EXPRESS: Accuracy of intraoperative computed tomography to determine implant position in the feline vertebral spine

OBJECTIVES: The aim of this study was to evaluate the accuracy of cone-beam computed tomography for predicting implant position relative to the vertebral canal in the feline thoracolumbar vertebral column. METHODS: This in vitro imaging and anatomic study included twenty-two feline cadavers. A realistic surgical approach was performed at three thoracolumbar locations. Four smooth 1.2mm Kirschner wires were inserted per location using recommended insertion points. Perforation of the spinal canal was not avoided. End-on fluoroscopy (eoF) images, multi-slice computed tomography (MSCT), and cone beam computed tomography (CBCT) using a C-arm were obtained. The images were randomized, and the implant position was assessed by four evaluators who classified implant position and recorded their subjective certainty. Sensitivity, specificity, and accuracy were calculated using anatomic dissection as the reference standard. Interrater agreement was assessed with Fleiss kappa. Duration of image acquisition was compared across modalities using a mixed-effects linear model. RESULTS: For eoF, the sensitivity and specificity were 81,9% and 80,7% with a balanced accuracy of 81,3% (95% CI 0.79 - 0.84) with good kappa agreement (0,63). For MSCT, sensitivity was 80,2% and specificity 83,1%. Balanced accuracy was 81,7 % (95% CI 0.79 - 0.84) and kappa was good (0,63). CBCT showed sensitivity of 88.5% and specificity of 83.4%, with a balanced accuracy of 85.9% (95% CI 0.84 - 0.88) and good kappa aggreement (0,72). Interrater reliability showed overall kappa values of 0.38 for eoF, 0.54 for MSCT, and 0.58 for CBCT. Interrater reliability was higher for completely perforating and non-perforating implants and lower for partially perforating implants. CBCT and eoF were performed faster than MSCT (p < 0,01). CONCLUSION AND RELEVANCE: Intraoperative c-arm based CBCT is an accurate and fast method for the assessment of pin position in relationship to the thoracolumbar spinal canal in cadaveric cats.