Jeong Soon-Taek, Park Young-Seop, Jung Gu-Hee
1 Department of Orthopaedic Surgery, College of Medicine, Gyeongsang National University, Gyeongsang National University Hospital, Jinju-si, Republic of Korea.
2 Department of Neurosurgery, Gyeongsang National University Changwon Hospital, Changwon-si, Republic of Korea.
J Orthop Surg (Hong Kong). 2019 Jan-Apr;27(1):2309499019836246. doi: 10.1177/2309499019836246.
To determine an easy and convenient method of sacral-alar-iliac (S2AI) screw fixation and introduce the surgical landmarks for fluoroscopic procedure by analyzing 3-D models of pelvis and virtual implantation in a 3-D model.
Eighty-two cadavers underwent computed tomography scans and the images imported into Mimics software to make the 3-D pelvis model. The pedicle screw (Ø 8.5 mm/length 115 mm) was processed into a 3-D model using a 3-D-sensor (Comet5) at the actual size and virtually placed as the S2AI screw. The ideal screw position was defined as the maximal intraosseous length without cortical perforation along the entire path. The ideal entry point and screw trajectory were verified and assessed to introduce the surgical landmark for fluoroscopic procedure.
There was no cortical violation around nerve root canal and greater sciatic notch through the entry point between first and second dorsal sacral foramen. There was no impossible model of S2AI screws. The average screw length was 99.8 mm (range, 59.8-115 mm; standard deviation, 16.1) and just one model had shorter than 65 mm S2AI screw. The factors limiting the intra-iliac screw length were sex ( p = 0.000) and the iliac groove around the sacroiliac joint ( p = 0.000). A free 360° rotation with magnification revealed that the screw trajectory was consistently directed toward the anteroinferior iliac spine (AIIS) in any plane.
The ideal entry point of S2AI screw showed a wide range of tolerance between the first and second dorsal sacral foramen; and thus, there was no need for deep dissection to identify the first dorsal sacral foramen. Considering the tendency to shift the pilot hole laterally and the ideal screw trajectory was consistently directed toward AIIS, the entry point is better to be located with a medial shift.
通过分析骨盆的三维模型及在三维模型中的虚拟植入，确定一种简便的骶骨-翼-髂骨（S2AI）螺钉固定方法，并介绍透视手术的手术标志。
82具尸体接受计算机断层扫描，图像导入Mimics软件以制作三维骨盆模型。使用三维传感器（Comet5）将椎弓根螺钉（直径8.5 mm/长度115 mm）按实际尺寸加工成三维模型，并虚拟放置为S2AI螺钉。理想的螺钉位置定义为沿整个路径无皮质穿孔的最大骨内长度。验证并评估理想的进针点和螺钉轨迹，以介绍透视手术的手术标志。
通过第一和第二骶后孔之间的进针点，神经根 canal 和坐骨大切迹周围无皮质侵犯。不存在S2AI螺钉的不可行模型。螺钉平均长度为99.8 mm（范围59.8 - 115 mm；标准差16.1），只有一个模型的S2AI螺钉长度短于65 mm。限制髂内螺钉长度的因素是性别（p = 0.000）和骶髂关节周围的髂沟（p = 0.000）。360°自由旋转并放大显示，在任何平面上螺钉轨迹始终指向髂前下棘（AIIS）。
S2AI螺钉的理想进针点在第一和第二骶后孔之间显示出较宽的耐受性范围；因此，无需进行深部解剖来识别第一骶后孔。考虑到导向孔有向外侧偏移的趋势且理想的螺钉轨迹始终指向AIIS，进针点最好向内偏移定位。
