Computed tomography evaluation of proposed implant corridors in canine thoracic vertebrae

Abstract

Objective Identify acceptable implant corridors in the normal canine thoracic vertebrae (T) from T1 to T9. Study Design Retrospective study. Sample Population Computed tomographic (CT) studies of normal canine thoracic spines (n = 39). Methods CT imaging studies of normal T1‐T9 canine spines were evaluated by five independent observers. Each identified a proposed corridor, measured the width, length, and angle off mid‐sagittal that the corridor occupied. Results CT studies were from 39 dogs weighing 3.19–60 kg (mean 10.72, SD 9.9 kg). Vertebral corridors ranged in average width from 3.8 to 5.2 mm, the widest being located at T1. They ranged in average length from 13.3 to 17.5 mm, shortest being T1 and longest being T6. The angle of corridors varied the most between individual vertebrae at T1‐T3. The average corridor angles were: T1 = 38°, T2 = 32°, T3 = 27°, T4 = 26°. T5‐T9 angle ranged from 23° to 24°. Conclusion The average dimensions of corridors measured in dogs weighing 3.1–60 kg were consistent with those of commercially available cortical screws and pins. Clinical Significance Corridor trajectories identified in this population can be achieved from a dorsal approach between T5 and T9. A dorsal approach for implant placement would be challenging for T1‐T4 due to the variability found in these vertebrae as well as regional anatomical constraints.

Influence of Breed and Body Conformation on Vertebral Implant Insert Angles in Dogs

“…Previous studies proved CT superior over radiographs and MRI in detecting vertebral osseous traumatic pathologies. 11 14 19 20…”

“…11 The possibility of 3D imaging allows measurements from all possible angles, valuable in surgical planning. 11 14…”

“…4 5 6 10 11 12 13 Other potential surgical complications include screws pulling out or technical failures such as pins breaching the cortex of the pedicles. 13 14…”

Accuracy and Safety of Neuronavigation for Minimally Invasive Stabilization in the Thoracolumbar Spine Using Polyaxial Screws-Rod: A Canine Cadaveric Proof of Concept

“…Also, in the thoracic spine, the corridors are drilled into the pedicles which make safe drilling challenging unlike in the lumbar vertebral column where they are drilled into the vertebral bodies. Although recommendations for safe thoracic corridors for freehand technique have been reported, 3,5 the safety and accuracy of 3D printed drill guides have proven to be an attractive technique in an anatomical region where little deviations could have great consequences. 28,29,31,32 The improvement in accuracy and safety observed in the thoracic region for the novice surgeon suggests the existence of a learning curve for surgeons that are not familiar with neuronavigation.…”

“…1 2 Training, experience, vertebra anatomy variation and resources available during surgery make the technique outcome variable and its safety unpredictable. Despite recommendations for pin insertion angles, 3 4 5 drilling of corridors for implant placement is a near-blind endeavour beyond the entry point and only guided by approximated angles of corridor, visual and tactile feedbacks. Although the accuracy and safety of the freehand technique have recently been evaluated, 6 studies on large cohorts of dogs are lacking.…”