The ultrasonographic appearance of the femoral nerve and cases of iatrogenic impairment

Objective. To assess the feasibility of ultrasonography of femoral nerves in a cadaveric specimen, healthy volunteers, and patients. Methods. in 1 unembalmed cadaveric specimen (female, 90 years) and 20 healthy volunteers (9 male and 11 female, 18-50 years; n = 40 scans), the topographic features, cross-sectional shapes (oval or triangular), and cross-sectional areas of the femoral nerves were evaluated by ultrasonography (5- to 12-MHz broadband linear array). In a subsequent study, 7 consecutive patients with postoperative findings assigned to the femoral nerve were evaluated and assessed by a neurologist. Results. The mean +/- SD anteroposterior and mediolateral diameters of the femoral nerves in the volunteers were 3.1 +/- 0.8 and 9.8 +/- 2.1 mm, respectively, at an average cross-sectional area of 21.7 +/- 5.2 mm(2). The cross-sectional shape was oval in 67.5% superior to the inguinal ligament and in 95% inferior to the ligament. The infrainguinal femoral nerve showed variable distances to the femoral artery. In the subsequent patient study, 5 patients had swelling of the femoral nerve in the affected side. In 1 patient, the nerve had a blurred echo structure due to a hematoma. In 1 patient, major damage of the femoral nerve was ruled out clearly. Conclusions. Ultrasonography allows the depiction and assessment of the femoral nerve from about 10 cm superior to 5 cm inferior to the inguinal ligament. In this region, ultrasonography is helpful in detection of impairments and, therefore, in decisions about planning and even acceleration of further treatment.