What is the pathogenesis of femoral nerve entrapment?

Updated: Oct 15, 2019
  • Author: Minoo Hadjari Hollis, MD; Chief Editor: Thomas M DeBerardino, MD  more...
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The femoral nerve can have several entrapment locations or causes of injury, including intrapelvic injury and injury in the inguinal region. Diabetic amyotrophy is the most common cause of femoral nerve neuropathy. Open injuries can occur from gunshots, knife wounds, glass shards, or needle puncture in some medical procedures.

The most worrisome complication of major trauma to the femoral triangle region is an associated femoral artery injury. The nerve can be injured at the time of the trauma or inadvertently sutured during repair of this injury. Large-blade self-retaining retractors used during pelvic operations can cause injury to the nerve as a consequence of compression. [17]

In a study that measured conduction of the femoral nerve in diabetic patients without clinical signs of femoral nerve involvement, a statistically significant difference was observed between diabetics and healthy individuals in terms of both femoral nerve motor latency and amplitude. [18] The authors observed that these abnormalities became more evident as the polyneuropathy of the patients became more serious.

Most entrapment neuropathies occur below the inguinal ligament. After passing beneath the inguinal ligament, the femoral nerve is in close proximity to the femoral head, the tendon insertion of the vastus intermedius, the psoas tendon, the hip, and the joint capsule. The nerve does not have significant protection in this area.

Heat developed by methylmethacrylate during a total hip arthroplasty can injure the femoral nerve. Pelvic procedures that require the lower extremity to be positioned in an acutely flexed, abducted, and externally rotated position for long periods can cause compression by angling the femoral nerve beneath the inguinal ligament. The nerve may be compromised by pressure from a fetus in a difficult birth. Pelvic fractures and acute hyperextension of the thigh may also cause an isolated femoral nerve injury.

Pelvic radiation, appendiceal or renal abscesses, and tumors can cause femoral nerve injuries as well. The nerve can also be injured by a compartmentlike compression from a hemorrhage (caused by a hemorrhagic disorder or by anticoagulant use).

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