Morphologic evaluation and surgical simulation of ossification of the posterior longitudinal ligament using helical computed tomography with three-dimensional and multiplanar reconstruction

Study design. Using helical computed tomography with three-dimensional and multiplanar reconstruction, ossification of the posterior longitudinal ligament in the cervical and thoracic region was observed. Preoperative simulation also was performed, and the availability of these methods was evaluated. Objective. To use preoperative evaluation and simulation with helical computed tomography to enhance the accuracy of excision of ossification of the posterior longitudinal ligament lesion. Summary of Background Data. Ossification of the posterior longitudinal ligament lesion is sometimes so complicated that preoperative morphologic evaluation and excision of the lesion are difficult when using only conventional imaging techniques. Methods. Seven cases of cervical and two cases of thoracic ossification of the posterior longitudinal ligament were scanned using helical computed tomography at 2-mm or 5-mm slice thickness. Three-dimensional and multiplanar reconstruction were performed at 0.7 mm or 2-mm intervals in the bone window. Surgical simulation of the anterior approach for cervical lesion and posterior approaches for thoracic lesion was performed. Results. Preoperative direct observation of the ossification of the posterior longitudinal ligament lesion was possible, and the complicated structures could be understood more easily than with other conventional methods. When surgical simulation was performed in the workstation, the ossification of the posterior longitudinal ligament lesion was removed sufficiently an arbitrarily reconstructed view in the spinal canal. When the viewpoint then was changed to the approaching side, the location and dimension of the removed area were determined. In all cases, surgical approach and excision of the ossification of the posterior longitudinal ligament lesion were performed more easily and precisely than in the surgery with no three-dimensional images. Conclusion. Helical computed tomography with three-dimensional, multiplanar reconstruction would be a valuable tool for evaluation and surgical simulation of ossification of the posterior longitudinal ligament lesion by enhancing the accuracy of the surgical procedure.