PURPOSE To determine the safe range of shortening the spinal column at middle thoracic spine and to observe the changes in blood-spinal cord barrier (BSCB), microglia/macrophage activation and inducible nitric oxide synthase (iNOS) activity after shortening-induced spinal cord injury. METHODS Dogs were allocated to four groups. Group A (control) underwent laminectomy of T7 without shortening the spinal column. Groups B, C and D had 1/3, 1/2, and 2/3 of T7 resected, respectively, followed by spinal shortening. Somatosensory evoked potential (SSEP) and hind-limb function were recorded periodically for 14 days after operation. Spinal cord blood flow (SCBF) and BSCB were detected at the acute phase of shortening. Microglia/macrophage reactions and iNOS activity were observed by immunohistochemistry. RESULTS Shortening of 1/3 of a vertebral height caused no significant changes in SSEP and hind-limb function after operation, whereas shortening of 1/2 of the height caused SSEP abnormality and paraparesis, and severe neurologic deficit of hind-limb was observed when the shortening reached 2/3 of the height. SCBF increased temporarily and showed a trend of recovery when the shortening was within 1/2 of a vertebral segment height. When it reached 1/2 or 2/3 of the height, SCBF at 6 h post-operation was 86.33% or 74.95% of the baseline, and an increasing BSCB permeability was observed. In the subsequent 7 days, obvious activation of macrophage and increased number of iNOS-positive cells were observed. CONCLUSION It is safe to shorten the spinal cord within 1/3 of a vertebral height in middle thoracic spine under two-segment laminectomy in canine. The BSCB disruption, macrophage activation, and increased iNOS activity were observed in the acute phase of the injury. These slides can be retrieved under Electronic Supplementary Material.

中文翻译：

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缩短中胸椎安全范围的一项犬类实验研究。

目的确定缩短胸中脊柱脊髓的安全范围，并观察缩短性脊髓损伤后的血脊髓屏障（BSCB），小胶质细胞/巨噬细胞激活和诱导型一氧化氮合酶（iNOS）活性的变化。 。方法将狗分为四组。A组（对照组）在不缩短脊柱的情况下进行了T7椎板切除术。B，C和D组分别切除了T7的1 / 3、1 / 2和2/3，然后进行了脊柱缩短。术后14天定期记录体感诱发电位（SSEP）和后肢功能。在缩短的急性期检测到脊髓血流（SCBF）和BSCB。通过免疫组织化学观察到小胶质细胞/巨噬细胞反应和iNOS活性。结果椎体高度缩短1/3不会引起SSEP和术后后肢功能的显着变化，而身高降低1/2则会导致SSEP异常和轻瘫，并且在观察到后肢严重神经功能缺损时缩短量达到高度的2/3。当缩短量在椎骨段高度的1/2以内时，SCBF暂时增加并显示出恢复的趋势。当其达到高度的1/2或2/3时，术后6 h的SCBF为基线的86.33％或74.95％，并且观察到BSCB渗透性增加。在随后的7天中，观察到巨噬细胞的明显活化和iNOS阳性细胞数量的增加。结论在犬二段椎板切除术中，将脊髓缩短至中胸椎椎高的1/3以内是安全的。在损伤的急性期观察到BSCB破坏，巨噬细胞激活和iNOS活性增加。这些幻灯片可以在电子补充材料下找到。