Accuracy of placement of pedicle screws in the thoracolumbar spine of dogs with spinal deformities with three-dimensionally printed patient-specific drill guides.

OBJECTIVE To determine the accuracy of pedicle screw placement in the thoracic spine of dogs with spinal deformities with three-dimensionally (3D) printed patient-specific drill guides. STUDY DESIGN Retrospective study. SAMPLE POPULATION Six dogs in which sixty pedicle screws were placed in the thoracolumbar spine. METHODS Medical records were searched between June 2017 and June 2018 for dogs with clinical signs associated with a thoracolumbar vertebral malformation. Inclusion criteria included MRI and computed tomography (CT) data that were used to create 3D printed patient-specific drill guides. All dogs were stabilized dorsally with guided bicortical pedicle screws and polymethylmethacrylate. Accuracy of screw placement was assessed by immediately postoperative CT according to a modified Zdichavsky classification. RESULTS Five pugs and one French bulldog met the inclusion criteria. Sixty bicortical pedicle screws were placed; 96.7% were graded as I (optimal placement), and 3.3% were classified as IIa (partial penetration of the medial pedicle wall) according to a modified Zdichavsky classification. CONCLUSION Three-dimensionally printed patient-specific drill guides allowed safe and accurate placement of pedicle screws in the thoracolumbar spine in dogs with vertebral malformation. CLINICAL SIGNIFICANCE Three-dimensionally printed patient-specific drill guides are a safe and effective method of placing pedicle screws in dogs with thoracolumbar vertebral malformations.