CT-guided Establishment Of Non-compressive Lumbar Nucleus Pulposus Induced Nerve Root Injure In A Piglet Model

Objective: To assess the feasibility of CT-guided establishment ofnon-compressive lumbar nucleus pulposus induced nerve root injure in apiglet model. And determine the relations between the histologic changs ofthe nerve root and MR features in T1WI, T2WI and DWI.Materials and Methods: A total of18Chinese mini-pigs wererandomly divided into six subgroups: the blank group,1,4,7,14and21daysgroup. Autologous nucleus pulposus, harvested from L1/2and L2/3discusing a rotary cutter, was then mixed with saline and become mixed liquidsuspension. For operation groups, autologous nucleus pulposus and saline wasthen injected into the epidural space as model groups and sham groups,respectively. All of the puncture produres were guided by computedtomography. MR neurography were performed using T1WI, T2WI and DWIwith fat saturation. Signal intensity on T1-and T2-weighted imaging andADC value of the nerve root were measured respectively. The mini-pigs weresccrificed at1,4,7,14, and21days and the nerve root were quickly removed.The histology and immunohistochemistry change of nerve root were observed.Statistical analyses were performed with SPSS statistical software (version16.0).Results:1. HE stain: Acute inflammatory cell infiltration was observedin model group since day1after surgery, with inflammatory cells graduallyincreased over time and peaked at14days. Inflammatory cell infiltration wereobserved in nerve fibers and epineurial membrane. Myelin breakdown wasobvious in the model group. Immunohistochemistry stain: Lymphocytes were observed in1,4,7,14and21days in model group. The proportion ofactivated T cells (CD8) was significantly higher in14and21days.2. Signalintensity on T1WI of the model group and sham group before modeling andpostoperative1,4,7,14, and21days of nerve root did not changesignificantly (P>0.05).3. Signal intensity on T2WI of the model group in1and4days increased slightly. There were no significant differences (P>0.05).The signal intensity on T2WI at7,14and21days in model group wasgradually increased and peaked at14days (393.0±31.4). There was astatistically significant difference (P <0.05). Differences were not foundbetween sham group before modeling and postoperative1,4,7,14, and21days (P>0.05). The singal intensity on T2WI of nerve root in model groupwas higher than that of sham group at7,14and21days (P <0.05).4. TheADC value in model group was gradually increased and peaked at14days as(1.49±0.13)×10-3mm2/s (P <0.05). In the sham group, ADC value increasedsignificantly in1day (P <0.05) and then gradually decreased (P>0.05). MeanADC values of model group were significantly higher than sham group at4,7,14and21days (P <0.05), whereas similar at1day (P>0.05).Conclusions:1. A non-compressive lumbar nucleus pulposus inducednerve root injure model was established successfully using computedtomography-guided percutaneous puncture technology in the piglet. Thesimple, reproducible method provided a more ideal animal model for thestudy of non-compressive lumbar disc herniation.2. The degree of nerve rootinjury induced by autologous nucleus pulposus can be evaluated by observingchanges in signal intensity on T2WI and ADC value on DWI.