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A novel radiographic targeting guide for percutaneous placement of transfacet screws in the cervical spine with limited fluoroscopy: A cadaveric feasibility study

David M. Jackson, MD,1 Jacqueline E. Karp, MD,1 Joseph R. O'Brien, MD,2 D. Greg Anderson, MD,3 Daniel E. Gelb, MD,1 Steven C. Ludwig, MD1

1Department of Orthopaedics, University of Maryland, Baltimore, MD 2Department of Orthopaedic Surgery, George Washington University Hospital, Washington, DC 3Department of Orthopaedic Surgery, Thomas Jefferson University Hospital, Philadelphia, PA

Abstract 

Background

We describe a technique for percutaneous transfacet screw placement in the cervical spine without the need for lateral-view fluoroscopy.

Methods

Previously established articular pillar morphometry was used to define the ideal trajectory for transfacet screw placement in the subaxial cervical spine. A unique targeting guide was developed to allow placement of Kirschner wires across the facet joint at 90° without the guidance of lateral-view fluoroscopy. Kirschner wires and cannulated screws were placed percutaneously in 7 cadaveric specimens. Placement of instrumentation was performed entirely under modified anteroposterior-view fluoroscopy. All specimens were assessed for acceptable screw placement by 2 fellowship-trained orthopaedic spine surgeons using computed tomography. Open dissection was used to confirm radiographic interpretation. Acceptable placement was defined as a screw crossing the facet joint, achieving purchase in the inferior and superior articular processes, and not violating critical structures. Malposition was defined as a violation of the transverse foramen, spinal canal, or nerve root or inadequate fixation.

Results

A total of 48 screws were placed. Placement of 45 screws was acceptable. The 3 instances of screw malposition included a facet fracture, a facet distraction, and a C6-7 screw contacting the C7 nerve root in a specimen with a small C7 superior articular process.

Conclusions

Our data show that with the appropriate radiographic technique and a targeting guide, percutaneous transfacet screws can be safely placed at C3-7 without the need for lateral-view fluoroscopy during the targeting phase. Because of the variable morphometry of the C7 lateral mass, however, care must be taken when placing a transfacet screw at C6-7.

Clinical Relevance

This study describes a technique that has the potential to provide a less invasive strategy for posterior instrumentation of the cervical spine. Further investigation is needed before this technique can be applied clinically.

keywords: 
Transfacet screws, Cervical Spine, Radiographic targeting guide, Minimally invasive surgery of the spine
Volume 6
doi: 
10.1016/j.ijsp.2011.12.003