Tonetti J, Cloppet O, Clerc M, Pittet L, Troccaz J, Merloz P, Chirossel J
Laboratoire d'Anatomie de Grenoble, Laboratoire TIMC-IMAG, Université Joseph Fourier, Grenoble, France.
Rev Chir Orthop Reparatrice Appar Mot. 2000 Jun;86(4):360-9.
Percutaneous iliosacral screws are used advantageously to fix unstable pelvic girdle avoiding the morbidity of open access for conventional screw fixation. The insertion technique must be precise due to the risk of injury to the lumbosacral nerve trunk, the cauda equina roots, and the first sacral nerve. We undertook a study of the implantation site of iliosacral screws looking for a means of standardizing the drilling procedure on the basis of 3D computed tomography (CT) data.
A CT series with 3D reconstruction was performed on 11 pelvis bones. We retained pelvis parameters and characterized the axis and narrow zone of the sacral wing. The insertion routes of 6.5 mm cancelous bone screws were simulated: two iliosacral routes fixing S1, and two iliosacroiliac routes fixing S1 and S2. The values of the pelvic parameters and the positions of the screws were compared with the Spearman correlation test and graphic regression.
The pelvic incidence was a mean 47 degrees. The length of the sacral wing was a mean 73 mm. The narrow zone of the wing was 47 mm from the lateral iliac fossa. In the narrow zone, the wing section showed an oval shape: 22 mm largest diameter, 11 mm smallest diameter. The wing was oriented 84 degrees in the paracoronal plane perpendicular to the plane of the sacral plate, 67 degrees in the para-axial plane parallel to the sacral plate, and 37 degrees in the sagittal plane of the subject. The length of the upper S1 screw was a mean 80 mm. This upper screw was inclined 89 degrees in the para-coronal plant, 61 degrees in the para-axial plane and 28 degrees in the sagittal plane. The length of the lower S1 screw as a mean 80 mm. This lower screw was inclined 74 degrees in the para-coronal plane, 91 degrees in the para-axial plane and 110 degrees in the sagittal plane. The fixation screws could be inserted in 12 out of 22 cases. Correlations were found with height of the subject, length of the wing and the screw, and screw inclination. The inclination of the upper S1 screw in the para-coronal plane was correlated with the larger diameter of the sacral wing.
The pelvis parameters measured were comparable with data in the literature. The very small dimensions of the narrow zone dictate a very precise drilling for the narrow zone. This narrow zone determines the inclination of the screw insertion. In the sagittal plane the standard deviation was very large making it impossible to interpret the data. The route of the upper screw runs obliquely forward in the plane parallel to the sacral plate. The lower screw runs upwardly in the plane perpendicular to the sacral plate. It does not appear possible to insert fixation screws in a routine procedure. Preoperative assessment would be necessary before percutaneous insertion.
The 3D CT reconstructions of the sacral wing can be used to determine the precise optimal position of the two iliosacral screws. The principle orientations can be deducted from the plane of the sacral plate. Approximate indications can help reduce operative time and exposure to irradiation (patient and surgeon). Percutaneous iliosacroiliac screw fixation cannot be proposed for all patients.
经皮髂骶螺钉有利于固定不稳定骨盆环，可避免传统螺钉固定开放入路带来的并发症。由于存在损伤腰骶神经干、马尾神经及第一骶神经的风险，插入技术必须精确。我们基于三维计算机断层扫描（CT）数据，对髂骶螺钉的植入部位进行了研究，以寻找标准化钻孔程序的方法。
对11块骨盆骨进行了带有三维重建的CT扫描。我们记录了骨盆参数，并对骶骨翼的轴线和狭窄区域进行了特征描述。模拟了6.5毫米松质骨螺钉的插入路径：两条髂骶路径固定S1，两条髂骶髂路径固定S1和S2。采用Spearman相关性检验和图形回归比较骨盆参数值和螺钉位置。
骨盆倾斜度平均为47度。骶骨翼长度平均为73毫米。翼部狭窄区域距髂窝外侧47毫米。在狭窄区域，翼部截面呈椭圆形：最大直径22毫米，最小直径11毫米。翼部在垂直于骶骨板平面的副冠状面中方向为84度，在平行于骶骨板的副轴面中为67度，在受试者矢状面中为37度。上部S1螺钉长度平均为80毫米。该上部螺钉在副冠状面中倾斜89度，在副轴面中倾斜61度，在矢状面中倾斜28度。下部S1螺钉长度平均为80毫米。该下部螺钉在副冠状面中倾斜74度，在副轴面中倾斜91度，在矢状面中倾斜110度。22例中有12例可插入固定螺钉。发现与受试者身高、翼部和螺钉长度以及螺钉倾斜度存在相关性。上部S1螺钉在副冠状面中的倾斜度与骶骨翼较大直径相关。
所测量的骨盆参数与文献数据可比。狭窄区域尺寸极小，这就要求在狭窄区域进行非常精确的钻孔。这个狭窄区域决定了螺钉插入的倾斜度。在矢状面中标准差非常大，无法解释数据。上部螺钉路径在平行于骶骨板的平面中向前倾斜。下部螺钉在垂直于骶骨板的平面中向上走行。按常规程序似乎无法插入固定螺钉。经皮插入前需要进行术前评估。
骶骨翼的三维CT重建可用于确定两枚髂骶螺钉的精确最佳位置。主要方向可从骶骨板平面推导得出。近似指征有助于减少手术时间和辐射暴露（患者和外科医生）。并非所有患者都适合经皮髂骶螺钉固定。
