Hart Robert A, Hansen Brenden L, Shea Marie, Hsu Frank, Anderson Gregory J
Department of Orthopaedics & Rehabilitation, Oregon Health Sciences University, Portland, OR, USA.
Spine (Phila Pa 1976). 2005 Jun 15;30(12):E326-31. doi: 10.1097/01.brs.0000166621.98354.1d.
A cadaveric study comparing image guidance technology to fluoroscopic guidance as a means of pedicle screw placement in the thoracic spine, using a unique starting point for screw placement.
To assess accuracy of thoracic pedicle screw placement using image guidance versus fluoroscopic guidance for screw insertion.
While use of pedicle screws in the thoracic spine has been increasing, its adoption has been slower than for the lumbar spine, reflecting concern regarding possible vascular or spinal cord injury due to screw malplacement. Given these risks, efforts to improve the accuracy of thoracic pedicle screw placement remain appropriate. Stereotactic guidance has been applied in other aspects of spinal surgery to improve the accuracy of instrumentation placement.
Pedicle screws were placed in the thoracic spines of eight cadavers, using either a stereotactic guidance or a manual, fluoroscopically guided technique. A slightly more superior and lateral starting point from prior descriptions was used. Each cadaver was instrumented with pedicle screws in the upper thoracic (T1-T2), middle thoracic (T4-T7), and lower thoracic (T9-T10) regions. In the upper and middle thoracic regions, screws with a 4.0-mm shank diameter were used while in the lower thoracic region a shank diameter of 4.5 mm was used. Postinstrumentation CT scans, followed by anatomic dissections, were used to evaluate screw exit rates and orientation relative to the pedicle axis. Exit rates for the two techniques and the effect of vertebral level on exit rate were compared using a chi analysis. The effect of pedicle diameter was tested using a Pearson correlation coefficient.
No significant differences in the overall exit rates or orientation were found between the two techniques. There were significant differences in exit rates between the middle (47%), compared with the upper (9%) and lower (16%) thoracic regions, respectively (P < 0.001). A significant correlation between pedicle diameter and exit rate was also found (P < 0.0001).
Our study showed no significant differences in the overall exit rates between the two techniques. Image guidance may increase confidence of surgeons with limited experience in thoracic pedicle screw placement. Successful placement of screws within the pedicle varies with the anatomic diameter of the pedicle itself. Concerns regarding accuracy of screw placement should be greatest in the middle thoracic vertebrae (T4-T7), where pedicle diameters are smallest and proximity of the great vessels is nearest.
一项尸体研究，将图像引导技术与荧光镜引导技术进行比较，作为在胸椎中置入椎弓根螺钉的一种方法，采用独特的螺钉置入起始点。
评估使用图像引导与荧光镜引导进行螺钉置入时胸椎椎弓根螺钉置入的准确性。
虽然胸椎椎弓根螺钉的使用一直在增加，但其应用速度比腰椎慢，这反映出人们对螺钉误置可能导致血管或脊髓损伤的担忧。鉴于这些风险，努力提高胸椎椎弓根螺钉置入的准确性仍然是合适的。立体定向引导已应用于脊柱手术的其他方面，以提高器械置入的准确性。
使用立体定向引导或手动荧光镜引导技术，在8具尸体的胸椎中置入椎弓根螺钉。采用比先前描述稍高且稍外侧的起始点。每具尸体在上胸椎（T1-T2）、中胸椎（T4-T7）和下胸椎（T9-T10）区域置入椎弓根螺钉。在上胸椎和中胸椎区域，使用柄直径为4.0毫米的螺钉，在下胸椎区域，使用柄直径为4.5毫米的螺钉。置入器械后进行CT扫描，随后进行解剖，以评估螺钉穿出率以及相对于椎弓根轴线的方向。使用卡方分析比较两种技术的穿出率以及椎体节段对穿出率的影响。使用Pearson相关系数测试椎弓根直径的影响。
两种技术在总体穿出率或方向上未发现显著差异。中胸椎（47%）的穿出率与上胸椎（9%）和下胸椎（16%）的穿出率之间存在显著差异（P < 0.001）。还发现椎弓根直径与穿出率之间存在显著相关性（P < 0.0001）。
我们的研究表明，两种技术在总体穿出率上没有显著差异。图像引导可能会提高在胸椎椎弓根螺钉置入方面经验有限的外科医生的信心。螺钉在椎弓根内的成功置入因椎弓根本身的解剖直径而异。对螺钉置入准确性的担忧在中胸椎（T4-T7）应最为严重，因为该区域椎弓根直径最小且大血管最接近。
