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Computer-assisted Patient-specific Prototype Template for Thoracolumbar Cortical Bone Trajectory Screw Placement

A Cadaveric Study

Kim, Sang Bum, MD, PhD*; Rhee, John M., MD; Lee, Gi Soo, MD; Lee, Hee Young, MD§; Kim, Taehyung, MD; Won, Yougun, MD*

doi: 10.1097/BTO.0000000000000285
Novel Research Methods and Models

The cortical bone trajectory (CBT) screw technique yields effective mechanical and clinical results, improving the holding screw strength with a less invasive exposure. Accurate and safe screw placement is crucial. A patient-specific drill template with a preplanned trajectory was considered a promising solution; however, it is critical to assess the efficacy and safety of this technique. This study aims to evaluate the accuracy of patient-specific computed tomography (CT)-based rapid prototype drill guide templates for the CBT technique. CT scanning was performed in 7 cadaveric thoracolumbar spines, and a 3-dimensional reconstruction model was generated. By using computer software, we constructed drill templates that fit onto the posterior surface of thoracolumbar vertebrae with drill guides to match the CBT. In total, 80 guide templates from T11 to L5 were created from the computer models by using rapid prototyping. The drill templates were used to guide the drilling of CBT screws without any fluoroscopic control, and CT images were obtained after fixation. The entry point and direction of the planned and inserted screws were measured and compared. In total, 80 screws were inserted from T11 to L5. No misplacement or bony perforation was observed on postoperative CT scan. The patient-specific prototype template system showed the advantage of safe and accurate cortical screw placement in the thoracolumbar spine. This method showed its ability to customize the patient-specific trajectory of the spine, based on the unique morphology of the spine. The potential use of drill templates to place CBT screws is promising.

*College of Medicine, Konyang University, Daejeon

§Changwon Fatima Hospital, Changwon

College of Medicine, Yonsei University, Seoul

Department of Orthopedic Surgery, Chungnam National University, School of Medicine, Daejeon, South Korea

Department of Orthopaedic Surgery, Emory University, Atlanta, GA

Supported in part by Konyang University Myunggok Research Fund 2015.

The authors declare that they have nothing to disclose.

For reprint requests, or additional information and guidance on the techniques described in the article, please contact Yougun Won, MD, at ; or by mail at Department of Orthopaedic Surgery, Konyang University College of Medicine. You may inquire whether the author(s) will agree to phone conferences and/or visits regarding these techniques.

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