Contributions of vertebral and disc wedging to the Cobb angle in adolescent idiopathic scoliosis with different curve pattern：radiographic discrepancy and clinical significance

English Keywords:Scoliosis  Vertebrae  Disc  Wedging

English Abstract:

  【Abstract】 Objective：To investigate the difference of contribution to the Cobb angle between vertebral and disc wedging in adolescent idiopathic scoliosis（AIS） with different curve pattern and its clinical significance.Method：Form January 2007 to June 2009，110 AIS patients were divided into three groups according to their curve patterns，which included 39 patients with a major thoracic curve（group A），33 with a thoracolumbar curve（group B） and 38 with major lumbar curve（group C）.According to the Cobb angle（<40° or ≥40°），each group was divided into two subgroups.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.Result：The average age，Cobb angle and Risser sign of all patients was 13.6±1.9 years，34.4°±10.5° and 2.4±1.7 respectively.No difference with respect to the average age，Cobb angle and Risser sign was observed among three groups（P>0.05）.The wedging angle and wedging percentage of vertebrae were significantly higher than those of discs in group A（21.9°±5.6° vs 13.7°±5.9°，and 62.3% vs 37.7%，P<0.001），however the reverse results in group B and C（24.1°±9.2° vs 10.4°±3.8°，69.0% vs 31.0%，P<0.001；and 25.1°±7.2° vs 7.7°±2.4°，76.6% vs 23.4%，P<0.001）.The wedging angle of vertebra and discs in patients with Cobb angle ≥40° was significantly higher than that in patients with Cobb angle <40°（P<0.001）.Along with the increase of Cobb angle，vertebral wedging still played a major role in contribution to Cobb angle in group A，while disc wedging accounted for the main part in group B and C.Additionally，the wedging angle of apical vertebrae was linearly correlated with the Cobb angle in each group（P<0.001）.Conclusion：Various vertebral and disc wedging exist in adolescent idiopathic scoliosis regardless of the curve patterns.The vertebral wedging contribute more to the Cobb angle in major thoracic curve than discs，while disc wedging contribute more to the Cobb angle in thoracolumbar and lumbar curves，which indicate different biomechanical pathogenesis among varied curve types.