Optimal Trajectories of C1 Lateral Mass Screws and C2 Pars-Pedicle Screws.
10.4184/jkss.2004.11.4.202
- Author:
Jin Sup YEOM
1
;
Yoon Ju KWON
;
Seung Min YOO
;
Seong Kyu PARK
;
Young Hee AN
;
Kun Woo PARK
;
Kwang Sup SONG
;
Dong Ho LEE
;
Hyung Min KIM
;
Cheol Young KIM
;
Bong Soon CHANG
;
Choon Ki LEE
Author Information
1. Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul, Korea. bschang@snu.ac.kr
- Publication Type:Original Article
- Keywords:
C1-2 screw fixation;
C1 lateral mass screw;
C2 pars-pedicle screw;
computer simulation
- MeSH:
Computer Simulation;
Humans;
Spine;
Tomography, X-Ray Computed;
Vertebral Artery
- From:Journal of Korean Society of Spine Surgery
2004;11(4):202-209
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
STUDY DESIGN: Surgical simulation using CT images of the cervical spine and computers. OBJECTIVES: The optimal trajectories for C1 lateral mass screws and C2 pars-pedicle screws were sought, and their accuracy evaluated. LITERATURE REVIEW SUMMARY: There have been a few suggestions for the trajectories of the screws listed above, but these are somewhat vague or impractical. MATERIALS AND METHODS: Using 1 mm-sliced CT scan images of 128 patients, and a V-works spine surgery simulator 4.0 (Cybermed, Inc., Korea), the optimal trajectories with which 4.0 mm screws can be inserted without breaching bone cortices were determined. The anatomical characteristics of the cases having a cortical perforation were analyzed. RESULTS: The insertion point suggested for a C1 screw was 1 mm lateral to the middle of the junction of the posterior arch and posterior inferior part of the lateral mass. The screw was directed 15 degrees medially and toward the junction of the superior 2/3 and inferior 1/3 of the anterior tubercle in the lateral fluoroscopic view. The C2 screw was directed 30 degrees medially, and toward the anterior end of the superior articular process, in the lateral fluoroscopic view. The insertion point was one where the screw was inserted close to the superomedial border of the pedicle. Using these trajectories, all (256/256) of the C1 screws were inserted safely. However, 6.3% (16/256) of the C2 screws breached the inferolateral cortices of the pedicles, due to the pedicles being either too narrow or too medially angulated. CONCLUSIONS: Herein, more practical and safe screw trajectories have been suggested. Using these trajectories, all the C1 and most of the C2 screws were able to be inserted safely. However, there were some cases in which the C2 screws could not be inserted without breaching the vertebral artery groove. Therefore, preoperative thin-slice CT scanning, with three-dimensional reconstruction and/or three-dimensional CT-angiography, is recommended for these cases.
