title: Iso-C3D navigation assisted pedicle screw placement in deformities of the cervical and thoracic spine.
abstract: BACKGROUND
  Pedicle screw instrumentation of the deformed cervical and thoracic spine is challenging to even the most experienced surgeon and associated with increased incidence of screw misplacement. Iso-C3D based navigation has been reported to improve the accuracy of pedicle screw placement, however, there are very few studies assessing its efficacy in the presence of deformity. We conducted a study to evaluate the accuracy of Iso-C3D based navigation in pedicle screw fixation in the deformed cervical and thoracic spine.
  
  
  METHODS
  We inserted 98 cervical pedicle screws (18 patients) and 242 thoracic pedicle screws (17 patients) using Iso-C3D based navigation for deformities of spine due to scoliosis, ankylosing spondylitis, post traumatic and degenerative disorders. Two independent observers determined and graded the accuracy of screw placement from postoperative computed tomography (CT) scans.
  
  
  RESULTS
  Postoperative CT scans of the cervical spine showed 90.8% perfectly placed screws with 7 (7%) grade I pedicle breaches, 2 (2%) grade II pedicle breaches and one anterior cortex penetration (< 2mm). Five lateral pedicle breaches violated the vertebral artery foramen and three medial pedicle breaches penetrated the spinal canal; however, no patient had any neurovascular complications. In the thoracic spine there were 92.2% perfectly placed screws with only six (2%) grade II pedicle breaches, eight (3%) grade I pedicle breaches and five screws (2%) penetrating the anterior or lateral cortex. No neuro-vascular complications were encountered.
  
  
  CONCLUSIONS
  Iso-C3D based navigation improves the accuracy of pedicle screw placement in deformities of the cervical and thoracic spine. The low incidence of pedicle breach implies increased safety for the patient.
authors.affiliation: Department of Orthopaedics and Spine Surgery, Ganga Hospital, 313, Mettupalayam Road, Coimbatore - 641 011, Tamil Nadu, India.
authors.forename: Vinod
authors.initials: V
authors.lastname: V Rajan
authors.forename: Vijay
authors.initials: V
authors.lastname: Kamath
authors.forename: Ajoy Prasad
authors.initials: AP
authors.lastname: Shetty
authors.forename: S
authors.initials: S
authors.lastname: Rajasekaran