| Objective: This study made goat models for cervical anterior discectomy tricortical iliac crest autograft both with or without Orion cervical spine locking plate, observed the fusion rate of bone-graft, the height of interbody in fusion level by radiographic analysis; evaluated the stiffness of interbody in fusion level by biomechanical test; observed trabecular bridge reconstruction and bone fusion by light microscope. Comparesions were draw with radiographic, biomechanical and histologic data in order to discuss the value of cervical spine locking plate in anterior cervical discectomy and fusion. Methods: 30 mature goats were used in this study. The goats weighted between 45 and 50 Kg and were all female. All of the goats underwent a surgical procedure under general endotracheal anesthesia using intravenous valium and ketamine for induction and inhalation halothane for maintenance anesthesia. The goats were divided into six treatment groups consisting of five goats each. Group Ia underwent anterior cervical discectomy and fusion (ACDF) with plating at C2-3; Group Ib underwent ACDF at C2-3. Group IIa underwent ACDF with plating at C2-3, C3-4;Group IIb underwent ACDF at C2-3, C3-4. Group IIIa underwent ACDF with plating at C2-3, C3-4, C4-5; Group IIIa underwent ACDF at C2-3, C3-4, C4-5. All of the surgery used autogenous tricortical iliac crest grafts. The anterior neck was prepared in a sterile fashion and a right anterolateral approach to the cervical spine was carried out through a longitudinal skin incision. To incise the skin, fascia, tetragonus and reach to longus coli and ventral fascia of cervical spine via the gap between vagina carotica and trachea, esophagus. The longus coli muscle and ventral fascia of cervical spine was incised in the midline and the disc spaces at C2-3,C3-4,C4-5 exposed. Anterior cervical discectomies were carried out at each level by first excising the soft disc. Crest in front of cervical spine was excised, and to make surface of cervical spine to planus. End-plate and intervertebral cartilages were excised by trypesis. To make the hole rectagle by a curet, To wash by physiological saline, excise ferment. After tricortical iliac crest autograft being inserted in the hole. To wash by physiology ical saline. If the plate was installed, the surgical procedure was continued. Firstly, we choosed suitable Orion plate, bended it to contact the ventral surface of cervical spine. To install screw after punching. After installing , the animals were maintained under observation until fully recovered from general anesthesia. A soft bandage was applied to the neck. Neurological examinations were performed weekly along with monitoring of the animals eating habits, ambulatory activities and wound healing. No attempt was made to immobilive the animals necks. They received penicillin 80million unite intramuscular daily for 7 days. Routine anteroposterior and lateral radiographic films of the surgical sites were done immediately postoperatively to check the position of the grafts and plates. All of goats received lateral radiographic films of the surgical sites at 3, 6, 9 and 12 weeks. The radiographic films on the day of surgery and 12-week were compared to evaluate the change of the height of interbody in fusion level. 12-week radiographic films were analyzed for presence or absence of radiologic fusion. Fusion was identified by the absence of a radiolucent gap between the graft and the end-plate; and the presence of continuous bridging bony trabeculae at the graft-endplate junction. Biomechanical testing : The spine specimens were brought fresh to the Biomechanics Laboratory for biomechanical testing. The spines were mounted into frames. The biomechanical tests were performed on CSS-44000 tester. The load of forward bending was cycled from 0 to 200 newtons. The three were considered conditioning cycles for spinal connective tissues, with the third cycle used for analysis. Date acquisition was storaged in a computer date file. Histologic analysis: The plate was extracted. The vertebral spinal column itself was then sectioned using a saw. We obtained sagittal sections of the C2-3, C3-4, C4-5 disc spaces in the midline and harsted sagittal 5 mm thick slices of fusion zones. The slices were fix by fixative, decalcification, paraffin section, HE stain. Histological analysis included inspection of each of the fusion level for the determination of solid fusion.Histologically, fusion sites from all specimens consisted of mixture of fibrous tissue, cartilage and new bone. We evaluate the percentage of them. Data were analyzed using SPSS 11.0. Differences between groups were statistically analyzed using Students't test or Fisher's exact test. Results: No cervical spine or iliac crest wound infections occurred in all of goats. There were no neurologic complications. The animals restored normal diet at the first day postoperatively. Radiographic fusion rate: There was no significant difference between Group Ia ( 100%) and Group Ib (80%) (p>0.05); Group IIa (90%) was significantly higher than Group IIb (40%) (p<0.05); There was no significant difference between Group IIIa (46.7%) and Group IIIb (26.7%) (p>0.05); The change of height of interboby in fusion level: Group Ia [(0.68±0.24) mm] was significantly lower than Group Ib [(1.46±0.32) mm] (p<0.01); Group IIa [(1.22±0.19) mm] was significantly lower than Group IIb [(2.46±0.36) mm] (p<0.01); Group IIIa [(2.34±0.34) mm] was significantly lower than Group IIIb [(4.52 ±0.40) mm] (p<0.01). Biomechanical data: The dislocation of load of forward bending: Group Ia [(0.53±0.15) mm] was significantly lower than Group Ib [(1.39±0.43) mm] (p<0.01); Group IIa [(1.11±0.24) mm] was significantly lower than Group IIb [(1.93±0.41) mm] (p<0.01); Group IIIa [(1.63±0.27) mm] was significantly lower than Group IIIb [(2.96±0.43) mm] (p<0.01). The dislocation of load of backward bending: Group Ia [(0.77±0.28)mm] was significantly lower than Group Ib [(1.59±0.33) mm](p<0.01); Group IIa [(1.18±0.23) mm] was significantly lowethan Group IIb [(1.96±0.40) mm] (p<0.01); Group IIIa [(1.59±0.33) mm] was significantly lower than Group IIIb [(3.16±0.55) mm] (p<0.01). Histologic results: histologic fusion rateThere was no significant difference between Group Ia ( 100%and Group Ib (80%) (p>0.05); Group IIa (80%) wassignificantly higher than Group IIb (30%) (p<0.05); Therewas no significant difference between Group IIIa (40%) andGroup IIIb (13.3%) (p>0.05). Percentage of new bone, cartilagetissue and fibrous tissue in fusion area was not significantlydifferent between Group Ia and Group Ib, Group IIa and GroupIIb, Group IIIa and Group IIIb respectively. Conclusion: 1. In single-level ACDF, plating improved thefusion rate, but this difference was not statistically significantIn single-level ACDF, the fusion rate was satisfactory. Thechange of height of interbody in fusion level was less than 2mm . The plating was not supported in the single-level ACDF. 2In two-level ACDF, fusion rate was less, dislocation rate andpseudarthrosis rate were higher. The missing of the height ofinterbody in fusion level and cervical spine lordosis wereappearer. But in two-level ACDF and plating, fusion rate wasimproved, graft did not dislocate. The height of interbody infusion level was maintained well. Biomechaincal stiffness infusion level was improved. The plating maintained sagittaalignment of cervical spine, shared the load of graft. The... |
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