Surgical Anatomy And Clinical Study For The Operation Of Ventral Thoracic Spinal Cord Tumor

Objective: To study the morphology and dimension and relation of the osseous thoracic vertebra canal (TVC) and its adjacent bony structures for further study of surgical approach in this area.Methods: Bony TVC and its adjacent bony structures were observed and measured on 15 dry thoracic spine(TS). CT scans of six wet adult cadaveric TS specimens were obtained. The exposure area and angle of view were observed after the lateral structure of thoracic vertebra were removed. Efilm software was utilized to analyse the data.Results: The TVC was located posterior to the vertebral body and anterior to the lamina and articular process. The pedicle was lateral to it and the transverse process with which the rib articulated was lateral to the pedicle. The TVC was relative narrow. Among them the vertebra foramen of T1 was the broadest one(19.82 ± 0.56mm). The height of the pedicle increased from T1 to T12 and the thickness was less than 1cm(the most narrow level was less than 4mm). The superior vertebral incisure was not obvious but inferior vertebral incisure was deep(the depth was 8.5-10.5mm). The superior articular process(SAP) was v-shaped from superior-posterior view. The distance between left and right SAP of T1 was the broadest(about 19mm) and T5, 6 was the most narrow level. The transverse process extended posteriorly and formed an angle with the median sagittal plane, which decreased from T1 to T10(about 60° at T1 level and about 36° at T10 level). The length of the transverse processdecreased from T1 to T12, too. The distance from the end of the transverse process to the median rim of the SAP was 25-30mm and the distance from the end of the transverse process to the median rim of the inferior articular process was about 30mm. After the removal of the lateral bony structure which simulated with the different surgical approach , the view of angle exposing the vental part of the TVC of the lateral-anterior approach was larger, which increased 20 ° than the trans-pedicle trans-articular approach.Conclusion: The TVC was relative small. It was difficult to expose its ventral part via posterior approach. The pedicle, articulation of articular process, transverse process and little segment of the adjacent rib were the primary bony obstacle to the ventral TVC. Part Two Study of lateral-anterior approach for thoracic vertebraObjective: To study a lateral-anterior approach by which the anterior thoracic vertebra canal and ventral spinal cord could be well exposed. Methods: The microsurgical anatomy and the exposure of the lateral-anterior approach were examined in 12 wet adult cadaveric thoracic spine specimens, its exposing scale and advantages and disadvantages were studied. Exposure and view of angle were compared among this approach , posterior approach and modified posterior-lateral approach by means of simulated operation and imaging study. Results: A hockey-stick shaped skin incision was made at the posterior median line and the lateral muscles were freed step by step. The costotransversal articulatio and part of rib was exposed and the rib wasfreed subperiosteally. The pleura and intercostal neurovessel bundle was intact. The transverse process and little segment of rib was resected. Intervertebral foramen was found along with the intercostal nerve , then the pedicle and articulation of articular process was removed rostrally and the anterior dural sac was exposed. The dura was incised parellel to the posterior rim of the vertebral body, after that , the ventral part of the spinal cord could be exposed without retraction of the spinal cord. Exposure and view of angle of the lateral-anterior approach were better than that of posterior approach and modified poterior-lateral approach through the simulated operation and imaging study. Conclusion: The lateral-anterior approach could not only expose anterior TVC and ventral part of the thoracic spinal cord clearly, but also it was unnecessary to manipulate the spinal cord, therefore , it is a mininvasive approach.Part 3Surgical treatment for ventral spinal cord tumor of thethoracic vertebraObjective: To summarize the surgical approach and operative technique for ventral thoracic spinal cord tumor.Methods: The clinical data of 35 patients with ventral thoracic spinal cord tumor treated in our department from January 2000 to January 2006 were studied retrospectively. There were 21 male and 14 female who aged 15 to 67 years (mean age, 40.8 years) among these cases. All the tumors located at ventral or ventro-lateral spinal cord. There were twenty-six intradural tumors, three extradural tumors, one intramedullary and fivedumbbell tumors. These series consisted of twenty neurinomas, twelvemeningiomas, two enterogenous cysts, one ependymoma.Results: thirty-two patients underwent total excision of tumor and threepatients underwent subtotal excision. Twenty-eight patients hadsignificant neurological improvement. Postoperative neurologicalexamination was unchanged in 4 patients, deteriorated in 3 patients.Twenty-six patients were followed up for three months to six years andno recurrent cases.Conclusion: To achieve a good operative outcome , it is very importantto design the approach individually based on its location and size andoperate mini-invasively and resect tumor totally as possible as we canin the primary stage. Most ventral thoracic spinal tumor can be resectedvia posterior approach. It is necessary to rotate spinal cord to achievemore ventral exposure for tumor, but this manipulation may compromise thevulnerable spinal cord. As an alternative way, anterior-lateral approachcan not only increase the exposure for tumor, but also decrease theretraction for spinal cord.Part fourPreliminary construction of three dimensional finite elements model of middle thoracic vertebraeObjective: To construct a preliminary three dimensional finite elementsmodel of middle thoracic vertebrae and expect to form an effectivebiomechanical model based on which mechanical analysis could beperformed.Methods: An operated patient's middle thoracic spines was scanned bythe computer-assisted tomography (CT) . According to the materialproperties from literature and the mathematical model of T8 vertebraebased on CT scanning image of the patient' s middle thoracic spines , thethree-dimensional finite elements model of T8 vertebrae structure wasconstructed with substantiality-model cnstruction by MIMICS V9. 11.software.Results: The constructed three-dimensional finite elements model of T8vertebrae had 27646 nodes and 55340 triangle elements. Besides , corticalshell ,cancellous core , endplates and posterior elements includingpedicle , lamina , transverse processes , spinous processes , articularprocesses were also simulated.Conclusion: The advantages of the constructed model include intactstructure , precise elements , outstanding key points and high measureaccuracy.