SURGICAL MANEUVERS PLACING THE SCIATIC-NERVE AT RISK DURING TOTAL HIP-ARTHROPLASTY AS ASSESSED BY SOMATOSENSORY-EVOKED POTENTIAL MONITORING

The sciatic nerve in 52 hip arthroplasties was evaluated using intraop erative somatosensory evoked potentials (SSEPs). Twenty-nine of these cases involved the lateral transtrochanteric approach, and 23 involved the posterior approach. A total of 11 incidents of SSEP changes occur red in eight patients. Six episodes occurred during lateral retraction of the proximal femur, and three occurred during anterior retraction of the proximal femur. Tracings returned to baseline with prompt cessa tion of femoral retraction in each case. One SSEP change occurred in a revision following reduction of the prosthetic components, and this r esolved with shortening of the prosthetic neck to less than anatomic l ength. One change occurred during tightening of cables securing strut allografts to the femur, and this resolved spontaneously. No correlati on was found between frequency of SSEP changes and age, sex, limb leng thening, or preoperative range of motion. It is concluded that routine lateral or anterior retraction may place the sciatic nerve at risk.