Department of Anatomy, University of Bristol, Southwell Street, Bristol BS2 8EJ, UK.
Bone. 2010 Apr;46(4):1050-7. doi: 10.1016/j.bone.2009.11.036. Epub 2009 Dec 11.
Kyphoplasty is gaining in popularity as a treatment for painful osteoporotic vertebral body fracture. It has the potential to restore vertebral shape and reduce spinal deformity, but the actual clinical and mechanical benefits of kyphoplasty remain unclear. In a cadaveric study, we compare the ability of vertebroplasty and kyphoplasty to restore spine mechanical function, and vertebral body shape, following vertebral fracture.
Fifteen pairs of thoracolumbar "motion segments" (two vertebrae with the intervening disc and ligaments) were obtained from cadavers aged 42-96 years. All specimens were compressed to induce vertebral body fracture. Then one of each pair underwent vertebroplasty and the other kyphoplasty, using 7 ml of polymethylmethacrylate cement. Augmented specimens were compressed for 2 hours to allow consolidation. At each stage of the experiment, motion segment stiffness was measured in bending and compression, and the distribution of loading on the vertebrae was determined by pulling a miniature pressure transducer through the intervertebral disc. Disc pressure measurements were performed in flexed and extended postures with a compressive load of 1.0-1.5 kN. They revealed the intradiscal pressure (IDP) which acts on the central vertebral body, and they enabled compressive load-bearing by the neural arch (F(N)) to be calculated. Changes in vertebral height and wedge angle were assessed from radiographs. The volume of leaked cement was determined by water displacement. Volumetric bone mineral density (BMD) of each vertebral body was calculated using DXA and water displacement.
Vertebral fracture reduced motion segment compressive stiffness by 55%, and bending stiffness by 39%. IDP fell by 61-88%, depending on posture. F(N) increased from 15% to 36% in flexion and from 30% to 58% in extension (P<0.001). Fracture reduced vertebral height by an average 0.94 mm and increased vertebral wedging by 0.95 degrees (P<0.001). Vertebroplasty and kyphoplasty were equally effective in partially restoring all aspects of mechanical function (including stiffness, IDP, and F(N)), but vertebral wedging was reduced only by kyphoplasty (P<0.05). Changes in mechanical function and vertebral wedging were largely maintained after consolidation, but height restoration was not. Cement leakage was similar for both treatments.
Vertebroplasty and kyphoplasty were equally effective at restoring mechanical function to an injured spine. Only kyphoplasty was able to reverse minor vertebral wedging.
椎体后凸成形术作为治疗骨质疏松性椎体骨折的一种方法越来越受到关注。它具有恢复椎体形状和减少脊柱畸形的潜力，但椎体后凸成形术的实际临床和机械效益仍不清楚。在一项尸体研究中，我们比较了椎体成形术和后凸成形术在椎体骨折后恢复脊柱力学功能和椎体形状的能力。
从 42-96 岁的尸体中获得 15 对胸腰椎“运动节段”（两个椎体和相邻的椎间盘和韧带）。所有标本均受压以诱导椎体骨折。然后，每对中的一个进行椎体成形术，另一个进行后凸成形术，使用 7 毫升聚甲基丙烯酸甲酯水泥。增强后的标本在压缩下放置 2 小时以允许固结。在实验的每个阶段，通过在椎间盘内拉动微型压力传感器来测量运动节段的弯曲和压缩刚度，并确定椎体上的加载分布。在 1.0-1.5kN 的压缩载荷下，在弯曲和伸展姿势下进行椎间盘压力测量。它们显示了作用于中央椎体的椎间盘内压力（IDP），并计算了神经弓的压缩载荷（F（N））。从射线照片评估椎体高度和楔形角度的变化。通过水置换确定泄漏水泥的体积。使用 DXA 和水置换计算每个椎体的容积骨密度（BMD）。
椎体骨折使运动节段压缩刚度降低了 55%，弯曲刚度降低了 39%。IDP 下降了 61-88%，取决于姿势。在弯曲时，F（N）从 15%增加到 36%，在伸展时从 30%增加到 58%（P<0.001）。骨折平均降低了 0.94 毫米的椎体高度，并增加了 0.95 度的椎体楔形（P<0.001）。椎体成形术和后凸成形术在部分恢复力学功能的所有方面（包括刚度、IDP 和 F（N））同样有效，但仅后凸成形术可减少椎体楔形（P<0.05）。固结后，力学功能和椎体楔形的变化基本保持不变，但高度恢复不变。两种治疗方法的水泥渗漏相似。
椎体成形术和后凸成形术在恢复受伤脊柱的力学功能方面同样有效。只有后凸成形术才能逆转轻微的椎体楔形。
