| Background: Chronic compressive cervical myelopathy, which is often encountered in cases of cervical spondylotic myelopathy, cervical disc hemiation, cervical spinal canal stenosis, ossification of the posterior longitudinal ligament in the cervical spine, and extradual tumors within cervical spinal canal, is caused mechanically by some external compressive factors which compress the spinal cord. Morbidity due to it is an increasing health problem. Most researchers believe that neurological deficit is closed related to the extent of spinal cord compression and surgical decompression is an effective treatment. But the mechanisms of decompression have not been fully elucidated. At the present, the reports relating to the surgical decompression are associated with clinical experience. There are few reports about the mechanism of the decompression, especially on the cytomolecular level.With the development of aging population, morbidity due to chronic compressive cervical myelopathy increases gradually. More and more patients have had intends to choice surgical decompression to alleviate their pains. Because of the unclear mechanism of surgical decompression for neurological improvement, there remains much controversy about surgical indications and surgical timing. The unclear mechanism may objectively affect the postoperative outcomes evaluation. To clear the mechanism of surgical decompression for neurological improvement has become an urgent research in the spinal surgery.Biomedical development depends on the development of animal experimental science. Experimental animal models are widely used in all fields of medicine. Much basic knowledge and clinical experience of spinal surgery is come from experimental animal models. This study was conducted in order to establish an quantitative and duplicated experimental model which can be efficiently produce ventral spinal cord compression with an anterior metal screw implanted gradually and be useful in the studies on myelopathy due to chronic compressive cervical myelopathy. After anterior decompression, we observedthe relationship between postoperatively neurological improvement and related indexes by using neurological evaluation, cortical somatosensory evoked potentials(CSEP), magnetic resonance imaging, histopathological study and immunohistochemistrical study. Then we implored the pathophysiological mechanism of neurological improvement due to surgical decompression. Objectives:1. To establish an animal model of experimental chronic compressive cervical myelopathy.2. To know the neurological improvement procedures after decompressive surgery for chronic compressive cervical myelopathy.3. To observe the relationship between the decompression outcomes and the extent of compression and decompression timing.4. To explore the pathophysiological mechanism of neurological improvement due to surgical decompression.Material and methods:Twenty-seven China rabbits which underwent clinical chronic cervical cord compression produced by compress the ventral cervical cord gradually with an anterior screw implanted gradually, were evaluated in terms of motor function by using the modification of Tarlov s classification. The final motor function level were Grade 3 in all models . The rabbits were divided into four groups: Group I (n=15), middle compression with decompression, spinal canal involved 50%~60%; Group II (n=3), serious compression with decompression, spinal canal involved 61%~83%; GroupIII(n=3), middle compression with delayed decompression, spinal canal involved 50%~60%; GroupIV(n=6), compression without decompression, spinal canal involved 50%~60%; Then another 6 normal rabbits were used as control group.Modification of Tarlov s classification evaluation and cortical somatosensory evoked potentials(CSEP) were obtained before and on days 1,7,15,30 and 60 after decompression. MRI were performed to observe significant signal and construal changes in spinal cord. Microscopy, electron microscopy and immunohistochemistry were performed to f...
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