Efficacy and safety of ultrasound-guided above-knee lateral approach for popliteal sciatic nerve block in surgeries below the knee: a randomized controlled trial

Abstract

Background: Ultrasound guidance has become a standard method for detection of nerve structures in regional anesthesia. During ultrasound-guided blockade, to identify anatomical structures is crucial but can be challenging. In clinical practice, we find a wide difference in the visibility score of the sciatic nerve (SN) through different approaches. This study aimed to compare SNB through the anterior and above-knee lateral approach in terms of identification ease, performance efficacy, and safety.Methods: Patients scheduled for below-knee surgery were randomized to either receive SNB using the above-knee lateral approach (Group L, n=27) or the anterior approach (Group A, n=26). The primary outcome was the visibility score of SN. Secondary outcomes included the time taken to identify the SN, nerve depth, success rate of SN identification, number of needle passes, time to elicit foot flexion, needle depth, and occurrence of SNB complications. Additionally, the sensory block onset and analgesia duration were assessed.Results: We included 53 adult patients. Compared with Group A, Group L showed a higher SN visibility score [3.25 (3.17, 3.67) vs. 2.50 (1.86, 2.68), P<0.001]. The scan time was significantly shorter in Group L 8.70 (6.01) s vs. 31.54 (11.87) s, P<0.001). The depth of the SN was 3.20 (0.56) cm in Group L and 5.53 (0.84) cm in Group A (P<0.001), and the needle insertion depth was 7.15 (0.90) cm in group L and 8.32 (1.13) cm in Group A (P<0.001). The number of needle passes was less in Group L, as well as the time to elicit foot flexion, and the time taken to perform the SN block (all P<0.001). The success rate of SN identification was non-significantly higher in Group L. There was no significant between-group difference in the onset of sensory block, as well as postoperative analgesia duration. None of the approaches involved acute systemic toxicity and hematoma occurrence.Conclusions: Based on the visibility score, the above-knee lateral approach allowed easy SN identification and safe SNB. Using the ultrasound-guided above-knee lateral approach for SNB in below-knee surgeries could be a reliable choice.

Evaluation of a New Method of Sciatic Nerve Block: A Prospective Pilot Study

“…For instance, Van Elstraete et al reported that the first attempt to locate the sciatic nerve was successful in only 7 of 20 patients (35.0%), 18 while Zhu et al reported that a satisfactory position was achieved during the first attempt in only 8 of 26 patients (30.8%), and 8 of 26 patients (30.8%) required more than two attempts to obtain a satisfactory position. 16 In the present study, we obtained a satisfactory position during the first attempt in 19 of 26 patients (73.1%), and only one patient (3.8%) required three attempts to obtain a satisfactory position. The reason for the repeated punctures in that patient might have been related to the age (over 70 yrs) or higher BMI (32 kg/m 2 ).…”

“…Zhu et al reported that in 10 of their 26 patients (38.5%) who underwent the anterior approach, the obtained image of the SN had poor quality (visibility score <2). 16 Our new method uses two well-defined ultrasonographic landmarks, the AMM and the femur, which can be obtained easily at the level of the upper middle thigh. The AMM, which is attached to the femur, covers the sciatic nerve.…”

Reevaluation of the topographical anatomy of the mid‐thigh: A magnetic resonance and ultrasound imaging study

“…Although we do not know the exact value, we think that a person with a higher BMI also has a higher SCAT value. We found only one other study that measured the depth of the SN from the same point as we did (Zhu et al, 2021). They conducted their study on living patients, and found the SN depth (which Zhu et al defined as the distance from the skin to the superficial SN surface) to be 5.53 cm, similar to that of Kendir et al's study.…”

“…Kendir et al also declared that the route of the needle passed through only the adductor magnus, and that no neurovascular structure was at risk of injury with this method. Zhu et al compared this method with an above-knee lateral approach and reported that this method required less time and fewer attempts to block the SN (Zhu et al, 2021). This method may be used when combining two blockades in selected patients.…”

Advancing pain management for extremity trauma: the evolution of ultrasound-guided nerve blocks for patients in the supine position in trauma centers

“…Zou Yinghua et al validated an improved anterior sciatic nerve block approach in which the puncture needle is nearly perpendicular to the ultrasound beam during the puncture process, making the needle visualization clearer, enhancing the safety of the puncture process, and providing nerve block effects comparable to traditional anterior sciatic nerve block [62]. Zhu et al, through the lateral approach at the upper outer thigh, demonstrated that this approach has a higher puncture success rate, better analgesic effects, and similar safety to the traditional approach [66].…”