Injury to the femoral nerve often presents with difficulty in ambulation, climbing stairs, and rising from a seated position. Concomitant complaints of altered sensation over the anterior thigh and medial leg support the diagnosis of femoral neuropathy. In cases of suspected hemorrhage causing compression of the femoral nerve, immediate imaging using computed tomography or ultrasound will aid in the development of an effective management plan. Electrodiagnostic studies are best performed 3 to 4 weeks after the injury, so as to help with localization and prognostication. A key aspect of management may be surgical intervention, especially in the case of an expanding hematoma. Ultimately restoration of function and symptom management are key considerations. A controlled strengthening of hip flexor and knee extensor musculature is paramount in the case of incomplete injuries. In cases of complete femoral nerve injuries, bracing to stabilize the knee and facilitate ambulation is often required.
Keywordsfemoral neuropathy, gait disturbance, hemorrhage, leg numbness, thigh weakness
|G57.20||Lesion of femoral nerve, unspecified lower limb|
|G57.21||Lesion of femoral nerve, right lower limb|
|G57.22||Lesion of femoral nerve, left lower limb|
|G57.90||Mononeuropathy of unspecified lower limb|
|G57.91||Mononeuropathy of right lower limb|
|G57.92||Mononeuropathy of left lower limb|
|R20.9||Disturbance of skin sensation|
Femoral neuropathy is the focal injury of the femoral nerve causing various combinations of pain and sensory loss in the leg and foot and weakness 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. In fact it is estimated that 60% of all femoral nerve injuries are iatrogenic. Hemorrhage, most often due to anticoagulation therapy, also is common. Table 54.1 lists other possible causes of femoral neuropathy.
|Retraction during abdominal-pelvic surgery|
|Penetration trauma (e.g., gunshot and knife wounds, glass shards)|
|Retroperitoneal bleeding after femoral vein or artery puncture|
|Central line placement|
|Injury during femoral nerve block|
|Acute stretch injury due to a fall or other trauma|
|Hemorrhage after a fall or other trauma|
|Spontaneous hemorrhage—typically due to anticoagulant therapy|
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 ). 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 ).
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 climbing 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.
The examination should include a complete neuromuscular evaluation of the low back, hips, and both lower limbs. Inspection for asymmetry or atrophy, manual muscle testing, muscle stretch reflexes, and sensory testing for light touch and pinprick are all essential aspects of the physical examination in patients with suspected neuropathy.
The clinician may see atrophy or asymmetry of the quadriceps muscles. Weakness of hip flexion or knee extension may be present. Strength testing may be limited because of pain. Quadriceps strength should be compared with adductor strength, which typically is normal. Palpation over the inguinal ligament may reveal a fullness or exacerbate the patient’s pain symptoms. There is often a decreased or loss of quadriceps reflex and decreased sensation to the anterior thigh and anterior and medial leg. The thigh and groin may be tender to palpation. Pain may be exacerbated with hip extension ( Fig. 54.3 ).