Our institution uses lower extremity somatosensory evoked potentials from the fibular (peroneal) and tibial nerves during posterior open reduction and internal fixation of the acetabulum to monitor the functional integrity of the sciatic nerve. This allows identification of compromised function caused by operative maneuvers. However, nonsurgical factors can also significantly affect the responses. In this article, we present one case where positioning of the leg and foot apparently caused diminished responses and was resolved by changing the manner of wrapping and securing the leg and foot. The second case is unusual because positioning improved the responses from being absent to identifiable and stable. Investigation of changes in peripheral responses should include examination of the position of the affected leg for ischemia and edema, and particularly the stimulation site for possible compromise.
Keywords: Acetabulum fracture fixation; compartment syndrome; intraoperative monitoring; somatosensory evoked potentials; surgical positioning.