Three-dimensional analysis of pedicle screw channel，screw entry point and lateral surface of cervi-cal vertebr body

李严兵(Li Yanbing，Dept Human A-natomy，Univ Southern China，Hengyang 421001)…∥Chin J Clin Basic Orthop Res.－2010，2(2).－107～112

Three-dimensional analysis of pedicle screw channel，screw entry point and lateral surface of cervi-cal vertebr body

李严兵(Li Yanbing，Dept Human A-natomy，Univ Southern China，Hengyang 421001)…∥Chin J Clin Basic Orthop Res.－2010，2(2).－107～112

ObjectiveTo explore three-dimensional relations of pedicle screw channel(PSC)，screw entry point and lateral surface of cervical vertebral body by digital techniques.MethodsCT scan images of cervical vertebral of 6 healthy adult were digitally analyzed by Mimics 10.01 software and their three-dimensional models were established.These data were saved as* .stl format，then imported into UG Imageware 12.0 to perform computer aided design.Located at 3D coordinate system for the subject，the centrum was divided into 10 equal parts from front to back，and those 10 equal parts were taken as the standards of borderline depth accordingly.The radius of inscribed circle，transverse screw angle(TSA)and PSC length in 90%borderline depth were gained，perpendicularity distances from best entering point to middle horizontal plane through pedicle，and to pedicle projection lateral borderline in 0°TSA of T3-T12 and to lateral borderline of lateral mass were determined respectively.Results1.Inscribed circle radii of C3-C7 PSC increased gradually from 2.6 to 3.8 mm，radius of C7 PSC was the biggest and that of C3 was the smallest(left side:2.6 mm，2.7 mm，2.9 mm，3.1 mm，3.4 mm;right:2.5 mm，3.0 mm，3.1 mm，3.1 mm，3.8 mm).2.The lengths of C3-C7 PSC increased gradually from 23.9 to 28.2 mm，length of C7 PSC was the biggest and that of C3 PSC was smallest(left siixe:23.9 mm，23.9 mm，24.5 mm，27.9 mm，27.8 mm;right side:23.4 mm，23.8 mm，24.5 mm，26.7 mm，28.2 mm).3.TSA scope of C3-C7 PSC was 33.2°－ 37.9°(left side:33.2°，33.2°，35.0°，35.3°，33.5°;right side:33.2°，37.9°，37.0°，36.3°，34.3°).4.Perpendicularity distances from ideal screw entry point corresponding on the lamina surface to middle horizontal plane through pedicle of C3-C7 were measured respectively:left side:－ 0.5 mm，0.8 mm，－0.3 mm，－0.4 mm，－0.5 mm;right side:－0.1 mm，0.5 mm，0.1 mm，－0.3 mm，－0.1 mm.The position of entry point was about 1 mm below reference plane 5.The perpendicularity distances from ideal screw point corresponding on the lamina surface to pedicle projection lateral borderline were measured respectively:left side:－5.8 mm，－5.3 mm，－6.9 mm，－5.7 mm，－2.7 mm;right side:－5.4 mm，－6.3 mm，－6.5 mm，－5.9 mm，－3.0 mm.The position of entry point to C3-C6 was 5－7 mm on the lateral side of pedicle projection lateral borderline，that of entry point to C7 was about 3 mm on the lateral borderline.6.Perpendicularity distances from ideal screw entry point corresponding on the lamina surface to lamina mass lateral borderline of C3-C7 were measured respectively:left side:4.1 mm，4.8 mm，3.6 mm，2.7 mm，3.8 mm;right side:4.1 mm，3.3 mm，3.3 mm，3.4 mm，3.3 mm.The position of entry point to C3-C7 was 3－5 mm on the medial lamina mass borderline.ConclusionPedicle projection lateral mass borderline and lamina lateral boundary are taken as reference mark lines for entering screw point of C3-C7，the position of best entering screw point of C3-C6 is outside of median line between two reference marks line，and that of C7 is inside of median line between two references marks line.14 refs，4 figs，2 tabs.

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