Optimizing Neuronavigation for Anterior Approach to Cervicothoracic Junction
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.325360
Source of Support: None, Conflict of Interest: None
Keywords: Anterior cervical discectomy, cervicothoracic junction, navigationKey Message: Navigation can be used in anterior approach to cervical spine. It can be particularly helpful when the area of interest is lower cervical spine and one is dealing with pathologies like tumor where complete excision is required to prevent recurrence.
Anterior cervical surgery is well known since it was described independently by Robinson and Smith, and Cloward in 1950s., This approach is one of the most commonly used approaches in spinal surgery. The common indications of anterior cervical surgery are degenerative conditions, tumors, traumatic fracture dislocations, deformity correction etc. Intraoperative radiological assistance is required to localize the level of interest and to guide instrumentation. Usually, fluoroscopy is used for this purpose which is widely available in operating rooms. However, fluoroscopy has limited role at the cervicothoracic junction. It is very difficult to visualize the cervicothoracic junction due to the shoulder joints. Hence, this area remains a grey zone where spinal surgeries have to be done without significant fluoroscopic guidance.
Intraoperative navigation is widely used in spine surgery since Nolte first described its use in 1995.,, It is widely used for posterior spinal fixations throughout all the segments of spine. There is ample amount of literature to support the usefulness of intraoperative navigation in spinal surgeries.,, The reference frame of all the navigation systems is required to be fixed to a rigid and stable part of the spine. It is usually fixed to the spinous process in posterior spinal surgeries. However, the use of intraoperative navigation is limited in the anterior approaches to the cervical spine. The reason behind this might be the nonavailability of a rigid structure where the reference frame can be fixed. We overcame this problem by fixing the reference frame to a Mayfield head clamp (Integra Life Sciences, Princeton, NJ), as is done routinely in cranial surgeries. We describe the use of this technique by describing a representative case.
A 20-year-old male patient presented to us with complaints of axial neck pain and left C8/T1 radiculopathy for the past 1 year. He developed weakness in left upper limb 1 month before visiting our outpatient department and became quadriparetic (right > left) when he came to us. On examination, he had signs suggestive of myelopathy. He had a power of 3/5 in the right side and 4+/5 in the left side. The right-side hand grip was reduced to 30% of the normal.
CT cervicodorsal spine revealed an expansile cystic lesion within the D1 vertebral body with the involvement of the posterior elements of C7 and D1 [Figure 1]. Axial section MRI revealed a lesion with multiple fluid levels centered on the right side of the D1 posterior column with the involvement of the D1 vertebral body and compression over the spinal cord [Figure 2] and [Figure 3]. There was extension of the lesion into the posterior elements of the C7 and the paraspinal space on the right side at the D1 level. Radiological differential of an aneurysmal bone cyst was kept.
He was planned for excision of the lesion and 360 degree fixation. He first underwent the excision of the lesion and fixation from C5 to D3 from the posterior approach. An anterior approach was done next and the plan was D1 corpectomy in order to achieve complete excision of the lesion.
There were few challenges in the anterior approach. We could visualize up to C5 using fluoroscopy after positioning the patient for surgery. Using a fluoroscope meant that we will have to expose from C5 to D2 to localize the level of interest as he was planned for a D1 corpectomy and placement of a mesh cage and anterior cervical plating from C7 to D2. Moreover, whole of the D1 body needed to be taken out as we were dealing with a lesion which can recur after subtotal excision. This made intraoperative radiographic guidance must as only visual inspection during D1 corpectomy is not sufficient due to the curvature of the spine. Fixing a plate is not simple at the D2 level because of it being required rarely leading to inexperience, the awkward angle, and nonvisualization of D2 by fluoroscopy.
These difficulties made us think about using intraoperative navigation. We used an O-arm® and Stealth Station Intra-Operative Imaging System (Medtronic, Inc. Minneapolis, MN, USA) during the anterior surgery to overcome the above mentioned difficulties. One need to have a fixation point for the reference frame for intraoperative navigation and finding an optimal place to fix the reference frame is challenging in the anterior cervical spine. Hence, we used a Mayfield clamp (Integra Life Sciences, Princeton, NJ) to fix the head and attached the reference frame to it as is done in cranial surgeries. A radiolucent table was used as the target was the cervicothoracic junction. The position of the reference frame was adjusted in a way that it was close to the area of interest and did not hinder the surgical procedure at the same time.
There was no risk of cervical spinal motion or collapse as the spine was stable as it had been already fixed from the posterior aspect. We acquired a CT scan for the navigation purpose before surgical exposure as it gave us an idea about the location of the vertebra of interest. The accuracy of the navigation was checked using the landmark-like edges of the vertebral body. The D1 vertebral body was localized using navigation and corpectomy was performed, the completeness of which was ensured using navigation. A mesh cage of appropriate size was placed in the corpectomy defect to prevent collapse or overdistraction of the dorsal spine. A cervical plate of appropriate length was placed and secured with screws. Navigation was used to place the screws in the desired trajectory. After confirming the appropriate placement of the cage and screw position with the help of CT, the wound was closed in layers. The patient reported improvement in power in all four limbs in the postoperative period and is recurrence-free for 1 year following surgery [Figure 4].
Intraoperative navigation is an example of technological advancement. The role of intraoperative navigation in spinal surgeries has been proven beyond doubt.,, However, intraoperative navigation is used very sparingly in the anterior cervical surgeries as it does not add much to what one gets from intraoperative fluoroscopy and needs during the routine procedures done by anterior cervical approach. However, there are certain situations where intraoperative fluoroscopy is insufficient. Surgeries in the lower cervical spine and the cervicothoracic junction through anterior approach is one such example where an alternate to normal fluoroscopy is required. Common indications for surgery around cervicothoracic junction include degenerative disorders, traumatic fracture dislocations, and tumors. The use of navigation by attaching the passive reference frame to the Mayfield head clamp has recently been described in anterior screw fixation in odontoid fractures., The use of navigation in the anterior approach to cervicothoracic junction has been described by attaching the passive frame to the patient table. We think that attaching the reference frame to the Mayfield head clamp is better as the chances of relative motion between the patient's head and reference frame will be the least.
Neo et al. described the use of navigation system in cranial surgeries for lesions involving upper cervical spine by anterior approach in patients who had undergone occipitocervical fusion earlier. The upper cervical spine behaved as a part of skull base as there was fusion posteriorly. However, this method cannot be applied to the subaxial cervical spine. The first described method of navigation for spinal surgeries was based on the preoperative CT acquisition which can be inaccurate if the position of the spine in which CT is acquired is different from its intraoperative position. However, nowadays CT is acquired intraoperative most of the times.
One has to be careful in positioning the reference frame in this technique as it should be close to the area of interest to increase accuracy. It should be placed in such a way so as to avoid interference with the surgical procedure and tools, which is very important in the anterior cervical approach as the corridor is very small. The assistant has to be very careful to avoid any inadvertent movement of the reference frame. Mayfield can also be used along with headrest in some tables, if one is worried about the motion or instability or collapse of the cervical spine. The advantage of using an O arm is that fluoroscopy can be done to confirm the accuracy of the navigation in case of doubt.
The major role of navigation is in the localization of the level, outlining the borders of corpectomy or bone removal and defining screw trajectory at the cervicothoracic junction. Another advantage of using navigation is the reduced radiation exposure of the surgeon. There is high radiation exposure during cervical surgeries during fluoroscopy as the surgeon is standing in the radiation field when the fluoroscopy is done. Cumulative radiation exposure of spine surgeons, especially the ones who routinely do complex spinal procedures is very high and using navigation may be helpful.
Navigation may be helpful in patients with ossified posterior longitudinal ligament when one is drilling the ossified ligament. It can also be used during oblique corpectomy and transcorporeal anterior cervical microforaminotomy/discectomy to ensure that that to localize the area of interest., It can be particularly helpful in defining the midline and other anatomical landmarks in re-exploration surgeries. The role of navigation in the management of complex odontoid screws has also been described in literature.
Lee et al. described their experience of using C arm-based intraoperative navigation during multilevel oblique corpectomy in patients with multisegmental cervical spondylotic myelopathy due to OPLL. They used a dynamic reference frame which was attached to the operating table with an external frame and C-arm views were acquired for navigation using the Stealth Station system. They used navigation for assistance in drilling the bone. The mean completeness of multilevel oblique corpectomy and improvement in Japanese Orthopedic Association score was better in the image guidance group than the control group.
Pirris et al. described their experience of using 3D-based navigation in anterior cervical surgeries like corpectomy, tumor removal, and deformity correction. They found navigation to be particularly useful in patients undergoing repeat surgeries. Ohmori et al. described the use of 3D CT-based navigation in anterior corpectomy in three patients with thoracolumbar vertebral collapse. Another study described the role of intraoperative navigation in mini-open lateral corpectomy for thoracolumbar burst fractures. Pisapia et al. described the use of O arm-assisted odontoid screw insertion in eight patients using the same technique.
C arm can also be used to acquire images intraoperatively in the place of O arm., Navigation can then be used after transferring the images to a planning/navigation system. Kantelhardt et al. described the management of C2 fractures using Iso-C3D guidance using the same technique. The Iso C3D can also be used to confirm the position of the screws intraoperatively. However, this is not possible in case of surgery at the cervicothoracic junction.
Intraoperative navigation is a useful adjunct for spinal surgeries. It can be very helpful for areas of spine which are not well visualized by fluoroscopy. Anterior approach to cervicothoracic junction is one such area where the use of intraoperative navigation can make the surgery more safer. We describe our method of frame fixation for the use of navigation in the anterior cervical surgery.
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There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4]