Case Report: Dorsal stabilization of an occipito-atlanto-axial malformation in a Miniature Dachshund using 3D planning and a patient-specific titanium implant.

INTRODUCTION: The craniocervical junction can be affected by various congenital or acquired disorders in dogs. When the normal alignment of occipital bone, atlas, and axis is altered, the resulting instability and spinal cord compression can cause mild to severe neurological signs. Occipito-atlanto-axial malformation (OAAM) is a relatively rare craniocervical junction disorder that may require surgical intervention to stabilize the bones and resolve neurological signs. Because OAAM can present in different anatomical forms, individualized decision-making and surgical planning are recommended to treat the malformation and associated instability effectively.

METHODS: A 5-month-old female Miniature Dachshund was referred for cervical pain and progressive gait abnormalities with proprioceptive ataxia. Neurological examination was consistent with C1-C5 myelopathy. Magnetic resonance imaging (MRI) confirmed craniocervical spinal cord compression, and computed tomography (CT) identified severe C1 vertebral malformation, flattened occipital condyles, aplasia of the dens, and subluxation at the atlanto-occipital and atlanto-axial joints. CT-based virtual surgical planning was performed to create a patient-specific drilling guide and a 3D-printed customized Grade-23 titanium locking plate. Surgery was performed via a dorsal approach and included partial dorsal arch resection of the atlas and partial resection of the spinous process of the axis, followed by drilling at predefined positions, trajectories, and depths for screw placement. The implant was fixed to the occiput-atlas-axis complex using ten 2.4 mm titanium locking screws.

RESULTS: Postoperative radiographs confirmed proper implant positioning and alignment, and no intraoperative or postoperative complications were observed. Neurological status did not deteriorate, and progressive improvement was noted from the second postoperative week. At 13 months, the dog had normal gait and spinal reflexes, showed no signs of pain or neurological deficits, and follow-up radiographs confirmed stable positioning of the implant and screws without evidence of loosening.

DISCUSSION: Considering the postoperative outcome and other available techniques, this case supports the feasibility of dorsal stabilization of the craniocervical junction. Careful preoperative 3D planning may help identify fixation points and drilling trajectories (particularly when safe corridors are limited), thereby enhancing the surgical safety and enabling the use of a patient-specific biocompatible titanium plate for the fixation.