We describe our experience with the clinical application of intraoperative spinal ultrasonography (IOSU) and discuss its utility and limitations.
Materials: A Sonolayer SSA-260A (Toshiba Medical Co., Ltd.) ultrasound unit, with 7-MHz and 5-MHz sector transducers, was used to evaluate 40 patients, beginning in April 1994. Diagnose included 12 cases of spondylosis, 10 of tumor, 9 of syringomyelia, 5 of vascular malformation and 4 of miscellaneous diseases. After exposing the dura, the operative field was immersed in sterile saline. Real time scanning was performed by the stand-off method.
Results: In cases where an anterior approach was used for treatment of spondylosis and ossification of the posterior longitudinal ligament, IOSU was valuable for determining the degree of lateral corpectomy. Also spinal cord vascular pulsation could be confirmed to assess the completeness of decompression. In case where a posterior approach was utilized for lesion resection, IOSU was particularly useful for lesion localization. This allowed the dural incision to be tailored to a particular lesion, and for evaluating the completeness of resection. Lesions were confidently identified in all cases prior to resection. However, sonographic visualization of the surgical bed following resection of the lesion was suboptimal.
Obscuration of the surgical site was caused by air bubbles, hemorrhage, obstruction of the sonographic window by hemostats or other instruments, or by synthetic dural patches.
Conclusions : IOSU is a non-invasive and reproducible technique that is valuable for real-time intraoperative planning and monitoring of spinal surgical procedures. The technique does not significantly increase operation time. Limitations include the requirement of an unobstructed sonographic window, and the value of the technique is highly dependent on operator experience in image acquisition and interpretation. Routine use of this technique would offer the benefits described above, and would soon overcome the major limitations resulting from lack of user familiarity with its performance.
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