The Reciprocal Relationship Between Thoracic and Spinal Deformity and Its Effect on Pulmonary Function in a Rabbit Model

In Brief Study Design. Investigate the association between growth of the spine and thorax under conditions that create symmetric or asymmetric growth disturbances of the spine or thorax in a growing rabbit. Objective. Prove growth of the spine and growth of the thorax are directly related. Summary of Background Data. Understanding the association between growth of the thorax and growth of the spine may explain the occurrence of thoracic insufficiency in patients with congenital scoliosis. Methods. Symmetric or asymmetric growth disturbances of the spine or thorax were established in 5-week-old rabbits. During growth of the rabbits, structural changes in the spine, thorax, and lung volume were assessed using serial CT scans. Measures of pulmonary function, spine, and thoracic deformity were related to one another across groups. Results. The mean Cobb angle and distortion of the thoracic cage were significantly greater for the unilateral tethered rib group. There were no significant differences in total lung volume among the experimental groups. However, the left/right lung volume ratio was significantly different for the unilateral tethered rib group compared with the control group. Conclusions. Unilateral deformity of the spine or thorax induces both a scoliosis and thoracic cage deformity with asymmetric lung volumes. A unilateral deformity of the spine or rib cage induces both a scoliosis and thoracic cage deformity with asymmetric lung volumes in a growing rabbit model. The deformity induced by unilateral tethered ribs is much greater than the deformity induced by unilateral tethered spine.