Objective The aim of this study was to validate an imaging technique for evaluation of spinal surgery accuracy and to establish accuracy and safety of freehand technique in the thoracolumbar spine of large breed dogs.

Study Design After thoracolumbar spine computed tomography (CT), 26 drilling corridors were planned then drilled to receive 3.2 mm positive profile pins using a freehand technique. After pin removal, CT was repeated. All entry points, exit points and angles of the preoperative planned trajectories were compared with postoperative ones using an image registration and fusion technique by three observers. Corridor coordinates for entry and exit points were evaluated in three dimensions and angles were measured in one plane. Intraclass correlation coefficient (ICC) was used to establish the imaging technique reliability and descriptive statistics were used to report on the freehand technique accuracy. Safety was evaluated using a vertebral cortical breach grading scheme.

Results Intraclass correlation coefficient for the entry points, exit points and angle were 0.79, 0.96 and 0.92 respectively. Mean deviations for the entry points, exit points and angle were 3.1 mm, 6.3 mm and 7.6 degrees respectively. Maximum deviations were 6.3 mm, 11.0 mm and 16.4 degrees. Most deviations were lateral and caudal. All corridors were judged as safe.

Conclusion The imaging technique reliability was good to excellent to study spinal surgery accuracy. Implant deviations should be anticipated when planning stabilization surgery in large breed dogs using the freehand-guided technique.

目的 本研究的目的是验证用于评估脊柱手术准确性的成像技术，并建立大型犬胸腰椎徒手技术的准确性和安全性。

研究设计 在胸腰椎计算机断层扫描 (CT) 之后，计划了 26 个钻孔通道，然后使用徒手技术钻孔以接收 3.2 mm 正轮廓销。取下针后，重复 CT。三个观察者使用图像配准和融合技术将术前计划轨迹的所有进入点、退出点和角度与术后进行比较。入口和出口点的走廊坐标在三个维度上进行评估，角度在一个平面上进行测量。组内相关系数（ICC）用于建立成像技术的可靠性，描述性统计用于报告手绘技术的准确性。使用椎骨皮质断裂分级方案评估安全性。

结果 进入点、退出点和角度的类内相关系数分别为0.79、0.96和0.92。入口点、出口点和角度的平均偏差分别为 3.1 毫米、6.3 毫米和 7.6 度。最大偏差为 6.3 毫米、11.0 毫米和 16.4 度。大多数偏差是横向和尾部。所有走廊都被判断为安全。

结论 影像技术的可靠性在研究脊柱手术准确性方面具有良好至优秀的水平。在使用徒手引导技术对大型犬进行稳定手术时，应预料到种植体偏差。