Anatomic Considerations for the Placement of C2 Laminar Screws

Cassinelli, Ezequiel H.; Lee, Michael; Skalak, Anthony; Ahn, Nicholas U.; Wright, Neill M.

doi:10.1097/01.brs.0000245869.85276.f4

Cited by 87 publications

(85 citation statements)

References 24 publications

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“…Cassinelli et al [2] measured the laminar thickness (LT) in the narrowest laminar section in American populations and reported that more than 70% of the specimens they studied had a LT [5 mm. Several other scholars examining the LT in Korean, Chinese and Turkish populations [7,11,19] came to similar conclusions: most of the specimens they examined had a LT larger than the diameter of the commonly used cervical screw (3.5 mm).…”

Section: Discussionmentioning

confidence: 99%

“…Several other scholars examining the LT in Korean, Chinese and Turkish populations [7,11,19] came to similar conclusions: most of the specimens they examined had a LT larger than the diameter of the commonly used cervical screw (3.5 mm). Although the minimum laminar thickness required to allow for safe placement of a screw was not described, there is a common idea that a thickness [5 mm with a precise screw trajectory may be acceptable [2,22].…”

Section: Discussionmentioning

confidence: 99%

“…Wright [24] described in his initial papers, a parallel screw trajectory to the downslope of the dorsal aspect of the contralateral lamina. Cassinelli [2] recommended a slightly more dorsal trajectory that may result in slight penetration into the dorsal cortex. Andrew [1] described a modification by drilling an 'exit window' at the facet laminar junctions.…”

Section: Discussionmentioning

confidence: 99%

“…Compared to transarticular screw (Jeanneret and Magerl) [9] and pedicle screw techniques, this method can provide similar stability to the atlantoaxial complex [5,12,13], which is considered to be simpler and safer due to the less intraoperative exposure and minimal risk of vertebral artery injury [2,3,8,15,24]. Subsequent morphological studies reported the applicability of this technique in different populations and showed that this method could be applied safely in most of the specimens they studied [2,7,11,19,22]. With increasing number of reports of its successful clinical applications, the C2 crossing laminar screw technique is believed to be a safe and effective method for upper cervical surgery [6, 16-18, 20, 21, 23].might violate the inner laminar cortex and screw into the spinal canal [1,23,24].…”

Section: Introductionmentioning

confidence: 99%

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Morphometric trajectory analysis for the C2 crossing laminar screw technique

et al. 2010

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This paper reports a morphometric study of the C2 laminae to provide quantitative anatomical data for safe crossing laminar screw placement. A valid trajectory is essential for C2 crossing laminar screw placement. Although several clinical technique notes and modifications to define a safe screw trajectory have been introduced in the recent years, no morphometric analysis has been performed to confirm the accuracy of screw trajectory using this technique. In this study, morphometric analysis was performed on 100 Korean C2 three-dimensional reconstruction CT images. The reconstructive C2 vertebrae from the post-edge of the spinal canal to the spinal process were divided into several zones, 1 mm each. Each zone was chosen as the entry point to imitate a crossing laminar screw (3.5 mm diameter) placement. In each 1-mm zoned trajectory, the screw pass ratio (PR), safe screw angle range (SAR) and maximum screw length (MSL) were measured and compared with the data from the other zoned trajectories. The zone '5-6 mm posterior to the post-edge of the spinal canal' was found to be a more feasible and safer entry point for guiding a crossing laminar screw placement than the other zones because this zone could provide a trajectory with maximal PR (85%), SAR (9.57 ± 4.368) and a larger MSL (21.74 ± 2.44 mm) than the other areas. The recommended safe screw angle in the axial plane is 49.68 ± 4.94 to 59.19 ± 4.708. However, the screw angle can vary considerably according to the individual variance. A preoperative evaluation of the screw trajectory is essential for safe screw placement using this technique.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Morphometric trajectory analysis for the C2 crossing laminar screw technique

et al. 2010

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“…Previously, Resnick et al [13] and Cassinelli et al [2] studied the anatomic suitability for C2 pedicle and laminar screw placement in the general adult population, and established guidelines for these techniques. However, the feasibility of such techniques in KFS patients with C2-3 CF has not yet been reported.…”

Section: Introductionmentioning

confidence: 99%

Pedicle versus laminar screws: what provides more suitable C2 fixation in congenital C2–3 fusion patients?

Wang

Passias

et al. 2010

Eur Spine J

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Patients with Klippel-Feil syndrome (KFS) have congenital fusions of at least 1 cervical motion segment, and often present with compensatory hypermobility or symptomatic stenosis of the cranio-vertebral junction which requires occipitocervical reconstruction and fusion. One subgroup of KFS patients in which this is particularly common is those with isolated C2-3 congenital fusion (C2-3 CF). The anatomic suitability for C2 pedicle and laminar screw placement had been analyzed in the general adult population, and guidelines for their techniques had been established. However, the feasibility and safety of the two techniques in KFS patients with congenital C2-3 fusion has not been reported. This radiographic study was performed to evaluate the feasibility of these two widely used methods in such patients. We recruited 108 patients with atlantoaxial dislocation and reconstructed CTs were performed. Among them, 53 had C2-C3 congenital fusion diagnosed as KFS and 55 had normal cervical segmentation (NCS). The maximum possible diameters and length were measured along the ideal screw trajectories. Both of mean diameters and lengths of the C2 laminar screw trajectory in the C2-3 CF group were significantly larger than that in NCS. Mean diameters of the C2 pedicle screw trajectory in this group were significantly smaller than that in NCS group, however, C2-3 CF patients had longer pedicle paths than NCS. In the C2-3 CF group, all 53 cases had suitable trajectory for C2 laminar screw, while 21 (39.6%) had a pedicle diameter less than 4.5 mm. In the NCS group, 5 cases (9.1%) had a pedicle diameter less than 4.5 mm. All 108 cases had sufficient diameters for C2 laminar screw placement. Klippel-Feil patients with C2-3 CF are good candidates for the technique of C2 laminar screw. Preoperative radiography should be carefully evaluated and the option of C2 fixation be determined with a thorough consideration in these patients.

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