Experimental scoliosis in an immature goat model: A method that creates idiopathic-type deformity with minimal violation of the spinal elements along the curve

Study Design. Experimental scoliosis was created in an immature goat model. Objectives. To create a progressive, structural, idiopathic-type, lordoscoliotic curve convex to the right in the thoracic spine of the immature goat while maintaining the anterior and posterior elements of the spine along the maximal curve in a pristine state. Summary of Background Data. Progressive scoliotic curves in a small animal model have been created using a posterior asymmetric tether. However, attempts in larger animal models have had less success and typically required violation of the spinal elements. Methods. Scoliosis was created in 40 Spanish Cross X female goats ( age 1 - 2 months, weight 8 - 12 kg) using a left posterior asymmetric tether from T5 to L1. Convex rib resection and concave rib tethering from T8 to T13 were performed before compression across the rigid construct. Goats were followed over a 6- to 15-week period with serial radiographs to document progression of the deformity. Results. Of the 40 goats that underwent posterior assymetric tethering with rib procedures, 7 ( 18%) encountered substantial complications ( five deaths and two neurologic injuries). Of the 33 available for analysis, 27 goats (82%) developed progressive, structural, idiopathic-type, lordoscoliotic curves in convex to the right in the thoracic spine. All curves demonstrated characteristic radiographic features of idiopathic scoliosis including significant displacement of the apical vertebra from the midline, wedging of both the vertebral bodies and discs, rotation, and decreased flexibility. Initial scoliosis after posterior asymmetric tethering measured 42degrees on average ( range 33 - 50degrees) and progressed to 60degrees on average ( range 44 - 73degrees) over 6 to 15 weeks. The average progression of +18degrees (range 6 - 37degrees) was statistically significant ( P < 0.001). Conclusions. This study establishes an experimental model for scoliosis that creates progressive, structural, idiopathic-type, lordoscoliotic curves convex to the right in the thoracic spine of the immature goat with high statistical significance ( P < 0.001). In addition, this method of experimental scoliosis creation avoids violation of the spinal elements throughout the maximal portion of the curve providing an ideal opportunity subsequent study of the deformity.