CT重建技术评估枢椎椎弓根螺钉安全置钉可行性方法的对比研究

A comparative study of CT reconstruction for preoperative evaluation of safe C2 pedicle screws placement

中文关键词:  枢椎椎弓根螺钉  CT重建  椎弓根峡部复合体  椎动脉高跨  术前评估

英文关键词:C2 pedicle screw  Pediculoisthmic component  High-riding vertebral artery  CT reconstruction  Preoperative evaluation

中文摘要:

  【摘要】 目的：应用CT血管造影多平面重建（CT angiography multiplanar reconstruction，CTA MPR）测量枢椎椎弓根峡部复合体（pediculoisthmic component，PIC）最狭窄部位尺寸，评估枢椎椎弓根螺钉置钉的安全性（CTA MPR测量法），并与CT标准水平轴位测量评估方法（CT AXIS测量法）、椎动脉高跨变异（high-riding vertebral artery，HRVA）评估方法（HRVA定义法）对比，评价两种临床常用术前评估方法的假阳性率和假阴性率。方法：选取已行普通CT平扫及头颈部CTA检查的152例患者作为研究对象，使用CT AXIS测量法测量患者枢椎双侧椎弓根髓腔宽度（a1）及外径宽度（a2）；使用CT骨窗正中矢状位测量患者枢椎双侧椎管内壁外侧3mm处的峡部高度（b）及侧块内高（c），并定义是否存在HRVA；使用CTA MPR测量法测量枢椎PIC最狭窄部的髓腔宽度（d1）、外径宽度（d2）、髓腔高度（e1）及外径高度（e2）。比较CT AXIS测量法测量参数与CTA MPR测量法测量参数的差异，计算三种方法判定不适合安全置入枢椎椎弓根螺钉的比例，并以CTA MPR测量法作为判定金标准，评价CT AXIS测量法和HRVA定义法的假阳性率和假阴性率。结果：使用CTA MPR测量法与CT AXIS测量法分别测量152例患者的304个枢椎椎弓根峡部尺寸，两种方法测量的髓腔宽度（3.82±1.58mm vs 2.55±1.16mm）和外径宽度（6.54±1.91mm vs 5.48±1.49mm）均有统计学差异（P＜0.001）；CTA MPR测量PIC的高度显著大于其宽度（髓腔：6.55±1.34mm vs 3.82±1.58mm；外径：10.20±1.22mm vs 6.54±1.91mm）（P＜0.001）。以CTA MPR测量法作为判定金标准，CT AXIS测量法的假阴性率为6.91%，假阳性率为20.69%；HRVA定义法的假阴性率为11.64%，假阳性率为3.45%。CTA MPR测量法与CT AXIS测量法、HRVA定义法评估置钉可行性之间存在显著性差异（P＜0.01）。结论：CTA MPR测量法可模拟枢椎椎弓根钉道，获取钉道最狭窄部重建截面并准确测量宽度，是术前评估枢椎椎弓根螺钉安全置钉可行性的准确方法。CT AXIS测量法与HRVA定义法均存在一定的假阳性率和假阴性率，可能导致误判或漏判置钉可行性，从而增加椎动脉损伤的风险或选择生物力学性能不足的置钉术式。

英文摘要:

  【Abstract】 Objectives: To evaluate the feasibility of safe placement of C2 pedicle screws by measuring the morphometric diameters on the narrowest portion of C2 pediculoisthmic component(PIC) with CT angiography multiplanar reconstruction(CTA MPR), and to compare with the two commonly used clinical methods of axial CT(CT AXIS) and the definition of high-riding vertebral artery(HRVA) to assess their false positive rates and false negative rates. Methods: Consecutive patients who had undergone CT examination and head and neck CT angiography(CTA) scan were included. The width of the endosteal cavity(a1) and outer diameter(a2) of C2 bilateral pedicles were measured by means of CT AXIS. The isthmus height(b) and internal height(c) were measured on an orthogonal sagittal CT image at 3mm lateral to the cortical margin of the spinal canal wall at C2, and HRVA was defined. The width of the endosteal cavity(d1), width of the outer diameter(d2), the height of the endosteal cavity (e1) and height of the outer diameter (e2) were measured by means of CTA MPR at the narrowest section of C2 PIC. Disparities of the morphometric parameters between CT AXIS method and CTA MPR method were compared. Unfeasible proportions of C2 pedicle screw placement evaluated by all the three methods were calculated, and the false positive rates and false negative rates of CT AXIS method and HRVA definition were analyzed based on CTA MPR method as the "gold standard". Results: A total of 304 C2 PICs of 152 patients were measured with CTA MPR and CT AXIS methods separately, the endosteal diameter(3.82±1.58mm vs 2.55±1.16mm) and outer diameter(6.54±1.91mm vs 5.48±1.49mm) each were with statistical differences between the two methods(P<0.001). Besides, with the CTA MPR method, the height measured was significantly bigger than the width(endosteal: 6.55±1.34mm vs 3.82±1.58mm; outer: 10.2±1.22mm vs 6.54±1.91mm) (P<0.001). Regarding CTA MPR method as the "gold standard", the false negative rate and false positive rate of CT AXIS method were 6.91% and 20.69%, respectively; the false negative rate and false positive rate of HRVA definition were 11.64% and 3.45%, respectively. There were significant differences between CTA MPR method and the methods of CT AXIS and HRVA definition in evaluating the placement feasibility of pedicle screws(P<0.01). Conclusions: CTA MPR measurement is able to simulate C2 pedicle screw path and measure the morphometric parameters at the narrowest section of C2 PIC accurately, which is a precise method in evaluating the feasibility of safe placement of C2 pedicle screw preoperatively. Whereas, the evaluation methods of CT AXIS and HRVA definition have partly false positive rate and false negative rate that may lead to misjudgment or omission of the feasibility of C2 pedicle screw placement, increasing the risk of vertebral artery injury or choosing biomechanically deficient C2 screw placement.