CHAPTER 54
Femoral Neuropathy
Earl J. Craig, MD; Daniel M. Clinchot, MD
Definition
Femoral neuropathy is the focal injury of the femoral nerve causing various combinations of pain, weakness, and sensory loss in the anterior thigh. The exact incidence of femoral neuropathy is not clear. However, the most common etiology is iatrogenic followed by tumor-related injury [1]. Hemorrhage, most often due to anticoagulation therapy, also is common. Table 54.1 lists other possible causes of femoral neuropathy.
Table 54.1
Possible Causes of Focal Femoral Neuropathy [1,2]
Open Injuries
Retraction during abdominal-pelvic surgery [3,4]
Hip surgery—heat used by methyl methacrylate, especially in association with leg lengthening [5,6]
Penetration trauma (e.g., gunshot and knife wounds, glass shards)
Closed Injuries
Retroperitoneal bleeding after femoral vein or artery puncture [7]
Cardiac angiography
Central line placement
Retroperitoneal fibrosis
Injury during femoral nerve block
Diabetic amyotrophy
Infection
Cancer [8]
Pregnancy
Radiation
Acute stretch injury due to a fall or other trauma
Hemorrhage after a fall or other trauma
Spontaneous hemorrhage—typically due to anticoagulant therapy
Idiopathic
Hypertrophic mononeuropathy [9]
The femoral nerve arises from the anterior rami of the lumbar nerve roots 2, 3, and 4. After forming, the nerve passes on the anterolateral border of the psoas muscle, between the psoas and iliacus muscles, down the posterior abdominal wall, and through the posterior pelvis until it emerges under the inguinal ligament lateral to the femoral artery (Fig. 54.1) [2–4]. The course continues down the anterior thigh, innervating the anterior thigh muscles. The sensory-only saphenous nerve branches off the femoral nerve distal to the inguinal ligament and courses through the thigh until the Hunter (subsartorial) canal, where the nerve dives deep. The femoral nerve innervates the psoas and iliacus muscles in the pelvis and the sartorius, pectineus, rectus femoris, vastus medialis, vastus lateralis, and vastus intermedius muscles in the anterior thigh. The femoral nerve provides sensory innervation to the anterior thigh. The saphenous nerve provides sensory innervation to the anterior patella, anteromedial leg, and medial foot (Fig. 54.2).
Symptoms
The symptoms depend on how acute the injury is and what caused the injury. A patient will often first complain of a dull, aching pain in the inguinal region, which may intensify within hours. Shortly thereafter, the patient may note difficulty with ambulation secondary to leg weakness. The patient may or may not complain of weakness in the hip or thigh but will often notice difficulty with functional activities, such as getting out of a chair and traversing stairs or inclines. Numbness over the anterior thigh and medial leg is common. The numbness may extend into the anteromedial leg and the medial aspect of the foot.
