| Low back pain is a commom disease in modern time.Disc is thought to be a main source for a large number of severe low back pain cases.This type of pain originating from the disc is called discogenic pain.It is estimated that 40%of chronic low back pain cases are caused by internal disc disruption(IDD).Radial anular tear is the transection of the lamellar structure of annulus fibrosus,which starts from the fissure of nucleus pulposus and pains will be caused when the fissure reaches the posterior 1/3 part of annulus fibrosus with a high density of nerve fibers.MB(methylene blue)is a kind of medicine frequently used in clinic.Clinical reseach indicate that it has effects for the treatment of IDD.But the mechanisms of action are not identified.The overall purpose of the present study was to establish a model of internal disc disruption(IDD)by injuring the inner layers of posterior annulus fibrosus of the tail of rat via the anterior side of intervertebral disc with needles of defined gauges.Histologic,imageologic and immunohistochemistric studies were performed to observe the progress of disc degeneration.And to study the mechanisms of the therapeutical effect for the degenerative disc of MB.Objective(1)To establish the animal model of internal disc disruption(IDD)to observe acute,subacute and chronic pathological change and imaging change of theinjured discs.(2)To study the possible mechanisms of the therapeutical effect for the degenerative disc of MB.Method 18 old rats,weight 300-350g).Using 18G puncture pinhead in parallel with the adjacent upper and lower endplates,the fibrosus of Tai15/6 intervertebral discs was penetrated via the anterior side of intervertebral disc as the experimental intervertebral disc.Tai14/5 was treated as above,as the positive control intervertebral disc.As the intact control intervertebral discs,the same operation as above was not performed on the Tai14/5 intervertebral discs.X-rays,MRI scan were performed on the tail intervertebral discs of each experimental animal before and 11weeks after operation.HE and Masson stain was performed,and the morphological characteristics of intervertebral disc nucleus pulposus were observed under light microscope at each experimental time points after operation (2 Weeks,6 Weeks and 11 Weeks).MB was injected in Tai15/6 intervertebral discs at the time of 11weeks after operation.Nerves in intervertebral discs was examined using immunohistochemistry withSP(nerve transmitter)and PGP9.5＜nerve fibre) antibody at the time of 12 weeks after operation.ResultsFor the Tai14/5,Tai15/6 fibrosus intervertebral discs,the anterior annulus fibrosus injured disruption did not healed.Qualitative X-rays and MRI analysis were performed on the degenerative changes of intact and injured intervertebral discs.All the Tai14/5 and Tai15/6 nucleus pulposus signal intensity were lower than the preoperative values.Nerves were observed in the anterior 1/4 regions of Tai14/5 discs easily,in addition,they also were observed further ingrowth into the disc along the puncture tract and periphery tissue,the immunopositive cells were absent in the same of regions of Tai16/7 discs.Nerves were rarely seen in Tai15/6 discs at 12 weeks postoperatively.SP,PGP9.5 immunopositive cells were not observed in the nucleus pulposus of any disc examined.Conclusion(1)After the all layers of anterior annulus fibrosus of the tail of rats were injured via the anterior side of intervertebral disc,and the tails was reflexed after that,the disruption was diffculty to heal,the intervertebral disc degeneration occurred in the early stage.(2)After the all layers of anterior annulus fibrosus of the tail of rats were injured via the anterior side of intervertebral disc,and the tails was reflexed after that,there were a reliable animal model of intervertebral disc degeneration to be developed.(3)This finding suggests that discogenic low back pain was closely associated with nerve ingrowth.(4)MB may be relieve the symptom of IDD via inhibit nerve ingrowth. |
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