Intraoperative Ultrasound in Spinal Surgery

Intraoperative ultrasound for spine surgery is very useful for intradural pathology or ventral spinal cord pathology that allow the surgeon to visualize the lesion before opening dura. This also help the surgeon to locate where the lesion is and also to confirm the adequate decompression of the spinal cord after the lesion removal, tumor removal. It provides the real time information that's very, very useful for the spine surgeon during the case.

The main advantage of this technique is to allow the surgeon to visualize the lesion intradurally before opening dura in the real time. Before beginning the procedure, perform a Magnetic Resonance Imaging, or MRI scan, to identify the spinal lesion. After general anesthesia administration, position the patient so the back is exposed, and sterilize the surgical area with a povidone-iodine scrub.

Next, use a scalpel to make an incision along the length of the spine over the appropriate vertebrae levels. Continuing the incision down through the tissue until the bone is reached. Perform a subperiosteal dissection by electrosurgical cautery and expose the spinous process.

Turn the cutting edge of the cautery ventrally, and sweep it across the laminar, and use a combination of a Lexer bone plier and a high speed drill to remove the bony lamina and spinous process to expose the ligamentum flavum underneath. Use an angled curette and Karrison bone punch to remove the ligamentum flavum to reveal the dura mater underneath. Then use a bipolar and hemostatic matrix to achieve hemostasis.

After the bony removal and dura exposure, fill the surgical field with 100 to 500 Ml saline solution such that an ultrasound tranducer probe with a 20 mm diameter can be submerged. Turn on the mobile ultrasound machine and place the ultrasound probe within the saline bath at the level of interest to begin acquiring images. To visualize the spinal cord and the lesion similar to the sagittal images from the MRI move the probe in line with the direction of the spinal canal and acquire realtime images in the longitudinal plane.

To visualize the spinal cord and the lesion, like the axial images from the MRI, place the probe perpendicular to the spinal canal and acquire real-time images in the transverse plane. Then acquire real-time images to verify the location of any lesions that cannot be directly visualized to correlate with the preoperative computer tomography or MRI images to guide the surgical tool placement, and/or to confirm the resolution of the pathology. Preoperative imaging approximates the location of an intradural mass with respect to its known adjacent structures.

Here, the intraoperative ultrasound correlated with the preoperative MRI imaging revealing a fluid collection above the lesion site. An axial intraoperative ultrasound showed the mass encompassing the majority of the spinal cord and a 0.5 by 0.5 centimeter piece of sterile compressed sponge was used to confirm the card limit of the tumor. A post resection intraoperative ultrasound was then obtained to confirm a complete removal of the tumor and the resolution of the mass effect.

In asymptomatic thoracic disc herniation, resection by a posterior approach an intraoperative ultrasound aided in evaluating the decompression and ensuring that all of the compressive disc fragments were excised. Similarly, in the case of a lumbar burst fracture, an intraoperative ultrasound was useful in confirming an adequate decompression and the removal of all of the fragments. So while performing the intra ultrasound for spine surgeries, is important to be patient and provide a wider view for the area and use a big probe to obtain a clean imaging.

Take the patient to obtain nice clean axial and sagittal view of the spinal cord so that the relationship between the spinal cord and the tumor or the lesion is cleanly defined with the ultrasound images.