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. 2018 Aug;8(5):507-511.
doi: 10.1177/2192568217744530. Epub 2017 Dec 10.

Quantitative Assessment of the Anatomical Footprint of the C1 Pedicle Relative to the Lateral Mass: A Guide for C1 Lateral Mass Fixation

Brian W Su  1 , Alexander A Theologis  2 , Robert H Byers  1 , Adam L Shimer  3 , Gregory D Schroeder  4 , Alexander R Vaccaro  4 , Bobby Tay  2
Affiliations

Quantitative Assessment of the Anatomical Footprint of the C1 Pedicle Relative to the Lateral Mass: A Guide for C1 Lateral Mass Fixation

Brian W Su et al. Global Spine J. 2018 Aug.

Abstract

Study design: Anatomic study.

Objectives: To determine the relationship of the anatomical footprint of the C1 pedicle relative to the lateral mass (LM).

Methods: Anatomic measurements were made on fresh frozen human cadaveric C1 specimens: pedicle width/height, LM width/height (minimum/maximum), LM depth, distance between LM's medial aspect and pedicle's medial border, distance between LM's lateral aspect to pedicle's lateral border, distance between pedicle's inferior aspect and LM's inferior border, distance between arch's midline and pedicle's medial border. The percentage of LM medial to the pedicle and the distance from the center of the LM to the pedicle's medial wall were calculated.

Results: A total of 42 LM were analyzed. The C1 pedicle's lateral aspect was nearly confluent with the LM's lateral border. Average pedicle width was 9.0 ± 1.1 mm, and average pedicle height was 5.0 ± 1.1 mm. Average LM width and depth were 17.0 ± 1.6 and 17.2 ± 1.6 mm, respectively. There was 6.9 ± 1.5 mm of bone medial to the medial C1 pedicle, which constituted 41% ± 9% of the LM's width. The distance from C1 arch's midline to the medial pedicle was 13.5 ± 2.0 mm. The LM's center was 1.6 ± 1 mm lateral to the medial pedicle wall. There was on average 3.5 ± 0.6 mm of the LM inferior to the pedicle inferior border.

Conclusions: The center of the lateral mass is 1.6 ± 1 mm lateral to the medial wall of the C1 pedicle and approximately 15 mm from the midline. There is 6.9 ± 1.5 mm of bone medial to the medial C1 pedicle. Thus, the medial aspect of C1 pedicle may be used as an anatomic reference for locating the center of the C1 LM for screw fixation.

Keywords: C1; atlas; lateral mass; pedicle; upper cervical spine.

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Conflict of interest statement

Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.
Coronal (A) and axial (B) images of representative cadaveric C1 vertebra. Anatomic measurements included (1) lateral mass (LM) height (maximum), (2) LM height (minimum) (3) inferior pedicle to inferior LM, (4) pedicle height, (5) LM width (maximum), (6) LM width (minimum), (7) LM depth, and (8) pedicle width.
Figure 2.
Figure 2.
Schematic representation of anatomic relationships between C1’s pedicle and lateral mass (LM). Medial pedicle to medial LM (red), medial pedicle to lateral LM (blue), and lateral pedicle to lateral LM (yellow).
Figure 3.
Figure 3.
Anatomic landmarks relative to C1 pedicle’s medial border. Midline to medial pedicle (green) and center of lateral mass (LM) (“Start-Point”) to medial pedicle (red).
See this image and copyright information in PMC

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