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Anatomy of Shoulder Complex
Dr. Fadel Naim
Orthopedic Surgeon
Faculty of Medicine
IUG-Gaza
Trapezius

Origin
–
–
–
–
–
Medial third superior nuchal line on the occipital bone
External occipital protuberance
Ligament nuchae
Spine of 7th cervical vertebra
Spinous processes and supraspinous ligaments to T12
 INSERTION
– Upper fibers to lateral third of posterior border of
clavicle
– Middle fibers to medial acromion and superior lip of
spine of scapula
– Lower fibers to medial end of spine of scapula
 Action
– Laterally rotates, elevates and retracts scapula.
– If scapula is fixed, extends and laterally flexes neck
 Nerve
– Motor fibers form spinal accessory nerve (Cranial
nerve XI)
– Sensory fibers spinal nerves C3 and C4
Levator Scapulae
 Origin
– Posterior tubercles of transverse processes of C1-4
 INSERTION
– Upper part of medial border of scapula opposite the
supraspinous fossa
 Action
– Raises medial border of scapula
– In conjunction with middle fibers of trapezius and rhomboids,
pulls the scapula medially and upward
 Nerve
– Anterior primary rami of C3 and C4 and dorsal scapular
nerve (C5)
Rhomboid Minor
 Origin
– Lower ligamentum nuchea
– Spines of C7 and T1
 INSERTION
– Small area of posteromedial border of scapula at level of
spine, below levator scapulae
 Action
– Elevates the medial border of the scapula and pulls it
medially
 Nerve
– Dorsal scapular nerve (C5)
Rhomboid Major
 Origin
– Spines of T2-T5 and supraspinous ligaments
 INSERTION
– Lower half of posteromedial border of scapula,
opposite the infraspinous fossa
 Action
– Elevates the medial border of the scapula and
pulls it medially
 Nerve
– Dorsal scapular nerve (C5) (from root )
Deltoid
 ORIGIN
– Anterior fibers: Lateral third of clavicle
– Middle fibers: Acromion
– Posterior fibers: spine of scapula to
deltoid tubercle
 INSERTION
– Deltoid tuberosity
– Middle of lateral surface of humerus
 ACTION
– Abducts arm
– anterior fibers flex and medial rotate
– posterior fibers extend and lateral rotate
 NERVE
– Axillary nerve (C5, 6) (from posterior
cord)
Forms the rounded
contour of the
shoulder
Supraspinatus
 Origin
– Medial three quarters of supraspinous fossa of scapula
– Upper surface of spine
 INSERTION
– Superior facet on greater tuberosity of humerus
– Capsule of shoulder joint
 Action
– Abducts arm
– Stabilizes shoulder joint
 Nerve
– Suprascapular nerve
Infraspinatus
 Origin
– Medial three quarters of infraspinous fossa of scapula
 INSERTION
– Middle facet of greater tuberosity of humerus
– Capsule of shoulder joint
 Action
– Laterally rotates arm
– Stabilizes shoulder joint
 Nerve
– Suprascapular nerve
Teres Minor
 Origin
– Middle third lateral border of scapula above teres major
 INSERTION
– Inferior facet of greater tuberosity of humerus (below
infraspinatus)
– Capsule of shoulder joint
 Action
– Laterally rotates arm
– Stabilizes shoulder joint
 Nerve
– Axillary nerve
Pectoralis Minor
 Origin
3, 4, 5 ribs
 INSERTION
– Medial and upper surface of coracoid process of scapula
 Action
– Elevates ribs if scapula fixed
– Pulls shoulder downward and forward
 Nerve
– Medial pectoral nerve (from medial cord of brachial plexus)
Quadrangular space
Triangular space
Triangular interval
Quadrangular space

It is bounded:
– Superiorly by:
• Subscapularis
• Teres minor
– Inferiorly by:
• Teres major
– Medially by:
• Long head of triceps
– Laterally by:
• Humerus
The axillary nerve and the
posterior circumflex humeral
vessels pass backward
through this space
Triangular space


an area of
communication between
the axilla and the
posterior scapular region
formed by:
– the medial margin of the
long head of triceps
brachii
– the superior margin of
teres major
– the inferior margin of teres
The circumflex scapular artery and
minor
vein pass through this gap
Triangular interval

formed by:
– the lateral margin of the
long head of triceps
brachii;
– the shaft of the humerus;
– the inferior margin of teres
major
The radial nerve, the profunda
brachii artery and associated veins
pass through it
Quadrangular space syndrome



Hypertrophy of the quadrangular space
muscles or fibrosis of the muscle edges may
impinge on the axillary nerve.
Uncommonly, this produces weakness of the
deltoid muscle.
Typically it produces atrophy of the teres
minor muscle
– which may affect the control that the rotator cuff
muscles exert upon shoulder movement
Rotator Cuff Muscles
 Four of the scapulohumeral muscles
–
–
–
–
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
 Referred to as SITS muscles
 Called rotator cuff muscles because they
form a musculotendinous cuff around the
glenohumeral joint {Dynamic stabilizers
(“cuff”)}
 All except the supraspinatus are rotators of
the humerus
 The tendons of the muscle
blend with the fibrous capsule of
the glenohumeral joint to form a
musculotendinous rotator
cuff, which reinforces the
capsule on three sides:
– Anteriorly
– Superiorly
– Posteriorly
 The cuff is weakest anteroinferiorly, making shoulder
dislocation most common in this
direction.
 Injury to rotator cuff can occur in any of the following
manners:
– Acutely, following trauma;
– As a result of chronic impingement and overuse
(excessive abduction);
– Compromised blood supply.
 The most frequently injured tendon is the
supraspinatus, probably because it is relatively
avascular
 Additionally, the supraspinatus tendon is subject to
significant trauma as it is compressed between the
acromion and the humeral head during
abduction
Impingement
Types Of
Acromion
 Three distinct types of acromion can be seen on the angled
outlet Y view:
– The type I acromion, which is flat, is the "normal" acromion.
– The type II acromion is more curved and downward dipping,
– the type III acromion is hooked and downward dipping, obstructing
the outlet for the supraspinatus tendon.
 Cadaveric studies have shown an increased incidence of
rotator cuff tears in persons with type II and type III
acromions
Rotator Cuff Injuries

Injury or disease may damage the musculotendinous rotator cuff,
producing instability of the glenohumeral joint

Trauma may tear or rupture one or more of the tendons of the
muscles forming the rotator cuff

Acute tears may occur when the arm is violently pushed into
abduction

The patient reports a sharp pain in the anterosuperior part of the
shoulder

Rotator cuff injuries are also common in persons with throwing
activities

Rotator cuff tears also follow dislocation of the shoulder





Degenerative tendonitis of the rotator cuff is
common, especially in old people.
To test for this disease, the person is asked to
lower the fully abducted limb slowly and
smoothly.
From an approximately 90 ° abduction, the limb
will suddenly drop to the side in an uncontrolled
manner if the rotator cuff (especially the
supraspinatus part) is diseased and torn
The injury often results from an indirect force to
the abducted arm, such as a fall in a person older
than 45 years
Acute tears are uncommon in young persons.


This injury causes tenderness around the
greater tubercle of the humerus and pain
during 45 ° of passive abduction.
X-rays may be normal, but can reveal:
– Narrowing of the distance between the acromion
and humeral head (impingement)
– Erosion of the inferior acromion
– Sclerosis of the greater tuberosity
Subacromial Bursitis
130°
50°


The tendon of the supraspinatus is separated from the
coracoacromial ligament, acromion, and deltoid by the subacromial
bursa.
Painful arc syndrome
– When this bursa is inflamed abduction of the arm is extremely painful
during the arc of 50 to 130 °.



The pain may radiate as far distally as the hand.
Acute pain is also felt lateral to the acromion.
A painful arc signifies an impingement of a painful structure
during the movement of the humerus in relation to the roof of
the shoulder
 The commonnest
pathological situations
causing painful arc are:
– 1. Tendinitis of Supraspinatus
– 2. Tendinitis of Infraspinatus
– 3. Tendinitis of Subscapularis
– 4. Tendinitis of the long head of
the Biceps
– 5. Subacromial Bursitis
– 6. AC Sprain
 Less frequent pathologies
associated with a painful arc
are:
• metastases in the head of
the humerus
• metastases in the
acromion
• Instability of the shoulder
Glenohumeral motions
Glenohumeral motions
Glenohumeral motions
Scapular motions
Scapular motions
Protraction – Retraction
Scapular Motions
Rotational Elevation Of Glenoid Cavity
Rotational Depression Of Glenoid Cavity
4-43
Muscles Involved In Shoulder Movements
Movement
Prime movers
Secondary movers
Glenohumeral
Flexion
Anterior deltoid
Coracobrachialis
Pectoralis major
(clavicular head)
Extension
Latissimus dorsi
Teres major
Posterior deltoid
Teres minor
Triceps
Abduction
Deltoid (mid)
Supraspinatus
Anterior/posterior deltoid
Serratus anterior
Muscles Involved In Shoulder Movements
Movement
Prime movers
Secondary movers
Glenohumeral
Adduction
Pectoralis major
Teres major
Latissimus dorsi
External rotation
Infraspinatus
Posterior deltoid
Teres minor
Internal rotation
Subscapularis
Pectoralis major
Latissimus dorsi
Teres major
Anterior deltoid
Muscles Involved In Shoulder Movements
Movement
Prime movers
Secondary movers
Scapular
Retraction
Rhomboid
major/minor
Trapezius
Protraction
Serratus anterior
Upward rotation
Trapezius (upper and
lower)
Serratus anterior
(upper and lower)
Pectoralis minor
Muscles Involved In Shoulder Movements
Movement
Prime movers
Secondary movers
Scapular
Downward
rotation
Rhomboids
(major/minor)
Pectoralis minor
Elevation
Trapezius
Levator scapulae
Rhomboids
Depression
Latissimus dorsi
Pectoralis minor
Latissimus dorsi


The supraspinatus initiates abduction and the
deltoid takes over once the humerus is abducted
past 15 degrees
During full abduction of the arm we have to
laterally rotate our humerus to move the
greater tuberosity out of the way.

Even with this maneuver, space is too limited to
allow for the range of motion that is seen in a
normal individual.

The remainder of the range of motion is made
possible by scapular rotation.

Once we have abducted the arm past 20 degrees
or 30 degrees, for every 3 degrees of abduction at
the glenohumeral joint, 1 degree occurs at the
scapulothoracic surface and only 2 degrees
occurs at the glenohumeral joint.
Spinal Part (ramus externus) Of the accessory nerve




Runs downward in the posterior
triangle of the neck on levator
scapulae muscle
Accompanied by branches from
anterior rami of the 3rd and 4th
cervical nerves
Runs beneath the anterior border
of the trapezius muscle
It supplies the trapezius muscle
The suprascapular nerve




The suprascapular nerve arises from
the trunk formed by the union of the 5th
and 6th cervical nerves.
It innervates the suprasinatus and
infraspinatus muscles.
It enters the supraspintous fossa through
the suprascapular notch, below, the
superior transverse scapular lig.
It then passes beneath the
supraspinatous, and curves around the
lateral border of the spine of the scapula
to the infraspintous fossa
 The pectoral girdle involves the:
 SC joint
 AC joint
 Glenohumeral joint
 Generally, these joints move at the same time
 Functional defects in any of the joints impair
movements of the pectoral girdle.
Sternoclavicular Joint


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

The only articulation between the upper limb and the axial
skeleton
A saddle type of synovial joint functions as a ball and socket
joint
The sternal end of the clavicle articulates with the manubrium
of the sternum and the 1st costal cartilage
Can be palpated because the sternal end of the clavicle lies
superior to the manubrium of the sternum
The articular surfaces are covered with fibrocartilage
Articular capsule:
– The fibrous part of the articular capsule surrounds
the SC joint, including:
• the epiphysis at the sternal end of the clavicle
• the periphery of the articular disc
– attached to the margins of the articular surfaces
A synovial membrane:
– lines the fibrous part of the articular capsule and
both surfaces of the articular disc.
Nerve supply:
– The Supraclavicular nerve and nerve to Subclavius
Blood Supply:
– The SC joint is supplied by internal thoracic and
suprascapular arteries
Ligaments of the
SC Joint

Anterior and posterior SC ligaments:


The interclavicular ligament
–
–
Strengthens the capsule superiorly
It extends from the sternal end of one clavicle and passes to the
sternal end of the other clavicle.
Attached to the superior border of the manubrium of the sternum.
–

Reinforce the capsule anteriorly and posteriorly.
The costoclavicular ligament:

Anchors the inferior surface of the sternal end of the clavicle to the 1st
rib and its costal cartilage, limiting elevation of the pectoral girdle
articular disc
Articular disc
 Divides the SC joint into two compartments
 Attached to:
–
–
–
–
–
Anterior and posterior SC ligaments
The interclavicular ligament.
The interior capsule
Superiorly to clavicle
Inferiorly to 1st costal cartilage
 The articular disc serves as a shock absorber of
forces transmitted along the clavicle from the upper
limb
Movements of the SC Joint
 Although the SC joint is extremely strong, it is
significantly mobile to allow movements of the
pectoral girdle and upper limb
 Mobility of the clavicle at the sternoclavicular joint
is essential for the freedom of movement of
the upper limb.
 During full elevation of the limb, the clavicle is
raised to approximately a 60 ° angle.
 The SC joint moves up to 25 to 30 ° along its long
axis in several direction:
– anteriorly
– Posteriorly
– Inferiorly
 Forward and backward in the medial
compartment
 Elevation and depression in the lateral
compartment
Dislocation of
the SC Joint




The rarity of dislocation of the SC joint attests to its
strength
The force of a blow is usually transmitted along the long axis
of the clavicle.
The clavicle may break near the junction of its middle and
lateral thirds, but it is uncommon for the SC joint to
dislocate.
Most dislocations of the SC joint in persons younger than
25 years result from fractures through the epiphyseal
plate because the epiphysis at the sternal end of the clavicle
does not dose until 23 to 25 year


Anterior dislocations of the SCJ may occur from an
indirect mechanism such as a blow to the anterior
shoulder.
The force of blow causes rotation of the shoulder
backwards and transmits the stress to the SCJ
 Posterior SCJ dislocation may occur secondary to
direct trauma to the anteromedial aspect of the
clavicle that drives it backward
 Often serious associated injuries require
treatment that take treatment precedence over the
dislocation, for example:
•
•
•
•
Tracheal rupture or erosion
Pneumo-thorax
Laceration of the superior vena cava
Occlusion of the subclavian artery and/or vein
Acromioclavicular Joint
 The AC joint is a plane type of synovial joint
 It is located 2 to 3 cm from the point of the shoulder formed
by the lateral part of the acromion
 The acromial end of the clavicle articulates with the
acromion
 The articular surfaces, covered with fibrocartilage, are
separated by an incomplete wedge-shaped articular disc.
 Blood Supply of the Acromioclavicular Joint
– suprascapular and thoracoacromial arteries
 Nerve Supply of the AC Joint
– Supraclavicular, lateral pectoral, and axillary nerves supply the
AC joint
Articular Capsule of the AC Joint



The sleeve-like, relatively loose fibrous
capsule is attached to the margins of the
articular surfaces
A synovial membrane lines the fibrous
capsule.
Relatively weak, strengthened superiorly by
fibers of the trapezius
Ligaments of the AC Joint
 The integrity of the joint is maintained by extrinsic
ligaments, distant from the joint itself.
 The superior and inferior AC ligament:
– a fibrous band extending from the acromion to the
clavicle strengthens the AC joint superiorly
The coracoclavicular
ligament

The coracoclavicular ligament:
–
–
1.
a strong pair of bands that unites the coracoid process of the scapula to the
clavicle, anchoring the clavicle to the coracoid process.
The coracoclavicular ligament consists of two ligaments which are often separated
by a bursa. :
The conoid ligament
–
–
–
2.
The vertical conoid ligament is an inverted triangle (cone),
The apex inferiorly is attached to the root of the coracoid process in front of the
scapular notch.
Its wide attachment is to the conoid tubercle on the inferior surface of the
clavicle
Trapezoid ligament
–
–
Horizontal ligament attached to the superior surface of the coracoid process
extends laterally to the trapezoid line on the inferior surface of the clavicle.
The coracoclavicular
ligament
 The strength of the AC joint depends on the strong coracoclavicular
ligament
 provides the means by which the scapula and free limb are (passively)
suspended from the clavicular strut
A greater part of the body weight is transmitted through it
 The rotatory movements of the scapula occur at this important
ligament
 As long as the coracoclavicular ligament is intact, the acromion cannot
be driven inferior to the clavicle.
 The ligament, however, does permit protraction and retraction of the
acromion.
Movements of
the AC Joint

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

The acromion rotates on the acromial end of the
clavicle
These movements are associated with motion at the
scapulothoracic joint
No muscles connect the articulating bones to move
the AC joint
The thoraco-appendicular muscles that attach to
and move the scapula cause the acromion to move
on the clavicle.
Dislocation of the AC Joint
"shoulder separation"

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The AC joint itself is weak and easily injured by a direct
blow.
In contact sports it is not uncommon for dislocation of the
AC joint to result from a hard fall on the shoulder or from a
fall on the outstretched upper limb.
The AC injury, often called a "shoulder separation"
When the coracoclavicular ligament tears, the shoulder
separates from the clavicle because of the weight of the
upper limb.
Rupture of the coracoclavicular ligament allows the fibrous
capsule of the joint to also be torn so that the acromion
can pass inferior to the acromial end of the clavicle.
Dislocation of the AC joint makes the acromion more
prominent, and the clavicle may move superior to this
process
Glenohumeral (Shoulder) Joint


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

A ball-and-socket type of
synovial joint
Relatively unstable
The large, round humeral head
articulates with the relatively
shallow glenoid cavity of the
scapula
The glenoid is deepened slightly
but effectively by the ringlike
glenoid labrum
The glenoid cavity accepts little
more than a third of the humeral
head, which is held in the cavity by
the tonus of the rotator cuff
muscles
Both articular surfaces are covered
with hyaline cartilage.
Glenoid labrum
A fibrocartilaginous ring that attaches to the
rim of the glenoid fossa
 Encompasses the proximal portion of the
head of the humerus.
 If it is damaged then the joint becomes
very unstable and is prone to dislocation

Articular Capsule of the
Glenohumeral Joint

The loose fibrous capsule surrounds the glenohumeral
joint

Attached medially to the margin of the glenoid cavity
and laterally to the anatomical neck of the humerus

Superiorly, the articular capsule encroaches on the root
of the coracoid process so that the fibrous capsule
encloses the proximal attachment of the long head of
the biceps brachii (supraglenoid tubercle of scapula )
within the joint.
The articular capsule of
the glenohumeral joint
has two apertures:
– The opening between the
tubercles of the humerus is
for passage of the tendon of
the long head of the biceps
brachii
– The other opening situated
anteriorly, inferior to the
coracoid process, allows
communication between the
subscapular bursa and the
synovial cavity of the joint.
 The inferior part of the articular capsule
is the only part not reinforced by the
rotator cuff muscles
 Its weakest area.
 Here the capsule is particularly lax and
lies in folds when the arm is adducted
 It becomes taut when the arm is
abducted.
 The synovial membrane lines the
fibrous capsule and reflects from it onto
the glenoid labrum and neck of the
humerus, as far as the articular margin
of the head
 The synovial membrane also forms a
tubular sheath for the tendon of the
long head of the biceps brachii,
where it passes into the joint cavity and
lies in the intertubercular groove,
extending as far as the surgical neck of
the humerus
Ligaments of the
Glenohumeral Joint
 The glenohumeral ligaments:
– strengthen the anterior aspect of the articular capsule
– three fibrous bands: evident only on the internal aspect of the capsule
– radiate laterally and inferiorly
• from the glenoid labrum at the supraglenoid tubercle of the scapula
• blend distally with the fibrous capsule as it attaches to the anatomical
neck of the humerus.
Ligaments of the
Glenohumeral Joint
 The coracohumeral ligament
– a strong, broad band strengthens the capsule superiorly
– passes from the base of the coracoid process to the
anterior aspect of the greater tubercle of the humerus
Ligaments of the
Glenohumeral Joint
The transverse
humeral ligament
– a broad fibrous band that runs obliquely from the greater to
the lesser tubercle of the humerus, bridging over the
intertubercular groove.
– The ligament converts the groove into a canal that holds
the synovial sheath and tendon of the biceps brachii in
place during movements of the glenohumeral joint
The Coracoacromial Arch
 An extrinsic, protective osseoligamentous structure
formed by:
– The smooth inferior aspect of the acromion
– The coracoid process of the scapula
– The coracoacromial ligament
 Overlies the head of the humerus, preventing its superior
displacement
 So strong that a forceful superior thrust of the humerus will
not fracture it
 The supraspinatus muscle passes under this arch
 Movement of the supraspinatus tendon, is facilitated as it
passes under the arch by the subacromial bursa, which
lies between the arch and the tendon and tubercle.
Bursae Around the Glenohumeral Joint


Several bursae containing synovial fluid
Bursae are located where
– Tendons rub against bone, ligaments, or
other tendons
– Where skin moves over a bony prominence.

Some of them communicate with the joint
cavity (the subscapular bursa)
opening a bursa may mean entering the
cavity of the shoulder joint.
Subacromlal Bursa

Large bursa lies between the deltoid, the supraspinatus tendon, and
the fibrous capsule of the glenohumeral joint.

It does not communicate with the glenohumeral joint cavity unless
there has been a full-thickness rotator cuff tear

The subacromial bursa is located inferior to the acromion and
coracoacromial ligament, between them and the supraspinatus.

This bursa facilitates movement of the supraspinatus tendon under
the coracoacromial arch and of the deltoid over the fibrous capsule
of the shoulder joint and the greater tubercle of the humerus.
Subdeltoid Bursa


This bursa lies between the deltoid muscle
and the fibrous joint capsule over the head
of the humerus.
It does not communicate with the
glenohumeral joint cavity, but may
communicate with the subacromial bursa.


In patients who have injured their shoulder or who
have supraspinatus tendinopathy, the bursa may
become inflamed, making movements of the
glenohumeral joint painful.
These inflammatory changes may be treated by
injection of a corticosteroid and local anesthetic agent
Subscapular
Bursa


Located between the neck of the scapula and
the subscapularis muscle
Often communicates with the glenohumeral
joint cavity through an opening in the fibrous
joint capsule
Movements of the Glenohumeral Joint

The glenohumeral joint has more freedom of movement
than any other joint in the body.

This freedom results from:
1.
2.

The glenohumeral joint allows movements around three
axes and permits:
1.
2.
3.
4.

the laxity of its articular capsule
the large size of the humeral head compared with the small size
of the glenoid cavity.
Flexion-extension
Abduction-adduction
Rotation (medial and lateral) of the humerus
Circumduction.
Circumduction is an orderly sequence of flexion,
abduction, extension, and adduction or the reverse.
Blood Supply of the Glenohumeral Joint
– The glenohumeral joint is supplied by the
anterior and posterior circumflex humeral
arteries and branches of the suprascapular
artery.
Innervation of the Glenohumeral Joint
– The suprascapular, axillary, and lateral
pectoral nerves supply the glenohumeral joint.
Dislocation of the Glenohumeral Joint

Because of its freedom of movement and instability, the
glenohumeral joint is commonly dislocated by direct or
indirect injury.

Most dislocations of the humeral head occur in the
downward (inferior) direction
1.
2.
the presence of the coracoacromial arch
the support of the rotator cuff

Anterior or posterior dislocations

Posterior dislocations account for only 2-3% of shoulder
dislocations



Anterior dislocation of the glenohumeral joint
occurs most often in young adults, particularly
athletes.
It is usually caused by excessive extension and
lateral rotation of the humerus.
The head of the humerus is driven inferoanteriorly, and the fibrous capsule and glenoid
labrum may be stripped from the anterior aspect
of the glenoid cavity in the process.