8 Thorax

Chapter contents

Sternum

Fractures

Ribs

Atypical ribs

1st rib

2nd rib

10th rib

11th rib

12th rib

Costal cartilages

Fractures

Sternum (Figs 8.1 and 8.2)

Type

Flat bone.

Fig. 8.1 Sternum (anterior aspect).

A–Jugular notch (suprasternal notch)

B–Clavicular notch

C–Manubrium sterni

D–Facet for 1st costal cartilage

E–Sternal angle

F–Body

G–Xiphisternal angle

H–Xiphoid process

I–Facet for 7th costal cartilage

J–Facet for 6th costal cartilage

K–Facet for 5th costal cartilage

L–Facet for 4th costal cartilage

M–Facet for 3rd costal cartilage

N – Facet for 2nd costal cartilage.

Fig. 8.2 Sternum (lateral aspect).

1 – Clavicular facet

2 – Facet for 1st costal cartilage

3 – Sternal angle

4 – Xiphisternal angle

5 – Xiphoid process

6 – Facet for 7th costal cartilage

7 – Facet for 6th costal cartilage

8 – Facet for 5th costal cartilage

9 – Facet for 4th costal cartilage

10 – Facet for 3rd costal cartilage

11 – Facet for 2nd costal cartilage.

Position

Lies on the anterior aspect of the thorax in the midline.

Articulations

The clavicular notch with the sternal end of the clavicle to form the sternoclavicular joint.

Notches on the lateral aspect of the sternum articulate with the first 7 costal cartilages to form the sternocostal joints.

Main parts

Manubrium sterni

Jugular (suprasternal) notch on the superior border; lies at the level of the 2nd–3rd thoracic vertebrae.

Clavicular notches on either side of the jugular notch; articulate with the clavicles to form the sternoclavicular joints.

Facet for the 1st costal cartilage, at the upper end of the lateral border.

Demi-facet for the 2nd costal cartilage, at the lower end of the lateral border.

Inferior border articulates with the body to form the sternal angle, which lies at the level of the 4th–5th thoracic vertebrae and can be easily palpated.

Body

4 segments –

form the long, thin body.

3 ridges –

connect the segments.

4 notches –

on each lateral aspect for the 3rd–6th costal cartilages.

2 demi-facets –

on each lateral aspect for the 2nd and 7th costal cartilages.

Xiphoid process

Superior angle –

completes the notch for the 7th costal cartilage.

Xiphisternal joint –

at the junction of the body and the xiphoid process at the level of the 9th–10th thoracic vertebrae.

Ossification

Primary centres

6 centres:

Manubrium –

5th month intrauterine life.

Body –

4 centres (1 per segment):

1st and 2nd segments – 5th month of intrauterine life.

3rd and 4th segments – 5th–6th month of intrauterine life.

Xiphoid process –

age 3.

Body begins to fuse after puberty – from the inferior aspect to the superior aspect and continues to age 25.

Radiographic appearances of the sternum (Figs 8.3 and 8.4)

Fig. 8.3 Sternum: anterior oblique projection.

A–Right sternoclavicular joint

B–5th rib

C–Manubrium

D–Sternal angle

E–Body of sternum

F–Xiphisternal joint

G–Xiphoid process

H–10th rib

I–Thoracic vertebra

J–Left sternoclavicular joint

K–Suprasternal notch.

(From Bryan 1996.)

Fig. 8.4 Sternum: lateral projection of a child.

1 – Sternoclavicular joints

2 – Manubrium

3 – Sternal angle Segments of the body of the sternum:

4 – 1st

5 – 2nd

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