the shoulder region

The shoulder region

The shoulder region
Deltoid Teres major Subscapularis Supraspinatus Infraspinatus Teres minor Rotator cuff Subacromial bursa
Shoulder joint Abduction mechanics Supraspinatus tendonitis Painful arc Supraspinatus rupture The shoulder in sections

Deltoid

Arises from the clavicle and scapula (acromion and spine) immediately below the attachment of trapezius muscle.
Origin
clavicle
acromion
spine

Deltoid

the two muscles, deltoid and trapezius may be regarded as being one large continuous sheet with the spine of the scapula, the acromion, and the lateral third of the clavicle exposed between them
trapezius
deltoid

Deltoid

Inserted into the deltoid tuberosity of the humerus.
Insertion

Deltoid

The muscle crosses the shoulder joint and forms the rounded contour of the shoulder owing to the underlying upper end of the humerus, this rounded appearance is lost when the shoulder dislocates.
Dislocation of the shoulder

Deltoid

The muscle is triangular in shape when viewed from the lateral side, hence its name (G. delta-like).

Deltoid

Axillary nerve from the brachial plexus
Nerve supply

Deltoid

The central fibers are multipennate while the anterior and posterior fibers are parallel
Action
Central fibers

Deltoid

Acting in part the anterior fibers flex and medially rotate the humerus.
Action
Medial rotation

Deltoid

The middle fibers abduct the humerus.
Action

Deltoid

The posterior fibers extend and laterally rotate the humerus.
Action
lateral rotation

Deltoid

The anterior and posterior fibers are alternating in action when swinging the arm during walking
Action

Teres major

Arises from the dorsal surface of the inferior angle of the scapula
Origin

Teres major

Inserted into the medial lip of the intertubercular groove of the humerus
Insertion

Teres major

The the tendon of that latissimus dorsi curves around the lower border of teres major and comes to lie in front of it since the former is inserted lateral to the tendon of teres major
Insertion

Teres major

Lower subscapular nerve.
Nerve supply



Teres major
An adductor and extensor of the humerus at the shoulder joint
Action

Teres major

it is also an important stabilizer of the proximal end of the humerus during abduction of the shoulder joint
Action

Subscapularis

Subscapular fossa
Origin

Subscapularis

Medial to it, serratus anterior is attached to the anterior aspect of the medial border of the scapula;
Origin


these two muscles, serratus anterior and subscapularis thus separate the scapula from the thoracic cage
Subscapularis


The tendon of subscapularis extends in front of the shoulder joint, separated from the joint by the subscapular bursa
Subscapularis

Attached to the lesser tubercle of the humerus

Subscapularis
Insertion

Subscapularis

The muscle is an obvious medial rotator of the humerus.
Action

Subscapularis

Upper and lower subscapular nerves
Nerve sypply

Supraspinatus

Supraspinous fossa of the scapula (deep to trapezius)
Origin

Supraspinatus

its tendon passes beneath the coraco-acromial ligament separated from it by the subacromial bursa superior to the shoulder joint
Coraco-acromial ligament
Subacromial bursa

Superior facet on the greater tubercle of the humerus

Supraspinatus
Insertion

Supraspinatus

An obvious abductor
Action

Function of a bursa

a bursa is a flattened sac containing a film of synovial fluid, it is usually present where tendons rub against bones or ligaments; here supraspinatus tendon against coraco-acromial ligament]

The greater tubercle of the humerus carries 3 smooth facet: superior, middle, and inferior. The superior one is for the attachment of supraspinatus The middle for infraspinatus The inferior for teres minor muscle


Infraspinatus
Infraspinous fossa
Origin

Infraspinatus

Its tendon passes behind the shoulder joint to be attached to the humerus

Infraspinatus

The middle facet on the greater tubercle of the humerus
Insertion

Infraspinatus

An obvious lateral rotator of the humerus
Action

Suprascapular nerve

Both supraspinatus and infraspinatus muscles are supplied by suprascapular nerve. This is a branch of the brachial plexus in the neck that passes beneath the suprascapular ligament
Nerve supply

Suprascapular vessels

the accompanying vessels pass superior ligament into the supraspinous fossa then passes through spino-glenoid notch to supply infraspinatus

Teres minor

Extends from the lateral margin of the scapula to the inferior facet on the greater tubercle of the humerus
Origin & insertion

Teres minor

It is thus a lateral rotator
Action

Teres minor

deltoid
teres minor
Axillary nerve (similar to deltoid).
Nerve supply



Teres major & minor
Note that teres major passes to the front of the humerus but teres minor to the back, so that the humerus is like a cigarette held between two fingers

Rotator cuff muscles

The four muscles subscapularis, supraspinatus, infraspinatus, and teres minor form what is termed the rotator cuff

Rotator cuff action

The rotator cuff except supraspinatus are rotators of the humerus

The rotator cuff forms a musculotendinous cuff around the shoulder joint

Rotator cuff action


The tone of these muscles is very important in holding the head of the humerus into the glenoid fossa of the scapula So they are important in the stability of the shoulder joint.
Rotator cuff action

Rotator cuff action

Stability of the shoulder joint is the function that you should never forget The other functions of rotation are probably less important and can be performed by other more powerful muscles


Rotator cuff action
The tendons of the muscles of the rotator cuff are not only attached very to those to the shoulder joint but they fuse with the lateral part of the capsule (thus preventing the lax capsule from being nipped ).

Rotator cuff action

Since there is no cuff inferiorly, the capsule is attached below the articular margin to prevent it from being nipped

Rotator cuff action

Note that the cuff lies on the anterior (subscapularis), superior (supraspinatus), and posterior (infraspinatus and teres minor) aspect of the joint. The cuff is deficient inferiorly and this is a site of potential weakness of the shoulder joint which commonly dislocates inferiorly
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Subacromial bursa

Lesions of the cuff are a common cause of pain in the shoulder region. During abduction supraspinatus tendon is exposed to friction against the acromion process.

Subacromial bursa

Normally the friction is reduced by the subacromial bursa

Subacromial bursa

The subacromial bursa extends laterally beneath deltoid, hence its name "subdeltoid bursa"

Shoulder joint

A synovial joint of the ball and socket variety There is a marked disproportion between the large head of the humerus (the ball) and the small shallow glenoid fossa (the socket)
Type & articulation

Shoulder joint

The glenoid fossa only accepts about one-third of the humeral head

Shoulder joint

Is therefore very mobile
Cyclograph showing range of abduction at shoulder girdle and joint
Mobility

Shoulder joint

As a quick and useful clinical guide to rotation at the shoulder, the patient can be asked if the can do their own hair
Mobility

Shoulder joint

If a woman, they can fasten brassiere straps at the back
Mobility



Shoulder joint
If a man, he can touch the opposite scapula
Mobility

Shoulder joint

Though very mobile, is easily dislocated

Glenoid labrum

The glenoid fossa is deepened slightly by a rim of fibrocartilage (the glenoid labrum) but is still very shallow

Capsule

The capsule is loose (thus it allows wide range of movement) it is attached close to the margin of the articular surfaces.

Capsule

Medially it encloses the labrum and the origin of the long head of biceps muscle which arises from the supraglenoid tubercle.

Long head of biceps

The long head of triceps which arises from the infraglenoid tubercle is outside the capsule


Capsule
Laterally the capsule is attached to the anatomical neck of the humerus except inferiorly where its attachment extends down to the surgical neck

Openings of the capsule

one between the tubercles of the humerus which allows the passage of the tendons of the long head of biceps
2

Openings of the capsule

The other opening is located anteriorly and allows communication with the subscapularis bursa.

Subacromial bursa

The subacromial bursa does not communicate with the cavity of the shoulder joint

ligaments

The capsule is strengthened by intrinsic and extrinsic ligaments

Intrinsic ligaments

Are thickenings of the capsule itself, these are the three parts of the glenohumeral ligament anteriorly
Has extensions indicated by its name
superior
anterior
inferior

Intrinsic ligaments

coracohumeral ligament superiorly
Has extensions indicated by its name

Intrinsic ligaments

the transverse humeral ligament which bridges over the superior end of the intertubercular groove converting it into a canal for the passage of the tendon of the long head of biceps as it emerges from the anterior opening of the capsule.

Extrinsic ligaments

An extrinsic ligament the coraco-acromial ligament is more important than the previously mentioned intrinsic ligaments. This strong ligament links the coracoid and acromion processes together. These three structures form the coraco-acromial arch

Coraco-acromial ligament

they prevent the superior displacement of the shoulder joint. Don't forget that the capsule is further strengthened by the tendons of the rotator of muscles fusing with its

Stability

The shoulder joint is unstable because of the disproportion of the articular surfaces shallowness of the glenoid fossa laxity of the capsule all these provide a wide range of movement on the expense of stability

Stability

As for the shoulder joint, muscles are the most important factor in providing stability particularly the rotator cuff muscles the long head of biceps and triceps; the latter during abduction lies beneath the head of the humerus, this is the weakest parts of the joint being bare of rotator cuff muscles.


Shoulder joint
Other factors include the coraco-acromial arch which supports the joint superiorly

Dislocation

Since the inferior aspect is unprotected by muscle, it is here that, in violent abduction, the humeral head may slip away from the glenoid to lie in the subglenoid region, whence it usually passes anteriorly into a subcoracoid position


The dislocated head is held adducted by the shoulder girdle muscles and internally rotated by subscapularis
Dislocation


when the arm is by the side of the body, deltoid contraction is ineffective sense it pulls vertically on the humerus therefore, the initial stage of abduction (the first 15-20 degrees) is done by supraspinatus
Abduction mechanics
The muscles

deltoid then takes over up to 90 degrees by means of its central multipennate fibers

Abduction mechanics
The muscles



shortly after, the movement at the glenohumeral joint is supplemented by rotation of the scapula produced by the lower fibers of serratus anterior and the upper and lower fibers of trapezius.
Abduction mechanics
The muscles


During abduction teres major stabilizes and holds down the proximal end of the humerus the long head of triceps lying immediately beneath the head provides further stability
Abduction mechanics
The muscles

Abduction mechanics

During abduction the greater tubercle of the humerus hits the acromion
The bones

Abduction mechanics

The greater tubercle can be released by lateral rotation of the arm
The bones



Abduction mechanics
It is therefore necessary to rotate the arm laterally to attain full abduction This must be remembered when carrying out the movement on an unconscious patient, since further abduction without lateral rotation would produce dislocation.
The bones

Abduction mechanics

Others believe that it is NOT the interlocking of the greater tubercle and the acromion that necessitates lateral rotation, but this is due to the fact that no further articular surface is available on the humerus
The bones

Abduction mechanics

lateral rotation in this case would bring the articular surface from below to above the glenoid
The bones

Blood supply

Is derived from the anterior and posterior circumflex humeral arteries (from the axillary) and the suprascapular artery (from the subclavian artery).

Nerve supply

Is derived from the suprascapular, axillary, and lateral pectoral nerves


Supraspinatus tendonitis
The tendon of supraspinatus undergoes degenerative changes and calcification in old age
wear

Supraspinatus tendonitis

The tendon of supraspinatus undergoes degenerative changes and calcification in old age
tear

Supraspinatus tendonitis

The tendon of supraspinatus undergoes degenerative changes and calcification in old age
repair

Supraspinatus tendonitis

The tendon of supraspinatus undergoes degenerative changes and calcification in old age
calcification

Painful arc

In long standing cases of degeneration of rotator cuff tendons It is characterized by painful arc of shoulder movement between 50-130 degrees in this range the tendon and the overlying acromion are in intimate contact


Painful arc
In long standing cases of degeneration of rotator cuff tendons It is characterized by painful arc of shoulder movement between 50-130 degrees in this range the tendon and the overlying acromion are in intimate contact

Painful arc

In long standing cases of degeneration of rotator cuff tendons It is characterized by painful arc of shoulder movement between 50-130 degrees in this range the tendon and the overlying acromion are in intimate contact

Rupture of the calcified supraspinatus tendon prevents active initiation of abduction

Supraspinatus rupture


the patient has to develop the trick of tilting the body towards the injured side so that gravity passively swings the arm from the trunk in order that deltoid comes into play
Supraspinatus rupture

Greater tubercle

Lesser tubercle
Head of humerus
Glenoid fossa

Clavicle

Acromion
Coracoid process
Glenoid fossa

Greater tubercle

Lesser tubercle
Head of humerus
Glenoid fossa
Axial MRI

Subscapularis

Infraspinatus
Deltoid
Long head of biceps

Subscapularis

Infraspinatus
Deltoid
Long head of biceps
Axial MRI



Pectoralis major
Pectoralis minor
Coracobrachialis & short head of biceps
Suprascapular vessels

Pectoralis major

Pectoralis minor
Coracobrachialis & short head of biceps
Suprascapular vessels
Axial MRI

Trapezius

Deltoid
Supraspinatus
Clavicle
Oblique coronal MRI

Glenoid fossa

Glenoid labrum
Head of humerus
Greater tuberosity
Oblique coronal MRI