脊椎截骨后脊柱短缩安全范围的实验研究

The safety range of acute shortening of spinal column after total vertebrectomy

目的探讨单脊椎切除对脊髓形态和功能的影响，并确定脊柱短缩的安全范围。方法采用120只4巧月龄健康雄性新西兰大耳白兔，随机分为单椎板切除（A）组、双椎板切除（B）组及三椎板切除（C）组，每组40只，行k全脊椎切除术。再根据压缩L1椎体总体高度的25％、50％、75％及100％将每组分成4个亚组，每亚组10只。测量不同脊柱短缩程度下硬膜囊长度、迂曲最大处硬膜囊直径、硬膜囊-神经根交角、硬膜囊矢状位迂曲角、术中体感诱发电位变化情况及Tarlov评分。术后72h处死动物，HE染色观察脊髓皱缩最严重部位病理改变情况。结果压缩高度≤总体高度50％时，各组硬膜囊均出现一定程度的形变，但术中脊髓功能监护及术后Tarlov评分差异无统计学意义（P〉0．05）；病理切片仅A组可见脊髓出现少量出血灶。压缩高度为总体高度75％时，A组硬膜囊形变及Tarlov评分与术前相比差异均有统计学意义（氏0．05），且与B组及C组比较差异有统计学意义（P〈0．05）；A组病理切片可见髓内出血灶增多、白质水肿，而B组及C组仅出现少量髓内出血灶。完全压缩时，B组及C组硬膜囊形变及术后Tarlov评分差异有统计学意义（P〈0．05）；病理切片见A组出现大片出血、神经元皱缩，而B组及C组可见髓内较多出血灶。结论脊柱短缩的高度及椎板切除范围对脊髓形态及功能有较大影响。单椎板切除组压缩安全范围仅为总体高度的50％，而双椎板及三椎板切除组可安全压缩至75％。同样压缩高度下，增加椎板切除范围可有效改善脊髓迂曲、避免术中脊髓皱缩造成的脊髓损伤。

Objective To investigate the change of morphologic and neurological function of spinal cord after acute spinal column shortening, to enlighten the safety range of acute shortening on the spinal column following total spondylectomy. Methods One-hundred and twenty New Zealand white rabbits were used as experimental animals. The animals were randomly divided into three groups： single-level laminecto- my group（A）, double-level laminectomy group （B）, and three-level laminectomy group（C）. Each group was divided into four subgroups according to the percent of spinal column shortening： 25%, 50%, 75% and 100% subgroups. After total vertebrectomy of L3, we performed spinal column shortening and measured the diameter and length of spinal cord, angle between spinal cord and L3 nerve root, the latency and amplitude of somatosensory evoked potential （SEP） accordingly. Tarlov scales were recorded 72 h after surgery, and HE stain was used to observe the histopathological changes of the spinal cord. Results The morphology and neurological function of spinal cord had no significant change when spinal column shortening was less than 50% in all groups （P〉0.05）. The morphology and neurological function were significantly changed when spinal column shortening was 75% in group A （P〈0.05）, and massive hemorrhages and shrinkage of neurons were observed in the pathological sections. The morphology and neurological function of spinal cord had no significant change until spinal column shortening was more than 75% in group B and C. There was no significant difference between group B and C. Conclusion The safety range of spinal column shortening after vertebrectomy and single laminectomy was no more than 50% of vertebral height. However, it can be extended to 75% by performing double or three levels laminectomy to avoid spinal cord injury caused by spinal cord kinking. The range of laminectomy has obvious effect on the morphologic change and neurological function of spinal cord after spinal column shortening.