The original lateral approach was found to be technically difficult to localize the sciatic nerve even performed by an experienced hand using nerve stimulation guidance.
We have introduced ultrasound guidance to facilitate identification of the nerve with the lateral approach.
The lateral approach for proximal sciatic nerve block can be performed in patients lying supine, similar to the ultrasound-guided anterior approach.
•Prospective, randomized, controlled, observer-blind, trial
•Patients who were scheduled for unilateral knee surgery
•ASA PS ≥4
•Inability to communicate
•Age <20 years old
•Body weight <40 kg
•Body mass index >35 kg/m2
•Allergy to local anesthetic
•Pre-existing sensory impairment in the lower extremities
•Infections at the injection site
•Surgical history involving the hip or femur on the present operated side
•The frequency of complete blockade of the posterior femoral cutaneous nerve assessed by pinprick 30 min after the sciatic nerve block
•The frequency of complete sensory block in the area supplied by the sciatic nerve
•The frequency of motor sciatic nerve block
•Pre-scan time required to identify the sciatic nerve under ultrasound
•Sciatic nerve block performance time (time from initial insertion to withdrawal of the needle)
•The depth of sciatic nerve (distance from the skin to the sciatic nerve)
•The needle depth (distance from the skin to the needle tip during injection of local anesthetic)
•The incidence of adverse effects (e.g. inadvertent vessel puncture, LAST, infection)
The ultrasound-guided lateral approach was simulated in four legs in three female adult cadavers using 20 ml of water-soluble dye to validate the feasibility that the injectate would reach both the sciatic and the posterior femoral cutaneous nerves.
The technical difficulty of the lateral approach can be alleviated by ultrasound guidance.
The ultrasound-guided lateral approach for proximal sciatic nerve block can be performed as successfully as the anterior approach.
The ultrasound-guided lateral approach provides concomitant blockade of the posterior femoral cutaneous nerve more often than the anterior approach.