title: Inter- and intra-observer reliability of measurement of pedicle screw breach assessed by postoperative CT scans.
abstract: BACKGROUND
  Pedicle screws are used increasingly in spine surgery. Concerns of complications associated with screw breach necessitates accurate pedicle screw placement. Postoperative CT imaging helps to detect screw malposition and assess its severity. However, accuracy is dependent on the reading of the CT scans. Inter- and intra-observer variability could affect the reliability of CT scans to assess multiple screw types and sites. The purpose of this study was to assess the reliability of multi-observer analysis of CT scans for determining pedicle screw breach for various screw types and sites in patients with spinal deformity or degenerative pathologies.
  
  
  METHODS
  Axial CT scan images of 23 patients (286 screws) were read by four experienced spine surgeons. Pedicle screw placement was considered 'In' when the screw was fully contained and/or the pedicle wall breach was ≤2 mm. 'Out' was defined as a breach in the medial or lateral pedicle wall >2 mm. Intra-class coefficients (ICC) were calculated to assess the inter- and intra-observer reliability.
  
  
  RESULTS
  Marked inter- and intra-observer variability was noticed. The overall inter-observer ICC was 0.45 (95% confidence limits 0.25 to 0.65). The intra-observer ICC was 0.49 (95% confidence limits 0.29 to 0.69). Underlying spinal pathology, screw type, and patient age did not seem to impact the reliability of our CT assessments.
  
  
  CONCLUSIONS
  Our results indicate the evaluation of pedicle screw breach on CT by a single surgeon is highly variable, and care should be taken when using individual CT evaluations of millimeters of breach as a basis for screw removal. This was a Level III study.
authors.affiliation: Department of Orthopaedic Surgery, State University of New York Upstate Medical University, Syracuse, NY.
authors.forename: William F
authors.initials: WF
authors.lastname: Lavelle
authors.affiliation: Department of Orthopaedics, SKN Medical College & Hospital, Deenanath Mangeshkar Hospital, Pune, India.
authors.forename: Ashish
authors.initials: A
authors.lastname: Ranade
authors.affiliation: Shriners Hospitals for Children-Philadelphia, Philadelphia, PA.
authors.forename: Amer F
authors.initials: AF
authors.lastname: Samdani
authors.affiliation: Biostatistics Consulting Center, Temple University School of Medicine, Philadelphia, PA.
authors.forename: John P
authors.initials: JP
authors.lastname: Gaughan
authors.affiliation: Brandywine Institute of Orthopaedics, Pottstown, PA.
authors.forename: Linda P
authors.initials: LP
authors.lastname: D'Andrea
authors.affiliation: Institute for Spine & Scoliosis, Lawrenceville, NJ.
authors.forename: Randal R
authors.initials: RR
authors.lastname: Betz
keywords: CT imaging; inter/intra observer reliability; pedicle screw breach