34th Annual Scientific Meeting proceedings

Congenital vertebral malformations are common incidental findings during postmortem examinations or radiographic evaluations of the vertebral column in dogs (Morgan 1968, Moses 2024, Brocal 2018, Ryan 2019). Most of these malformations can be identified using orthogonal, well-positioned radiographs (Bouma 2016). However, they often remain asymptomatic unless significant compression of nervous tissue results in neurological signs or spinal discomfort.

Screw-tail breeds are particularly predisposed to congenital thoracic vertebral malformations, with 97% of French Bulldogs, 90% of English Bulldogs, and 77% of Pugs exhibiting at least one malformed vertebra (Moses 2024). This suggests a likely hereditary component (Schlenkser 2016). A classification system has been proposed to standardize nomenclature for these malformations (Gutierrez 2014). In French Bulldogs, the height of the vertebral canal does not differ significantly between those with and without compressive hemivertebrae, indicating that abnormal angulation and/or subluxation may be the primary cause of spinal cord compression (Moissonier 2011). Furthermore, most screw-tail dogs with a Cobb angle greater than 35% develop neurological signs (Guevar 2014).

Neurological signs range from mild ataxia to paraplegia. Affected animals typically show progressive gait abnormalities as early as 4 months of age, although skeletally mature dogs may also present with chronic, progressive neurological deficits. No gender predisposition has been observed.

Since only malformations that compress nervous tissue produce neurological signs—and radiographs reveal only bony abnormalities—advanced imaging techniques such as myelography, CT, myelo-CT, MRI, or combinations thereof are often necessary to demonstrate spinal cord impingement. While myelography has been traditionally used to assess the degree of compression, it remains a reasonable option when advanced imaging is unavailable, provided complications are avoided through proper technique (Meheus 2010, Moissonier 2011, Farré 2021). High-field MRI provides detailed visualization of the compression and intramedullary changes such as edema, gliosis, syringomyelia, or arachnoid diverticula that may affect prognosis. Computed tomography, with or without contrast, offers superior spatial resolution and facilitates 3D reconstruction of the malformation. Ideally, a combination of high-field MRI and high-resolution CT enables optimal surgical planning, including determining implant entry points, angles, exits, and lengths.

Medical management is generally associated with progressive neurological decline (Wyatt 2018). It may be appropriate in cases of financial constraint or for younger animals (under 9 months), where skeletal growth is ongoing. Surgical intervention is preferred to address spinal cord compression directly and must be tailored to the type and severity of compression. Progressive deterioration in growing animals may necessitate early surgery.

Various surgical strategies have been employed, including dorsal decompression alone, decompression with dorsal stabilization using Steinmann pins around the spinous processes, or positive-threaded pins with PMMA (Jeffery 2007, Charalambous 2014, Picon 2025). Given that canal height does not differ significantly between normal and affected French Bulldogs, realignment and fixation may alone suffice to resolve neurological signs (Moissonier 2011). Transthoracic approaches have been utilized to partially realign severe kyphosis and stabilize the spine using screws and PMMA, yielding better long-term outcomes than earlier techniques (Farré 2021, Picon 2025).

The use of 3D printing in veterinary medicine, especially in planning surgeries for congenital vertebral malformations, has gained considerable attention. This technology allows precise modeling of anatomical structures, significantly enhancing pre-operative planning and surgical outcomes.

Applications of 3D technology include:

• Anatomical Visualization: 3D-printed models enable surgeons to visualize abnormal vertebrae and their spatial relationships with surrounding structures (Suñol 2019). This enhances anatomical understanding and surgical preparation.
• Surgical Rehearsal: Printed models allow for surgical rehearsals and pre-contouring of implants prior to the actual procedure (Mathiesen 2018).
• Custom Drill Guides: Patient-specific drill guides designed to fit the vertebral contour help establish safe implant trajectories, avoiding neural and vascular structures while maximizing bone purchase (Guilman 2023, Guevar 2021, Mariani 2021).
• Custom Implants: Design of specific constructs (e.g., meshes, plates) using various materials tailored to the bony anatomy provides robust stabilization (Guirguis 2024, Kimura 2021).

Several companies now offer customized solutions in collaboration with biomechanical engineers and veterinary surgeons. While certain components, such as plastic 3D-printed rehearsal models, may be cost-effective for in-house production, others—like custom metal guides and implants—can be costly due to equipment and labor requirements.

For custom-made devices, close collaboration between the surgeon and engineer is crucial. The surgeon's expertise allows anticipation of surgical challenges, enabling modification of the design to optimize clinical outcomes.

To maximize the chances of recovery, surgery should be performed as early as possible. Chronic spinal cord compression can lead to irreversible damage, including gliosis, syringomyelia, and arachnoid diverticula or fibrosis. However, dogs younger than 9 months should only be operated on if neurological deterioration is rapidly progressive, as insufficient vertebral calcification may impair implant anchorage.

Given the variety of available surgical techniques, the choice must consider the surgeon’s expertise, timing, potential complications, and cost implications for the client.

3D technology is not a substitute for surgical expertise but serves as a powerful tool for experienced surgeons. It makes complex spinal procedures more manageable, safer, and more efficient, albeit with increased costs.

List of references available on request