compare the efficacy of ankle block versus sciatic-saphenous nerve bock for elective hallux valgus surgery.
Materials and methods
A total of 42 patients who underwent elective hallux valgus surgery under regional anaesthesia were randomized to undergo either ankle block (group I) or combined sciatic-saphenous nerve block (group II). Both blocks were performed using 0.5% bupivacaine mixed with 2% lignocaine.
Hemodynamic analysis had shown statistically nonsignificant difference between groups I and II. With regard to the duration of postoperative analgesia, there was a statistically nonsignificant difference in the time elapsed before the first analgesic dose between group I (105 min) and group II (88.7 min). However, there was a statistically significant difference in total fentanyl consumption and the need for pethidine injection between group I and group II (P < 0.005). Regarding the visual analogue score, there was a statistically significant difference in the visual analogue score between group I (5.5 ± 4.5) and group II (3.5 ± 3.2) in the 12-h postoperative period (P < 0.005).
Combined sciatic-distal saphenous nerve block is as efficient as ankle block with anaesthesia, with no difference in hemodynamics. However, sciatic-saphenous block provides longer postoperative analgesia than ankle block alone and allows the use of thigh tourniquet, thus reducing bleeding and operative time.
Keywords: ankle block, hallux valgus, saphenous block, sciatic block
|How to cite this article:|
Tharwat AI, El Shazly O. Efficacy and safety of ankle block versus sciatic-saphenous nerve block for hallux valgus surgery. Ain-Shams J Anaesthesiol 2014;7:376-80
|How to cite this URL:|
Tharwat AI, El Shazly O. Efficacy and safety of ankle block versus sciatic-saphenous nerve block for hallux valgus surgery. Ain-Shams J Anaesthesiol [serial online] 2014 [cited 2020 Aug 5];7:376-80. Available from: http://www.asja.eg.net/text.asp?2014/7/3/376/139571
| Introduction|| |
Hallux valgus is one of the most common pathologies in orthopaedics. There are more than 130 surgical procedures for correction and treatment of hallux valgus . Some of these procedures are simple short procedures, such as bunionectomy and McBride's release, whereas others are more technically demanding and lengthy procedures, such as distal osteotomies and scarf metatarsal osteotomy [2-4]. The type of anaesthesia is crucial in foot surgery. Unlike general anaesthesia, regional blocks are well tolerated, provide good postoperative analgesia, and have low or no risk of cardiac complications, pulmonary complications, etc. [5,6]. This is especially useful in patients with multiple medical problems, as well as healthy patients who would like to have longer postoperative analgesia and want to avoid complications of general anaesthesia. There are different regional methods that are suitable for foot and ankle surgery . Distal regional block does not permit the use of pneumatic tourniquet, whereas proximal block procedures would allow the use of thigh tourniquet . Sciatic-saphenous nerve block may provide the advantage of complete foot anaesthesia and the ability of using thigh tourniquet. To the best of our knowledge, there are no published articles describing this combination in elective foot surgery. In this study, we aimed to compare the efficacy of ankle block alone with combined sciatic-saphenous nerve block in the setting of operative hemodynamics, toxicity, operative time and bleeding, and finally postoperative analgesia.
| Materials and methods|| |
This is a prospective randomized comparative study with retrospective analysis of data on 42 patients who had elective hallux valgus surgery during the period from January 2009 to January 2013. The inclusion criteria were patients who accepted to receive regional block anaesthesia, whereas the exclusion criteria were diabetic patients, age less than 18 years, morbid obesity, renal failure, contraindications to local anaesthesia (LA) (e.g. coagulopathy, local infection), or hypersensitivity to bupivacaine or lignocaine.
In a randomized manner, 22 patients underwent ankle block (group I), and 22 patients underwent combined sciatic-saphenous nerve block (group II). The method of randomization was by odd/even number method.
The nerve blocks were performed in the orthopaedic operating theatre at Ain-Shams University by a senior anaesthetist, with the assistance of a qualified anaesthesia nurse.
Ankle block was performed with the patient in the supine position and the foot on a padded support, aiming to block the superficial peroneal nerve, the deep peroneal nerve, the saphenous nerve, the sural nerve and the posterior tibial nerve. The saphenous nerve is a terminal branch of the femoral nerve, whereas all the other nerves are branches of the sciatic nerve system. With a nerve stimulator, a 23-G needle, 3-4 cm in length, was appropriate for all injections. Aspiration before injection of LA was carried out to exclude intravascular injection. We used 0.5% bupivacaine mixed with an equal volume of 2% lignocaine in all our blocks. For blockage of the posterior tibial nerve, the tibial artery was first palpated just posterior and inferior to the medial malleolus. A 50-mm stimulator needle was inserted to pass 2-3 mm posterior to the artery, looking for flexion of the great toe, or, less commonly, flexion of the other toes, and then 5 ml of the LA mix was injected. For blockage of the sural nerve, the needle was introduced along the lateral border of the Achilles tendon at the level of the cephalic border of the lateral malleolus. Then the needle was advanced anteriorly towards the fibula, and 5-7 ml of LA was injected [Figure 1].
|Figure 1: Sural nerve block. The needle is introduced along the lateral border of the Achilles tendon at the level of the cephalic border of the lateral malleolus.|
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For blockage of the superficial peroneal nerve, the needle was inserted subcutaneously at the most anterior point of the lower leg at the level of the cephalic borders of the malleoli. Then the needle was turned towards the lateral malleolus, and 3 ml LA was injected in a subcutaneous band between the lateral malleolus and the anterior border of the tibia.
For blockage of the saphenous nerve at the same puncture, the needle was withdrawn to just stay in the skin and then it was turned to point towards the medial malleolus. Then a 3 ml LA was infiltrated subcutaneously as the needle was advanced towards the medial malleolus [Figure 2].
For blockage of the deep peroneal nerve, after palpation of the dorsalis pedis artery, the needle was inserted superficial into the artery between the tendons of extensor hallucis longus (medially) and extensor digitorum (laterally), about one-third of the way down the foot from the ankle to the toes, and passed posteriorly to the left and then the right of the artery, injecting 2 ml LA deep into the fascia on each side [Figure 3].
For the sciatic nerve block, the patient was placed in the lateral (Sim's) position, with the operative side nondependent. The operative extremity was flexed 45° at the hip and 90° at the knee and rested against the dependent lower extremity. The posterior superior iliac spine, greater trochanter, and sacral hiatus were identified and marked with a skin marker. A line was drawn with a skin marker between the greater trochanter and posterior superior iliac spine. This line was bisected. A perpendicular line was dropped 3-5 cm from the midpoint of this line to the point of needle insertion, which should lie along a third line drawn between the greater trochanter and the sacral hiatus.
The area of needle insertion was prepared and draped in a sterile manner. A wheal of LA was placed, and a 6-inch 22-G Stimuplex insulated needle was advanced perpendicular to the skin. The nerve lies about 6-8 cm deep. Stimulation intensity was initially set at 1.5-2.0 mA and adjusted downwards as the evoked motor response increased. Plantar flexion at less than 0.5 mA was the desired motor response and indicated placement of the needle near the medial part (tibial component) of the nerve. After negative aspiration, the needle was held immobile and LA was injected incrementally, with attention paid to the presence of paresthesias, reflex movement and resistance to injection. Because the nerve trunk is large, injection of LA was administered into more than one location. The endpoint for nerve localization was contraction of the target musculature, with a 0.5 mA stimulating current. Upon localization, the current was reduced to the lowest level that still produced visible contractions of the target muscle. In addition to sciatic nerve block, saphenous nerve block in the foot is blocked as mentioned before, as the saphenous nerve in the foot is the only branch remaining from the femoral nerve.
Nerve blocks were performed with a sham block behind a surgical drape, blocking the patient's view. Conscious sedation was administered to our patients on demand according to what has been decided in the preoperative visit with midazolam (0.03 mg/kg).
A thigh tourniquet was applied for all cases who received sciatic nerve block, whereas the use of tourniquet was not possible in the patients who received local ankle block.
The surgical technique varied from bunionectomy and McBride release in mild grades of hallux valgus, to distal chevron osteotomy and scarf osteotomy in higher degrees of hallux valgus [Table 1].
|Table 1 Operative time and bleeding amount in the different procedures and in both groups|
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Quality of anaesthesia, sensory and motor block, intraoperative hemodynamics, and the need for general anaesthesia or sedation were recorded, along with requirements for postoperative analgesia. Visual postoperative pain scores and LA side effects were also reported.
Both the patients and the sergeants were asked postoperatively to give a score for their satisfaction with the anaesthetic procedure from 0 to 5, where 0 stands for unsatisfied; 5 stands for 100% satisfied; and 1, 2, 3, and 4 stand for 20, 40, 60, and 80% satisfaction, respectively. The time of regional anaesthesia (procedure time), mobilization time postoperatively, patient's and surgeon's satisfaction scores, and complications were recorded.
It was estimated that a sample size of 20 patients per group would have a power of 80% to detect a standardized difference (d) between the two groups with regard to the primary outcome measures. The type I error was set at 0.05 using a two-sided t-test. This relatively large effect size was targeted as we considered it a clinically relevant effect to seek.
The collected data were revised, coded, tabulated and introduced to a PC using Statistical Package for Social Science (SPSS 15.0.1 for Windows; SPSS Inc., Chicago, Illinois, USA). Data were presented and suitable analysis was performed according to the type of data obtained for each parameter. Analytical statistics was carried out using Student's t-test to assess the statistical significance of the difference between two study group means. Post-hoc test was used for comparisons of all possible pairs of group means. P-value level of significance was ranked as follows: P-value greater than 0.05, nonsignificant (NS); P-value less than 0.05, significant (S); and P-value less than 0.01, highly significant (HS). The data were presented in form means and SDs.
| Results|| |
The mean ± SD age of patients in group I was 41 ± 4.3 years old, whereas the mean ± SD age of patients in group II was 47 ± 5.1. The male to female ratio was 1 : 1.9 in group I, and 1 : 1.7 in group II. The types of the procedures in each group and difference in operative time are shown in [Table 1].
Hemodynamics analysis had shown statistically nonsignificant difference between groups I and II in terms of postblock mean arterial blood pressure and the intraoperative average heart rate (P > 0.05). The differences between group I and group II with regard to the hemodynamics are shown in [Table 2].
Regarding the duration of postoperative analgesia, there was a statistically nonsignificant difference in the time elapsed before the first analgesic dose between group I (88.7 min) and group II (105 min). However, there was a statistically significant difference in total fentanyl consumption and the need for pethidine injection between group I and group II (P < 0.05). With regard to the visual analogue score, there was a statistically significant difference in the visual analogue score between group I and group II in the 12-h postoperative period [Table 3].
| Discussion|| |
Regional nerve blocks for foot reconstructive surgeries have been widely used for the past 20 years, but few studies have been conducted to assess their efficacy [5,6]. Lower morbidity, postoperative pain control and less hospitalization are just examples of advantages of regional anaesthesia over general anaesthesia; however, patient nonacceptance was an obstacle, especially among not well-educated people. Moreover, we believe that once the patient chooses GA, no attempts should be made to convince him, and also patient expectations and needs from regional anaesthesia should not be exaggerated during the preoperative visit . For foot surgery, the most common concerns about regional anaesthesia was surprisingly the fear of hearing and seeing things in the operative theatre and not the fear of pain .
Combined sciatic-distal saphenous nerve block is, to the best of our knowledge, an unusual combination for reconstructive foot surgery. Among our patients, we did not experience the need for general anaesthesia, only conscious sedation as required by our patients during the procedure or decided during the preoperative visit. Our results showed that ankle block required more postoperative pain killers, but both nerve blocks provided a good intraoperative anaesthesia and a satisfactory postoperative pain control, with minimal requirements for pain killers in the immediate postoperative period. Sciatic nerve block gave us the advantage of using a thigh tourniquet. There was a statistically nonsignificant increase in the operative time and bleeding amount between group I and group II, which may be attributed to the lack of use of tourniquet in group I [Table 4].
|Table 4 Procedure and mobilization time, patient's and surgeon's satisfaction scores|
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Mcleod et al.  compared the postoperative analgesic effect of lateral popliteal sciatic nerve block versus ankle block in 40 patients who had foot surgery. All patients in their study had general anaesthesia at first with laryngeal mask. Group I (21 patients) underwent a lateral popliteal sciatic nerve block, and group II (19 patients) underwent an ankle block. Both groups were administered 20 ml bupivacaine 0.5% plain. They found that ankle block is more reliable, providing more consistent analgesia with less consumption of morphine. However, the duration of postoperative analgesia in the popliteal sciatic group was longer than the duration of postoperative analgesia in the ankle block group.
The main limitation of our study was the absence of standardization of the surgical procedure. Three different procedures were performed for the correction of hallux valgus, which differ in the magnitude of complexity and subsequently in the level of postoperative pain. However, these limitations did not affect the results of comparison between both groups as the number of cases was almost homogenous in both the groups.
| Conclusion|| |
Both sciatic-saphenous nerve block and ankle block provide good anaesthesia for foot hallux valgus surgery. Sciatic-saphenous nerve block provides longer postoperative analgesia and allows the use of thigh tourniquet, hence reducing the amount of bleeding and operative time.
| Acknowledgements|| |
| References|| |
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]