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Design and Assessment of Accuracy of a Patient-Specific Drill Guide Template for Thoracic Pedicle Screw Placement

Ashouri Sanjani, Mehran | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52999 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Arjmand, Navid
  7. Abstract:
  8. Fusion surgery or fixation of vertebrae in the spine is used to treat scoliosis, fractures, infections, tumors, spinal cord injuries, and disc herniation. In this type of surgery, two or more vertebrae are connected by special screws called pedicle screws to eliminate movement between the vertebrae. Given the serious risks of spinal fusion surgery, if the slightest mistake is made at the entry point or angle of the screw inside the vertebrae, the risk of spinal cord injury is very high, which is one of the complications of fusion surgery. Therefore, in order to increase the accuracy of screw placement, patient-specific template guides are used as drill guides in this operation. For this purpose, in this study, a novel 3D printed template guide for the placement of a pedicle screw in the thoracic region of the spine was presented. To do this, scans of the spine of two people (a person with scoliosis with a deviation angle of 47 degrees and a patient without scoliosis) were taken and 3D model of the spines were created in Mimics software. Determination of the entry point and angle of the pedicle screws inside each vertebra and design of drill guides were conducted in CATIA software. Then, the 3D model of each patient's spine and the guides were created in two versions using the 3D printing method. The pedicle screw placement was performed manually for the spine of each patient with and without a template guide. After placing the pedicle screw inside all four spinal specimens (two specimens placed with a guide and two specimens manually), a CT scan was performed and a 3D model of them was created in software. The accuracy of the placement of the pedicle screws in each sample was compared using the pre-surgical model and post-surgical model, and the accuracy of placement in both surgical procedures was determined by the amount of error at the point of entry of the screw into the vertebra and the angle. Also, the success rate of surgery in both manual and guided method was determined by Gretzbein's criterion. The results of comparing the mean error of the angle and the entry point of the screw and the of error of the screw angle relative to the axial and sagital plates using T-pair statistics showed that all parameters have a significant difference with 95% probability (p <0.05). The average of all error parameters in two patients with and without scoliosis in free hand surgery is higher than the guided method. According to Gartzbein's criterion, the placement of the screws in the first two categories was considered acceptable and successful. The success rates of the placement of the screws by manual and guided method in the patient without scoliosis were 81% and 95% respectively. Meanwhile, the success rates in manual and guided surgery in the patient with scoliosis were reported 62% and 92% respectively. As a result, the use of the proposed template guide was evaluated as an appropriate method to increase the accuracy of the placement of the pedicle screw in the thoracic region for patients with scoliosis as well as patients without scoliosis
  9. Keywords:
  10. Rapid Prototyping ; Screw Placemant Accuracy ; Guided Template ; Fusion Surgery ; Spine Surgery ; Pedicel Screw

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