A Novel Patient-Specific Navigational Template for Cervical Pedicle Screw Placement

Study Design. Prospective trial. Objective. To develop and validate a novel, patient-specific navigational template for cervical pedicle placement. Summary of Background Data. Owing to the narrow bony anatomy and the proximity to the vertebral artery and the spinal cord, cervical instrumentation procedures demand the need for a precise technique for screw placement. Patient. Specific drill template with preplanned trajectory has been thought as a promising solution for cervical pedicle screw placement. Methods. Patients with cervical spinal pathology (n = 25) requiring instrumentation were recruited. Volumetric CT scan was performed on each desired cervical vertebra and a 3-dimensional reconstruction model was generated from the scan data. Using reverse engineering technique, the optimal screw size and orientation were determined and a drill template was designed with a surface that is the inverse of the posterior vertebral surface. The drill template and its corresponding vertebra were manufactured using rapid prototyping technique and tested for violations. The navigational template was sterilized and used intraoperatively to assist with the placement of cervical screws. In total, 88 screws were inserted into levels C2–C7 with 2 to 6 screw in each patient. After surgery, the positions of the pedicle screws were evaluated using CT scan and graded for validation. Results. This method showed its ability to customize the placement and the size of each screw based on the unique morphology of the cervical vertebra. In all the cases, it was relatively very easy to manually place the drill template on the lamina of the vertebral body during the surgery. The required time between fixation of the template to the lamina and insertion of the pedicle screws was about 80 seconds. Of the 88 screws, 71 screws had no deviation and 14 screws had deviation <2 mm, 1 screw had a deviation between 2 to 4 mm and there were no misplacements. Fluoroscopy was used only once for every patient after the insertion of all the pedicle screws. Conclusion. The authors have developed a novel patient-specific navigational template for cervical pedicle screw placement with good applicability and high accuracy. This method significantly reduces the operation time and radiation exposure for the members of the surgical team. The potential use of such a navigational template to insert cervical pedicle screws is promising. This technique has been clinically validated to provide an accurate trajectory for pedicle screw placement in the cervical spine.

[1]  Marcel Rooze,et al.  Evaluation of a transpedicular drill guide for pedicle screw placement in the thoracic spine , 2003, European Spine Journal.

[2]  M. Richter,et al.  Computer-assisted surgery in posterior instrumentation of the cervical spine: an in-vitro feasibility study , 2000, European Spine Journal.

[3]  Paul S D'Urso,et al.  Biomodeling as an Aid to Spinal Instrumentation , 2004, Spine.

[4]  K. Radermacher,et al.  Computer assisted orthopaedic surgery with image based individual templates. , 1998, Clinical orthopaedics and related research.

[5]  L. Claes,et al.  Pedicle Screws Enhance Primary Stability in Multilevel Cervical Corpectomies: Biomechanical In Vitro Comparison of Different Implants Including Constrained and Nonconstrained Posterior Instumentations , 2003, Spine.

[6]  K. Kaneda,et al.  Transpedicular screw fixation for traumatic lesions of the middle and lower cervical spine: description of the techniques and preliminary report. , 1994, Journal of spinal disorders.

[7]  A. Minami,et al.  Improved accuracy of computer-assisted cervical pedicle screw insertion. , 2003, Journal of neurosurgery.

[8]  Yang Huilin,et al.  CT evaluation of cervical pedicle in a Chinese population for surgical application of transpedicular screw placement , 2008, Surgical and Radiologic Anatomy.

[9]  A. Prescher,et al.  Computer-Assisted Orthopedic Surgery With Individual Templates and Comparison to Conventional Operation Method , 2001, Spine.

[10]  Axial computed tomography of the pedicle in the lower cervical spine. , 2001, American journal of orthopedics.

[11]  C. Edwards,et al.  Cervical Pedicle Screws: Comparative Accuracy of Two Insertion Techniques , 2000, Spine.

[12]  M. Neo,et al.  The Clinical Risk of Vertebral Artery Injury From Cervical Pedicle Screws Inserted in Degenerative Vertebrae , 2005, Spine.

[13]  H N Herkowitz,et al.  Spinal pedicle fixation. Confirmation of an image-based technique for screw placement. , 1993, Spine.

[14]  J. Gilsbach,et al.  Virtual placement of posterior C1-C2 transarticular screw fixation , 2006, Neurosurgical Review.

[15]  Cloward Dowel,et al.  SPINE , 1995, Bone &amp; Joint 360.

[16]  René Schmidt,et al.  Cervical Pedicle Screws: Conventional Versus Computer-Assisted Placement of Cannulated Screws , 2005, Spine.

[17]  B B Seedhom,et al.  Personalised image-based templates for intra-operative guidance , 2005, Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine.

[18]  J Vander Sloten,et al.  Three-Dimensional Computed Tomography-Based, Personalized Drill Guide for Posterior Cervical Stabilization at C1–C2 , 2001, Spine.

[19]  B. Cunningham,et al.  Biomechanical Analysis of Cervical Stabilization Systems: An Assessment of Transpedicular Screw Fixation in the Cervical Spine , 1994, Spine.

[20]  R. Bale,et al.  [Computer-assisted retrograde drilling of osteochondral lesions of the talus]. , 2001, Der Orthopade.

[21]  R. Yeasting,et al.  Morphometric Evaluation of Lower Cervical Pedicle and Its Projection , 1997, Spine.

[22]  Kevin T Foley,et al.  Intraoperative Spinal Navigation , 2003, Spine.

[23]  S. Burch,et al.  Computer-Assisted Surgical Planning and Image-Guided Surgical Navigation in Refractory Adult Scoliosis Surgery: Case Report and Review of the Literature , 2008, Spine.

[24]  R. Yeasting,et al.  Morphology of the Second Cervical Vertebra and the Posterior Projection of the C2 Pedicle Axis , 1995, Spine.

[25]  R. Gaines,et al.  Morphologic Characteristics of Human Cervical Pedicles , 1997, Spine.

[26]  Timothy C Ryken,et al.  Rapid prototype patient-specific drill template for cervical pedicle screw placement , 2007, Computer aided surgery : official journal of the International Society for Computer Aided Surgery.

[27]  T. Albert,et al.  Transpedicle screw fixation of the cervical spine. , 1999, Clinical orthopaedics and related research.