李嚴兵(Li Yanbng，Dept Human Anat，Univ Southern China，Hengyang，Hunan 421001)…∥Chin J Clin Basic Orthop.－2010，2(2).－120～124

The digital anatomic study of the changing regularity of thoracic pedicle screw channels in different transverse screw angle

李嚴兵(Li Yanbng，Dept Human Anat，Univ Southern China，Hengyang，Hunan 421001)…∥Chin J Clin Basic Orthop.－2010，2(2).－120～124

ObjectiveTo investigate the changing regularity of thoracic pedicle screw channel(PSC)in different transverse screw angle(TSA).MethodsCT scan images of thoracic vertebrae of a healthy adult ware digitally analyzed by Mimics 10.01 software to establish three-di-mensional models which were saved as.stl format and then imported into Image ware 12.0 software.Cross section planes were located in the vertebral middle sagittal section and the pedicle central transverse plane.Thoracic PSC were projected along in a vertical direction，inner borderline of each direction project and the following inscribed circle of each inner borderline were obtained.The radius of inscribed circle of each inner borderline was recorded，PSC length was measured.ResultsIn different segments，radius of inscribed circle of T2-T12 was 2.3 －4.5 mm，the smallest of was T7.In different angles，that of T2-T12 was 2.3 ～ 3.5 mm.Radius of left and right inscribed circle of T2-T12 from 0°to 20°was 3.4 ～3.5 mm and 3.3 ～3.5 mm respectively，while the difference between both sides was 0.1 ～ 0.2 mm.In different segments，PSC length of T2-T12 was 26.9 ～ 47.8 mm which that of T2 was the shortest and that of T9 was the longest.In different angles，PSC length of T2-T12 was 23.1 ～53.2 mm while that of left and right side from 0°to 20°was respectively 23.1 ～39.7 mm and 24.8 ～41.6 mm.With the increased TSA，thoracic PSC length also lengthened while radius of inscribed cirecle increased gradually at first，and subsequently decreased.Radius of inscribed circle and PSC length were different in different thoracic segment and different TSA，and those in partial segments between left and right side containing differences.Conclusion1.PSC is the channel of interior boundary of positive projection of pedicle three-dimensional space corresponding to the centrum and lamina in any random orientation.In certain scope，a three-direction is corresponding to a PSC while this PSC corresponds to the biggest screw channel，and the biggest channel corresponds to the best axis and entering screw point.2.Between left and right side of T2-T12，radius of inscribed circle is relatively bigger and PSC length is relatively shorter in 0～20°TSA，but while that in 25°～40°TSA is the opposite.12 refs，4 figs，4 tabs.

(Authors)