Scoliosis Model Created by Pedicle Screw Tethering in Immature Goats

Abstract

An in vivo model of scoliosis was established in immature goats. To assess the feasibility, reliability, and complications of the innovative animal model. Among the methods of creating a scoliotic model, posterior asymmetric tethering of spine yielded encouraging results. However, some shortcomings associated with the use of posterior asymmetric tether are apparent. Fourteen female goats (age: 5-8 weeks old, weight: 6-8 kg), were instrumented and tethered using unilateral pedicle screws and contralateral rib resections. Twelve of the goats were followed up for 8 weeks by serial radiography. Six goats were removed of the posterior load and no treatment was given. Two goats were selected randomly from the 6 animals and subjected to computed tomography (CT) three-dimensional reconstruction after another 8 weeks. All the 6 goats were killed and spine specimens were harvested for histologic study 16 weeks after observation. Radiographic observation showed that 12 goats developed scoliosis with convex toward the right side, and the curvature increased with time in 11 goats, and it remained unchanged in 1 animal. The angle immediately after the procedures averaged 29.0 degrees (23 degrees -38 degrees ) and increased to an average of 43.0 degrees (36.0 degrees -58.0 degrees ) over a period of 8 to 10 weeks, with average angle increment being 14.0 degrees (P < 0.001). The curvature ceased to increase in 6 goats during the subsequent 2 months after the tether were removed (P > 0.05). Three-dimensional CT reconstruction revealed that the vertebral bodies were wedged, the 2 sides of the thoracic skeleton were asymmetric, and the vertebrae in the major curve were rotated. Histologic study revealed that the goats remained in growth stage and the growth potential of 2 sides of the spine was not identical. Radiography and three-dimensional CT reconstruction of vertebrae revealed that the architectural alterations found in the model were similar to those of idiopathic-type deformity observed in clinical practice.