#247 Determination of Cutting Sites in Minimally Invasive Pedicle-lengthening Osteotomy
MIS Techniques and Outcomes
Poster Presented by: Z.-P. Luo
Z.-P. Luo (1)
Z.-G. Zhang (1)
X. Mei (1)
H.-L. Yang (1)
(1) Department of Orthopedics of 1st Affiliated Hospital and Orthopedic Institute, Soochow University, Suzhou, China
Purpose: Pedicle-lengthening osteotomy is a new minimally invasive technique for surgical treatment of lumbar spinal stenosis. With the assistance of fluoroscopy, the technique involves making a pedicle passage, pedicle osteotomy from inside the pedicle passage, and lengthening using an implant bilaterally which results in the enlargement of the spinal canal and neural foramen. By largely preserving the normal anatomical structures, the procedure reduces major bleeding, complications, perineural scarring and postoperative instability. The critical component of the procedure is the determination and accuracy of the osteotomy site. The purpose of this study was to test if a fluoroscopic positioning method could be used to guide the osteotomy and to define the cutting site.
Methods: The test was performed on cadaveric vertebra (L3, L4 and L5, n=6). Under lateral C-arm fluoroscopy, a guide pin was driven through the pedicle into the vertebral body. Pedicle osteotomies were then performed bilaterally using a manual bone saw cutting the pedicles from inside the pedicle passages. The one-line sign technique was used to determine the posterior vertebral body line, 2 mm posteriorly to which was the targeted transaction site. With the fluoroscopic guidance and tactile feedback, the surgeon manually operated and controlled the saw until the pedicles were cut circumferentially one at a time.
After the pedicles were transected, the pedicle-lengthening implants were screwed into the pedicle passages. The implants lengthened a total of 3 mm, leading to an increase in the area of the spinal canal. 3D CT reconstruction was used to evaluate the cutting site and to calculate the enlargement of the spinal canal.
Results: The manual saw consistently cut the pedicles at the desired sites with 2.3±0.5 mm from the posterior vertebral body line, which was only 0.3 mm from the targeted cutting site. Comparing to the theoretical simulation of CT reconstruction, the difference was insignificant. The spinal canal was also increased in the average of the across sectional area.
Conclusions: The study tested systematically a fluoroscopic guiding method in vitro to be used in the new minimally invasive pedicle-lengthening osteotomy for lumbar spinal stenosis. The average cutting site was 0.3 mm from the targeted site, suggesting the possible clinical application of this technique although further verifications are necessary in vivo.