Original ArticleAnatomic Study of Nutrient Foramina of Posterior Axis with Application to C2 Pedicle Screw Placement
Introduction
Pedicle screw placement into C2 necessitates a thorough understanding of this bone's unique anatomy. Although multiple landmarks and measurements have been used by spine surgeons, these are often varied in the literature with no consensus. In addition, relatively few anatomic studies of this pedicular anatomy have been performed.1, 2, 3 Herein, we performed an anatomic study of one recently proposed landmark using the nutrient foramina of the posterior aspect of C2 as an entry point for pedicle screw placement.
Section snippets
Materials and Methods
To ascertain the origin of the vessel entering the C2 nutrient foramina, a latex-injected male Caucasian cadaveric head (73 years old at death) was used. The head was positioned in the prone position. A skin incision was made into the posterior neck extending from the external occipital protuberance to the spinous process of C5. Soft tissues were removed from medial to lateral over the laminae of C2. The nutrient foramen of the pedicle was used as the entry point of the C2 pedicle screw (
Results
For the cadaveric specimen, using the nutrient foramen, the pedicle screw was correctly placed and did not fracture the pedicle (Figure 6). The vessel entering the nutrient foramina was also identified as an artery and was found to be a distal branch of the deep cervical artery (Figure 7).
For dry C2 specimens, the number of nutrient foramina ranged from 0–5 (mean; 1.84 ± 0.87) (Table 1) (Figure 8). The diameter of the foramina ranged from 0.30–1.89 mm (mean; 0.57 ± 0.25 mm) (Table 2) (Figure 9
Discussion
We found that the number of foramina ranged from 0–5 with a mean of 1.84. On 3 sides no foramina were identified. The mean diameter of the foramina was 0.57 mm. The location of the foramina was at position 1 on 9.5% of sides, position 2 on 66.4% of sides, and position 3 on 24.1% of sides. The mean horizontal distance from the midline of the spinous process of C2 to the foramina was 25.17 mm. There was no significant difference between the right and left sides. In the cadaveric specimen, the
Conclusions
We found that the nutrient foramina of the posterior aspect of C2 are useful for pedicle screw placement and are located, on average, 2.5 cm from the midline. However, there are minor variations in the number and position of these structures. The foramen in position 2 could be a useful landmark for pedicle screw placement. Lastly, on the basis of our study, 7.9% (n = 3) of sides will not have such foramina so that this landmark could not be used for pedicle screw placement.
Acknowledgment
The authors wish to thank the individuals who donated their bodies for the advancement of education and research.
References (9)
- et al.
The vertebral artery cave at C2: anatomic study with application to C2 pedicle screw placement
World Neurosurg
(2016) - et al.
Anatomic study on the entry point and implant technique for C2 pedicle screw fixation
Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi
(2015) - et al.
Comparison of the anatomical risk for vertebral artery injury associated with the C2-pedicle screw and atlantoaxial transarticular screw
Spine
(2006) - et al.
Development of the anatomical quality assurance (AQUA) checklist: guidelines for reporting original anatomical studies
Clin Anat
(2017)
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Conflict of interest statement: The authors have no conflicts of interest to declare.