title: Evaluating Accuracy of Free-hand Pedicle Screw Insertion in Adolescent Idiopathic Scoliosis Using Postoperative Multi-Slice Computed Tomography Scan.
abstract: BACKGROUND
  Pedicle screw instrumentation has many advantages for correction of adolescent idiopathic scoliosis (AIS) deformity including better correction and fewer late complications. On the other hand, screw insertion in AIS is challenging. Intraoperative fluoroscopy or navigation techniques are expensive, time-consuming, and exposed to high radiation. Free-hand technique relies on the surgeon's experience and locating the pedicle entry point with anatomical landmarks. There are few studies that evaluated pedicle screw position accuracy with postoperative multi-slice computed tomography scan.
  
  
  METHODS
  We prospectively considered 38 consecutive AIS cases, who underwent corrective surgery with all pedicle screw technique. All the screws were inserted with free-hand technique using anatomic landmarks as a guide for an entry site. We divided pedicle penetration in medial, lateral, inferior, superior, and anterior vertebral body as Grades 0-4, that Grade 0 is fully contained within the pedicle, Grade 1 (<2 mm), Grade 2 (2.1-4 mm), Grade 3 (4.1-6 mm), and Grade 4 (>6 mm).
  
  
  RESULTS
  A total of 720 screws were inserted, of which 623 screws (86.5%) were perfect and 97 screws (13.5%) were misplaced. Of those which were misplaced, 39 screws (40.2%) were medial and 58 (59.8%) were lateral, which shows that the prevalence of lateral misplacement was more in comparison to medial misplacement. However, in all misplaced cases, the deviation of the screw was <2 mm (Grade 1). There was no misplacement in the inferior and superior.
  
  
  CONCLUSIONS
  Pedicle screw insertion in AIS with the free-hand technique is a safe and reliable method.
authors.affiliation: Department of Orthopedic and Spine Surgery, Al-Zahra Hospital, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Mohammadreza
authors.initials: M
authors.lastname: Etemadifar
authors.affiliation: Department of Orthopedic and Spine Surgery, Al-Zahra Hospital, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Mohammadhossein
authors.initials: M
authors.lastname: Jamalaldini
keywords: Free-hand technique; pedicle screw; scoliosis