Reliability of subaxial vertebral lamina and lateral mass for the orientation of pedicle screw insertion

English Keywords:Subaxial cervical vertebra  Vertebral lamina  Lateral mass  Direction of pedicle screw insertion  Pedicle screw

English Abstract:

  【Abstract】 Objectives: To explore reliability of subaxial vertebral lamina and lateral mass as anatomic landmark for the orientation of pedicle screw insertion. Methods: Pedicle screws were inserted into C3-C7 pedicles on 10 adult cervical vertebral specimens(5 males and 5 females). Vertebral lamina and lateral mass was regarded as anatomic landmark defined as transverse and sagittal angle of pedicle screw insertion respectively. Pedicle-lamina angle(PL angle, the transverse angle) between the central axis of each pedicle and vertebral lamina, and pedicle-lateral mass angle(PLM angle, the sagittal angle) between the central axis and lateral mass were measured preoperatively on computed tomography(CT) images. On the postoperative CT, the grade of pedicle perforation was analyzed(Grade 0 was defined when the entire screw was placed within the cortical bone of the pedicle, grade 1 was defined as less than 25% of the screw diameter violation, grade 2 was defined as 25% to 50% of the screw diameter violation, and grade 3 was defined as more than 50% of the screw diameter violation). Grade 0 and 1 were considered to be the correct position, whereas grade 2 and 3 were considered to be wrong positions.Correlative analysis between the grade of each pedicle screw position and the pedicle width or height was performed. From October 2011 to December 2012, 6 patients underwent pedicle screw insertion on subaxial cervical vertebra. Complications and accuracy of pedicle screw placement were evaluated. Results: Among 10 cervical spine specimens, PL angles of C3-C7 pedicles on axial CT images were C3, C4>C5, C6>C7. PLM angles of C3-C7 pedicles on sagittal CT images were C3, C4