Intraoperative transligamentous ultrasound in the evaluation of thoracic intraspinal disease : technique

Intraoperative transligamentous ultrasonography was used in a variety of different thoracic surgical procedures for spinal cord compression secondary to neoplastic disease. The utility and practicality of intraoperative transligamentous ultrasonography for thoracic intraspinal disease was evaluated. Because intraoperative localization and evaluation of targeted levels in the thoracic spine using radiographs is often difficult or imprecise, alternative or complementary techniques may be helpful. Intraoperative transligamentous ultrasound, performed before laminectomy, via an interlaminar window, has not been widely used for thoracic intraspinal pathology. A standard 7.5-MHz hand-held probe, used in conjunction with a Codman OR 330 ultrasound machine, was used to evaluate the practicality of intraoperative transligamentous ultrasound in the thoracic spine. A clear sonographic window, permitting visualization of the spine and the intraspinal contents, can frequently be found. However, densely calcified ligamentum flavum or overlapping laminas do not allow effective insonation. Four illustrative cases are presented. Transligamentous ultrasound before laminectomy can be used for localization and evaluation of intraspinal disease in many patients. Overlapping laminas or calcified ligamentum flavum can impede adequate sonographic visualization, but in these cases adequate intraoperative transligamentous ultrasound evaluation is usually possible through a small laminotomy. Evaluation of intraspinal lesions and localization of the correct surgical level is facilitated by dynamic real time sonographic imaging.