Sternum

Question 1

what is the sternum and where is it located?

Answer 1

The sternum (or breastbone) is a flat bone located at the anterior aspect of the thorax

Question 2

where does the sternum lie?

Answer 2

It lies in the midline of the chest and has a ‘T’ shape

Question 3

what does the sternum help with?

Answer 3

As part of the bony thoracic wall, the sternum helps protect the internal thoracic viscera

Question 4

what are internal thoracic viscera examples?

Answer 4

the heart, lungs and oesophagus

Question 5

how can the sternum be divided into? what are they?

Answer 5

into three parts; the manubrium, body and xiphoid process. In children, these elements are joined by cartilage. The cartilage ossifies to bone during adulthood

Question 6

what are the 3 parts of the sternum joined by in children? in adults?

Answer 6

In children, these elements are joined by cartilage. The cartilage ossifies to bone during adulthood

Question 7

what is the manubrium?

Answer 7

The manubrium is the most superior portion of the sternum

Question 8

what shape is the manubrium?

Answer 8

trapezoid

Question 9

what is the superior aspect of the manubrium?

Answer 9

concave

Question 10

what does the concave superior aspect of the manubrium produce? known as?

Answer 10

a depression known as the jugular notch – this is visible underneath the skin

Question 11

what is present either side of the jugular notch?

Answer 11

Either side of the jugular notch, there is a large fossa lined with cartilage

Question 12

what do the large fossa either side of jugular notch articulate with? forming?

Answer 12

the medial ends of the clavicles, forming the sternoclavicular joints

Question 13

what is present on the lateral edges of the munubrium?

Answer 13

there is a facet (cartilage lined depression in the bone)

Question 14

what does the facet on the lateral edges of the manubrium articulate with?

Answer 14

articulate with the costal cartilage of the 1st rib, and a demifacet (half-facet) for articulation with part of the costal cartilage of the 2nd rib

Question 15

Inferiorly, what does the manubrium articulates with? what does this form?

Answer 15

the body of the sternum, forming the sternal angle

Question 16

how can the sternal angle be felt? where?

Answer 16

This can be felt as a transverse ridge of bone on the anterior aspect of the sternum

Question 17

what is the sternal angle commonly used as?

Answer 17

as an aid to count ribs, as it marks the level of the 2nd costal cartilage

Question 18

what is the body of the sternum like?

Answer 18

The body is flat and elongated – the largest part of the sternum

Question 19

what does the body of the sternum articulate with superiorly and inferiorly?

Answer 19

articulates with the manubrium superiorly and the xiphoid process inferiorly

Question 20

what does superior sternum and manubrium articulation form?

Answer 20

manubriosternal joint

Question 21

what does the inferior sternum and xiphoid process articulation form?

Answer 21

xiphisternal joint

Question 22

what are the lateral edges of the body marked by?

Answer 22

by numerous articular facets

Question 23

what are articular facets?

Answer 23

cartilage lined depressions in the bone

Question 24

what do the articular facets of the lateral edges of the body articulate with?

Answer 24

costal cartilages of ribs 3-6

Question 25

what is present on the 2nd & 7th ribs? what are they known as?

Answer 25

There are smaller facets for articulation with parts of the second and seventh ribs – known as demifacets

Question 26

what is the xiphoid process?

Answer 26

the most inferior and smallest part of the sternum

Question 27

what is the shape of the xiphoid process?

Answer 27

variable is shape and size

Question 28

where is the xiphoid process located?

Answer 28

at the level of the T10 vertebrae

Question 29

what is the xiphoid process largely composed of in structure?

Answer 29

The xiphoid process is largely cartilaginous in structure

Question 30

what happens to the xiphoid process later on in life? when?

Answer 30

and completely ossifies late in life – around the age of 40

Question 31

what does the xiphoid process articulate with in some individuals?

Answer 31

the xiphoid process articulates with part of the costal cartilage of the seventh rib

Question 32

what are sternal fractures associated with? e.g.?

Answer 32

severe blunt trauma to the chest, such as in a vehicular accident. They are relatively uncommon

Question 33

typically, how will the sternum break? what is this type of fracture known as?

Answer 33

Typically, the sternum will break into several pieces – this type of fracture is classified as a comminuted fracture

Question 34

what is the most common site of fracture?

Answer 34

the manubriosternal joint

Question 35

what is the manubriosternal joint?

Answer 35

where the manubrium meets the body of the sternum

Question 36

what happens to the fragments of the sternum? why?

Answer 36

Despite the degree of damage to the sternum, the fragments are not usually displaced due to the attachment of the pectoralis muscles

Question 37

what is the mortality rate of sternal fractures?

Answer 37

Sternal fractures have a high mortality rate (25-45%)

Question 38

why do sternal fractures have such a high mortality rate?

Answer 38

This is not due to the fracture itself, but usually as a result of heart and lung injuries, which are likely to occur simultaneously with the primary trauma

Question 39

what is crucial to check in patients with sternal fractures?

Answer 39

it is crucial to check patients with sternal fractures for visceral injury

Question 40

what are common investigations to check for visceral injury?

Answer 40

X-ray, CT and ultrasound