| Objective To explore the affect on the cervical stability after 1~3 cervical discectomy and the effect of bone grafting and internal fixation on the recovery of cervical stability.Methods 10 C2-T1 spine specimens of fresh adult male corpses, from age 21 to 38. 31 years old on average, were produced integrally. Muscles attached on the spine were cut away and the supraspinous ligament, interspinous ligament, flavum ligament and the articular capsules were carefully reserved. All the above specimens were sealed in double layers plastic bags at -20C in refrigerator from 26 to 38 days, 31 days on average. X-ray films of anteroposterior position, lateral position and oblique position of each specimen were taken before experiment to prove that each specimen has no osseous structure abnormality. The specimen wasdefrosted naturally at room temperature before experiment. The two sides of the specimen was hold by special clips. The space between the clips and the spine was filled and fixed tightly using auto-coagulate tooth support powder to keep the clips parallel to each other. Most of the anterior part of C3-4 C4-5 C5-6 disks were removed using trephine, the posterior longitudinal ligament was reserved integrally. One to three segmental spinal injury models were established. Iliac osseous mass was acquired by trephine from the same corps to make bone graft model. Based on the bone-grafting model, Orion steel plate with corresponding length was selected to establish anterior internal fixation model. The angle of the Orion plate screws to the cerebral side and the caudle side was 15 degree, respectively. Locking screws were used to prevent the receding of the fixation screws. All the experiments were progressed under non-destructive principle. Ten tests were done on these 10 specimens respectively. There were as following. 1. integrity model, 2.one segmental diskectomy; 3. one segmental diskectomy with bone grafting; 4. one segmental diskectomy with bone grafting and anterior steel plate internal fixation; 5.two segmental diskectomy; 6.two segmental diskectomy with bone grafting; 7.two segmental diskectomy with bone grafting and anterior steel plate internal fixation; 8. three segmental diskectomy; 9. three segmentaldiskectomy with bone grafting; 10. three segmental diskectomy with bone grafting and anterior steel plate internal fixation. The loading point and the loading weight were defined according to the result of advanced-experiment. Compression test was done with the loading weight 300N. the loading point was at the right upper side of the specimen. The loading speed was 6mm/min. When the loading weight reached the pre-devised number, it would stay for 20s to detect the displacement of the middle point of the anterior border of C5 on sagittal plane. Putting 2Nm loading on the cervical specimen to bend it to the left side to did the lateral bending test. The loading speed was 6mm/min. When the loading weight reached the pre-devised number, it would stay for 20s to detect the displacement of the middle point of the anterior border of C5 on coronal plane. The cervical specimen was put on the electron torsion machine to detect the torsion test. The torsion loading was 2Nm with the loading speed 150 /min. When the loading weight reached the pre-devised number, it would stay for 20s to record the torsion angel of the cervical spine on axis. The loading was applied in the even speed during integrity test. The sensor was connected to the computer to record the curve of loading-displacement. Three times loading/disloading cycles were repeated before each detection. The number of the fourth time was measured to reduce viscoelaticity effect. Single factor analysis ofvariance was done using SPSS 10.0 software. Obvious difference could be defined if p<0.05.Results Severe cervical instability at multiple directions could be produced after diskectomy. The stability of the cervical spine after simple bone grafting at the intervertabral space was lower than that of integral cervical spine. The stability incre...
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