title: Accuracy of computer-assisted pedicle screw placement. An in vivo computed tomography analysis.
abstract: METHODS
  A computer-assisted planning and visualization system (the Orthopaedic Surgery Planning System) was tested for pedicle screw insertion in vivo.
  
  
  OBJECTIVE
  To evaluate the system's applicability for regular intraoperative use and its accuracy for pedicle screw placement in vivo.
  
  
  BACKGROUND
  Pedicle screw placement poses considerable anatomic and biomechanical risks. The reported rates of screw misplacement with conventional insertion techniques are unacceptably high. It previously has been shown in vitro that computer assistance offers the potential to decrease the number of screws perforating the pedicular cortex.
  
  
  METHODS
  The accuracy of 162 pedicle screws inserted with the Orthopaedic Surgery Planning System was assessed by means of postoperative computed tomography evaluation. Reconstructions of the horizontal, frontal, and sagittal planes were analyzed. Cortex perforations were graded in steps of 2 mm.
  
  
  RESULTS
  The cortex was perforated in 2.7% of pedicles. Complete preoperative computed tomography scanning of the levels to be operated on is essential to allow for a precise image reconstruction. Initial difficulties in applying the system contribute to the malplacements. A learning curve for general handling of the Orthopaedic Surgery Planning System was observed.
  
  
  CONCLUSIONS
  The system provides a safe and reproducible technique for pedicle screw insertion. Other applications in the field of spine surgery are under evaluation.
authors.affiliation: Department of Orthopaedic Surgery, Inselspital, Bern, Switzerland.
authors.forename: O
authors.initials: O
authors.lastname: Schwarzenbach
authors.forename: U
authors.initials: U
authors.lastname: Berlemann
authors.forename: B
authors.initials: B
authors.lastname: Jost
authors.forename: H
authors.initials: H
authors.lastname: Visarius
authors.forename: E
authors.initials: E
authors.lastname: Arm
authors.forename: F
authors.initials: F
authors.lastname: Langlotz
authors.forename: L P
authors.initials: LP
authors.lastname: Nolte
authors.forename: C
authors.initials: C
authors.lastname: Ozdoba
mesh_terms: D001863:Bone Screws; D005069:Evaluation Studies as Topic; D006801:Humans; D007432:Intraoperative Period; D008161:Lumbosacral Region; D011184:Postoperative Period; D013123:Spinal Fusion; D013131:Spine / Q000000981:diagnostic imaging*; D013813:Therapy, Computer-Assisted; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome