Sternoclavicular and acromiocalvicular and shoulder joints pdf - Upper limb

362

CHAPTER 9

scapula and the lateral end of the clavicle (Fig. 9.32).

This occurs between the acromion of the

Articulation:

phalic vein and the left common carotid artery

brachiocephalic artery; on the left, the left brachioce

The sternohyoid muscle; on the right, the

Posteriorly:

omastoid and pectoralis major muscles

The skin and some fibers of the sternocleid

Anteriorly:

Important Relations

subclavius muscles (Fig. 9.33).

of the clavicle is produced by the pectoralis minor and the

toid, levator scapulae, and rhomboid muscles. Depression

the clavicle is produced by the trapezius, sternocleidomas

duced by the trapezius and rhomboid muscles. Elevation of

serratus anterior muscle. The backward movement is pro

The forward movement of the clavicle is produced by the

of the clavicle take place in the lateral compartment.

place in the medial compartment. Elevation and depression

Forward and backward movement of the clavicle takes

to the subclavius muscle.

The supraclavicular nerve and the nerve

Nerve supply:

articular surfaces.

attached to the margins of the cartilage covering the

This lines the capsule and is

Synovial membrane:

the sternal end of the clavicle (Fig. 9.32).

rib with the 1st costal cartilage to the inferior surface of

strong ligament that runs from the junction of the 1st

costoclavicular ligament

The

Accessory ligament:

below.

face of the clavicle above and to the first costal cartilage

attached to the superior margin of the articular sur

to the interior of the capsule, but it is also strongly

compartments (Fig. 9.32). Its circumference is attached

within the joint and divides the joint’s interior into two

This flat fibrocartilaginous disc lies

Articular disc:

ments.

sternoclavicular liga

behind the joint by the strong

The capsule is reinforced in front of and

Ligaments:

margins of the articular surfaces.

This surrounds the joint and is attached to the

Capsule:

Synovial double-plane joint

Type:

lage (Fig. 9.32).

clavicle, the manubrium sterni, and the 1st costal carti

This occurs between the sternal end of the

Articulation:

The Upper Limb

Sternoclavicular Joint

■

is a

■

Movements

Muscles Producing Movement

■

Acromioclavicular Joint

■

scalenus anterior

suprascapular artery

highest thoracic artery

thoracoacromial artery

lateral thoracic artery

anterior and

posterior circumflex

humeral arteries

subscapular artery

circumflex scapular artery

deep branch of

superficial cervical

artery

subclavian artery

thyrocervical trunk

superficial cervical artery

FIGURE 9.31

Arteries that take part in anastomosis around the shoulder joint.

Basic Anatomy

363

articular disc

capsule and anterior sternoclavicular ligament

costoclavicular
ligament

joint cavity

superior acromioclavicular ligament and capsule

coracoclavicular ligament

coracoacromial ligament

articular disc

joint cavity

articular disc

capsule and anterior sternoclavicular ligament

costoclavicular
ligament

nt cavity

coracoacromial ligament

articular disc

joint cavity

FIGURE 9.32

Acromioclavicular joint.

Sternoclavicular joint. B.

trapezius (upper part)

sternocleidomastoid,

levator scapulae,

and rhomboid muscles

pectoralis

minor and

subclavius

trapezius

(middle fibers), levator

scapulae, and rhomboids

serratus

outer edge of

fourth rib

pectoralis

minor

FIGURE 9.33

The wide range of movements possible at the sternoclavicular and the acromioclavicular joints gives great

mobility to the clavicle and the upper limb.

Sternoclavicular Joint Injuries

is the more serious one because the displaced clavicle may

The strong costoclavicular ligament firmly holds the medial end

of the clavicle to the 1st costal cartilage. Violent forces directed

along the long axis of the clavicle usually result in fracture of that

bone, but dislocation of the sternoclavicular joint takes place

occasionally.

Anterior dislocation results in the medial end of the clav-

icle projecting forward beneath the skin; it may also be pulled

upward by the sternocleidomastoid muscle.

Posterior dislocation usually follows direct trauma applied to

the front of the joint that drives the clavicle backward. This type

press on the trachea, the esophagus, and major blood vessels in

the root of the neck.

If the costoclavicular ligament ruptures completely, it is

difficult to maintain the normal position of the clavicle once

reduction has been accomplished.

C L I N I C A L N O T E S

364

CHAPTER 9

The skin

Superiorly:

The trapezius muscle

Posteriorly:

The deltoid muscle

Anteriorly:

Important Relations

when the clavicle is elevated or depressed (Fig. 9.33).

A gliding movement takes place when the scapula rotates or

The suprascapular nerve

Nerve supply:

articular surfaces.

attached to the margins of the cartilage covering the

This lines the capsule and is

Synovial membrane:

the upper limb from the clavicle.

responsible for suspending the weight of the scapula and

undersurface of the clavicle (Fig. 9.32). It is largely

extends from the coracoid process to the

lar ligament

coracoclavicu

The very strong

Accessory ligament:

joint cavity from above (Fig. 9.32).

projects into the

fibrocartilaginous disc

wedge-shaped

reinforce the capsule; from the capsule, a

ligaments

inferior acromioclavicular

Ligaments: Superior

margins of the articular surfaces.

This surrounds the joint and is attached to the

Capsule:

Synovial plane joint

Type:

The Upper Limb

■

and

■

Movements

■

ing blocking or tackling in football or any severe fall, can result

and rotary movements of the scapula occur at this important

upper limb is transmitted to the clavicle through this ligament,

eral part of the clavicle. The greater part of the weight of the

binds the coracoid process to the undersurface of the lat

depends on the strong coracoclavicular ligament, which

upper surface of the acromion. The strength of the joint

dency for the lateral end of the clavicle to ride up over the

The plane of the articular surfaces of the acromioclavicular

Acromioclavicular Joint Injuries

joint passes downward and medially so that there is a ten-

ligament.

Acromioclavicular Dislocation

A severe blow on the point of the shoulder, as is incurred dur-

in the acromion being thrust beneath the lateral end of the

clavicle, tearing the coracoclavicular ligament. This condition

is known as shoulder separation. The displaced outer end of

the clavicle is easily palpable. As in the case of the sternocla-

vicular joint, the dislocation is easily reduced, but withdrawal

of support results in immediate redislocation.

C L I N I C A L N O T E S

Shoulder Joint

head of the humerus against the glenoid fossa of the

cle initiates the movement of abduction and holds the

supraspinatus, are involved. The supraspinatus mus

367). The middle fibers of the deltoid, assisted by the

thoracic wall (see scapular–humeral mechanism, page

at the shoulder joint and between the scapula and the

Abduction of the upper limb occurs both

Abduction:

dorsi, and teres major muscles.

formed by the posterior fibers of the deltoid, latissimus

Normal extension is about 45° and is per

Extension:

biceps, and coracobrachialis muscles.

by the anterior fibers of the deltoid, pectoralis major,

Normal flexion is about 90° and is performed

Flexion:

The following movements are possible (Fig. 9.36):

capsule is the weakest area.

support to the humerus. In addition, the inferior part of the

bows downward because of its length and gives little actual

humerus is supported by the long head of the triceps, which

the joint is abducted, the lower surface of the head of the

laris, supraspinatus, infraspinatus, and teres minor. When

front, above, and behind the joint—namely, the subscapu

the tone of the short rotator cuff muscles that cross in

in its movements.) The strength of the joint depends on

(Compare with the hip joint, which is stable but limited

the stability of the joint has been sacrificed to permit this.

The shoulder joint has a wide range of movement, and

The axillary and suprascapular nerves

Nerve supply:

subscapularis muscle (Fig. 9.34).

beneath the

subscapularis bursa

the capsule to form the

biceps brachii. It extends through the anterior wall of

lar sheath around the tendon of the long head of the

articular surfaces (Figs. 9.34 and 9.35). It forms a tubu

attached to the margins of the cartilage covering the

This lines the capsule and is

Synovial membrane:

(Fig. 9.34).

Its function is to protect the superior aspect of the joint

extends between the coracoid process and the acromion.

coracoacromial ligament

The

Accessory ligaments:

the humerus (Fig. 9.34).

root of the coracoid process to the greater tuberosity of

strengthens the capsule above and stretches from the

coracohumeral ligament

tuberosities (Fig. 9.34). The

ens the capsule and bridges the gap between the two

strength

transverse humeral ligament

the capsule. The

weak bands of fibrous tissue that strengthen the front of

are three

glenohumeral ligaments

The

Ligaments:

(the rotator cuff muscles).

supraspinatus, infraspinatus, and teres minor muscles

by fibrous slips from the tendons of the subscapularis,

allowing a wide range of movement. It is strengthened

of the humerus (Fig. 9.35). The capsule is thin and lax,

labrum; laterally, it is attached to the anatomic neck

ally to the margin of the glenoid cavity outside the

This surrounds the joint and is attached medi

Capsule:

Synovial ball-and-socket joint

Type:

(Figs. 9.34 and 9.35).

glenoid labrum

called the

deepened by the presence of a fibrocartilaginous rim

by hyaline articular cartilage, and the glenoid cavity is

cavity of the scapula. The articular surfaces are covered

of the humerus and the shallow, pear-shaped glenoid

This occurs between the rounded head

Articulation:

■

Movements

■

Basic Anatomy

vessels and brachial plexus

The subscapularis muscle and the axillary

Anteriorly:

Important Relations

movements.

This is a combination of the above

Circumduction:

deltoid muscle.

mus dorsi, the teres major, and the anterior fibers of the

55°. This is performed by the subscapularis, the latissi

Normal medial rotation is about

Medial rotation:

minor, and the posterior fibers of the deltoid muscle.

45°. This is performed by the infraspinatus, the teres

Normal lateral rotation is 40° to

Lateral rotation:

teres minor muscles.

the pectoralis major, latissimus dorsi, teres major, and

45° across the front of the chest. This is performed by

Normally, the upper limb can be swung

Adduction:

joint.

to contract and abduct the humerus at the shoulder

scapula; this latter function allows the deltoid muscle

365

■

coracohumeral ligament

capsule of shoulder joint

transverse humeral ligament

synovial sheath

tendon of long

head of biceps

pectoralis major tendon

latissimus dorsi

teres major

capsule of shoulder joint

subscapularis

subacromial bursa

coracoclavicular ligament

coracoacromial ligament

subscapularis bursa

acromion

supraspinatus

deltoid

infraspinatus

glenoid fossa

glenoid labrum

teres minor

posterior circumflex

humeral artery

long head of triceps

teres major

axillary vein

axillary artery

radial nerve

axillary nerve

posterior cord of brachial plexus

pectoralis major

subscapularis

capsule

cephalic vein

short head of biceps

coracoid process

subscapularis bursa

long head of biceps

deltoid

coracoacromial ligament

FIGURE 9.34

Shoulder joint and its relations.

Sagittal section.

Anterior view.

366

CHAPTER 9

The Upper Limb

acromium

subacromial bursa

part of rotator cuff

supraspinatus

capsule

synovial membrane

glenoid labrum

glenoid fossa

scapula

synovial membrane

capsule

axillary nerve

teres major

long head of triceps

quadrangular space

posterior

axillary

vessels

surgical

neck of

humerus

long head of biceps

deltoid

FIGURE 9.35

Interior of the shoulder joint.

extension

flexion

adduction

abduction

lateral rotation

medial rotation

circumduction

FIGURE 9.36

The movements possible at the shoulder joint. Pure glenohumeral abduction is possible only as much as about

120°; further movement of the upper limb above the level of the shoulder requires rotation of the scapula (see text).

Basic Anatomy

through the joint and emerges beneath the transverse

The tendon of the long head of the biceps muscle passes

lary nerve, and the posterior circumflex humeral vessels

The long head of the triceps muscle, the axil

Inferiorly:

bursa, coracoacromial ligament, and deltoid muscle

The supraspinatus muscle, subacromial

Superiorly:

The infraspinatus and teres minor muscles

Posteriorly:

367

■

ligament.

intercostobrachial nerves

(T1) and the

the arm

medial cutaneous nerve of

of the arm is supplied by the

(C5 and 6). The skin of the armpit and the medial side

a branch of the radial nerve

cutaneous nerve of the arm,

lower lateral

the arm below the deltoid is supplied by the

lary nerve (C5 and 6). The skin over the lateral surface of

a branch of the axil

lateral cutaneous nerve of the arm,

upper

over the lower half of the deltoid is supplied by the

(C3 and 4). The skin

supraclavicular nerves

is from the

point of the shoulder to halfway down the deltoid muscle

The sensory nerve supply (Fig. 9.38) to the skin over the

Superficial Sensory Nerves

these movements.

shows the direction of pull of the muscles responsible for

summarizes the movements of abduction of the arm and

head is accomplished by rotating the scapula. Figure 9.37

of the acromion. Further elevation of the arm above the

ity of the humerus comes into contact with the lateral edge

At about 120° of abduction of the arm, the greater tuberos

joint and a 1° abduction occurs by rotation of the scapula.

abduction of the arm, a 2° abduction occurs in the shoulder

as well as movement at the shoulder joint. For every 3° of

Abduction of the arm involves rotation of the scapula

clavicular ligament.

of rotation may be considered to pass through the coraco

so that the position of the glenoid fossa is altered, the axis

tone of muscles. When the scapula rotates on the chest wall

cle by the strong coracoclavicular ligament assisted by the

The scapula and upper limb are suspended from the clavi

The Scapular–Humeral Mechanism

The Upper Arm

Skin

(T2). The

skin of the back of the arm (Fig. 9.38) is supplied by
the
the radial nerve (C8).

a branch of

posterior cutaneous nerve of the arm,

Stability of the Shoulder Joint

example, diseases of the spinal cord and vertebral column and

Injury to the shoulder joint is followed by pain, limitation of

nerve. The joint is sensitive to pain, pressure, excessive traction,

displacement of the humerus can also stretch and damage the

of skin sensation over the lower half of the deltoid. Downward

nerve, as indicated by paralysis of the deltoid muscle and loss

into the quadrangular space can cause damage to the axillary

muscle. A subglenoid displacement of the head of the humerus

the humerus is no longer bulging laterally beneath the deltoid

shoulder is seen to be lost because the greater tuberosity of

with shoulder dislocation, the rounded appearance of the

violence to the front of the joint. On inspection of the patient

Posterior dislocations are rare and are usually caused by direct

tendons of these muscles are fused to the underlying capsule of

of the short muscles that bind the upper end of the humerus to

ble structure. Its strength almost entirely depends on the tone

The shallowness of the glenoid fossa of the scapula and the lack

of support provided by weak ligaments make this joint an unsta-

the scapula—namely, the subscapularis in front, the supraspi-

natus above, and the infraspinatus and teres minor behind. The

the shoulder joint. Together, these tendons form the rotator cuff.

The least supported part of the joint lies in the inferior loca-

tion, where it is unprotected by muscles.

Dislocations of the Shoulder Joint

The shoulder joint is the most commonly dislocated large joint.

Anterior Inferior Dislocation
Sudden violence applied to the humerus with the joint fully

abducted tilts the humeral head downward onto the inferior

weak part of the capsule, which tears, and the humeral head

comes to lie inferior to the glenoid fossa. During this move-

ment, the acromion has acted as a fulcrum. The strong flexors

and adductors of the shoulder joint now usually pull the humeral

head forward and upward into the subcoracoid position.

Posterior Dislocations

radial nerve.

Shoulder Pain

The synovial membrane, capsule, and ligaments of the shoulder

joint are innervated by the axillary nerve and the suprascapular

and distention. The muscles surrounding the joint undergo reflex

spasm in response to pain originating in the joint, which in turn

serves to immobilize the joint and thus reduce the pain.

movement, and muscle atrophy owing to disuse. It is important

to appreciate that pain in the shoulder region can be caused by

disease elsewhere and that the shoulder joint may be normal; for

the pressure of a cervical rib (see page XXX) can cause shoul-

der pain. Irritation of the diaphragmatic pleura or peritoneum

can produce referred pain via the phrenic and supraclavicular

nerves.

C L I N I C A L N O T E S

368

CHAPTER 9

The Upper Limb

FIGURE 9.37

Movements of abduction of the shoulder joint and rotation of the scapula and the muscles producing these

SA, serratus anterior.

mion. Elevation of the arm above the head is accomplished by rotating the scapula. S, supraspinatus; D, deltoid; T, trapezius;

rotation of the scapula. At about 120° of abduction, the greater tuberosity of the humerus hits the lateral edge of the acro

movements. Note that for every 3° of abduction of the arm, a 2° abduction occurs in the shoulder joint, and 1° occurs by

Dermatomes and Cutaneous Nerves

The skin over the point of the shoulder and halfway down the

of the same segment, pass to the skin in two or more different

upper limb; the C7 dermatome is situated on the middle finger;

cal segments C3 to 6 are located along the lateral margin of the

upper limb. It is seen that the dermatomes for the upper cervi

It may be necessary for a physician to test the integrity of the

spinal cord segments of C3 through T1. The diagrams in Figures

1.23 and 1.24 show the arrangement of the dermatomes of the

and the dermatomes for C8, T1, and T2 are along the medial mar-

gin of the limb. The nerve fibers from a particular segment of the

spinal cord, although they exit from the cord in a spinal nerve

cutaneous nerves.

lateral surface of the deltoid muscle is supplied by the supracla-

vicular nerves (C3 and 4). Pain may be referred to this region as a

result of inflammatory lesions involving the diaphragmatic pleura

or peritoneum. The afferent stimuli reach the spinal cord via the

phrenic nerves (C3, 4, and 5). Pleurisy, peritonitis, subphrenic

abscess, or gallbladder disease may therefore be responsible

for shoulder pain.

C L I N I C A L N O T E S