The influence of the Risser sign on the post-operative sagittal profile of idiopathic thoracic scoliosis patients treated with the anterior instrumentation

Abstract

Objective To analyze the influence of the Risser sign on the sagittal compensatory mode of the spine in idiopathic thoracic scoliosis after anterior spinal fusion.Methods Between June 2002 and November 2006,43 adolescent idiopathic scoliosis(AIS)patients(Lenke 1)undergone anterior correction with a minimum 2 years follow-up were included in this study.The patients were divided into three groups according to the Risser sign:group A(Risser 0),group B(Risser 1-3),and group C(Risser 4-5).The preoperative,postoperative and follow-up sagittal profile were evaluated by the following radiological parameters measured on the lateral radiograph,including the thoracic kyphosis,the lumbar lordosis,the thoracolumbar junction kyphosis,the distal junctional kyphosis,and the sagittal vertical axis.Results In group A,the thoracolumbar junction kyphosis significantly changed from-1.7° preoperative to 6.6° at the final follow-up,with an average increase of 8.3°.Similarly,in group B,the thoracolumbar junction kyphosis changed from -7.3° before surgery to 0.6° at the final follow-up,with an average variation of 7.9°.No obvious change of the thoracolumbar junction kyphosis was observed in group C.At the final follow-up,the average thoracic kyphosis in three groups was 21.2°,18.4° and 14.7°,respectively.No significance of the variation of the thoracic kyphosis was observed in the three groups,however,in group A and B,the thoracic kyphosis showed an ascending trend during the follow-up without significant statistical difference,in addition; the ratio of the thoracic kyphosis increased in group A was higher compared with group B and C.Conclusion For AIS patients with low Risser sign,the increased thoracic kyphosis,and the thoracolumbar junction kyphosis may be ascribed to the decompensation of thoracolumbar region caused by the reconstruction of sagittal alignment due to the continued growth of posterior elements of the thoracic spine. Key words: Scoliosis; Adolescent; Spinal fusion