Anat Cell Biol.  2023 Sep;56(3):350-359. 10.5115/acb.23.015.

An anatomical investigation of the suboccipitaland inferior suboccipital triangles

• Regan KS
• Venter G

• KMID: 2546463
• DOI: http://doi.org/10.5115/acb.23.015

Abstract

The suboccipital triangle (ST) is a clinically relevant landmark in the posterior aspect of the neck and is used to locate and mobilize the horizontal segment of the third part of the vertebral artery before it enters the cranium. Unfortunately, this space is not always a viable option for vertebral artery exposition, and consequently a novel triangle, the inferior suboccipital triangle (IST) has been defined. This alternative triangle will allow surgeons to locate the artery more proximally, where its course is more predictable. The purpose of this study was to better define the anatomy of both triangles by measuring their borders and calculating their areas. Ethical clearance was obtained from the University of Pretoria (reference number: 222/2021) and both triangles were subsequently dissected out on both the left and right sides of 33 formalin-fixed human adult cadavers. The borders of each triangle were measured using a digital calliper and the areas were calculated using Herons Formula. The average area of the ST is 969.82±153.15 mm 2 , while the average area of the IST is 307.48±41.31 mm 2 . No statistically significant differences in the findings were observed between the sides of the body, ancestry, or sex of the cadavers. Measurement and analysis of these triangles provided important anatomical information and speak to their clinical relevance as surgical landmarks with which to locate the vertebral artery. Of particular importance here is the IST, which allows for mobilisation of this artery more proximally, should the ST be occluded.

Keyword

Cervical vertebrae; Inferior suboccipital triangle; Obliquus capitis inferior; Suboccipital triangle; Vertebral artery

Figure

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  Fig. 1 Specimen image illustrating the borders of the ST (blue) and IST (yellow) triangle, indicating that the vertebral artery runs through both triangles. ST, suboccipital triangle; IST, inferior suboccipital triangle.

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  Fig. 2 (A) Image of exposed right suboccipital region with the right ST and IST and associated muscles visible, while the left semispinalis is still intact, covering the left ST and IST. (B) Image of trapezius, splenius capitis, semispinalis capitis muscles reflected to expose both the left and right suboccipital regions. ST, suboccipital triangle; IST, inferior suboccipital triangle; RCPm, rectus capitis posterior minor; RCPM, rectus capitis posterior major; OCS, obliquus capitis superior; OCI, obliquus capitis inferior.

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  Fig. 3 Image indicating the relevant measurements taken for both the ST (blue measurements) and the IST (yellow measurements). ST, suboccipital triangle; IST, inferior suboccipital triangle; RCPM, rectus capitis posterior major; OCS, obliquus capitis superior; OCI, obliquus capitis inferior; PI, posterior intertransversarii.

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  Fig. 4 Average lengths (mm) obtained of all the borders of the triangles. Comparing these measurements for the black- and white ancestry groups (A), females, males (B) as well as left- and right sides (C). Letters in brackets refer to the reference points inserted, and distance measured between the points.

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  Fig. 5 Average areas (mm2) obtained for the suboccipital triangle (ST) and the inferior suboccipital triangle (IST). Comparing these areas for the black- and white ancestry groups (A), females, males (B) as well as left- and right sides (C).

Reference

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