title: Advantages of the paraspinal muscle splitting approach in comparison with conventional midline approach for s1 pedicle screw placement.
abstract: METHODS
  A retrospective comparative study of the S1 pedicle screw (S1PS) position obtained using 2 surgical approaches.
  
  
  OBJECTIVE
  To determine whether the paraspinal approach leads to more medially oriented placement of the S1PS compared with the midline approach.
  
  
  BACKGROUND
  To obtain a stronger as well as safer fixation of the S1PS, medially oriented screw placement is very important. However, no study has recommended a surgical approach to achieve this object.
  
  
  METHODS
  The positions of 32 screws placed by the midline approach and 34 screws placed by the paraspinal approach were compared using postoperative computed tomography. The location of the bilateral common iliac veins (CIV) in relation to the S1PS tips was also analyzed to evaluate their safety.
  
  
  RESULTS
  There was no statistical difference in screw insertion point regardless of the approach employed. However, in the paraspinal group the S1PS were placed with significantly greater medial direction and with longer screws. In addition, they pierced the anterior sacral cortex closer to the midline compared with the midline approach. Four left screws in the midline approach group made contact with the left CIV, whereas no screw in the paraspinal approach group lay adjacent to the CIV.
  
  
  CONCLUSIONS
  Our results demonstrate that the paraspinal approach for S1PS placement may be superior to the midline approach in terms of the medially oriented screw placement that is biomechanically stronger and less risky for the CIV.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, Japan. otamasa@kuhp.kyoto-u.ac.jp
authors.forename: Masato
authors.initials: M
authors.lastname: Ota
authors.forename: Masashi
authors.initials: M
authors.lastname: Neo
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Fujibayashi
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Takemoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D000328:Adult; D000368:Aged; D001863:Bone Screws; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012447:Sacrum / Q000000981:diagnostic imaging / Q000601:surgery*; D013122:Spinal Diseases / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*; D018709:Statistics, Nonparametric