[A model of lumbar disc degeneration on the early stage in rhesus monkey with minimally invasive technique].

Objective: To establish a novel model of lumbar disc degeneration on the early stage in the rhesus monkey using percutaneous needle puncture guided by CT.

Methods: (1) Thirteen rhesus monkeys aged from 4 to 7 years, female 7 and male 6 were selected for establishing a model of the early stage of lumbar disc degeneration. (2)13 monkeys, 91 discs were divided into 3 groups: 64 discs from L1/2 to L5/6 were percutaneous punctured with a needle 20G as experimental group and 1 disc with a needle 15G as puncture control group and 26 discs were not be punctured from L6,7 to L7-S1 as control group. (3) Lumbar disc localization for needle puncture was guided by CT. All discs were examined by MRI, the HE, Masson's trichrome, Safranine-O and immunohistochemical staining of type II collagen before disc puncture and after puncture at 4, 8 and 12 weeks.

Results: MRI: (1) Experimental group: Pfirmann's Grade I was shown at postoperation 4, 8 and 12 weeks; (2) Puncture control group: Grade III was shown at postoperation 4 weeks and Grade IV at 8 weeks; (3) CONTROL GROUP: Grade I was shown at postoperation 4, 8 and 12 weeks. Histological examination: (1) In experimental group, there was no any change at postoperation 4 weeks, and the cell population of the nucleus was decreased at 8 weeks and more decreased at 12 weeks in HE. (2) There was no any change at postoperation 4 weeks, the clefts among the lamellae of the annulus fibrosus (AF) were shown at 8 weeks and more wider of the clefts of AF at 12 weeks in Masson's trichrome. (3) No any change was shown at postoperation 4 weeks, proteoglycan were progressively decreased at 8 and 12 weeks in Safranine-O. (4) No statistically significant difference in positive rate was observed at 4 and 8 weeks compared with control group in immunohistochemical staining of type II collagen. There was statistical difference at 12 weeks compared with control group (P<0.05). In puncture control group postoperation 8 weeks, the morphology of cell of nucleus pulposus was not clear in HE. The wider clefts of lamellae of the AF were shown in Masson's trichrome. The proteoglycan was obviously decreased in Safranine-O. Immunohistochemical staining collagen II synthesized was decreased. In normal control group, no any change was shown at 4, 8 and 12 weeks.

Conclusions: The degeneration of lumbar intervertebral disc on the early stage could be induced by the percutaneous needle puncture (20G) to the annulus fibrosus. The assessment of disc degeneration on early stage is not shown on MRI and only confirmed by histological examination.