title: At What Levels Are Freehand Pedicle Screws More Frequently Malpositioned in Children?
abstract: METHODS
  Retrospective case series.
  
  
  BACKGROUND
  Previous studies report that 5% to 17% of pedicle screws placed in children are malpositioned. Knowledge of the long-term effects of malpositioned screws is limited. We sought to further characterize risk factors for malpositioned pedicle screws in order to establish a more proactive role in limiting future complications.
  
  
  OBJECTIVE
  We undertook this study to answer the following: 1) Is the rate of freehand pedicle screw malpositioning higher in children with spinal deformity, particularly at the apical concavity? 2) At what vertebral levels do freehand pedicle screws have the highest rates of malpositioning? 3) In which direction (medial or lateral) do freehand pedicle wall violations occur most often?
  
  
  METHODS
  Incidental postoperative computed tomographic (CT) exams were retrospectively reviewed in 85 pediatric patients (605 screws) treated with posterior spinal fusion using freehand pedicle screw technique. Of the screws imaged, 355 were in patients without deformity and 250 in patients with deformity. Breaches were categorized as mild (<2 mm), moderate (2-4 mm), or severe (>4 mm).
  
  
  RESULTS
  Screws in pediatric deformity patients were more frequently malpositioned by 2 mm or more than were screws in patients without deformity (26% vs. 19%, p = .02). In patients with deformity, no higher rate of screw malposition was detected at the apical region. Overall, the highest rates of severe screw malposition were between T3 and T8. Pedicle breaches were more commonly in a medial direction compared with lateral (74% vs. 26%, p < .0001). However, severe breaches within the T3-T8 region were more often directed lateral than medial (92% vs. 8%, p ≤ .0001).
  
  
  CONCLUSIONS
  The clinical significance of asymptomatic pedicle screw breaches in children has not yet been determined. In this study, screws at the apical concavity were no more likely to be malpositioned than those at other sites. Efforts to reduce pedicle screw malposition would likely be most effective at the T3-T8 levels.
  
  
  METHODS
  Level IV, Therapeutic Study. See the Guidelines for Authors for a complete description of the levels of evidence.
authors.affiliation: Mayo Medical School, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Heidenreich
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA.
authors.forename: Yaser M K
authors.initials: YM
authors.lastname: Baghdadi
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA.
authors.forename: Amy L
authors.initials: AL
authors.lastname: McIntosh
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Shaughnessy
authors.affiliation: The CORE Institute, 18444 North 25th Avenue Suite 320, Phoenix, AZ 85023, USA.
authors.forename: Mark B
authors.initials: MB
authors.lastname: Dekutoski
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Stans
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA. Electronic address: larson.noelle@mayo.edu.
authors.forename: A Noelle
authors.initials: AN
authors.lastname: Larson
keywords: Malposition; Pediatric; Pedicle screws