Newton Peter O, Upasani Vidyadhar V, Farnsworth Christine L, Oka Richard, Chambers Reid C, Dwek Jerry, Kim Jung Ryul, Perry Andrew, Mahar Andrew T
Rady Children's Hospital San Diego, 3030 Children's Way, Suite 410, San Diego, CA 92123, USA.
J Bone Joint Surg Am. 2008 Dec;90(12):2695-706. doi: 10.2106/JBJS.G.01424.
Spinal growth modulation by tethering the anterolateral aspect of the spine, as previously demonstrated in a nonscoliotic calf model, may be a viable fusionless treatment method for idiopathic scoliosis. The purpose of the present study was to evaluate the radiographic, histologic, and biomechanical results after six and twelve months of spinal growth modulation in a porcine model with a growth rate similar to that of adolescent patients.
Twelve seven-month-old mini-pigs underwent instrumentation with a vertebral staple-screw construct connected by a polyethylene tether over four consecutive thoracic vertebrae. The spines were harvested after six (n = 6) or twelve months (n = 6) of growth. Monthly radiographs, computed tomography and magnetic resonance imaging scans (made after the spines were harvested), histologic findings, and biomechanical findings were evaluated. Analysis of variance was used to compare preoperative, six-month postoperative, and twelve-month postoperative data.
Radiographs demonstrated 14 degrees +/- 4 degrees of coronal deformity after six months and 30 degrees +/- 13 degrees after twelve months of growth. Coronal vertebral wedging was observed in all four tethered vertebrae and progressed throughout each animal's survival period. Disc wedging was also created; however, in contrast to the findings associated with vertebral wedging, the tethered side was taller than the untethered side. Magnetic resonance images revealed no evidence of disc degeneration; however, the nucleus pulposus had shifted toward the side of the tethering. Midcoronal undecalcified histologic sections showed intact bone-screw interfaces with no evidence of implant failure or loosening. With the tether cut, stiffness decreased and range of motion increased in lateral bending away from the tether at both time-points (p < 0.05).
In this porcine model, mechanical tethering during growth altered spinal morphology in the coronal and sagittal planes, leading to vertebral and disc wedging proportional to the duration of tethering. The resulting concave thickening of the disc in response to the tether was not anticipated and may suggest a capacity for the nucleus pulposus to respond to the compressive loads created by growth against the tether.
如先前在非脊柱侧弯小牛模型中所证实的，通过束缚脊柱前外侧来调节脊柱生长，可能是一种治疗特发性脊柱侧弯的可行的非融合治疗方法。本研究的目的是评估在生长速率与青少年患者相似的猪模型中，脊柱生长调节6个月和12个月后的影像学、组织学和生物力学结果。
12只7月龄的小型猪接受了一种器械植入，该器械通过聚乙烯束带连接四个连续胸椎的椎弓根钉-螺钉结构。在生长6个月（n = 6）或12个月（n = 6）后取出脊柱。评估每月的X线片、计算机断层扫描和磁共振成像扫描（在取出脊柱后进行）、组织学结果和生物力学结果。采用方差分析比较术前、术后6个月和术后12个月的数据。
X线片显示生长6个月后冠状面畸形为14度±4度，生长12个月后为30度±13度。在所有四个被束带束缚的椎体中均观察到冠状椎体楔形变，且在每只动物的存活期内持续进展。椎间盘也出现了楔形变；然而，与椎体楔形变的结果相反，被束带束缚侧比未被束缚侧更高。磁共振成像未显示椎间盘退变的证据；然而，髓核已向束带束缚侧移位。中冠状面未脱钙组织学切片显示骨-螺钉界面完整，没有植入物失败或松动的迹象。在两个时间点，切断束带后，远离束带侧的侧弯刚度降低，活动范围增加（p < 0.05）。
在这个猪模型中，生长期间的机械束缚改变了脊柱在冠状面和矢状面的形态，导致椎体和椎间盘楔形变，且与束缚持续时间成比例。椎间盘因束带束缚而出现的凹面增厚是未预料到的，这可能表明髓核有能力对生长过程中对抗束带产生的压缩负荷做出反应。
