Accuracy of 3D Printed Drill Jigs for Lumbosacral Stabilization in Dogs

Introduction: Dorsal lumbosacral stabilization risks injury to neurovascular structures. 3D printed drill jigs designed from CT scans can potentially decrease surgical risk.

Materials and Methods: Cadavers of 20 mixed breed dogs were CT scanned. A CAD drill jig (to guide placement of L7 pedicle screws, transarticular screws, and screws in the sacral body) was printed in ABS plastic. A novice (intern) drilled and placed 3.5-mm titanium screws in 10 cadavers (on the right side) by eye without seeing the jig design. The jig for each specimen was then placed on the left dorsal surface of the lamina of L7 and the sacral body and accurately positioned. The screws were placed using the jig. An expert surgeon then performed the same process on the remaining 10 cadavers. The specimens were rescanned, and the images graded for position of the screws from 1 = optimal to 4 = significant penetration of the spinal canal or intervertebral foramina.

Results: The total score for the 69 screws was 108 (placed by jig), 112 (placed by eye). Eleven screws placed by jig were only fair/poor (score 3 or 4), whereas 14 screws were fair/poor when placed by eye. Drilling and screw insertion by jig was better than by eye in eight cadavers (six by the novice) and placement by eye was better than by jig in seven cadavers (five by the expert).

Discussion/Conclusion: Use of a jig improved the accuracy of screw placement for lumbosacral stabilization by a novice.

Acknowledgment: Funding for this project was provided by the Massey University Working Dog Centre.