title: Accuracy of pedicle screw insertion in the thoracic and lumbar spine: a comparative study between percutaneous screw insertion and conventional open technique.
abstract: BACKGROUND
  In the last decade, posterior instrumented fusion using percutaneous pedicle screws (PPSs) had been growing in popularity, and its safety and good clinical results have been reported. However, there have been few previous reports of the accuracy of PPS placement compared with that of conventional open screw insertion in an institution. This study aimed to evaluate the accuracy of PPS placement compared with that of conventional open technique.
  
  
  METHODS
  One hundred patients were treated with posterior instrumented fusion of the thoracic and lumbar spine from April 2008 to July 2013. Four cases of revised instrumentation surgery were excluded. In this study, the pedicle screws inserted below Th7 were investigated, therefore, a total of 455 screws were enrolled. Two hundred and ninety-three pedicle screws were conventional open-inserted screws (O-group) and 162 screws were PPSs (P-group). We conducted a comparative study about the accuracy of placement between the two groups. Postoperative computed tomography scans were carried out to all patients, and the pedicle screw position was assessed according to a scoring system described by Zdichavsky et al. (Eur J Trauma 30:241-247, 2004; Eur J Trauma 30:234-240, 2004) and a classification described by Wiesner et al. (Spine 24:1599-1603, 1999).
  
  
  RESULTS
  Based on Zdichavsky's scoring system, the number of grade Ia screws was 283 (96.6 %) in the O-group and 153 (94.4 %) in the P-group, whereas 5 screws (1.7 %) in the O-group and one screw (0.6 %) in the P-group were grade IIIa/IIIb. Meanwhile, the pedicle wall penetrations based on Wiesner classification were demonstrated in 20 screws (6.8 %) in the O-group, and 12 screws (7.4 %) in the P-group. No neurologic complications were observed and no screws had to be replaced in both groups.
  
  
  CONCLUSIONS
  The PPSs could be ideally inserted without complications. There were no statistically significant differences about the accuracy between the conventional open insertion and PPS placement.
authors.affiliation: Department of Orthopaedic Surgery, Kitakyushu Municipal Medical Center, 2-1-1 Bashaku, Kokurakita-ku, Kitakyushu, Fukuoka, 802-0077, Japan. hiroko.ikeuchi.777@gmail.com.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Ikeuchi
authors.affiliation: Department of Orthopaedic Surgery, Japanese Red Cross Karatsu Hospital, 1-5-1 Futago, Karatsu, Saga, 847-0861, Japan.
authors.forename: Ko
authors.initials: K
authors.lastname: Ikuta
mesh_terms: D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D065289:Pedicle Screws; D019919:Prosthesis Implantation / Q000379:methods*; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D013904:Thoracic Vertebrae / Q000601:surgery*
keywords: Accuracy; Comparative study; Percutaneous pedicle screw; Posterior instrumented fusion