A biomechanical comparison of open and thoracoscopic anterior spinal release in a goat model

Study Design. A biomechanical assessment of anterior release and discectomy in the thoracic spine was performed on an animal model using thoracoscopic and open thoracotomy techniques. Objectives. To compare the relative efficacy of these two techniques of release in achieving increased spinal mobility. Background Data. The clinical use of video-assisted thoracoscopy in the correction of spinal deformity is increasing. The effectiveness of thoracoscopic anterior spinal release with discectomy has not been evaluated biomechanically. Methods. Anterior release with discectomy was performed on six midthoracic motion segments in five mature goats. The thoracoscopic technique was used for three levels on one side, and an open thoracotomy was used for the alternating three levels of the contralateral side. The duration of surgery for disc excision and the amount of blood loss for each technique were recorded. The intact cranial and caudal motion segments served as controls. The motion segments were individually subjected to nondestructive biomechanical testing. Torsional, sagittal, and coronal bending torques were applied, and the resulting angular displacement was measured. Results. The duration of surgery to remove a disc thoracoscopically decreased as experience was gained by the surgeon. The amount of intraoperative blood loss was comparable using the two methods. There was significantly increased flexibility in the released segments with both techniques, compared with the flexibility in the intact levels for all three loading directions. There was no difference in the motion obtained after release between the two techniques. Conclusion. Open and thoracoscopic anterior release and discectomy have been demonstrated, through biomechanical in vitro testing, to increase the flexibility of the spine to a similar extent.