Ultrasound imaging accurately identifies the lateral femoral cutaneous nerve

Anesthesia of the lateral femoral cutaneous nerve (LFCN) is useful in surgery involving the anterolateral thigh. We investigated the accuracy of ultrasound compared with anatomical landmarks in identifying the LFCN in human cadavers and volunteers.

Twenty cadavers were examined. A needle was inserted targeting the LFCN with ultrasound guidance and green dye was injected. A second needle was inserted using anatomical landmarks. The LFCN was identified by dissection, and coloring of the LFCN and needle positions were evaluated. A volunteer study with 10 individuals was performed. Transdermal nerve stimulation was used to identify the LFCN bilaterally. Its position was compared with marked positions identified in advance using ultrasound and anatomical landmarks.

Sixteen of 19 needles inserted under ultrasound guidance in the cadavers were in contact with the LFCN. The median horizontal distance from the needle tip to the nerve was 0.0 mm (interquartile range [IQR], 0.0-0.0 mm). Only 1 of 19 needles inserted using anatomical landmarks was in contact with the LFCN. The median horizontal distance from the needle tip to the nerve was 18.0 mm (IQR, 11.0-23.0 mm). Sixteen of 20 marked positions made using ultrasound guidance corresponded to the identified LFCN in volunteers. The median horizontal distance from the pen-mark to the LFCN was 0.0 mm (IQR, 0.0-0.0 mm). None of the 20 marked positions made with anatomical landmarks corresponded to the LFCN. The median horizontal distance from the pen-mark to the LFCN was 15.0 mm (IQR, 10.8-20.0 mm).

Identification of the LFCN by ultrasound is technically feasible and more accurate than anatomical landmarks.