*Department of Orthopaedic Surgery and the †Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University, Baltimore, MD.
Spine (Phila Pa 1976). 2014 Feb 1;39(3):E153-8. doi: 10.1097/BRS.0000000000000118.
Analysis via computed tomography imaging software.
To determine parameters for ideal intralaminar screw trajectory and the feasibility of screw placement at L3, L4, and L5 laminae for pars defect fixation.
To our knowledge, no studies provide anatomic parameters for ideal intralaminar screw trajectory for treating spondylolysis.
We used advanced imaging software for 3-dimensional interactive viewing to analyze 20 randomly selected normal adolescent lumbar computed tomographic scans. The ideal intralaminar screw trajectory was drawn from the inferior lamina, a point chosen to maximize cortical diameter at the isthmus of the lamina and bisect the pedicle. We measured and evaluated ideal trajectory parameters for percutaneous screw placement for pars defect fixation at the L3 to L5 laminae.
The ideal pathway was the thick portion of the lamina between the inferior edge of the lamina and the pedicle. This area was close to the inferior articular process (axial plane), becoming more so at progressively caudal levels. At the ideal trajectory, the mean (standard deviation) coronal angle slightly decreased (L3-L5): 7.3° (5.1°), 6.6° (3.7°), and 4.2° (2.5°), respectively. The trajectory distance increased from cranial to caudal. These parameters increased (L3-L5): mean distance (transverse plane) between the starting point and middle of the spinous process, 1.2 (0.18 cm), 1.3 (0.2 cm), and 1.6 (0.3 cm), respectively; mean screw sagittal angle with respect to the posterior skin, 15.5° (5.0°), 24.3° (6.5°), and 43° (5.8°), respectively; and mean distance for guide wire entry, 28.8 (10.6 cm), 20.1 (5.4 cm), and 11.9 (2.1 cm), respectively.
At the ideal screw trajectory, pars fixation by intralaminar screw is uniformly feasible at L3 to L5 laminae, where most patients can accommodate a 4.5-mm screw.
通过计算机断层扫描成像软件进行分析。
确定理想的椎板间螺钉轨迹参数，并确定在 L3、L4 和 L5 椎板上进行椎板螺钉固定的 pars 缺损固定的可行性。
据我们所知，尚无研究为治疗峡部裂提供理想的椎板间螺钉轨迹的解剖学参数。
我们使用先进的成像软件进行三维交互式观察，对 20 例随机选择的正常青少年腰椎 CT 扫描进行分析。从下椎板绘制理想的椎板间螺钉轨迹，选择该点是为了使椎板峡部的皮质直径最大化，并将椎弓根二等分。我们测量并评估了在 L3 到 L5 椎板上进行 pars 缺损固定的经皮螺钉放置的理想轨迹参数。
理想的路径是椎板下缘和椎弓根之间椎板的厚部分。该区域靠近下关节突（轴面），在逐渐向尾侧水平时更为接近。在理想的轨迹中，冠状角（矢状面）的平均值（标准差）略有减小（L3-L5）：分别为 7.3°（5.1°）、6.6°（3.7°）和 4.2°（2.5°）。轨迹距离从颅侧到尾侧增加。这些参数增加（L3-L5）：起点与棘突中点之间的横断面上的平均距离（1.2（0.18 cm）、1.3（0.2 cm）和 1.6（0.3 cm））、与后皮矢状面的平均螺钉矢状角（15.5°（5.0°）、24.3°（6.5°）和 43°（5.8°））和导丝进入的平均距离（28.8（10.6 cm）、20.1（5.4 cm）和 11.9（2.1 cm））。
在理想的螺钉轨迹中，L3 到 L5 椎板的椎板间螺钉固定均可行，大多数患者可容纳 4.5mm 螺钉。
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