. 2021 Sep 22;13(9):e18187.
doi: 10.7759/cureus.18187.
eCollection 2021 Sep.
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Cureus.
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Abstract
In spine surgery, instrumentation surgery using augmented reality (AR) and navigation systems have become widespread, while decompression surgery using those applications is not so common. However, we sometimes encounter intraoperative problems such as excessive blood loss or bony resection in decompression surgery. Therefore, a practical navigation system is needed for safer spinal decompression surgery. Furthermore, the cost of AR and navigation systems has been expensive. In this study, we report the utility of applying the AR system of the head-mounted display (HMD) at a lower cost to identify the osteotomy area of laminectomy for spinal decompression surgery. 3D CT/MRI fusion images are created preoperatively to generate 3D data consisting of the nerve elements, a dural tube and nerve roots, and the bony elements of the spine. Then, we made the 3D data of the bone after decompression by 3D editing free software. Uploading the created 3D data of both 3D CT/MRI fusion and preoperative planned laminectomy images to the AR software in the HMD, we could confirm the proper decompression area with the 3D images projected through the HMD. This system was useful for cervical and lumbar decompression for confirming the proper decompression area preoperatively. We could perform decompression surgery just designed with this system. This system is a preoperative planning system that allows 3D HMD visualization to keep track of surgical orientation. It does not allow preoperative verification so far. However, this system has various possible applications and is considered a promising system for the future.
Keywords:
augmented reality; foraminotomy; fusion image; head-mounted display; holoeyes; hololens; mixed reality; spine.
Copyright © 2021, Aoyama et al.
Conflict of interest statement
The authors have declared that no competing interests exist.
Figures
Figure 1. Preoperative MRI (a, d), CT (b, c), and postoperative MRI (e, f) of case 1
a. Preoperative MRI T2-weighted sagittal section showed the spinal canal stenosis from C3 to C6, with severe spinal cord compression at C5/6. b. Preoperative CT myelography sagittal section showed the ossification of the posterior longitudinal ligament at C4 to C6. c. Preoperative CT myelography transverse section of C5/6 showed compression of the left C6 nerve root due to the ossification of the posterior longitudinal ligament. d. Preoperative MRI T2-weighted transverse section of C5/6 showed compression of the left C6 nerve root and spinal canal stenosis. e. Postoperative MRI T2-weighted transverse image showed that the left C6 root and spinal canal were decompressed by laminectomy and foraminotomy. f. Postoperative MRI T2-weighted sagittal section showed that the spinal cord was decompressed.
Figure 2. Preoperative (a, b) and postoperative (c, d) MRI of case 2
a. Preoperative MRI T2-weighted sagittal section showed stenosis at L4/5 and a large herniation protruding at L5/S. b. Preoperative MRI T2-weighted transverse image showed a shift of the dural tube to the left due to the herniation (arrow) that prolapsed to the right at L5/S. c. Postoperative MRI T2-weighted transverse section showed the disappearance of the herniation, widening of the dural tube, and the decompressed right S1 nerve root. d. Postoperative MRI T2-weighted sagittal section showed that the stenosis of L4/5 and 5/S had been decompressed, and the hernia had disappeared.
Figure 3. CT/MRI fusion images of case 1
The left image (A) shows the nerve root in the 3D STIR sequence. The middle image (B) is a 3D MRI image of the dural tube and the nerve root taken with a 3D STIR sequence on the left image. The right image (C) is a CT/MRI fusion image of the 3D CT image and the 3D MRI image.
Figure 4. CT/MRI fusion image of case 2
The left image (A) shows the nerve root in the T2 FFE PROSET sequence. The S1 nerve root is disrupted by the herniation (arrow). The middle image (B) is a 3D constructed MRI image of the dural tube and the nerve roots in the T2 FFE PROSET sequence on the left image. The dural tube and nerve root are partially lost due to herniation at the arrow. The right image (C) is a CT/MRI fusion image of a 3D CT image and a 3D MRI image.
Figure 5. The creation of a laminectomy model using the 3D image editing software Blender
On the left picture (A), the cuboid (arrow) is used to create the laminectomy model. The spinous processes and the laminae that overlap the cuboid are removed. On the center picture (B), the lateral edge of the nerve root defect shadow can be used as a reference to determine the lateral edge of the intervertebral foraminotomy. The bone removal is performed by fabricating a cuboid of any size (any number of small units can be specified) in the same manner as in picture A. On the right picture (C), a model with C3-C6 laminectomy and left C5/6 foraminotomy is created. This model is output as STL data.
Figure 6. Uploading STL data to the Holoeyes MD system
The STL data are uploaded using a web browser. On the left (A) are the data from Case 2 upload, and on the right (B) are the data from Case 1 upload. On the right (B), the transparency of the bone model after decompression has been increased to make it easier to identify the nerve. The uploaded STL data will be reconstructed for Holoeyes MD in a few minutes, which can then be downloaded via the Internet using the Holoeyes MD software in the head-mounted display to view the created polygonal images.
Figure 7. Case 1 in the Holoeyes MD software
On the left (A) is the posterior view after C3-C6 laminectomy and the left C5/6 foraminotomy. In the right image (B), the bone transparency is increased to make it easier to identify the nerve, which makes it easier to confirm the positional relationship between the nerve compression sites (defect indicated by the arrow) and the surrounding bone and confirm whether the decompression site is appropriate in this model. The actual 3D image is more intuitive and easier to grasp because it can be seen in 3D.
Figure 8. Case 2 in the Holoeyes MD software
On the left (A) is the posterior view after L5 laminectomy and L4 and S1 partial laminectomy. The width of the laminectomy was set at 19 mm. The arrow indicates the position of the safe approach to the herniation. On the right (B), the bone is more transparent so that the location of the nerve can be easily identified. The actual 3D image is more intuitive and easier to grasp because it can be seen in 3D.
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