Download MBBS Anatomy PPT 24 Anatomy Of Shoulder Joint Notes

ARTICULATION

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Articulation is

between:

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The rounded

head of the
humerus and

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Glenoid

cavity

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The shallow,

pear-shaped
glenoid cavity
of the scapula.

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The articular surfaces are covered by hyaline cartilage.
The glenoid cavity is deepened by the presence of a

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fibrocartilaginous rim called the glenoid labrum.

TYPE

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Synovial
Ball-and-socket joint

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FIBROUS CAPSULE

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The fibrous capsule surrounds the joint and is attached:

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Medially to the margin of the glenoid cavity outside the labrum;
Laterally to the anatomic neck of the humerus.

The capsule is thin and lax, allowing a wide range of

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movement.

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LIGAMENTS

Accessory ligaments:

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The coracoacromial ligament

3. The coracohumeral ligament

extends between the coracoid process

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strengthens the capsule from

and the acromion. Its function is to

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above and stretches from the root

6 protect the superior aspect of the

of the coracoid process to the

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joint.

greater tuberosity of the humerus.

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2. The transverse

humeral ligament

strengthens the

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capsule and bridges

the gap between the

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two humeral

tuberosities.

1. The glenohumeral

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ligaments are three

weak bands of fibrous

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tissue that strengthen

the front of the capsule.

SYNOVIAL MEMBRANE

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It lines the fibrous

capsule.

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It is attached to

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the margins of

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the cartilage

covering the

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articular surfaces.

It forms a tubular

sheath around the

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tendon of the long

head of the biceps

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brachii.

It extends

through the

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anterior wall of

the capsule to

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form the

subscapularis

bursa beneath the

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subscapularis

muscle.

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NERVE SUPPLY

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Articular branches of the axillary & the suprascapular nerves

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The following movements

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are possible:

Flexion

? Abduction

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? Lateral rotation

Extension

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Circ ?

um Ad

du d

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c u

ti cti

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on on

? Medial rotation

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Flexion

Normal flexion

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is about 90?

It is performed

by the:

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1. Anterior fibers of

the deltoid

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2. Pectoralis major
3. Biceps brachii
4. Coracobrachialis

1

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Extension:

Normal

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extension is

about 45?

It is performed

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by the:

1.

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Posterior fibers of

the deltoid,

2.

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Latissimus dorsi

3.

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Teres major

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Abduction:

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Abduction of the upper limb occurs both at the shoulder joint and

between the scapula and the thoracic wall.

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It is initiated by supraspinatus from 0 to 18

Then from 19 to 120 by the middle fibers of the deltoid.

Then above 90 by rotation of the scapula by 2 muscles ( Trapezius &

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S.A..)

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The supraspinatus muscle:

initiates the movement of abduction(from 0 to 19) and
holds the head of the humerus against the glenoid fossa of the

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scapula;

This latter function of the supraspinatus allows the

deltoid muscle to contract and abduct the humerus at the

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shoulder joint.

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Adduction:

Normally the upper

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limb can be swung

45? across the front

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of the chest.

This is performed

by:

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1. pectoralis major

2. latissimus dorsi

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3. teres major

4. teres minor

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Lateral rotation:

Normal lateral

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rotation is about

40 to 45?.

This is

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performed by

the:

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1. infraspinatus

2. teres minor

3. the posterior

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fibers of the

deltoid muscle

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Medial rotation:

Normal medial

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rotation is about

55?.

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This is performed

by the:

1. subscapularis

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2. latissimus dorsi

3. teres major

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4. anterior fibers of

the deltoid.

Circumduction:

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This is a movement in

17 which the distal end

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of the humerus

moves in circular

motion while the

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proximal end

remains stable

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It is formed by

flexion,

abduction,

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extension and

adduction.

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Successively

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Important relations of

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shoulder joint

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Posteriorly:

Infraspinatus
Teres minor muscles.

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Superiorly:

1. Deltoid muscle

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2. Coracoacromial ligament
3. Subacromial (subdeltoid) bursa
4. Supraspinatus muscle & tendon

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2. the axil ary nerve

3. the posterior circumflex

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humeral vessels

1. the long head of

the triceps muscle

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Inferiorly:

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2

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The long head of the biceps brachii originates from the

supraglenoid tubercle of the scapula,

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It is intracapsular but extrasynovial
It's tendon passes through the shoulder joint and emerges

beneath the transverse humeral ligament.

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Inside the joint, the tendon is surrounded by a separate

tubular sheath of the synovial capsule.

Abduction involves

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rotation of the scapula as

well as movement at the

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shoulder joint.

23 For every 3? of abduction

of the arm, a 2? abduction

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occurs in the shoulder

joint and a 1? abduction

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occurs by rotation of the

scapula.

At about 120? of abduction

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of the arm, the greater

tuberosity of the humerus

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impinges on lateral border

of coraco-acromial arch.

Further elevation of the

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arm above the head

accomplished by rotating

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the scapula.

MUSCLES IN THE SCAPULAR-HUMERAL MECHANISM

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STABILITY OF THE SHOULDER JOINT

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This joint is unstable because of the:

shallowness of the glenoid fossa

weak ligaments

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Its strength almost entirely depends on the tone of the rotator cuff muscles.

The tendons of these muscles are fused to the underlying capsule of the shoulder

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joint.

The least supported part of the joint lies in the inferior location, where it

is unprotected by muscles.

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DISLOCATIONS OF THE SHOULDER JOINT

The shoulder joint is the most

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26commonly dislocated large joint.

Anterior-Inferior

Dislocation

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Sudden violence

applied to the

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humerus with the

joint fully abducted

pushes the humeral

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head downward

onto the inferior

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weak part of the

capsule, which

tears, and the

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humeral head

comes to lie

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inferior to the

glenoid fossa.

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Wrist drop

A subglenoid displacement of the head of the humerus into the

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quadrangular space can cause damage to the axillary nerve.

This is indicated by paralysis of the deltoid muscle and loss of

skin sensation over the lower half of the deltoid.

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Downward displacement of the humerus can also stretch and

damage the radial nerve.

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Lesions that are commonly seen with an anterior dislocation

include the Hil -Sachs fracture and the Bankart fracture.

A Hil -Sachs fracture is a fracture of the humeral head. It occurs

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along the posterior and superior aspect and is caused by the

impaction of the humeral head on the inferior aspect of the

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glenoid process.

A Bankart fracture is caused by the same mechanism, but it is

a fracture of the inferior aspect of the glenoid process.

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ROTATOR CUFF

TENDINITIS

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Lesions of the rotator cuff are

a common cause of pain in

the shoulder region.

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Excessive overhead

36 activity of the upper limb

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may be the cause of tendinitis,

although many cases appear

spontaneously.

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During abduction of the

shoulder joint, the

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supraspinatus tendon is

exposed to friction against

the acromion.

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Under normal conditions the

amount of friction is reduced

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to a minimum by the large

subacromial bursa, which

extends laterally beneath the

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deltoid.

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Degenerative changes in the bursa are followed by degenerative changes in

the underlying supraspinatus tendon, and these may extend into the other

tendons of the rotator cuff.

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Clinically, the condition is known as subacromial bursitis,

supraspinatus tendinitis, or pericapsulitis.

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It is characterized by the presence of a spasm of pain in the middle

range of abduction when the diseased area impinges on the acromion.

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Painful Arc Syndrome

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RUPTURE OF THE SUPRASPINATUS TENDON

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In advanced cases of rotator cuff

tendinitis, the necrotic supraspinatus

tendon can become calcified or rupture.

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Rupture of the tendon seriously interferes with the normal

abduction movement of the shoulder joint.

The main function of the supraspinatus muscle is to hold the head of

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the humerus in the glenoid fossa at the commencement of abduction.

The patient with a ruptured supraspinatus tendon is unable to

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initiate abduction of the arm.

However, if the arm is passively assisted for the first 15? of

abduction, the deltoid can then take over and complete the

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movement to a right angle.

SHOULDER PAIN

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The synovial membrane, capsule, and ligaments of the shoulder joint are

innervated by the axillary nerve and the suprascapular nerve.

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The joint is sensitive to pain, pressure, excessive traction, and distension.

The muscles surrounding the joint undergo reflex spasm in response to

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pain originating in the joint, which in turn serves to immobilize the joint

and thus reduce the pain.

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

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muscle atrophy owing to disuse.


ANASTOMOSES

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AROUND THE

SCAPULAR REGIONS

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BRANCHES FROM THE SUBCLAVIAN ARTERY

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The

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suprascapular

artery, (branch

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from 1st part of

subclavian artery)

distributed to the

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supraspinous and

infraspinous fossae

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of the scapula.

The superficial

cervical artery,

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which gives off a

deep branch that

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runs down the

medial border of the

scapula.

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BRANCHES FROM THE AXILLARY ARTERY

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The subscapular

artery and its

circumflex scapular

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branch supply the

subscapular and

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infraspinous fossae of the

scapula.

The anterior &

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posterior circumflex

humeral artery.

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Both the circumflex

arteries form an

anastomosing circle

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around the surgical neck

of the humerus.

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LIGATION OF THE AXILLARY

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ARTERY

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The existence of the

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anastomosis around

the shoulder joint is

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vital to preserving the

upper limb if it

should it be necessary

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to ligate the axillary

artery.

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MCQ

Which of the following is NOT a rotator cuff muscle
A. Supraspinatus

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B. Infraspinatus

C. Teres major

D. Subscapularis

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MCQ

Abduction of shoulder joint is initiated by :
A. supraspinatus

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B. infraspinatus
C. trapezius
D. subscapularis

MCQ

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Which part of deltoid muscle is involved only in

shoulder joint abduction ?

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Anterior fibres
Posterior fibres
Middle fibres
All fibres
MCQ

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Which two rotator cuff muscles laterally rotate the

arm at the shoulder?

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A.Infraspinatus and subscapularis

B.Supraspinatus and infraspinatus

C.Teres Minor and Infraspinatus

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D.Teres minor and Subscapularis