Computed Tomographic Evaluation of Mid-thoracic Vertebral Corridors in Normal French Bulldogs

Objectives: (1) To report internal measurements of thoracic vertebral bone morphology and (2) identify safe and clinically applicable surgical implant corridors in the T7-T9 thoracic vertebrae of French Bulldogs. Study Design: Observational, cross‐sectional, descriptive study. Sample Population: Seven client-owned French Bulldogs with normal thoracic vertebrae. Methods: Computed tomographic (CT) studies of normal French Bulldogs were reviewed. Multiplanar reconstruction of the CT images was used to determine thoracic vertebral corridors. Corridor measurements included the width, length, insertion distance off midline, and angle off midline (sagittal) for each thoracic vertebra. One‐way analysis of variance was used to detect differences between groups. Results: Measurements of vertebral corridor width (p>0.9848), length (p>0.8113), implant center (p>0.9282) and angle (p>0.3609) did not differ between each vertebra. The average vertebral corridor width was 4.5 ± 0.7 mm. The average corridor length was 17.2 ± 2.5 mm. The average corridor angle was 22.3 ± 1.9 °. The mean distance the proposed implant center was from the vertebral midline was 8.2 ± 1.1 mm. Inter-observer agreement of corridor length and implant center was good but poor for corridor angle and width. Conclusion: Based on average corridor width and length, commercially available cortical screws or pins can be utilized for implants in this region of the thoracic spine. The angle of corridor trajectory from a dorsal approach seems most applicable for T7-T9. Clinical Significance: Vertebral corridors can be measured using CT-MPR, and implant specifications and angles derived. Surgical guides can also be created to guide implant placement. This approach provides a simple and accurate method to guide the placement of thoracic vertebral implants.