An Primary Study Of Mechanical Modulation Of Spinal Growth

Objective: To evaluate the feasibility and the mechanism of the method that long or short segment mechanical modulation of spinal growth.Background: Currently, bracing and surgical treatment were commonly used dealing with idiopathic scoliosis. However, there are still some severe problems and complications.Methods: 1. Six specimens of the goat vertebrae were used to detect the anatomy characteristic and to design goat pedicule screws. Six goats were used in preliminary experiment of unilateral pedicle screw tethering to create scoliosis model. 2. 14 goats, age: 5-8 weeks, weight: 6-8 kilogram, were used performing unilateral pedicle screw tethering in combine with convex rib resection. 3. All animal models were classified in 2 groups randomly. Control group: remove the posterior tether, no treatment. Correct group: removing of the posterior tether and the stapling of anterior spinal epiphysis were performed simultaneously, and serial X-ray were performed. 4. 2 goats were selected randomly in each group to perform CT 3-demensional reconstruction. 5. Tetracycline was injected intramuscular at the 13^th and 3^rd before the animal sacrifice to double labeling the growth rate of the concave and convex side of the scoliosis. 6. Histology study: fluorescence microscope was use observing tetracycline labeling before Giemsa staining. With the help of microscope, the interface of bone-screw, the height of the intervertebral disc of the concave and convex side, etc, was investigated.Results: 1. Among 14 female goats, 1 goat died for overdose of anesthesia, 11 goats showed scoliosis with convex toward to the right side, and the curve increased with time (91.7%), only 1 goat exhibited no progression (8.3%). The initial curves created after the procedures measured an average of 29.0° (23.0°-38.5°) and progressed to an average of 43.0° (36.0°-58.0°) over 8 to 10 weeks. The immediate curvature did have a highly significant correlation with the final curvature (p<0.01). 2. Control group: The initial curves after the procedures measured an average of 40.8° (28°-56°), theaverage Cobb angle was 42.5° (30-58°) after 8 weeks, no statistics difference are found (p>0.05). Treatment group: the initial curves after the procedures measured an average of 44.5° (36°-57°), the Cobb angle decreased and the average was 42.5° (30-58°) after 8 weeks. There are statistics difference between the initial and final curves (p<0.05). 4. CT 3-dimentional reconstruction: (1) control group: structural change can be found in the spinal curvature, and the structure features is similar to those of AIS. (2) Treatment group: the location of all staples are perfect, no one broke, loosen. 5. Tetracycline fluorescent labeling. Control group: there are difference between concave and convex side in the mineralizing deposition distance (p<0.05). 6. Giemsa stain: (1) control group: The distances between growth plate and endplate in the concave side are lower than against side. The quantity of the chondrocytes in concave side decreased, paramorphia and disarrangement of epiphyseal cartilage cell. The cell multiplication of convex side is active, the layer hypertrophia is thicken, the cell nucleus are spherical, the hypertrophia cells are concentrated and arranged like a cone structure. New chondrocyte are concentrated in the cartilage multiplication nests. (2) Treatment group: the metals were surrounded with fibrous tissues. Conclusion: 1. It is possible to create scoliosis model by unilateral pedicel screws asymmetric tethering. 2. The animal model created by this method is a structure scoliosis which may be a phenomena rather than be caused etiologically. 3. The method creating scoliotic animal model is a fusionless technique, so, the models created by this method are suitable to those who want to study the correction of the scoliosis. 4. The mechanism of axial loading restrict the growth plate of vertebra may be interfering the multiplication and hypertrophia of the chondrocyte, and is correlation with the paramorphia of epiphyseal chondrocyte, disarrange structure, the abnormal direction and condition of ossification.