INTRAOPERATIVE SSEP MONITORING DURING EXTERNAL FIXATION PROCEDURES INTHE LOWER-EXTREMITIES

The efficacy of somatosensory evoked potentials (SSEPs) to detect acut e peripheral nerve injury during external-fixator application in the l ower extremities was evaluated in 40 children with 42 Ilizarov surgica l procedures. The study included patients who were either clinically n ormal or who had preexisting neuropathy but consistent and reliable SS EP responses preoperatively. SSEPs were recorded from the popliteal fo ssa and lumbar regions after alternating stimulation of the peroneal a nd posterior tibial nerves at the ankle. SSEP changes due to anesthesi a, Ilizarov apparatus application, and other intraoperative variables are described. Significant deterioration or total loss of SSEP respons e during surgery occurred in four cases. Two of these patients were no rmal preoperatively and had symptoms of neurologic deficit postoperati vely; the other two had exacerbations of pre-existing neuropathy. In g eneral, the peroneal nerve was at greater risk for injury during surge ry. SSEP monitoring proved to be technically feasible in external-fixa tion procedures on the lower extremities and may be a practical tool f or detection of intraoperative nerve compromise.