Relationships of the Lateral Femoral Cutaneous Nerve to Bony Landmarks

Abstract

The lateral femoral cutaneous nerve (LFCN) can be at risk during, for example, the insertion of pins in the anterior superior iliac spine (ASIS) during external fixation of the pelvis, total hip arthroplasty through a direct anterior approach, open surgery for impingement in the hip through an anterior approach, and periacetabular osteotomy. During surgery, the surgeon usually assumes the location of the LFCN by using the ASIS as a landmark. We investigated (1) whether there is any relationship between the LFCN and the ASIS and (2) the anatomy of the LFCN at the lateral border of the psoas major. Using 25 formalin-fixed cadavers, we determined the location of the LFCN emergence point as above, same level with, or below the iliac crest (IC). We measured the distances between the LFCN emergence point and the crossing of the IC and psoas major, ASIS, and pubic tubercle. We measured the distances between the ASIS and pubic tubercle (AB) and the ASIS and the point where the LFCN crossed the inguinal ligament (AC) and then calculated AC/AB. The LFCN was below the IC on 19 sides, at the same level on 13 sides, and above on 12 sides. The distances were -0.98 ± 5.57 cm to the IC, 12.39 ± 2.67 cm to the ASIS, and 17.76 ± 3.33 cm to the pubic tubercle. AB was 13.11 ± 1.08 cm, AC 2.95 ± 2.01 cm, and AC/AB 0.22 ± 0.16. The LFCN may emerge from the lateral border of the psoas major above or below the IC. The AC/AB ratio can help surgeons to find the LFCN in patients with different body types.