Anterior approach for sciatic nerve localization: A novel observational pilot study utilizing sonoanatomical landmarks

Abstract

Background: Anterior approach to sciatic nerve (SN) block has been an underutilized technique due to the technical difficulties and lack of accurate landmarks to guide the localization of the nerve. This prospective, observational study was planned to evaluate the sonoanatomical relationship of SN with femoral neurovascular complex and femoral shaft by anterior approach for easy identification. Materials and Methods: After ethics committee approval and written informed consent, sonoanatomy of SN in anteromedial thigh was observed in 30 American Society of Anesthesiologists I–III patients. Measurements of distance between SN, femoral shaft, and femoral neurovascular complex were taken. Surface landmark for probe positioning was also noted. Results: We observed that SN was consistently located in a triangular arrangement with femoral shaft and femoral neurovascular complex. Distance of SN from femoral shaft located superolaterally was 43.4 ± 12 mm. Distance of SN from femoral neurovascular complex located superiorly was 44.8 ± 11.4 mm. Distance between femoral shaft and femoral neurovascular complex was 39.1 ± 9.4 mm and distance of ultrasound probe placement for optimal visualization of SN from inguinal crease was 167 ± 29 mm. Conclusion: We propose a new and more distal sonoanatomical landmark for ultrasound-guided approach to anterior SN block which consistently localizes the SN in relation to femoral shaft and femoral neurovascular complex and can be easily performed in all patients in the supine position.

Keywords

• anterior approach
• femoral vessels
• femur
• sciatic nerve block
• sonoanatomical landmarks
• ultrasound guided
• upper midthigh approach