Progression of vertebral and disc wedging in immature porcine scoliosis model and its significance

English Keywords:Scoliosis  Biomechanics  Vertebrae  Disc  Wedging

English Abstract:

  【Abstract】 Objectives: To investigate the evolution of the disc and vertebral wedging under unilateral tethering in porcine scoliosis model and its significance. Methods: Seven female pigs underwent posterior asymetric tethering surgery. All pigs underwent serial postero-anterior X-ray films at 4-week intervals to document progression of the deformity. The disc and vertebral wedging in the curve was measured by Cobb′s method. The wedging angle of 5 vertebrae and 4 discs which included apex and 2 ending vertebrae as well as discs between these vertebrae were analyzed. The wedging angle of every disc and vertebra in whole major curve was measured, and the proportion to the Cobb angle was calculated(wedging percentage) respectively. Results: The wedging angle of the vertebra in the apical area increased over time. The wedging angle of the apical vertebra and disc was found larger than that of the adjacent vertebrae. Immediately after operation, the wedging of intervertebral discs contributed to the scoliosis completely. However, the contribution of the vertebral wedging to the scoliosis increased over time. The wedging of the vertebra contributed largely(71.5%) to the scoliosis at 8 weeks postoperatively. Conclusions: The relative contributions of vertebral and disc wedging to the Cobb angle vary over time under asymmetric tethering. To obtain a reliable scoliosis animal model, adequate tethering period is required to get prominent vertebral wedging.