Anatomic variations in the lateral femoral cutaneous nerve with respect to pediatric hip surgery.

Variations were documented in the course of the lateral femoral cutaneous nerve (LFCN) in the upper thigh relative to anatomic landmarks in 22 adult cadavers using the Smith-Petersen incision for the anterior approach to the hip. Distances from the anterior superior iliac spine (ASIS) to the point of nerve entry into the thigh were normalized as percentages of the distance from the ASIS to the pubic tubercle (PT) to relate the data to small children. In all cases, the LFCN passed deep to the inguinal ligament, entering the thigh a mean of 2.6 cm (SD, 1.9 cm) medial from the ASIS (19%+/-14% of the ASIS-PT distance), with distances ranging from 0.3 to 6.5 cm (2.6%-46.4%). With the data extrapolated to children, the LFCN may commonly be found medial to the ASIS about one fifth the distance from the ASIS to the PT. In 32% of cases, the LFCN ran directly inferiorly, but in 68% it coursed inferolaterally and then turned to run inferiorly close to the distal part of the incision. Expressed proportionally rather than only as mean measurements, these percentages provide a better estimate of the location of the LFCN in relation to patient size and thus are useful when operating in this region.