Image-based drill templates for cervical pedicle screw placement.

OBJECT Pedicle screws (PSs) in the cervical spine can provide fixation superior to current fixation methods; however, their implementation is challenging due to the small size of the cervical vertebrae. In this study, the authors explored and evaluated the use of patient-specific, rapid prototype drill templates for PS placement in the cervical spine. The goal of the study was to assess the accuracy of a drill template in the placement of cervical PSs at a single vertebral level. METHODS Volumetric CT scanning was performed in 4 cadaveric cervical spines. Using computer software, the authors constructed drill templates with a predefined trajectory designed to match the posterior surface of vertebrae C3-7. Twenty physical templates were created from the computer models using a rapid prototyping machine. The drill templates were used to guide pilot-hole drilling, and CT scanning was performed to assess the accuracy of the pilot holes. Pedicle screws (3.5-mm diameter) were placed in the pilot holes. The spines were then dissected to separate the vertebrae, and the trajectory of the screws was visually inspected. RESULTS The feasibility of this patient-specific, rapid prototyping technique was demonstrated. Imaging and visual inspection of pilot holes and cervical PSs revealed that the majority of trajectories did not violate the pedicle cortex (19 [95%] of 20). The single cortical violation was judged as noncritical and would probably not have resulted in injury to a patient. CONCLUSIONS The potential of drill templates to aid in the placement of cervical PSs is promising. The authors' methods appear to provide an accurate technique and trajectory for PS placement in the cervical spine.

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

[2]  K. Takaoka,et al.  Cervical pedicle screw insertion: assessment of safety and accuracy with computer-assisted image guidance. , 2000, Journal of spinal disorders.

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

[4]  T. Albert,et al.  Placement of pedicle screws in the human cadaveric cervical spine: comparative accuracy of three techniques. , 2000, Spine.

[5]  L. Sekhon.  Posterior Cervical Lateral Mass Screw Fixation: Analysis of 1026 Consecutive Screws in 143 Patients , 2005, Journal of spinal disorders & techniques.

[6]  L. Claes,et al.  Effect of constrained posterior screw and rod systems for primary stability: Biomechanical in vitro comparison of various instrumentations in a single-level corpectomy model , 2005, European Spine Journal.

[7]  G. Mao,et al.  Design of Cervical Pedicle Locator and Three-Dimensional Location of Cervical Pedicle , 2005, Spine.

[8]  P. Mertens,et al.  Biomechanical evaluation of cervical lateral mass fixation: a comparison of the Roy-Camille and Magerl screw techniques. , 2004, Journal of neurosurgery.

[9]  K. An,et al.  Biomechanical Evaluation of Posterior Screw Fixation in Cadaveric Cervical Spines , 2003, Clinical orthopaedics and related research.

[10]  M. Richter,et al.  Computer-assisted posterior instrumentation of the cervical and cervico-thoracic spine , 2004, European Spine Journal.

[11]  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.

[12]  W. Hutton,et al.  A Comparison of Pedicle and Lateral Mass Screw Construct Stiffnesses at the Cervicothoracic Junction: A Biomechanical Study , 2005, Spine.

[13]  Manabu Ito,et al.  Complications of Pedicle Screw Fixation in Reconstructive Surgery of the Cervical Spine , 2000, Spine.

[14]  Kevin T Foley,et al.  Percutaneous Placement of Posterior Cervical Screws Using Three-Dimensional Fluoroscopy , 2006, Spine.

[15]  M. Neo,et al.  Transpedicular Screw Placement Evaluated by Axial Computed Tomography of the Cervical Pedicle , 2004, Spine.

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

[17]  R. Gaines,et al.  Accuracy of Cervical Pedicle Screw Placement Using the Funnel Technique , 2001, Spine.

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

[19]  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.

[20]  D. Silcox,et al.  Cervical Pedicle Screws Versus Lateral Mass Screws: Anatomic Feasibility and Biomechanical Comparison , 1997, Spine.

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

[22]  M. Panjabi,et al.  The anatomic variability of human cervical pedicles: considerations for transpedicular screw fixation in the middle and lower cervical spine , 2000, European Spine Journal.

[23]  K. Kaneda,et al.  One-stage posterior decompression and reconstruction of the cervical spine by using pedicle screw fixation systems. , 1999, Journal of neurosurgery.

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

[25]  R. Gaines,et al.  Surgical anatomy of the cervical pedicles: landmarks for posterior cervical pedicle entrance localization. , 2000, Journal of spinal disorders.

[26]  K. Kaneda,et al.  Indirect posterior reduction and fusion of the traumatic herniated disc by using a cervical pedicle screw system. , 2000, Journal of neurosurgery.

[27]  H. Richter,et al.  Complications of transpedicular screw fixation in the cervical spine , 2006, European Spine Journal.

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

[29]  P. Hudgins,et al.  The Accuracy of Computed Tomography in Assessing Cervical Pedicle Screw Placement , 2003, Spine.

[30]  Shigenobu Sato,et al.  Spinal Reconstruction Using a Cervical Pedicle Screw System , 2005, Clinical orthopaedics and related research.

[31]  K. Kaneda,et al.  Correction of cervical kyphosis using pedicle screw fixation systems. , 1999, Spine.

[32]  I. Tekdemir,et al.  Surgical Anatomic Evaluation of the Cervical Pedicle and Adjacent Neural Structures , 2000, Neurosurgery.

[33]  R. Yeasting,et al.  Anatomic Consideration of Transpedicular Screw Placement in the Cervical Spine: An Analysis of Two Approaches , 1996, Spine.

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

[35]  M. Reinhold,et al.  Cervical pedicle screw placement: feasibility and accuracy of two new insertion techniques based on morphometric data , 2006, European Spine Journal.

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

[37]  E. Schneider,et al.  Biomechanical Analysis of Transpedicular Screw Fixation in the Subaxial Cervical Spine , 2004, Spine.

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

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