Youkilis A S, Quint D J, McGillicuddy J E, Papadopoulos S M
Department of Neurosurgery, University of Michigan Medical Center, Ann Arbor, USA.
Neurosurgery. 2001 Apr;48(4):771-8; discussion 778-9. doi: 10.1097/00006123-200104000-00015.
Pedicle screw fixation in the lumbar spine has become the standard of care for various causes of spinal instability. However, because of the smaller size and more complex morphology of the thoracic pedicle, screw placement in the thoracic spine can be extremely challenging. In several published series, cortical violations have been reported in up to 50% of screws placed with standard fluoroscopic techniques. The goal of this study is to evaluate the accuracy of thoracic pedicle screw placement by use of image-guided techniques.
During the past 4 years, 266 image-guided thoracic pedicle screws were placed in 65 patients at the University of Michigan Medical Center. Postoperative thin-cut computed tomographic scans were obtained in 52 of these patients who were available to enroll in the study. An impartial neuroradiologist evaluated 224 screws by use of a standardized grading scheme. All levels of the thoracic spine were included in the study.
Chart review revealed no incidence of neurological, cardiovascular, or pulmonary injury. Of the 224 screws reviewed, there were 19 cortical violations (8.5%). Eleven (4.9%) were Grade II (< or =2 mm), and eight (3.6%) were Grade III (>2 mm) violations. Only five screws (2.2%), however, were thought to exhibit unintentional, structurally significant violations. Statistical analysis revealed a significantly higher rate of cortical perforation in the midthoracic spine (T4-T8, 16.7%; T1-T4, 8.8%; and T9-T12, 5.6%).
The low rate of cortical perforations (8.5%) and structurally significant violations (2.2%) in this retrospective series compares favorably with previously published results that used anatomic landmarks and intraoperative fluoroscopy. This study provides further evidence that stereotactic placement of pedicle screws can be performed safely and effectively at all levels of the thoracic spine.
腰椎椎弓根螺钉固定已成为治疗各种脊柱不稳病因的标准方法。然而，由于胸椎椎弓根尺寸较小且形态更为复杂，胸椎螺钉置入极具挑战性。在多个已发表的系列研究中，采用标准透视技术置入的螺钉中，高达50%出现皮质骨穿破情况。本研究的目的是评估使用影像引导技术进行胸椎椎弓根螺钉置入的准确性。
在过去4年中，密歇根大学医学中心为65例患者置入了266枚影像引导下的胸椎椎弓根螺钉。其中52例患者术后接受了薄层计算机断层扫描，这些患者可纳入本研究。一名公正的神经放射科医生使用标准化分级方案对224枚螺钉进行了评估。研究纳入了胸椎的所有节段。
病历回顾显示无神经、心血管或肺部损伤发生。在224枚被评估的螺钉中，有19枚出现皮质骨穿破（8.5%）。11枚（4.9%）为II级（≤2 mm），8枚（3.6%）为III级（>2 mm）穿破。然而，只有5枚螺钉（2.2%）被认为出现了非故意的、具有结构意义的穿破。统计分析显示，胸椎中段（T4 - T8，16.7%；T1 - T4，8.8%；T9 - T12，5.6%）皮质骨穿孔率显著更高。
在这个回顾性系列研究中，皮质骨穿孔率（8.5%）和具有结构意义的穿破率（2.2%）较低，与之前使用解剖标志和术中透视的研究结果相比更具优势。本研究进一步证明，在胸椎各节段进行椎弓根螺钉的立体定向置入可安全、有效地进行。
