Stokes Ian A, Mente Peter L, Iatridis James C, Farnum Cornelia E, Aronsson David D
University of Vermont, Burlington, Vermont 05405, USA.
J Bone Joint Surg Am. 2002 Oct;84(10):1842-8. doi: 10.2106/00004623-200210000-00016.
Mechanical compression and distraction forces are known to modulate growth in vertebral growth plates, and they have been implicated in the progression of scoliosis. This study was performed to test the hypothesis that growth differences produced by sustained compression or distraction loading of vertebrae are associated with alterations in the amount of increase in the height of growth plate chondrocytes in the growth direction.
Compression or distraction force of nominally 60% of body weight was maintained for four weeks on a caudad vertebra of growing rats by an external apparatus attached, by means of transcutaneous pins, to the two vertebrae cephalad and caudad to it. Growth of the loaded and control vertebrae was measured radiographically. After four weeks, the animals were killed and histological sections of the loaded and control vertebrae were prepared to measure the height of the hypertrophic zone (average separation between zonal boundaries), the mean height of hypertrophic chondrocytes, and the amount of increase in cell height in the growth direction.
Over the four weeks of the experiment, the growth rates of the compressed and distracted vertebrae averaged 52% and 113% of the control rates, respectively. The reduction in the growth rate of the compressed vertebrae was significant (p = 0.002). In the compressed vertebrae, the height of the hypertrophic zone, the mean chondrocyte height, and the amount of increase in cell height averaged 87%, 85%, and 78% of the control values, respectively, and all were significantly less than the corresponding control values. In the distracted vertebrae, these measurements did not differ significantly from the control values. The height of the hypertrophic zone and the mean chondrocyte height correlated with the growth rate (r (2) = 0.29 [p = 0.03] and r (2) = 0.23 [p = 0.06], respectively), when each variable was expressed as a proportion of the control value. The percentage changes in the measurements of the chondrocytic dimensions relative to the control values were smaller than the percentage changes in the growth rates, a finding that suggested that the rate of chondrocytic proliferation was also modulated by the mechanical loading.
Mechanical loading of tail vertebrae in rats modulated their growth rate, which correlated with changes in the height of hypertrophic chondrocytes. The effects of compression were greater than those of distraction.
Information about the growth rate and chondrocytic response to mechanical loads in rat vertebrae undergoing mechanically modulated growth will be helpful in determining how human vertebral growth might respond to altered loading states during progression or treatment of scoliosis and other growth-related angular skeletal deformities.
已知机械压缩力和牵张力可调节椎骨生长板的生长，且与脊柱侧弯的进展有关。本研究旨在验证以下假设：椎骨持续受压或牵张负荷所产生的生长差异与生长板软骨细胞在生长方向上高度增加量的改变有关。
通过经皮针将外部装置连接到生长中大鼠的尾椎及其上方和下方的两个椎骨，对尾椎施加相当于体重60%的压缩力或牵张力，持续四周。通过X线摄影测量加载椎骨和对照椎骨的生长情况。四周后，处死动物，制备加载椎骨和对照椎骨的组织切片，以测量肥大带的高度（带边界之间的平均间距）、肥大软骨细胞的平均高度以及细胞在生长方向上的高度增加量。
在实验的四周内，受压椎骨和牵张椎骨的生长速率分别平均为对照速率的52%和113%。受压椎骨生长速率的降低具有统计学意义（p = 0.002）。在受压椎骨中，肥大带的高度、软骨细胞的平均高度以及细胞高度的增加量分别平均为对照值的87%、85%和78%，均显著低于相应的对照值。在牵张椎骨中，这些测量值与对照值无显著差异。当将每个变量表示为对照值的比例时，肥大带的高度和软骨细胞的平均高度与生长速率相关（r (2) = 0.29 [p = 0.03]和r (2) = 0.23 [p = 0.06]）。软骨细胞尺寸测量值相对于对照值的百分比变化小于生长速率的百分比变化，这一发现表明软骨细胞增殖速率也受到机械负荷的调节。
大鼠尾椎的机械负荷调节了其生长速率，这与肥大软骨细胞高度的变化相关。压缩的影响大于牵张。
关于经历机械调节生长的大鼠椎骨生长速率和软骨细胞对机械负荷反应的信息，将有助于确定在脊柱侧弯和其他与生长相关的角状骨骼畸形的进展或治疗过程中，人类椎骨生长如何对改变的负荷状态做出反应。
