Abstract
Objective-Study Design: Recognizing the value of intraoperative SEP monitoring in scoliosis and other spinal surgery, we applied prospectively continuous SEP recording during reconstructive procedures in 82 patients who sustained 20 cervical, 8 thoracic, 6 thoraco-lumbar, and 48 lumbar vertebral fractures or fractures-dislocations to investigate its efficacy in spinal trauma.
Material: Seventy-one patients underwent single anterior or posterior operations, and 11 combined anterior-posterior procedures. Forty patients had incomplete injuries, and 42 had no preoperative neurological deficit. SEP trace amplitude at insertion of electrode was considered as the baseline value, and was compared to the lowest intraoperative signal amplitude and the amplitude at completion of operation.
Results: Fifty-nine patients had a depression in wave amplitude of more than 25% during surgery; in 25 patients the trace fell by more than 50%, and in 7 cases a more than 75% diminution was recorded. A loss of 50% in SEP signal amplitude showed 67% sensitivity, and 71% specificity in predicting neurologic outcome. Patients with a fall in SEP amplitude of more than 50% that did not recover at completion of the surgical procedure demonstrated an increased risk of neurological compromise (p< .01). Increasing trace deterioration threshold from 50 to 60% improved specificity to 81% without compromising sensitivity. There was also 100% correlation between the side of the amplitude drop and the side of neurological loss in the trunk or limb (p< .001). A total number of 22 patients had improved SEP recordings before skin closure; 19 of these patients demonstrated an improved neurologic function after the operative procedure. In these 19 patients a positive statistical association could be documented between the signal changes and the neurological outcome (p< .05). Nevertheless, 2 of the patients with up to 20% improvement in the trace amplitude compared to the original control measurement presented deterioration in their neurological picture in the postoperative period. In 17 patients the SEP waveform amplitude was unchanged at conclusion of the operation; in those cases the neurological functional level post-surgery was equally unaltered. No significant difference was obtained when comparing the systolic blood pressures or the core temperatures at skin closure between the different outcome groups (p> .05). A loss of more than 50% in SEP amplitude occurred with significantly increased incidence during the anterior compared to the posterior spinal procedures (p< .001). More than 20% recovery in signal amplitude at conclusion of the procedure in patients with incomplete injuries was correlated with favorable neurological function.
Conclusions: Persistent intraoperative decrement in SEP amplitude and poor restitution at completion of surgery increase the risk for postoperative neurologic compromise. In this series, continuous intraoperative SEP monitoring appeared to be adequately reproducible, sufficiently reliable, and therefore a practical tool in monitoring operative procedures for spinal trauma. Even though compared to deformity surgery the method is less sensitive and specific, it may help reduce the incidence of devastating neurologic injury during the operation on an already compromised neural cord, and can provide good prediction in terms of postoperative neurological outcome. Thus, it could be considered a useful surgical adjunct in the management of patients with spinal trauma.
The abstracts were prepared by Eleni Koutsoukou. Correspondence should be addressed to him at the Hellenic Association of Orthopaedic Surgery and Traumatology (HAOST), 20, A. Fleming str, 15123 Marousi, Athens, Greece.
