| Study Design:A prospective observational study to evaluate the accuracy of 68 transpedicular thoracic screws placed in patients with and without idiopathic scoliosis using postoperative computed tomography (CT) and to establish its risks and benefits.Summary of Background Data:. Lumbar pedicle screw instrumentation has proven tobe reliable and effective in the spine surgical management of scoliosis. No domestic reports exist on the accuracy and benefits of pedicle screw instrumentation of the thoracic spine including in scoliosis surgery.Materials and Methods:In all the 68 thoracic pedicle screws placed in 10 patients,we use chinese fule pedicle screw system,and pedicle screws were by the same surgeon who has many years of experences on pedicle screw implantion,during opertion we use c armed x-ray to see the position of the screws.with regards to the entry site,we use the intersection of a vertical line bisecting the facet joint and a horizontal line located at the superior border of the transverse process for T1-T10 or the midline of the transverse process at T11-T12 defined the pedicle entrance point. 68 thoracic pedicle screws in 10 patients with and without idiopathic scoliosis were investigated shortly after surgery by computed tomography. The accuracy of thoracic screw placement within the pedicle and vertebral body were assessed by postoperative CT. Cortical perforations of the pedicle were graded in 2-mm increments. and grouped into 4 groups:I.0~2.0mm,II.2.1~4.0mm, III.4.1~6.0mm, IV.6.1~8.0mm . And defined "acceptably positioned (AP) screws" includes:<= 2 mm of medial or <= 6 mm of lateral pedicle perforation. Screws were regionally grouped for analysis. upper thoracic,middle thoracic and lower thoracic..The transverse screw angle (TSA) between with-penetration group and without-penetration group were measured and analysed. The accuracy of thoracic screw placement between with-deformity group and without coronal deformity group were compared and analysed.Results:68 titanium thoracic pedicle screws of various diameters (4.5-6.5mm)were placed in ten patients who underwent instrumented posterior spinal fusion. The regional distribution of the screws was 17 screws at T1-T4, 23 screws at T5-T8, and 28screws at T9-T12. 97% of the screws are mainly-totally within pedicles(acceptable positioned screws), 60% of screws were totally confined within the pedicle. Although medial perforation of the pedicle wall occurred in 12% of screws, in <1% there was > mm of canal intrusion. Lateral pedicular perforation occurred in 50% of perforating screws and was significantly more common than medial perforation (P < 0. 05). 6 screws penetrated the anterior vertebral cortex by an average of 1.7 mm. Screws inserted between T1 and T4 had no difference in the incidence of full containment within the pedicle and vertebral body (P >0.05) compared with T9–T12. The mean TSA for screws localized within the pedicle was 14.5° and was significantly different from screws with either medial (mean 17°) or lateral (mean 11.0°) pedicle perforation (P < 0. 05). Anterior vertebral penetration was associated with a smaller mean TSA of 10.0° (P <0.05) and with lateral pedicle perforation (P < 0.05). There was no statistic difference between the overall percentages of acceptably positioned screws (<= 2 mm of medial or <= 6 mm of lateral pedicle perforation) in patients with coronal plane spinal deformities (97%) versus patients without coronal plane spinal deformities (97%) (P>0.05).There were no neurologic or vascular complications.Conclusions:Ninety-Seven percent of screws were fully contained or were inserted with either <=2 mm of medial cortical perforation or an acceptable lateral breech. there is no neurologic and vascular compromise in both with-penetration and without-penetration groups. Thoracic pedicle screw fixation is a reliable method including treating spinalde formities. Anterior cortical penetration occurred significantly more often with lateral pedicle perforation and with a smaller mean...
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