Digital anatomic study of atlas pedicle screw channel

English Keywords:Atlas  Pedicle channel  Digital anatomy  Pedicle screw

English Abstract:

  【Abstract】 Objective：To investigate the regular pattern of atlas pedicle screw channels in different transverse section angles（TSA） when placed as 0° sagital section angles（SSA）.Method：CT scan images of atlas of 20 healthy adult volunteers（12 males，8 females；aged 24-68，average 45 years old） were digitally analyzed by Mimics 10.01 software（Materialise），and their three-dimensional（3D） models were established.These models were saved as .stl format，then imported to UG Imageware 12.0 software to establish the digital method for an?鄄alyzing the atlas pedicle screw channels，and determine the reference 3D plane，under the condition of SSA at 0° invariably，TSA changed evenly between 0°-30° at an interval of 5°.The changing pattern of the length and the inscribed circle radius of 280 atlas pedicle screw channels were analyzed.Result：The length of the 280 atlas pedicle screw channels was about 20.54-33.21mm.11 channels were shorter than the shortest screw length（<22mm）.The changing pattern of the length of atlas pedicle screw channels was that when the transverse section angles of the entering screw was 0°，the length was the longest.No side-related difference was noted（P>0.05）.When the angle was between 5°-30°，the side-related difference was significant（P<0.05）.Ipsilateral varied angle of the entering screw showed no significant difference（P>0.05）.The inscribed circle radius of 280 atlas pedicle screw channels was between 1.38-2.51mm；42 inscribed circle radius were shorter than the shortest ones（<1.75mm）.No side-related difference was significant（P<0.05）；Ipsilateral varied angle of the entering screw showed no significant difference（P>0.05）.Conclusion：The morphology of bilateral pedicle of C1 vary significantly in different patients，or even in the same patient.In some patients，the pedicle channels length and the inscribed circle radius are less than the minimum length and radius of pedicle screw，which will predispose the pedicle at risk.Customized screw placement can be reached by preoperative digital measurement of atlas pedicle screw channels.