The influence of lower bone mineral density on surgical outcomes in Lenke Ⅰ type adolescent idiopathic scoliosis

English Keywords:Adolescent idiopathic scoliosis  Bone mineral density  Surgical outcomes

English Abstract:

  【Abstract】 Objectives: To determine the role of preoperative lower bone mineral density(BMD) in surgical outcomes of patients with Lenke Ⅰ type adolescent idiopathic scoliosis(AIS). Methods: Thirty-seven female patients with Lenke Ⅰ type AIS who underwent posterior correction and fusion with pedical screw instrumentation between June 2007 and August 2008 were included in this study. The mean age of AIS patients was 14.3±1.3 years(rang from 11 to 17 years), and the mean Cobb angle was 48.9°±6.7°(rang from 40° to 66°). BMD was assessed in every patient before surgery by dual energy X-ray absorptiometry(DEXA).　All patients were divided into 2 groups according to the Z-score of their femur neck BMD: nonosteopenic patients(Z>-1.0) and osteopenic patients(Z≤-1.0). The radiography parameters including Cobb angle, thoracic kyphosis(TK), lumbar lordosis(LL) and apical vertebral translation(AVT) were measured preoperatively and immediatly postoperatively(3 months postoperation) as well as at the latest follow-up. C7 plumb line to center sacral vertical line(C7-CSVL) was used to evaluate the coronal balance while sagittal vertical axis(SVA) was measured to assess the sagittal balance. All the parameters between two groups were compared. Results: 15 patients were included in nonosteopenic group and 22 patients in osteopenic group, respectively. The mean age, Risser sign, instrumented level, implant density and follow-up time were similar(Ｐ>0.05). No difference with respect to the Cobb angle, AVT, C7-CSVL was observed between two groups preoperatively(Ｐ>0.05). There was no difference in the mean Cobb angle, correction loss, correction loss rate, AVT, C7-CSVL or the change of C7-CSVL immediatly postoperatively and at latest follow-up(Ｐ>0.05). In addition, there was no difference in terms of the mean TK, LL, SVA or the change of SVA between these two groups preoperatively and immediatly postoperatively as well as at the latest follow-up(Ｐ>0.05). Conclusions: Preoperative lower BMD in Lenke Ⅰ type AIS patients does not play a significant role in determining the surgical outcomes after using posterior correction and fusion with pedical screw instrumentation.