Can Postoperative Radiographs Accurately Identify Screw Misplacements?

Vishal Sarwahi, Saankritya Ayan, Terry Amaral, Stephen Wendolowski, Rachel Gecelter, Yungtai Lo, Beverly Ann Thornhill

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Study Design Retrospective case series. Objective The objective of this study was to determine the safety of postoperative radiographs to assess screw placement. Summary of Background Data Previously defined criteria are frequently employed to determine pedicle screw placement on intraoperative supine radiographs. Postoperatively, radiographs are typically used as a precursor to identify screws of concern, and a computed tomographic (CT) is typically ordered to confirm screw safety. Methods First, available postoperative PA and lateral radiographs were reviewed by 6 independently blinded observers. Screw misplacement was assessed using previously defined criteria. A musculoskeletal radiologist assessed all CT scans for screw placement. Pedicle screw position was classified either as acceptable or misplaced. Misplacements were subclassified as medial, lateral, or anterior. Results One hundred four patients with scoliosis or kyphosis underwent posterior spinal fusion and had postoperative CT scan available were included. In total, 2,034 thoracic and lumbar screws were evaluated. On CT scan, 1,772 screws were found to be acceptable, 142 were laterally misplaced, 30 medially, and 90 anteriorly. Of the 30 medially placed screws, 80% to 87% screws were believed to be in positions other than medial, with a median of 73% (63% to 92%) of these screws presumed to be in normal position. Similarly, of the 142 screws placed laterally, 49% to 81% screws were identified in positions other than lateral, with a median of 77% (59% to 96%) of these screws felt to be in normal position. Of the 90 anteriorly misplaced screws, 16% to 87% screws were identified in positions other than anterior, with 72% (20% to 98%) identified as normal. The criteria produced a median 52% sensitivity, 70% specificity, and 68% accuracy across the 6 observers. Conclusion Radiograph is a poor diagnostic modality for observing screw position. Level of Evidence Level IV.

Original languageEnglish (US)
Pages (from-to)109-116
Number of pages8
JournalSpine Deformity
Volume5
Issue number2
DOIs
StatePublished - Mar 1 2017

Keywords

  • CT scan
  • Pedicle screw accuracy
  • Pedicle screw misplacements
  • Posterior spinal fusion
  • Radiograph
  • Spinal deformity

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine

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