Accuracy of a patient‐specific 3D printed drill guide for placement of cervical transpedicular screws

Objective To develop a patient‐specific 3‐dimensional (3D) printed drill guide for placement of cervical transpedicular screws and to assess its accuracy. Study design Prospective case‐series. Sample Population Thirty‐two cervical pedicle screws (CPS) placed in 3 large breed dogs. Methods Computed tomographic (CT) data of the cervical vertebrae were exported to a medical image processing software and 3D virtual vertebral models were created for each vertebra. These models were processed in a computer aided design (CAD) software to determine the optimal trajectory and size of the CPS. Virtual drill guides were created for each patient, 3D‐printed, and used intraoperatively. Locking titanium screw heads were bonded with polymethylmethacrylate cement to stabilize affected vertebral segments. Postoperative CT was used to assess the radiological accuracy of CPS placement in each dog. For each screw, CAD files were analyzed to determine a screw‐diameter‐to‐pedicle‐width‐ratio (SDPWR) at the narrowest point of the pedicle. Results A total of 32 CPS were placed, measuring 3.5 mm (n = 20), 2.7 mm (n = 11), and 2.4 mm (n = 1) in diameter. The majority (29/32) of these screws were placed without evidence of vertebral canal breach (grade 0), whereas a vertebral canal breach