The Reliability of the Ball-Tipped Probe for Detecting Pedicle Screw Tract Violations Prior to Instrumenting the Thoracic and Lumbar Spine

Study Design. Cadaveric. Objective: To determine the confidence with which surgeons should rely on a flexible ball-tipped probe to detect pedicle breeches in the thoracic and lumbar spine. Summary of Background Data. The reliability of a ball-tipped probe for detecting cortical violations of the pedicle tract has not been studied among fellowship-trained surgeons. Methods. A total of 134 pedicles were randomized to have pedicle screw tracts with one of six possible options: no violation, anterior, superior, inferior, medial, or lateral violations. Five fellowship-trained spine surgeons examined each pedicle, using a standard flexible ball-tipped probe on three nonsequential occasions. The percentage of correctly identified violations, sensitivity, specificity, positive predictive value, and negative predictive value were calculated for the surgeons as a group and individually. The Cohen kappa coefficient was used to assess the accuracy of the observers and the interobserver and intraobserver agreement. Finally, we analyzed our results by spinal region to see whether this impacted the surgeons’ ability to detect a pedicle violation. Results. The surgeons were able to correctly identify 81% of intact pedicles, 39% of superior, 68% of medial, 74% of lateral, 62% of anterior, and 50% of inferior violations. The sensitivity varied considerably by breech location and surgeon with a range of 18% to 85%. Positive predictive value for each breech location ranged from 12% to 20%. The specificity was 81% and negative predictive value 98% overall. The intraobserver reliability was moderate and interobserver reliability was low in this series. The ability to detect a pedicle violation was significantly better in the lower thoracic region (T6–T12) than in other areas of the spine. Conclusion. The standard ball-tipped probe was much less reliable than expected. This technique can be used to confirm an intact pedicle but has an unacceptably high false-positive rate and should be used with caution. Our study suggests that overconfidence in pedicle probing might be dangerous.

[1]  L. Lenke,et al.  Evaluation of Pedicle Screw Placement in the Deformed Spine Using Intraoperative Plain Radiographs: A Comparison With Computerized Tomography , 2005, Spine.

[2]  L. Lenke,et al.  Pedicle Morphology In Thoracic Adolescent Idiopathic Scoliosis: Is Pedicle Fixation an Anatomically Viable Technique? , 2000, Spine.

[3]  Richard Assaker,et al.  Transpedicular Screw Placement: Image-Guided Versus Lateral-View Fluoroscopy:In Vitro Simulation , 2001, Spine.

[4]  J H Kim,et al.  Thoracic Pedicle Screw Fixation in Spinal Deformities: Are They Really Safe? , 2001, Spine.

[5]  Robert A Hart,et al.  Pedicle Screw Placement in the Thoracic Spine: A Comparison of Image-Guided and Manual Techniques in Cadavers , 2005, Spine.

[6]  Constantin Schizas,et al.  Pedicle Screw Placement Accuracy: A Meta-analysis , 2007, Spine.

[7]  D. Altman,et al.  Statistics Notes: Diagnostic tests 2: predictive values , 1994, BMJ.

[8]  P. Robertson,et al.  Radiation Exposure During Fluoroscopically Assisted Pedicle Screw Insertion in the Lumbar Spine , 2000, Spine.

[9]  C. Schizas,et al.  Inserting pedicle screws in the upper thoracic spine without the use of fluoroscopy or image guidance. Is it safe? , 2007, European Spine Journal.

[10]  Douglas G. Altman,et al.  Practical statistics for medical research , 1990 .

[11]  J. Grauer,et al.  Evaluation of a Novel Pedicle Probe for the Placement of Thoracic and Lumbosacral Pedicle Screws , 2004, Journal of spinal disorders & techniques.

[12]  R. Hart,et al.  Electrical Stimulation for Intraoperative Evaluation of Thoracic Pedicle Screw Placement , 2003, Spine.

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

[14]  Ganesh Rao,et al.  Comparison of computerized tomography and direct visualization in thoracic pedicle screw placement. , 2002, Journal of neurosurgery.

[15]  M. Walton,et al.  The Use of Evoked EMG in Detecting Misplaced Thoracolumbar Pedicle Screws , 2001, Spine.

[16]  R. Hedlund,et al.  Horizontal plane morphometry of normal and scoliotic vertebrae , 1995, European Spine Journal.

[17]  R. Gaines,et al.  The Accuracy of Pedicle Screw Placement in the Thoracic Spine Using the “Funnel Technique”: Part 1. A Cadaveric Study , 2002, Journal of spinal disorders & techniques.

[18]  Manabu Ito,et al.  Accuracy Analysis of Pedicle Screw Placement in Posterior Scoliosis Surgery: Comparison Between Conventional Fluoroscopic and Computer-Assisted Technique , 2007, Spine.

[19]  D. Polly,et al.  Probing for Thoracic Pedicle Screw Tract Violation(s): Is It Valid? , 2004, Journal of spinal disorders & techniques.

[20]  M. Millgram,et al.  Accuracy and Safety of Thoracic Pedicle Screw Placement in Spinal Deformities , 2005, Journal of spinal disorders & techniques.

[21]  Y. Yukawa,et al.  Cervical pedicle screw fixation in 100 cases of unstable cervical injuries: pedicle axis views obtained using fluoroscopy. , 2006, Journal of neurosurgery. Spine.

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

[23]  C Ozdoba,et al.  Planning and insertion of pedicle screws with computer assistance. , 1997, Journal of spinal disorders.

[24]  Imaging Assessment of Lumbar Pedicle Screw Placement: Sensitivity and Specificity of Plain Radiographs and Computer Axial Tomography , 2007, Spine.

[25]  Y. Rampersaud,et al.  Radiation Exposure to the Spine Surgeon During Fluoroscopically Assisted Pedicle Screw Insertion , 2000, Spine.

[26]  Won Bok Lee,et al.  Pedicle screw placement in the thoracic spine using a guide device A cadaveric study , 2000 .

[27]  J. R. Landis,et al.  The measurement of observer agreement for categorical data. , 1977, Biometrics.

[28]  R. Winter,et al.  Complications associated with pedicle screws. , 1999, The Journal of bone and joint surgery. American volume.

[29]  E. Simmons,et al.  Reliability of Roentgenogram Evaluation of Pedicle Screw Position , 1997, Spine.

[30]  T. Albert,et al.  Pedicle Screws With High Electrical Resistance: A Potential Source of Error With Stimulus-Evoked EMG , 2002, Spine.

[31]  Virginia Tsapaki,et al.  Estimation of radiation doses to patients and surgeons from various fluoroscopically guided orthopaedic surgeries. , 2007, Radiation protection dosimetry.

[32]  S R Garfin,et al.  Placement of pedicle screws in the thoracic spine. Part II: An anatomical and radiographic assessment. , 1995, The Journal of bone and joint surgery. American volume.

[33]  N. Theocharopoulos,et al.  Occupational exposure from common fluoroscopic projections used in orthopaedic surgery. , 2003, The Journal of bone and joint surgery. American volume.

[34]  C. Petersilge,et al.  Accuracy of Using Computed Tomography to Identify Pedicle Screw Placement in Cadaveric Human Lumbar Spine , 1997, Spine.

[35]  P. I. Lee,et al.  Accuracy of the funnel technique of thoracic pedicle screws insertion in scoliosis surgery--an evaluation by CT-scans. , 2005, The Medical journal of Malaysia.

[36]  A. Dhawan,et al.  In Vivo Accuracy of Thoracic Pedicle Screws , 2001, Spine.

[37]  L. Lenke,et al.  Free Hand Pedicle Screw Placement in the Thoracic Spine: Is it Safe? , 2004, Spine.

[38]  H. An,et al.  Placement of pedicle screws in the thoracic spine. Part I: Morphometric analysis of the thoracic vertebrae. , 1995, The Journal of bone and joint surgery. American volume.

[39]  E. Emel,et al.  Accuracy of Pedicle Screw Placement for Upper and Middle Thoracic Pathologies Without Coronal Plane Spinal Deformity Using Conventional Methods , 2006, Journal of spinal disorders & techniques.

[40]  R. Yeasting,et al.  Anatomic Considerations of Pedicle Screw Placement in the Thoracic Spine: Roy‐Camille Technique Versus Open‐Lamina Technique , 1998, Spine.

[41]  Sang-Min Lee,et al.  Thoracic Pedicle Screw Fixation in Spinal Deformities , 2001 .

[42]  H Labelle,et al.  Comparative results between conventional and computer-assisted pedicle screw installation in the thoracic, lumbar, and sacral spine. , 2000, Spine.

[43]  Charles Kuntz,et al.  Accuracy of Thoracic Vertebral Body Screw Placement Using Standard Fluoroscopy, Fluoroscopic Image Guidance, and Computed Tomographic Image Guidance: A Cadaver Study , 2003, Spine.

[44]  Amir H Fayyazi,et al.  Accuracy of Computed Tomography in Assessing Thoracic Pedicle Screw Malposition , 2004, Journal of spinal disorders & techniques.

[45]  J N Weinstein,et al.  Anatomic and technical considerations of pedicle screw fixation. , 1992, Clinical orthopaedics and related research.