Intraoperative somatosensory evoked potential monitoring of pelvic and acetabular fractures.

The efficacy of intraoperative somatosensory evoked potential (SSEP) monitoring was evaluated in the surgical management of 82 patients with pelvic and acetabular fractures. The injuries consisted of 45 acetabular fractures, 30 pelvic ring disruptions, and seven combined injuries. Preoperative neurological deficits were recorded in 34% of the study group (29% of those with an acetabular fracture and 47% of those with a pelvic ring injury). Three patients sustained an iatrogenic sciatic nerve injury during the study period (all of which were documented in the first 40 cases). Two patients sustained an exacerbation of an existing sciatic nerve injury. In the group of pelvic fractures, hazardous parts of the exposure, reduction, and fixation were identified by the SSEP monitoring. Removal of the provocative stimulus by the surgeon led to reversal of the SSEP abnormalities, and none of this group of patients sustained an iatrogenic injury. When the intraoperative SSEP changes were noted during an acetabular fracture fixation, immediate attempts were made to relieve the excessive tension on the sciatic nerve by replacing or removing a retractor, flexing the knee, extending the hip, or dividing the femoral insertion of the gluteus maximus. None of the SSEP changes were associated with the lacerative injury to the sciatic nerve. For the method to be clinically effective in reducing the incidence of neurological deficit, even subtle changes in the SSEP tracing must be recognized immediately by the neurophysiologist so that a corresponding corrective measure can be rapidly undertaken by the surgeon to remove the offending stimulus.