Computed tomographic validation of the porcine model for thoracic scoliosis

Abstract

Study design: Computed Tomographic Analysis of the Porcine Scoliosis Model.

Objective: To describe the spinal and rib cage modifications using computed tomography (CT).

Summary of background data: Optimal development of nonfusion techniques for treatment of adolescent idiopathic scoliosis (AIS) requires a reliable large animal model that achieves spinal and rib cage modifications similar to AIS. Previous work has described the global 3-dimensional nature of the progressive deformity.

Methods: This IACUC-approved study includes 11 extracted scoliotic spines from a previous investigation. Scoliosis was induced through unilateral posterior ligament tethering of the spine via pedicle screw fixation, and ipsilateral rib cage tethering. CT analysis was used to quantify rib cage asymmetry, axial rotation, and wedging of the apical functional unit (2 vertebrae and intervening disc) for each specimen.

Results: The mean coronal Cobb angle was 55.7 degrees (n = 11). Vertebral and intervertebral heights of the apical functional unit demonstrated convex heights (untethered) were always larger than concave (tethered) heights (P < 0.05). Axial rotation was maximal (mean, 20 degrees ) at 1 to 2 levels distal to the coronal apex. Maximal rib cage asymmetry was demonstrated at the transverse apex with significant coupling of the rotational and rib cage modifications (r = 0.82). A large initial Cobb index (tether tension) was significantly correlated with vertebral and intervertebral wedging and coronal curve progression.

Conclusion: The present study has used CT analysis to analyze spinal and rib cage modifications in the Porcine Scoliosis Model. Placement of a unilateral ligamentous spinal tether combined with concave rib cage ligament tethering during the rapid growth stage of the Yorkshire pig results in significant apical vertebral and intervertebral wedging and rotational and rib cage modifications. The porcine model is a reliable and duplicable model for scoliosis, which bears significant similarities to AIS.