Kioschos H C, Asher M A, Lark R G, Harner E J
Section of Orthopedic Surgery, University of Kansas Medical Center, Kansas City, USA.
Spine (Phila Pa 1976). 1996 May 15;21(10):1168-73. doi: 10.1097/00007632-199605150-00008.
This experimental study was designed to test the hypothesis that posterior spinal fusion and internal fixation, using a stiff transpedicular construct, would withstand additional anterior column growth without the need for an anterior procedure and would prevent the development of deformity secondary to asymmetric growth of the anterior column in the immature canine model.
This model revealed that a mechanical epiphysiodesis of the anterior spinal column can be created through a posterior approach in an immature growing animal using a stiff transpedicular construct. These results were correlated to the crankshaft mechanism clinically to provide a possible rationale for transpedicular posterior spinal instrumentation and fusion, without a concomitant anterior procedure, in immature patients.
All operative immature canines underwent posterior fusion of L1-L5 vertebral bodies with autogenous iliac crest bone graft. Instrumented canines underwent the additional placement of transpedicular screws at L1, L3, and L5 as well as 3/16-inch rods and a transverse connector. Previous studies have revealed that continued anterior spinal column growth after posterior arthrodesis causes a resultant deformity in quadrupeds. No previous study has assessed whether a transpedicular construct can overpower the anterior spinal growth plate in an immature growing model.
Twenty-five skeletally immature canines were randomized into four groups: control, fusion only, screw and fusion, and instrumentation and fusion. Disc space growth, vertebral body growth, and sagittal plane angulation were the variables analyzed. Management response variables were visualized graphically and radiographically.
Posterior tethering and anterior column growth occurred in the noninstrumented fusion groups, producing substantial lordosis. Anterior column growth was arrested in the instrumented canines as demonstrated by decreased vertebral body length, disc space narrowing, and, most importantly, prevention of lordosis.
The present study confirmed that in immature canines anterior column growth continues after posterior fusion without instrumentation. The magnitude of this growth, combined with a posterior tether, is sufficient to cause significant lordosis. The results are the first to document that a stiff posterior spinal instrumentation system is sufficient to overpower the residual anterior growth centers, even in the presence of a posterior tether (fusion mass). This technique creates a mechanical epiphysiodesis evidenced by arresting vertebral body length, narrowing disc space, and preventing lordosis, thus thwarting the deformity-producing mechanism without an additional anterior procedure.
本实验性研究旨在验证以下假设，即使用坚固的经椎弓根结构进行后路脊柱融合及内固定，无需前路手术即可承受前柱的额外生长，并可防止未成熟犬模型中因前柱不对称生长继发的畸形发展。
该模型显示，在未成熟的生长动物中，通过后路使用坚固的经椎弓根结构可实现脊柱前柱的机械性骨骺阻滞。这些结果与临床上的曲轴机制相关，为未成熟患者在不进行同期前路手术的情况下进行经椎弓根后路脊柱内固定及融合提供了可能的理论依据。
所有接受手术的未成熟犬均接受了L1-L5椎体的后路融合及自体髂骨植骨。植入器械的犬在L1、L3和L5额外置入了经椎弓根螺钉以及3/16英寸的棒和横向连接器。先前的研究表明，后路关节融合术后前柱的持续生长会导致四足动物出现继发畸形。此前尚无研究评估在未成熟的生长模型中经椎弓根结构能否克服前柱生长板的生长。
将25只骨骼未成熟的犬随机分为四组：对照组、单纯融合组、螺钉与融合组以及内固定与融合组。分析的变量包括椎间盘间隙生长、椎体生长和矢状面成角。管理反应变量通过图形和影像学进行可视化。
未植入器械的融合组出现了后路束缚和前柱生长，导致明显的脊柱前凸。植入器械的犬的前柱生长受到抑制，表现为椎体长度减小、椎间盘间隙变窄，最重要的是防止了脊柱前凸。
本研究证实，在未成熟犬中，后路融合后若不进行内固定，前柱生长仍会继续。这种生长的幅度加上后路束缚足以导致明显的脊柱前凸。这些结果首次证明，即使存在后路束缚（融合块），坚固的后路脊柱内固定系统也足以克服残留的前生长中心。该技术通过阻止椎体长度增加、缩小椎间盘间隙和防止脊柱前凸，创造了一种机械性骨骺阻滞，从而在不进行额外前路手术的情况下挫败了导致畸形的机制。
