Accuracy and Safety of Image-Guided Freehand Pin Placement in Canine Cadaveric Vertebrae

Abstract

Objective The aim of this study was to validate an imaging technique for evaluation of spinal surgery accuracy and to establish accuracy and safety of freehand technique in the thoracolumbar spine of large breed dogs. Study Design After thoracolumbar spine computed tomography (CT), 26 drilling corridors were planned then drilled to receive 3.2 mm positive profile pins using a freehand technique. After pin removal, CT was repeated. All entry points, exit points and angles of the preoperative planned trajectories were compared with postoperative ones using an image registration and fusion technique by three observers. Corridor coordinates for entry and exit points were evaluated in three dimensions and angles were measured in one plane. Intraclass correlation coefficient (ICC) was used to establish the imaging technique reliability and descriptive statistics were used to report on the freehand technique accuracy. Safety was evaluated using a vertebral cortical breach grading scheme. Results Intraclass correlation coefficient for the entry points, exit points and angle were 0.79, 0.96 and 0.92 respectively. Mean deviations for the entry points, exit points and angle were 3.1 mm, 6.3 mm and 7.6 degrees respectively. Maximum deviations were 6.3 mm, 11.0 mm and 16.4 degrees. Most deviations were lateral and caudal. All corridors were judged as safe. Conclusion The imaging technique reliability was good to excellent to study spinal surgery accuracy. Implant deviations should be anticipated when planning stabilization surgery in large breed dogs using the freehand-guided technique.

Accuracy and Safety of Neuronavigation for Minimally Invasive Stabilization in the Thoracolumbar Spine Using Polyaxial Screws-Rod: A Canine Cadaveric Proof of Concept

“…In the former, an overall positional error was found to be within 0.5mm and the accuracy of deep brain stimulation electrode placement was 1.55 to 1.65mm. 25 26 27 When compared with other surgical techniques also reporting Euclidean distances for accuracy, neuronavigation seems to be superior in accuracy to the freehand technique 6 (for the thoracic region only) but inferior to 3D printing. 28 29…”

“…Postoperatively, CBCT of the vertebral column was acquired with the overall alignment between preoperative and postoperative scans verified to be untouched. To identify the coordinates of the entry and exit points, we first registered together the postoperative CT to the preoperative CT (registration) before superposing them (fusion) one over another using a described technique 6 ( Fig. 3C ).…”

“…For the safety evaluation of navigated screw corridors, the CBCT data were reformatted using MPR to follow the corridor along its long axis, allowing assessment of any breach of the vertebral bodies or pedicles cortices. Every corridor was then graded according to a classification system previously reported 6 and judged as safe if it belonged to grades I, IIa and IIb.…”

“…Despite recommendations for pin insertion angles, [3][4][5] drilling of corridors for implant placement is a near-blind endeavour beyond the entry point and only guided by approximated angles of corridor, visual and tactile feedbacks. Although the accuracy and safety of the freehand technique have recently been evaluated, 6 studies on large cohorts of dogs are lacking. The use of novel technologies such as stereotactic computerassisted surgery in spine surgery, referred to as spinal neuronavigation, has been demonstrated as a beneficial technology in human neurosurgery with major advantages including the improvement in implants placement accuracy and reduction in the inherent risks of spinal surgery to critical neurovascular structures.…”

Thoracolumbar Spinal Stabilization with Three Dimensional-Printed Drill Guides and Pre-Contoured Polyaxial Bone Plates

“…We utilized the modified Zdichavsky classification to grade placement of the pedicle screws due to its reported high intra-and inter-observer reliability and the use of this classification system in recent and comparable veterinary studies. 12,14 To the knowledge of the authors, no grading system exists for pedicle screw placement in veterinary patients, with all classifications adapted from the human literature. 12,14,16 As the implants used are titanium, this lends flexibility, should the patient require further MRI postoperatively and the lesser degree of beam-hardening artefact induced by the titanium implants, when compared to stainless steel, allows for more accurate assessment of implant positioning postoperatively with CT.…”