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Clinical Trial
. 2007 May;16(5):613-7.
doi: 10.1007/s00586-006-0221-x. Epub 2006 Sep 12.

Computer tomography assessment of pedicle screw insertion in percutaneous posterior transpedicular stabilization

Constantin Schizas  1 , Jacky Michel, Victor Kosmopoulos, Nicolas Theumann
Affiliations
Clinical Trial

Computer tomography assessment of pedicle screw insertion in percutaneous posterior transpedicular stabilization

Constantin Schizas et al. Eur Spine J. 2007 May.

Abstract

Percutaneous insertion of cannulated pedicle screws has been recently developed as a minimally invasive alternative to the open technique during instrumented fusion procedures. Given the reported rate of screw misplacement using open techniques (up to 40%), we considered it important to analyze possible side effects of this new technique. Placement of 60 pedicle screws in 15 consecutive patients undergoing lumbar or lumbosacral fusion, mainly for spondylolisthesis, were analyzed. Axial, coronal, and sagittal reformatted computer tomography images were examined by three observers. Individual and consensus interpretation was obtained for each screw position. Along with frank penetration, we also looked at cortical encroachment of the pedicular wall by the screw. Thirteen percent of the patients (2/15) had severe frank penetration from the screws, while 80% of them (12/15) had some perforation. On axial images the incidence of severe frank pedicle penetration was 3.3% while the overall rate of screw perforation was 23%. In coronal images the overall screw perforation rate rose to 30% while the rate of severe frank pedicle penetration remained unchanged. One patient (6.6%) suffered S1 root symptoms due to a frankly medially misplaced screw, requiring re-operation. This study has shown that percutaneous insertion of cannulated pedicle screws in the lumbar spine is an acceptable procedure. The overall rate of perforation in axial images is below the higher rates reported in the literature but does remain important. Frank penetration of the pedicle was nevertheless low. It remains a demanding technique and has to be performed with extreme care to detail.

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Figures

Fig. 1
Fig. 1
Axial (a) and coronal (b) CT images of a frankly misplaced pedicle screw impinging on the right S1 nerve root
Fig. 2
Fig. 2
Axial CT image of a screw that was included in the overall perforation rate on the basis that the medial pedicle cortex (arrows) could not be visualized
See this image and copyright information in PMC

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