🔵 Note: This article is intended for healthcare professionals and contains advanced medical information.
Introduction
Traumatic pelvic injuries are often associated with vascular or visceral damage, but isolated peripheral nerve involvement is less frequently reported. Among these, femoral neuropathy is particularly rare and may be overlooked if not systematically assessed. Electromyography (EMG) plays a crucial role in differentiating femoral neuropathy from lumbosacral radiculopathy or plexopathy, guiding both prognosis and management.
Case Presentation
A 39-year-old man sustained a dramatic accident: he fell from a wall onto a metal bar (diameter 16 mm), firmly anchored to the ground at a construction site. The bar penetrated trans-pelvically, causing bladder and bowel injury. Emergency surgery was performed to remove the bar and repair the visceral lesions. Remarkably, no major vascular damage was noted.
The patient presented 14 days later for EMG evaluation, referred by orthopedic surgery without specific clinical indications.
Figure 1. 3D CT reconstruction showing trajectory of the bar (entry and exit points)
Clinical Findings
Detailed history was taken, including mechanism of injury and operative details (though the operative report was not available). Inspection of the surgical site was performed.
Muscle strength (MRC scale):
Right quadriceps: 5/5
Left quadriceps: 2–3/5 (clear deficit)
Hip adductors, iliopsoas, gluteus medius, tibialis anterior, and peroneals: 4–5/5, otherwise normal
Sensation: intact, bilaterally symmetric
Reflexes: present and symmetric
No low back pain or cruralgia was reported.
Electrophysiological Study
Sensory nerve conduction (sural, superficial peroneal, saphenous, tibial nerve, Common peroneal nerve): normal and symmetric
H and F responses: within normal limits
Needle EMG:
Left quadriceps (vastus lateralis): reduced recruitment, poor/fast pattern, no spontaneous activity at rest
Tibialis anterior and peroneal muscles: normal, rich interference pattern
Interpretation
The findings demonstrate an isolated weakness of the left quadriceps with normal sensation and reflexes. EMG confirmed a localized femoral nerve involvement.
Likely mechanisms:
Compression by retroperitoneal hematoma
Traction injury during trauma
More probably iatrogenic, since femoral nerve lesions are most frequently described after pelvic/abdominal surgery, and the surgical field was in close proximity to the femoral nerve trajectory
Arguments against L4 radiculopathy: paraspinal muscles and tibialis anterior were normal
Arguments against lumbar plexopathy: hip adductors and other plexus-innervated muscles were intact
Discussion
This case underlines the importance of correlating clinical findings with EMG results in the setting of trauma. Isolated femoral neuropathy, although rare, should be considered in patients presenting with quadriceps weakness, especially after pelvic surgery or trauma.
Differentiation from L4 radiculopathy and lumbar plexopathy is essential, since prognosis and management differ significantly. EMG provides the decisive evidence by identifying the site and extent of the lesion.
Conclusion / Key Learning Points
Isolated femoral neuropathy can occur after pelvic trauma and surgery, even in the absence of major vascular injury.
Careful muscle testing and sensory examination guide the diagnostic suspicion.
EMG is essential to localize the lesion and exclude radiculopathy or plexopathy.
Awareness of potential iatrogenic mechanisms is crucial for prevention and surgical planning.