Artikel
Accuracy of transpedicular screw placement in the cervical spine using frameless stereotaxy
Genauigkeit der navigationsgeführten Pedikelschraubenplatzierung an der HWS
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Autoren
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S. Rath
- Klinik für Neurochirurgie und interventionelle Neuroradiologie, Klinikum Deggendorf
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S. Moszko
- Klinik für Neurochirurgie und interventionelle Neuroradiologie, Klinikum Deggendorf
| Veröffentlicht: | 4. Mai 2005 |
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Gliederung
Text
Objective
Although biomechanical superiority of transpedicular fixation is evident, it is not currently applied to the cervical spine. Risk of neurovascular injury is considered high, since the diameter of cervical pedicles is very small and their angle of insertion into the vertebral body varies. However, spinal neuronavigation may provide saver screw placement and thus facilitate the use of transpedicular screw-rod systems. This study was conducted to analyze accuracy of stereotactically guided transpedicular screw insertion into the cervical spine in patients who require very stable posterior spinal fixation.
Methods
50 patients underwent posterior stabilization of their cervical spine for degenerative instability with myelopathy, fracture-dislocation, tumor, rheumatoid arthritis and pyogenic spondylitis. Fixation included 1-6 motion segments (mean 2.2). Transpedicular screws (3.5 mm diameter) were placed using frameless stereotactic guidance and lateral fluoroscopy during surgery in all cases. Intraoperative mean deviation in spinal neuronavigation was less than 1.9 mm for all procedures (average 0.8/1.2 mm).
Results
There was no new neurological deficit due to transpedicular screw insertion. Postoperative CT scans revealed correct intrapedicular screw positioning or only minor pedicular cortical breach in 212 (95.5%) out of 222 cervical and all 33 thoracic (T1) pedicles. A critical screw malplacement (4.5%) was always lateral: 10 screws encroached the canal of the vertebral artery by 25 up to 60% of its diameter; however, dopplersonographic controls did not reveal obstruction of the respective vessel. Screw malplacement was mostly due to a very small diameter of the pedicle and a required steep trajectory angle which could not be achieved because of anatomical limitation in the exposure of the surgical field.
Conclusions
Despite frameless stereotaxy, there remains some risk of critical transpedicular screw malpositionning in the subaxial cervical spine. Results may still be improved by intraoperative computed tomography and navigated percutaneous screw insertion which would allow to optimize the transpedicular trajectory.
