Hirabayashi S, Koshizuka Y
Department of Orthopaedic Surgery, International Medical Center of Japan, 1-21-1 Toyama, Shinjuku, Tokyo 162-0052, Japan.
J Orthop Sci. 1999;4(2):78-82. doi: 10.1007/s007760050078.
In the double-door laminoplasty procedure used for patients with cervical myelopathy, techniques to obtain a wider spinal canal have been tested. We hypothesized that making the lateral gutters as lateral as possible may be effective for obtaining a wider spinal canal. In this study we aimed to test our hypothesis by using a new measurement method to assess the postoperative cross-sectional area of the spinal canal. Fifty-six vertebrae were operated on in 11 patients, using the STSS spacer (Asahi Optical, Tokyo, Japan). On computed tomography (CT) scans, the most posterior edge of a space-occupying lesion was defined as point A and a horizontal line through point A was drawn parallel to the posterior wall of the vertebral body (line X). Two oblique lines were drawn along the medial margin of the bilateral split laminae (lines R and L). The triangular area enclosed by lines X, R, and L was defined as the substantial area of the spinal canal (SASC). A horizontal line through the median points of the bilateral facet joint in the anteroposterior direction was defined as line B. According to the relative position of line X to line B, two types of vertebra were observed: In type 1, line X was located ventral to line B; in type 2, line X was located dorsal to line B. The mean data values for type 1 vertebra were: SASC, 133.1 mm2; ATD, 22.9 mm; angle R, 61.3 degrees; and angle L, 61.8 degrees. The mean data values for type 2 vertebra were: SASC, 99.8 mm2; ATD, 20.1 mm; angle R, 58.6 degrees; and angle L, 57.5 degrees. There were significant differences between types 1 and 2 vertebrae in values both for SASC and ATD (P < 0.01). There were no significant differences between types 1 and 2 vertebrae regarding angles R and L. The difference in SASC in the two types appeared to arise from the difference in ATD. In other words, the degree of enlargement of the spinal canal was determined not by the inclination of the bilateral split laminae, but by the transverse diameter. This result supports the validity of our hypothesis. In a double-door laminoplasty, to obtain a wider spinal canal, the lateral gutters must be made as lateral as possible (i.e., at the medial border of the facet joints, especially in type 2 vertebra). On the preoperative CT scan, the relative positions of the large-volume lesion and the facet joint must be noted.
在用于治疗颈椎病患者的双开门椎管扩大成形术中，人们已经对获得更宽椎管的技术进行了测试。我们假设尽可能将侧方沟槽向外侧拓展可能对获得更宽的椎管有效。在本研究中，我们旨在通过一种新的测量方法来测试我们的假设，该方法用于评估术后椎管的横截面积。使用STSS椎间融合器（日本东京旭光学公司）对11例患者的56个椎体进行了手术。在计算机断层扫描（CT）图像上，占位性病变的最后缘定义为A点，并通过A点绘制一条与椎体后壁平行的水平线（X线）。沿着双侧椎板劈开的内侧边缘绘制两条斜线（R线和L线）。由X线、R线和L线围成的三角形区域定义为椎管实质面积（SASC）。在前后方向上通过双侧小关节中点的水平线定义为B线。根据X线与B线的相对位置，观察到两种类型的椎体：在1型中，X线位于B线腹侧；在2型中，X线位于B线背侧。1型椎体的平均数据值为：SASC，133.1mm²；前后径（ATD），22.9mm；R角，61.3度；L角，61.8度。2型椎体的平均数据值为：SASC，99.8mm²；ATD，20.1mm；R角，58.6度；L角，57.5度。1型和2型椎体在SASC和ATD值上存在显著差异（P<0.01）。1型和2型椎体在R角和L角方面无显著差异。两种类型在SASC上的差异似乎源于ATD的差异。换句话说，椎管扩大的程度不是由双侧椎板劈开的倾斜度决定的，而是由横径决定的。这一结果支持了我们假设的有效性。在双开门椎管扩大成形术中，为了获得更宽的椎管，必须尽可能将侧方沟槽向外侧拓展（即，在小关节的内侧边界，尤其是在2型椎体中）。在术前CT扫描上，必须注意大容量病变与小关节的相对位置。
