The efficacy of femoral nerve intraoperative somatosensory evoked potentials during surgical treatment of thoracolumbar fractures.

Somatosensory evoked potential (SEP) monitoring of thoracolumbar procedures typically includes posterior tibial and peroneal nerve recordings. The addition of femoral nerve SEP monitoring, however, should better predict the evolution of postoperative neurologic deficits affecting the midlumbar roots. To assess the value of intraoperative femoral SEPs, 26 cases of traumatic injury to the thoracolumbar spine between T12 and L4 were prospectively assessed. Twenty-four had clear femoral nerve responses bilaterally recorded from an epidural electrode. Five had significant intraoperative SEP changes: one had isolated femoral nerve changes, two had only peroneal or tibial nerve changes, and two had concomitant changes in both femoral and peroneal or tibial nerves. Loss of the femoral nerve response in one patient was correlated with marked postoperative knee extensor weakness, in spite of immediate action taken by the surgeon. The authors conclude that femoral nerve SEPs provide an effective tool to monitor the midlumbar roots intraoperatively.