Study On Mechanisms And Evoked Potential Monitoring Of Spinal Cord Injury During Scoliosis Correction Surgery

Background Idiopathic Scoliosis is one of the most important spine deformities Neural system injury is the severe complication of scoliosis correction surgery. To investicate the etiology and study on the intraoperative monitoring and prevention of the neural system injuries will be meaningful. To date several hypothesis of the etiology of the injuries are: (1) direct mechanical compression of the spinal cord or nerve roots by internal plants such as hooks, screws and wires. (2) Distraction of spinal cord; (3) Blood vessel original injuries such as epidural edema and postoperative persistent hypotension, which involves the delayed injuries of neural system. However, the investicate on the etiology of spinal cord distraction is deficiency and there is dispute on the etiology of distraction injury. During the last twenty years, especially last ten years the technical of evoked potential developed greatly and is still developing. To utilize the advanced technical to study on the etiology of the injuries and to develop the technic of IOM is demanded.Purpose To develop an animal model of spinal cord traction injury. To investicate the etiology and IOM strategies for neural system injuries during scoliosis correction operation.Methods We meliorate the animal model of spine traction injury developed by Jarzem et al. The range of the demage and pathology of the injury are studied. To envesticate the etiology of the injury we observed the variety of SEP, NMEP, SCBF and SP of the spinal cord during the distraction. We studied on the mechanical propoties of spinal cord by invitro traction. The varieties of SCBF, SEP and NMEP were observed while the nicardipine are used for hypotension control. The differency of the distraction injury is studied during normal blood pressure and controlled hypotension by nicadipine. The lenghth of the spine in 3 dimension are studied in all kinds of idiopathic scoliosis before and after correction surgery to observe the elongation of the spine. 3 dimension finite element model are created to simulate the correction sugery of idiopathic scoliosis and to study the elongation of spine in future. The correlation of the aneathesia events and surgery events and varieties of SEP are analysised in 32 cases of scoliosis patients.Results & ConclusionsStudy on spine distraction model of dog1. The meliorated animal model can achieve the staged spinal cord injury by single segment spine distraction. This modle is a reliable and reproducible.2. The distraction injury involves 3 segment up and below the segment distracted. The nerve roots of distracted segment and 1 segment up and below are envolved also. The most severe demage lie in the segment tracted.3. The pathology presentation of the early stage of the distraction are hemorrage of the grey matter area, death of the neurons and glial cells and swelling and disruption of the nerve fibers. The demage of the sensation fibers are more severe than motor fibers in white matter and spinal nerve roots. Chang of the latency and amplitude of the SEP is much earlier than NMEP.Etiology study of spine distraction Injury1. Decreased SCBF and increased SP were observed during the traction injury. The mechanical properties are assumed to be elastic and viscosity.2. Two machanism are envolve in the spinal cord injury. One is the decrease of the blood supplu of the spinal cord caused by the elevated tissue pressure. The second is the mechanical traction injury of the spinal cord and spinal nerve roots.Comparative analysis on normal blood pressure and hypotension controlled spinal cord distraction injury1. Nicadipine impose mild influence on SCBF and latency and amplitude of SEP when used as hypotension controlled medcine. The latency and amplotude of the NMEP remain unchanged.2. The susceptibility to distraction injury is not increased while in hypotension condition controlled by nicadipine.Relative analysis of aneathesia and surgery events and SEP1. The notable chang...