Surgery could be recommended even for larger dogs

Surgical management of single-level thoracolumbar vertebral body segmentation and formation failure causing progressive thoracolumbar myelopathy in three adult large-breed dogs

Francisca Couto 1, Joana Tabanez 1, Jeremy Rose 1, Colin Driver 1

Background
Congenital thoracic vertebral malformations are commonly observed in small-breed dogs but are rare in large-breed dogs. These malformations can cause progressive thoracolumbar myelopathy characterized by spinal cord compression and kyphosis. Non-surgical management often results in poor outcomes, while surgical decompression and stabilization offer better prognoses. This retrospective study evaluated the medium-term outcomes of spinal cord decompression and instrumented fixation in three adult large-breed dogs with single-level vertebral malformations causing thoracolumbar myelopathy.

Methods
Study Design: Retrospective clinical review of three adult large-breed dogs (>25 kg) with progressive T3–L3 spinal cord segment myelopathy and radiological evidence of complex thoracolumbar vertebral malformations.

Diagnostic Imaging:
Magnetic resonance imaging (MRI) and computed tomography (CT) were performed to assess vertebral anomalies, spinal cord compression, and adjacent pathology. Preoperative imaging included T2-weighted and short tau inversion recovery (STIR) sequences.

Surgical Procedures:
Decompression was achieved through bilateral mini-hemilaminectomy and partial corpectomy, followed by vertebral stabilization using pedicle screws, rods, pins, or polymethylmethacrylate (PMMA). Surgical planning utilized preoperative CT for trajectory and implant sizing.

Postoperative Follow-Up:
Neurological assessments and follow-up imaging (CT) were conducted at 6 weeks, 3 months, 6 months, and 12 months post-surgery to monitor recovery and implant positioning.

Results
Signalment and Presentation:
-All three dogs (Rottweiler, Bloodhound, and Irish Water Spaniel) presented with a history of chronic pelvic limb ataxia and paraparesis. Two dogs exhibited ambulatory paraparesis, and one was non-ambulatory preoperatively.

Imaging Findings:
-Vertebral malformations, such as incomplete segmentation and formation, caused focal kyphosis, canal stenosis, and ventral spinal cord compression.
-T2-weighted MRI revealed increased signal intensity in the spinal cord at the apex of compression, indicative of edema, inflammation, or gliosis.

Surgical Outcomes:
-All three dogs experienced improved neurological function, becoming ambulatory within 6 weeks post-surgery, although mild residual paraparesis persisted.
-Two dogs experienced transient postoperative neurological deterioration due to epidural hematoma formation, which required surgical revision.
-Follow-up CT demonstrated stable implant positioning and decompressed spinal canals.

Long-Term Results:
-At 12 months, all dogs exhibited persistent, mild ambulatory paraparesis with improved coordination and reduced paw-placement errors.

Limitations
The study involved a small sample size and was retrospective, limiting generalizability. Long-term outcomes beyond 12 months were not evaluated. Additionally, advanced testing for underlying coagulopathies in cases of hematoma formation was not performed.

Conclusions
This study demonstrates that surgical decompression and stabilization can effectively manage complex thoracolumbar vertebral malformations in large-breed dogs, resulting in significant neurological improvement. Despite mild residual deficits, these procedures provide good medium-term outcomes for dogs with progressive thoracolumbar myelopathy. Further studies are needed to assess long-term prognosis and refine surgical techniques for optimal results.

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