Patients
The local Ethics Committee approved the study protocol (approval date: 18 March 2013, approval no. 2013/125). This study was conducted between 18 March 2013 and 24 June 2016 in the Surgery Department of the Health Science University of Bagcilar Training and Research Hospital (Turkey), and was performed in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from each patient for inclusion in the study. Patients in this single-blinded, prospectively planned study were randomly assigned to anterior or posterior sciatic nerve block. At the beginning of the study, blockage failed in 80 patients, who were subsequently assigned to general anaesthesia (Figure 1) and thus excluded from further study. After the block was performed, the anaesthesiologist followed these general anaesthesia patients but was blinded to the type of block that had been performed. The single-blinded anaesthesiologist performed all posterior or anterior sciatic nerve and femoral nerve blocks, then exited the operating room after their completion; the patient was repositioned prior to beginning the operation. Another anaesthesiologist followed the patient without information regarding the direction of the blockage.
Inclusion criteria were patients aged 18–65 years with American Society of Anesthesiologists (ASA) physical status classes I or II, who had lateral and/or medial malleolus fractures.
Exclusion criteria were failed block, inability to visualise the sciatic nerve, and/or occurrence of delirium. In addition, patients with vascular, cardiac, or metabolic (diabetes mellitus)–renal–hepatic disease, or with neuropathic pain in the lower extremity were excluded, as were patients who were pregnant, had hemodynamic instability, or were currently taking medications likely to cause metabolic acid–base imbalance. Finally, patients with a history of steroid use or allergy, contraindications to regional anaesthesia, and/or alcohol/drug addiction were also excluded, as were those who did not graduate from primary school.
Procedure
Variables of interest included patient age, sex, height, weight, and American Society of Anesthesiologists physical status; operation time and tourniquet time; time to first fentanyl requirement before surgery and after blockade; time to first fentanyl requirement after surgery; mean fentanyl dose per patient before surgery and after blockade; mean fentanyl dose per patient after surgery; motor and sensory block start and end times after sciatic and femoral block; time to first diclofenac sodium dose; total dose of diclofenac sodium in the first 24 h postoperatively; VAS score; patient satisfaction; anaesthesia quality, as assessed by the anaesthesiologist; and surgical quality, as assessed by the surgeon.
Patient satisfaction was scored as 0: failed, 1: weak, 2: moderate, 3: good, and 4: excellent.11,12 Anaesthesia quality (anaesthesiologist) was scored as follows: 1: general anaesthesia was required, 2: complementary analgesic was needed, moderate complaints, 3: no need for complementary analgesia, few complaints, and 4: no complaints.11 Surgical quality (surgeon) was scored as follows: 1: failed, 2: moderate, 3: good, and 4: excellent.11
The patients received an explanation of the VAS on the day preceding surgery. No premedication was administered. In the regional block room, routine monitoring was conducted, including electrocardiography, non-invasive arterial sphygmomanometry, and peripheral pulse oximetry. Sciatic nerve blocks using an anterior approach were performed using a Stimuplex® A needle (21G 0.80-150) positioned at 30°, either isolated or in conjunction with a nerve block stimulator (Stimuplex HNS nerve stimulator; BRAUN, Germany) and USG (diagnostic ultrasound system, model SDU 450 XL class-1 type B; Shimadzu Corp., Japan). Local anaesthetic consisted of 15 mL of 0.5% isobaric bupivacaine, 5 mL of 2% lidocaine, and 20 mL of isotonic sodium chloride. In both the anterior and posterior approaches, nerve stimulation was performed with a frequency of 2 Hz and a current of 1 mA. The stimulus intensity was gradually reduced to 0.4 mA when a response was obtained.
For femoral nerve block, the nerve was visualised with concurrent USG and the needle was oriented to the nerve. When the vastus medialis had contracted, the vastus intermedialis and vastus lateralis muscles were visualised and 20 mL of the above-described local anaesthesia solution was administered. Dissemination of the solution was monitored by USG (linear probe) (Figure 2).
For anterior sciatic nerve block, the sciatic nerve was imaged by USG (convex probe) along the needle route and the needle was advanced to the nerve. Following plantar flexion, dorsal flexion, and eversion of the foot, 20 mL of the above-described local anaesthesia solution was administered and its spread was monitored by USG (Figure 3).
For posterior sciatic nerve block, the USG probe was placed between the greater trochanter and the coccyx at the entry point of the needle; the needle was advanced by imaging the nerve. Following plantar flexion, dorsal flexion, and eversion of the foot, 20 mL of the above-described local anaesthesia solution was administered and its spread was monitored by USG (Figure 4).
After the blocks had been completed, motor block was assessed by monitoring the movement of the ankle joint and knee, while sensory block was assessed by the application of a cold saline bag at 1-min intervals. The block start times were recorded. The time at which the patient no longer perceived cold stimulation of the sciatic and femoral stimulation areas was recorded as the start time of the full femoral-sciatic sensory block; the time at which the patient could not move the knee joint was recorded as the start time of full femoral motor block. The time at which the patient was unable to move the ankle joint was recorded as the start time of full sciatic motor block. After full block had been achieved, a tourniquet was applied to the target extremity and then inflated. Patients underwent surgery at 30 min after administration of the block. Patients with a VAS score ≥5 for pain were administered 1 μg fentanyl kg−1 intravenously. The mean fentanyl dose administered per patient after blockade and before surgery was recorded together with the following: mean fentanyl dose per patient after surgery; time to first fentanyl requirement before surgery and after blockade; time to first fentanyl requirement after surgery; time to first diclofenac sodium dose; and total dose of diclofenac sodium administered within the first 24 h postoperatively. Patients with a postoperative VAS score ≥5 for pain were also intravenously administered 1 μg fentanyl kg−1.
Statistical analysis
All data were evaluated using SPSS 11.5 for Windows. Sample size calculation was performed as follows: the required number of participants was determined based on the results of a pilot study that included 10 patients in each group. In that study, the time to sciatic nerve sensory block onset (mean ± standard deviation) was 8.88 ± 4.87 min for group A (anterior approach to sciatic nerve block + femoral nerve block) and 4.70 ± 2.05 min for group P (posterior approach to sciatic nerve block + femoral nerve block). The sample size was calculated as 29 (n=29) for group A and 29 (n=29) for group P, with α=5% and 90% power. Thus, 58 patients were enrolled in the present study.
The normality of the data was assessed using the Shapiro–Wilk test. Mean ± standard deviation values were used in parametric tests and median (minimum–maximum) values were used in nonparametric tests. Categorical data are presented as n (5). An independent samples t-test was used for binary comparisons of group data; the chi-squared test was used for between-group comparisons of categorical data. A p value <0.05 was considered to indicate statistical significance.