Umehara S, Zindrick M R, Patwardhan A G, Havey R M, Vrbos L A, Knight G W, Miyano S, Kirincic M, Kaneda K, Lorenz M A
Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, Maywood, Illinois 60153, USA.
Spine (Phila Pa 1976). 2000 Jul 1;25(13):1617-24. doi: 10.1097/00007632-200007010-00004.
Change in lumbar lordosis was measured in patients that had undergone posterolateral lumbar fusions using transpedicular instrumentation. The biomechanical effects of postoperative lumbar malalignment were measured in cadaveric specimens.
To determine the extent of postoperative lumbar sagittal malalignment caused by an intraoperative kneeling position with 90 degrees of hip and knee flexion, and to assess its effect on the mechanical loading of the instrumented and adjacent segments.
The importance of maintaining the baseline lumbar lordosis after surgery has been stressed in the literature. However, there are few objective data to evaluate whether postoperative hypolordosis in the instrumented segments can increase the likelihood of junctional breakdown.
Segmental lordosis was measured on preoperative standing, intraoperative prone, and postoperative standing radiographs. In human cadaveric spines, a lordosis loss of up to 8 degrees was created across L4-S1 using calibrated transpedicular devices. Specimens were tested in extension and under axial loading in the upright posture.
In patients who underwent L4-S1 fusions, the lordosis within the fusion decreased by 10 degrees intraoperatively and after surgery. Postoperative lordosis in the proximal (L2-L3 and L3-L4) segments increased by 2 degrees each, as compared with the preoperative measures. Hypolordosis in the instrumented segments increased the load across the posterior transpedicular devices, the posterior shear force, and the lamina strain at the adjacent level.
Hypolordosis in the instrumented segments caused increased loading of the posterior column of the adjacent segments. These biomechanical effects may explain the degenerative changes at the junctional level that have been observed as long-term consequences of lumbar fusion.
对接受经椎弓根器械辅助后外侧腰椎融合术的患者测量腰椎前凸的变化。在尸体标本上测量术后腰椎排列不齐的生物力学效应。
确定术中髋关节和膝关节屈曲90度跪姿导致的术后腰椎矢状面排列不齐的程度，并评估其对器械固定节段及相邻节段机械负荷的影响。
文献中强调了术后维持基线腰椎前凸的重要性。然而，几乎没有客观数据来评估器械固定节段术后腰椎前凸减小是否会增加交界区失效的可能性。
在术前站立位、术中俯卧位和术后站立位X线片上测量节段性前凸。在人体尸体脊柱上，使用校准的椎弓根器械在L4-S1节段造成高达8度的前凸丢失。标本在伸展位和直立姿势下轴向加载时进行测试。
接受L4-S1融合术的患者，融合节段内的前凸在术中及术后减少了10度。与术前测量相比，近端（L2-L3和L3-L4）节段的术后前凸各增加了2度。器械固定节段的腰椎前凸减小增加了经椎弓根后方器械的负荷、后方剪切力以及相邻节段椎板的应变。
器械固定节段的腰椎前凸减小导致相邻节段后柱负荷增加。这些生物力学效应可能解释了作为腰椎融合长期后果而观察到的交界区退变改变。
