Difference Between Sacrum and Coccyx

The key difference between sacrum and coccyx is that the sacrum is a triangular-shaped bone that consists of five fused segments (S1-S5) while the coccyx is the final segment of the vertebral column that includes three to five fused segments.

The adult vertebral column consists of 26 strong bones. It fulfils several major functions in our body such as enclosing and protecting the spinal cord, support to carry the weight of the body, acting as the main axis of the body and supporting the movements of our body, etc. Structurally, vertebral column has five different regions; namely, they are cervical, thoracic, lumbar, sacrum and coccyx. Sacrum and coccyx situate at the bottom of the vertebral column below the L5 vertebra. Both sacrum and coccyx are composing of fused small bones. Accordingly, the sacrum comprised of 5 fused vertebrae while the coccyx constituted of 3 to 5 fused small bones. Both sacrum and coccyx are mainly responsible for the backbone pains. However, they are important in weight-bearing and the functions such as walking, standing and sitting, etc.

CONTENTS

1. Overview and Key Difference
2. What is Sacrum
3. What is Coccyx
4. Similarities Between Sacrum and Coccyx
5. Side by Side Comparison – Sacrum vs Coccyx in Tabular Form
6. Summary

What is Sacrum?

Sacrum (sacral spine) is one of the main vertebrae in the human vertebral column. It is a flat triangular shape large bone formed from five fused segments (S1 –S5). It locates between the L5 vertebra and coccyx (last vertebra of the vertebral column).

Furthermore, it locates between the right and left iliac bones at the pelvic region. Its apex points inferiorly. And also its lateral walls have facets for articulation with the pelvis at the sacroiliac joints. The sacrum is important to support the upper body. Also, it is important in weight-bearing, maintaining balance and functional flexibility.

What is Coccyx?

Coccyx (tailbone) is the final segment or the bone of the vertebral column. It is a small triangular shaped bone composed of three to five small segments fused. It locates just below the sacrum and articulates with the apex of it. Structurally, it lacks vertebral arches and vertebral canal.

Moreover, though coccyx is a small bone, it is also important in weight bearing. Also, it is important in supporting and stabilizing the vertebral spinal column. Furthermore, it is important in walking, standing and sitting.

What are the Similarities Between Sacrum and Coccyx?

• Sacrum and coccyx locate at the bottom of the vertebral column below the L5 vertebra.
• Both are bones composed of fused small bones.
• Furthermore, they are triangular in shape.
• Both structures are important in weight-bearing and integral to functions such as walking, standing and sitting.
• They involve in the formation of the pelvis.

What is the Difference Between Sacrum and Coccyx?

The sacrum is a large triangular shaped vertebra that locates below the L5 vertebra of our vertebral column. On the other hand, the coccyx is a small triangular shaped vertebra that locates just below the sacrum. Therefore, this is the key difference between sacrum and coccyx. Furthermore, the structure contributes to another difference between sacrum and coccyx. That is; the sacrum is a structure composing five fused small segments while coccyx is a structure composing three to five small fused bones.

Moreover, the sacrum is attached to two iliac bones of the pelvis while coccyx is not attached to the iliac bones. Hence, it is another difference between sacrum and coccyx. We can also find a difference between sacrum and coccyx in their sizes too. When comparing the sizes of each bone, the sacrum is larger than the coccyx.

Below is an infographic on the difference between sacrum and coccyx that tabulates more details on these differences.

Summary – Sacrum vs Coccyx

Sacrum and coccyx are two segments of our vertebral column. Sacrum locates below the L5 vertebra and above the coccyx. On the other hand, the coccyx is the final bone of our vertebral column that locates just below the sacrum. Both sacrum and coccyx play an important role in our body. Hence, they support and stabilize our vertebral spinal column. Also, they are important to walk, standing and sitting. The sacrum is larger than coccyx. Furthermore, the sacrum is made from five fused bones. On the other hand, the coccyx is a small bone composing of three to five small bones. Thus, this is the summary of the difference between sacrum and coccyx.

Reference:

1. Eidelson, Stewart G. “The Sacrum and Coccyx.” SpineUniverse, SpineUniverse. Available here 
2. “Sacrum.” NeuroImage, Academic Press. Available here  

Image Courtesy:

1.”Blausen 0723 Pelvis”By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work, (CC BY 3.0) via Commons Wikimedia  
2.”Coccyx – posterior view02″ By DBCLS – Polygondata (CC BY-SA 2.1 jp) via Commons Wikimedia