Effect of apical pedicle screw placement on the surgical correction of Lenke 1 adolescent idiopathic scoliosis

English Keywords:Adolescent idiopathic scoliosis  Apical vertebra  Pedicle screw

English Abstract:

  【Abstract】　Objectives: To investigate the effect of apical pedicle screw instrumentation on the correction of thoracic adolescent idiopathic scoliosis(AIS).　Methods: From June 2009 to January 2010, 69 Lenke 1 type AIS patients treated with exclusive pedicle screw instrumentation were reviewed. The mean age at the time of surgery was 15.0 years old(range, 12-20 years), and the Cobb angle was 53.7° on average(range, 50°-70°). According to whether pedicle screws were inserted in the apical vertebrae, all cases were divided into two groups: group A(without apical instrumentation, 35 cases) and group B(instrumented with screws, 34 cases). The preoperative chronological age, sex, the Cobb angle of the major curve, and rotation degree of the apex were compared between two groups. The implant density, postoperative Cobb angle, the correction rate in Cobb angle, and derotation degree of the apical vertebra were also recorded and compared between two groups. While in group B, misplacement of the apical screws was calculated on CT scans.　Results: There was no statistical difference with respect to the chronological age, gender distribution, the preoperative Cobb angle, curve flexibility and rotation degree of the apex between the two groups. No case suffered from coronal or sagittal imbalance postoperatively. The loss of correction was also not significant in both groups.　The implant density averaged 63.4% in group A and 65.3% in group B. The fusion levels were 11.3 in group A and 11.6 in group B. The correction rate in Cobb angle was 73.9% in group A and 72.6% in group B. There was no statistical difference in terms of implant density, number of fused vertebrae or the Cobb angle correction rate between the two groups. However, as for the derotation degree of the apical vertebrae, group A had a signifi?鄄cantly lower degree(18.4%) than group B(34.8%)(P<0.05). In the 41 pedicle screws instrumented in the apical vertebrae in group B, 5(12.2%) were identified as misplacement.　Conclusions: For the patients with moderate thoracic adolescent idiopathic scoliosis, although the insertion of pedicle screws in apical vertebrae can not significantly improve the curve correction, it can correct the derotation of apical vertebrae. Therefore, with the accuracy of instrumentation, it is recommended to fix the apical vertebrae with pedicle screws.