Animal Experiment on CO2 Laser Discectomy

本研究旨在探讨年龄对椎间盘内治疗后椎间盘组织病理学改变的影响。材料与方法：选用青年猴15只，老年猴7只。在全身麻醉下，经腹膜入路暴露腰椎。每个椎间盘注入木瓜凝乳酶(500U/0.1ml)或软骨素酶-ABC(2U/0.1ml)。另外两个椎间盘接受了CO2激光摘除或髓核摘除。治疗后，每隔96周处死动物，获得腰椎。拍摄标本的T2加权MR(2.0Tesla)图像以评估水分含量。结果：治疗2天后，所有椎间盘在T2加权像上均表现为信号强度降低。治疗48周后，幼猴的所有椎间盘都显示出与正常对照相似的表现。然而，在老年猴子中，所有的椎间盘在治疗后48周甚至96周都表现出信号减弱。藏红素-O染色显示髓核、纤维内环和软骨终板中蛋白多糖消失。这些变化主要见于老年组。结论：激光腰椎间盘切除术治疗腰椎间盘突出症具有独特的优势，但治疗后腰椎间盘退变与受试者年龄相关。

This study was undertaken to investigate the influence of the subject age to histopathological changes of the intervertebral discs after intradiscal therapy.MATERIALS AND METHODS: Fifteen young monkeys and seven aged monkeys were used. Under general anesthesia, lumbar spine was exposed through transperitoneal approach. Chymopapain(500u/0.1ml) or Chondroitinase-ABC (2u/0.1ml) was injected into each disc. Two other discs were treated by CO2 laser discectomy or nucleotomy. After treatment, the animals were sacrificed at prescribed intervals of up to 96 weeks, and lumbar vertebral columns were obtained. T2-weighted MR(2.0Tesla) images of the specimen was taken to evaluate water content. Safranin-O stainability was also compared.RESULTS: All discs showed decreased signal intensity on T2- weighted MR images two days after treatment. Forty-eight weeks after treatment, all discs showed similar to those of the normal control in the young monkeys. However, in aged monkeys, all discs demonstrated decreased signal 48 and even 96 weeks after treatment. Safranin-O staining revealed the disappearance of proteoglycan from the nucleus pulposus, inner annulus fibrosus, and cartilagenous endplates of the treated discs. These changes predominated in the aged group. Although Safranin-O stainability was recovered within 48 weeks in the young group, which was remained lost in the aged group.CONCLUSION: This study suggests that laser discectomy offers unique advantages in the treatment of disc herniation, but also demonstrated that the disc degeneration after treatment correlated with the subject age.