What nerve is damaged in cases of anteromedial thigh pain after open inguinal hernia repair?

Nerve Damage Causing Anteromedial Thigh Pain After Open Inguinal Hernia Repair

The femoral nerve is the most likely nerve damaged when patients experience anteromedial thigh pain following open inguinal hernia repair. 1

Anatomy and Mechanism of Injury

The femoral nerve is particularly vulnerable during inguinal hernia repair due to its anatomical location. It runs beneath the inguinal ligament, lateral to the femoral vessels, and can be injured through several mechanisms:

• Direct injury from sutures or staples during mesh fixation
• Compression from improperly placed mesh
• Tissue scarring causing nerve entrapment
• Inadvertent inclusion in suture material during repair 1

The femoral nerve provides sensory innervation to the anteromedial thigh and motor function to the quadriceps muscles, which explains the characteristic location of pain when this nerve is damaged.

Clinical Presentation

Patients with femoral nerve injury after inguinal hernia repair typically present with:

• Pain in the anteromedial aspect of the thigh
• Possible weakness in knee extension (quadriceps function)
• Sensory changes in the anteromedial thigh region
• Symptoms that may worsen with hip extension or knee flexion

Differential Diagnosis

While the femoral nerve is the most likely culprit for anteromedial thigh pain, other potential nerve injuries include:

1. Genitofemoral nerve (particularly the femoral branch) - more commonly causes pain in the anterior thigh and genital region 2
2. Ilioinguinal nerve - typically causes pain in the groin, medial thigh, and genital area 3
3. Lateral femoral cutaneous nerve - causes lateral thigh pain (not anteromedial) 2

Diagnostic Approach

For patients presenting with anteromedial thigh pain after inguinal hernia repair:

1. Perform a detailed neurological examination focusing on:

   • Motor strength of quadriceps
   • Sensory testing of the anteromedial thigh
   • Patellar reflex

2. Consider electrodiagnostic studies:

   • EMG and nerve conduction studies can confirm femoral nerve injury 1

3. MRI may be helpful to:

   • Visualize the nerve and surrounding structures
   • Identify potential compression from mesh or scar tissue

Prevention Strategies

To prevent femoral nerve injury during inguinal hernia repair:

• Maintain thorough knowledge of inguinal canal anatomy
• Use careful dissection techniques in the preperitoneal space
• Avoid excessive lateral fixation of mesh
• Place sutures or staples medially away from the femoral nerve path
• Consider nerve identification during surgery 3

Management of Established Injury

For patients with confirmed femoral nerve injury:

1. Conservative management (for most cases):

   • Physical therapy for quadriceps strengthening
   • Pain management with neuropathic pain medications
   • Time (many cases resolve spontaneously within 3-6 months) 4

2. Surgical exploration (for persistent cases):

   • Consider if symptoms persist beyond 3-6 months
   • May involve removal of offending sutures or mesh adjustment
   • Neurolysis of the affected nerve

Prognosis

The prognosis for femoral nerve injury after inguinal hernia repair is generally favorable:

• Most cases are transient and resolve within 3-6 months
• Complete recovery is more likely with prompt recognition and management
• Persistent cases may require surgical intervention

Common Pitfalls

• Misdiagnosis as routine post-surgical pain
• Failure to recognize the pattern of symptoms specific to femoral nerve injury
• Overlooking the possibility of nerve injury during surgical planning and execution
• Delayed referral for electrodiagnostic studies in persistent cases

Understanding the anatomy and taking precautions during surgery remain the best approaches to preventing this complication of inguinal hernia repair.