幼猪脊柱侧凸模型中椎体生长板组织学变化的定量研究

目的 探讨幼猪脊柱侧凸模型中椎体生长板在不对称力学负荷下的组织学变化.方法选择13只雌性约克夏幼猪(6周龄,6～8 kg),实验组8只幼猪采用后路分段小切口单侧栓系的方式建立脊柱侧凸模型,术后8周,取出内固定,继续观察8周后处死.对照组5只作相同切口暴露,植入螺钉和钢缆,不予栓系,观察16周后处死.获取实验组侧凸顶椎(对照组在术后16周时相应节段取材)生长板并分为凸凹两侧以进行对比,石蜡包埋,脱钙切片,HE染色,镜下测量肥大层厚度、肥大层细胞巢面积、巢内细胞个数及增殖层细胞数等指标.结果 实验组中7只幼猪成功建立了脊柱侧凸模型,术后即刻Cobb角平均为27.8°,经过8周栓系,进展为59.3°.栓系去除后8周,侧凸仍然稳定在55.2°.对照组幼猪均未出现脊柱侧凸等畸形.实验组凹侧肥大层软骨细胞数量少、形态异常、排列不规则,凸侧软骨细胞增殖活跃,肥大层明显增厚.实验组椎体生长板肥大层厚度在凸凹侧对比,差异有统计学意义(凸侧460.3±26.0 μm,凹侧318.5±72.1 μm,P＜0.05),而对照组左右侧对比,差异无统计学意义(左侧480.4±93.4μm,右侧521.5±117.8 μm,P＞0.05).实验组凸凹侧的肥大层细胞巢面积为(18 269.6±3717.4)μm2和(9 719.0±1 979.7)μm2,巢内细胞数为12.9±2.5和8.3±1.0,差异有统计学意义(P均＜0.05),而增殖层细胞数差异无统计学意义(凸侧139.0±44.7,凹侧125.0±24.0,P＞0.05).对照组左右侧肥大层细胞巢面积为(17 855.2±6 844.0)μm2和(16 610.0±7 009.9)μm2、巢内细胞数为12.2±2.0和12.6±2.9)、增殖区细胞数为127.3±16.3和130.6±31.2,差异均无统计学意义(P＞0.05).结论 幼猪脊柱侧凸模型中,在不对称力学负荷下,顶椎凹侧生长板软骨细胞的生长明显受到抑制,且以肥大层软骨细胞更为显著,使椎体凹侧纵向生长显著小于凸侧,导致椎体楔形变.

Histomorphological change of growth plate under asymmetrical loading in porcine scoliosis model

Objective To explore the histological changes of vertebral growth plates under asymmetrical loading in porcine scoliosis model (PSM).Methods A total of 13 female Yorkshire pigs with an age of 6 weeks and a weight range of 6 8 kg were selected.In PSM group,8 pigs were instrumented and tethered ipsilaterally through 3 separate incisions.After 8 weeks,posterior instrumentation was removed.The animals were observed for 8 more weeks.In control group,internal fixation of spine was performed without tethering.After sacrificing,spines were harvested for histological study.The specimens were embedded in paraffin,decalcified and stained by hematoxylin & eosin (HE) for histomorphometry.The thickness of hypertrophic zone in iliac cartilage,area and number of chondrocytes in cell-nest and number of proliferative chondrocytes were analyzed by ImagePro Plus.Results In PSM group,7 pigs developed idiopathic-type scoliosis.The mean coronal Cobb's angle was 27.8 postoperatively and progressed to 59.3 after a tethering period of 8 weeks.The average scoliosis was 55.2 at an average of 8 weeks after tethering removal.No scoliosis was found in control group.In PSM group,the number of chondrocytes of hypertrophic zones was fewer at concave side than that at convex side.And irregular arrangement of chondrocytes was present in hypertrophic zones.In PSM group,inter-side thickness of hypertrophic zone differed significantly (convex:460.3 ±26.0μm,concave:318.5 ± 72.1 μm,P＜0.05).No inter-side differenee existed between growth plate in control group (left:480.4 ± 93.4μm,right:521.5 ± 117.8 μm,P＞0.05).At convex side,average area of cell-nest and average number of cells in cell-nest were larger than those at concave side in PSM group (18 269.6 ± 3 717.4 vs 9 719.0 ± 1 979.7 μm2,P＜0.05;12.9 ± 2.5 vs 8.3 ± 1.0,P＜0.05).However,no inter-side difference existed between number of proliferative chondrocytes (convex:139.0 ± 44.7,concave:125.0 ± 24.0,P＞0.05).In control group,no inter-side difference existed between average area of cell-nest (17 855.2 ± 6 844.0 vs 16 610.0 ± 7 009.9 μm2),average number of cells in cell-nest (12.2 ± 2.0 vs 12.6 ± 2.9) or number of proliferative chondrocytes (127.3 ± 16.3 vs 130.6 ± 31.2)(all P＞0.05).Conclusions In porcine scoliosis model,asymmetrical loading contributes to unbalanced bilateral growth and causes vertebral wedging.Growth activity on growth plate at concave side is highly suppressed so that there are significant reductions of cell number and zone height in hypertrophic zone.