PMC9852495_01
PMC9852495_02
(A) AP x-ray of cervical spine of Case 2 before operation. (B) Lateral x-ray of cervical spine of Case 2 before operation. (C) Sagittal section of CT scan of Case 2 before operation. (D) Sagittal section of MR scan of Case 2 before operation. (E) The C-arm image when a Kirschner wire was drilled into the middle of the odontoid process of the axis in operation. (F) The C-arm image showed the depth of Kirschner wire reach the front of the odontoid process rear cortex and do not penetrate the rear cortex of the odontoid process. (G) The C-arm image showed a 7.2-mm hollow ring saw remove an annular bone block around the Kirschner wire. (H) The C-arm image showed lifting the end of the ring saw (the supine position) to make the angle between the ring saw and the axis of the spine larger, and removing more cancellous bone of the dentate bottom with the ring saw. (I) Cross section of CT scan after surgery. (J) Sagittal section of CT scan after surgery.
fsurg-09-973064-g001.jpg
PMC9852495_03_fsurg-09-973064-g001.jpg
F1
The position of the Kirschner wire was recommended to be located in the center of the dens, verified by fluoroscopic images on two orthogonal planes (Figures 1E, 2B). Penetration of the dorsal cortex must to be avoided (Figure 1F). Then a 7.2-mm hollow ring saw (Figures 1G, 2C) was applied to remove an annular bone block around the Kirschner wire and the resection of bone block should progress carefully without breaching to the dorsal cortex. Then re-inserted the ring saw and tilted the end of the ring saw (the supine position) to increase the angle between the ring saw and the odontoid process, and removed more cancellous bone of the odontoid process's bottom (Figures 1H, 2D).
PMC9852495_03
(A) AP x-ray of cervical spine of Case 2 before operation. (B) Lateral x-ray of cervical spine of Case 2 before operation. (C) Sagittal section of CT scan of Case 2 before operation. (D) Sagittal section of MR scan of Case 2 before operation. (E) The C-arm image when a Kirschner wire was drilled into the middle of the odontoid process of the axis in operation. (F) The C-arm image showed the depth of Kirschner wire reach the front of the odontoid process rear cortex and do not penetrate the rear cortex of the odontoid process. (G) The C-arm image showed a 7.2-mm hollow ring saw remove an annular bone block around the Kirschner wire. (H) The C-arm image showed lifting the end of the ring saw (the supine position) to make the angle between the ring saw and the axis of the spine larger, and removing more cancellous bone of the dentate bottom with the ring saw. (I) Cross section of CT scan after surgery. (J) Sagittal section of CT scan after surgery.
fsurg-09-973064-g001.jpg
PMC9852495_03_fsurg-09-973064-g001.jpg
F1
The position of the Kirschner wire was recommended to be located in the center of the dens, verified by fluoroscopic images on two orthogonal planes (Figures 1E, 2B). Penetration of the dorsal cortex must to be avoided (Figure 1F). Then a 7.2-mm hollow ring saw (Figures 1G, 2C) was applied to remove an annular bone block around the Kirschner wire and the resection of bone block should progress carefully without breaching to the dorsal cortex. Then re-inserted the ring saw and tilted the end of the ring saw (the supine position) to increase the angle between the ring saw and the odontoid process, and removed more cancellous bone of the odontoid process's bottom (Figures 1H, 2D).
(A) A transverse incision was made at approximately the C-4 level on the right hand side of the patient, starting from the center line, extending to 3 cm in horizontal. (B) A Kirschner wire was drilled into the middle of the odontoid process of the axis. The position of the Kirschner wire was recommended to be located in center of the odontoid process in both AP and lateral x-ray. (C) A hollow ring saw was used to remove an annular bone block with the direction of the Kirschner wire. The hollow ring saw should also stop before odontoid process posterior cortex. (D) After removing the tip of the odontoid, simply lift the end of the ring saw (patient in the supine position) to make the angle between the ring saw and the axis of the spine larger and continue to remove more cancellous bone of the dentate bottom with the ring saw. (E) The odontoid process is removed and decompression of spinal cord is completed. (F) The 6.5-mm diameter coaxial spine endoscope. (G) The electric high-speed grinding drill, which is designed for endoscopy specifically and the direction of tip is changeable. (H) Feature of the tip of 7.2/8.2-mm hollow ring saw.
fsurg-09-973064-g002.jpg
PMC9852495_03_fsurg-09-973064-g002.jpg
F2
A transverse incision was made at approximately C-4 level on the right side of the patient, starting from the central line, horizontally extending to right side about 3-cm length (Figure 2A). The position of the Kirschner wire was recommended to be located in the center of the dens, verified by fluoroscopic images on two orthogonal planes (Figures 1E, 2B). Then a 7.2-mm hollow ring saw (Figures 1G, 2C) was applied to remove an annular bone block around the Kirschner wire and the resection of bone block should progress carefully without breaching to the dorsal cortex. The tip of the odontoid process was gradually resected from the inside to outside by an electric high-speed burr, which was especially designed for endoscopy, and the angle of the burr's tip was adjustable from 0  to 45  (Figure 2G). Then re-inserted the ring saw and tilted the end of the ring saw (the supine position) to increase the angle between the ring saw and the odontoid process, and removed more cancellous bone of the odontoid process's bottom (Figures 1H, 2D). Because the bottom portion of the odontoid process was little wider, a larger diameter sleeve and ring saw can be chosen in this procedure (Figure 2H), which can improve the efficiency of bone resection and decompression. The decompression of the medulla oblongata was completed until all the ventral bone was removed and the alar ligaments was exposed; however, the dura need not to be exposed (Figure 2E).