At What Levels Are Freehand Pedicle Screws More Frequently Malpositioned in Children?

Study Design: 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. Level of Evidence: Level IV, Therapeutic Study. See the Guidelines for Authors for a complete description of the levels of evidence.