Article
Risk of lumbar upper facet joint violation in pedicle screw placement: comparison between 2D and 3D planned screws
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Authors
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Eleftherios Archavlis
- Universitätsmedizin der Johannes Gutenberg-Universität Mainz, Klinik und Poliklinik für Neurochirurgie, Mainz, Deutschland
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Lucas Serrano
- Universitätsmedizin der Johannes Gutenberg-Universität Mainz, Klinik und Poliklinik für Neurochirurgie, Mainz, Deutschland
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Sven Rainer Kantelhardt
- Universitätsmedizin der Johannes Gutenberg-Universität Mainz, Klinik und Poliklinik für Neurochirurgie, Mainz, Deutschland
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Florian Ringel
- Universitätsmedizin der Johannes Gutenberg-Universität Mainz, Klinik und Poliklinik für Neurochirurgie, Mainz, Deutschland
| Published: | June 18, 2018 |
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Outline
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Objective: The purpose of this study was to compare the risk of upper facet joint violation by 2D versus 3D planned screws in an overall patient population of degenerative spondylolisthesis and a subset of patients with a severe facet joint arthropathy using computed tomography (CT) scan images and three-dimensional (3D) screw trajectory software.
Methods: We simulated the placement of 6.0 mm pedicle screws using 1-mm-sliced CT scans and 2D screw trajectory software. We then compared the frequency of facet joint violation by the two different planning methods. This was done in the overall patient population and in the subset of those with a severe facet joint osteoarthritis (defined and classified after Pathria et al.). Computed tomography scans of 250 consecutive patients, for a total of 500 potential screw insertion sites for each type of screw planning technique were analyzed. The outcome measures included rates of upper facet joint violations and differences in entry point location by two different techniques. Horizontal and vertical offsets of the 3D planned entry points from the conventional 2D planned entry points at the lateral edge of the pedicle and differences in the convergence transverse angles of the screws for both techniques were measured.
Results: 2D-planning resulted in 140 upper facet joint violations (28% of cases), while 3D planning resulted in 24 upper facet joint violations (4.8% of cases) only (p<0.05). A more lateral (3.5 mm mean distance) und inferior (2.5 mm mean distance) offset of the pedicle entry point and a larger medial angulation of the trajectory (mean angle 9°) were observed for the 3D planned screws at all levels. Among those with severe facet joint arthropathy Pathria grade 3 and 4, facet joint violation was significantly higher (p<0.05) in the 2D planned screws (18.7%) than in the 3D planned screws (3.2%).
Conclusion: This study demonstrates that the application of 2D fluoroscopic images for pedicle screw insertion only has a more inherent anatomic risk of upper facet joint violation. Application of 3D planning-tools moved the entry point more laterally and increased the rate of radiographically intact upper facet joints. In the presence of severe facet joint arthropathy, placement of 3D planned screws is significantly safer than the placement of 2D planned screws.
Figure 1 [Fig. 1]
