Experimental scoliosis in the rat: I. Methodology, anatomic features and neurologic characterization

The purpose of this study was to develop a simple and reproducible model of scoliosis In the rat without producing direct trauma to the spine, in order to both provide a system for the study of human scoliosis and to ultimately study the conditions under which distraction-induced trauma might occur. Right lateral curvatures were produced in three groups of rats (N = 36,59,25) at 18-21 days of age by suturing the inferior angle of the scapula to the ipsilateral bony pelvis. In the first group of animals, it was found that a minimum period of 6 weeks of tethering was required in order to produce permanent structural curvatures after release of the tethering sutures. In the second group of rats, a number of morphologic and histologic changes characteristic of human scoliosis were noted, Including apical wedging, deviation of the apical spinous process, pelvic'asymmetry, rib hump deformity, vertebral rotation, displacement of the nucleus pulposus, disorga¬nized columnization of disc cartilage cells, and an Increased number of Type I muscle fibers In paravertebral muscle on the convex side of the curve. Flnajiy, in the third group of rats, a mild spasticity was seen in the ipsilateral hlndlimh In approximately one-third of the animals with curvatures greater than 40°. This spasticity was not associated with a change of latency or amplitude of the somatosensory-evoked potential (SSEP). Each curvature group dlsplayied SSEP characteristics that-were not statistically different from unoperated contrql animals. These results indicate the validity of this model system for the study of scoliosis, and, In particular, its usefulness for the study of operative-induced trauma. The'production of the scoliotic curvature in these animals does not involve a direct trauma to the spine, nor does it cause major neurologic trauma or a change in the SSEP. The model also displays many of the secondary characteristics of human scoliosis. Finally, the model is technically easy to produce and allows for the generation of a wide range of lateral curvatures In a large number of animals in a relatively short period of time.