Shoulder Joint

Shoulder Joint Articulation: humerus

glenoid glenoid labrum

Capsule: attached outside the labrum + the anatomic neck (thin and lax)

Ligaments: glenohumeral ligaments =

#3

transverse humeral

coracohumeral ligament

Articulation: This occurs between the rounded head of the humerus and the shallow, pear-shaped glenoid cavity of the scapula. The articular surfaces are covered by hyaline articular cartilage, and the glenoid cavity is deepened by the presence of a fibrocartilaginous rim called the glenoid labrum Type: Synovial ball-and-socket joint Capsule: This surrounds the joint and is attached medially to the margin of the glenoid cavity outside the labrum; laterally, it is attached to the anatomic neck of the humerus The capsule is thin and lax, allowing a wide range of movement. It is strengthened by fibrous slips from the tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles (the rotator cuff muscles). Ligaments: The glenohumeral ligaments are three weak bands of fibrous tissue that strengthen the front of the capsule. The transverse humeral ligament strengthens the capsule and bridges the gap between the two tuberosities (Fig. 9.34). The coracohumeral ligament strengthens the capsule above and stretches from the root of the coracoid process to the greater tuberosity of the humerus (Fig. 9.34).

Accessory ligaments

coracoacromial ligament between the coracoid

process and the acromion

Relationship Above- deltoid/clavicle

Below supraspinatous

Between coracoacromial lig is a bursa

Accessory ligaments: The coracoacromial ligament extends between the coracoid process and the acromion. Its function is to protect the superior aspect of the joint ----------------- It is in relation, above, with the clavicle and under surface of the Deltoideus; below, with the tendon of the Supraspinatus, a bursa being interposed. Synovial membrane: This lines the capsule and is attached to the margins of the cartilage covering the articular surfaces (Figs. 9.34 and 9.35). It forms a tubular sheath around the tendon of the long head of the biceps brachii. It extends through the anterior wall of the capsule to form the subscapularis bursa beneath thesubscapularis muscle (Fig. 9.34). Nerve supply: The axillary and suprascapular nerves

Synovial membrane

lines the capsule

attached to the margins of the cartilage covering the articular surfaces

tubular sheath = long head of the biceps brachii

subscapularis bursa

Synovial membrane: This lines the capsule and is attached to the margins of the cartilage covering the articular surfaces (Figs. 9.34 and 9.35). It forms a tubular sheath around the tendon of the long head of the biceps brachii. It extends through the anterior wall of the capsule to form the subscapularis bursa beneath thesubscapularis muscle (Fig. 9.34).

Nerve supply The axillary and suprascapular nerves

Movements wide range of movement

Lax capsule

Shallow glenoid

* Low stability

Movements The shoulder joint has a wide range of movement, and the

stability of the joint has been sacrificed to permit this.

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

movements.)

Strength= Rotator Cuff SItS

Abducted= supported by the long head of the triceps

Inferior part of the capsule = weakest area

The strength of the joint depends on the tone of the short rotator

cuff muscles that cross in front, above, and behind the jointnamely, the subscapularis,supraspinatus, infraspinatus, and teres

minor.

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

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

downward because of its length and gives little actual support to

the humerus.

In addition, the inferior part of the capsule is the weakest area.

Movements

Flexion: Deltoid,pectoralis major, Biceps,

coracobrachialis muscles

Flexion: Normal flexion is about 90 and is performed by the anterior fibers of the deltoid, pectoralis major, biceps, and coracobrachialis muscles.

Extension: Normal extension is about 45 and is performed by the posterior fibers of the deltoid, latissimus dorsi, and teres major muscles.

Extension: Deltoid, latissimus dorsi, Teres major

Abduction

Deltoid (middle fibers )

supraspinatus - holds the

head of the humerus against the glenoid fossa of thescapula

*****shoulder joint and between the scapula

Abduction: Abduction of the upper limb occurs both at the shoulder joint and between the scapula and the thoracic wall (see scapularhumeral mechanism, page 367). The middle fibers of the deltoid, assisted by the supraspinatus, are involved. The supraspinatus muscle initiates the movement of abduction and holds the head of the humerus against the glenoid fossa of thescapula; this latter function allows the deltoid

muscle to contract and abduct the humerus at the shoulder joint.

Adduction pectoralis major, latissimus dorsi, teres major,

and teres minor

Adduction: Normally, the upper limb can be swung 45 across the front of the chest. This is performed by the pectoralis major, latissimus dorsi, teres major, and teres minor muscles.

Lateral rotation: infraspinatus, teres minor, deltoid

Lateral rotation: Normal lateral rotation is 40 to 45. This is performed by the infraspinatus, the teres minor, and the posterior fibers of the deltoid muscle.

Medial rotation: subscapularis, latissimus dorsi, teres major

deltoid muscle.

Medial rotation: Normal medial rotation is about 55. This is performed by the subscapularis, the latissimus dorsi, the teres major, and the anterior fibers of the deltoid muscle. Circumduction: This is a combination of the above movements.

Anteriorly: subscapularis, axillary vessels, brachial plexus

Posteriorly:infraspinatus, minor muscles

Superiorly: supraspinatus, subacromial bursa, coracoacromial ligament, deltoid

Inferiorly: long head of the triceps, axillary nerve, posterior circumflex humeral vessels

Important Relations Anteriorly: The subscapularis muscle and the axillary vessels and brachial plexus Posteriorly: The infraspinatus and teres minor muscles Superiorly: The supraspinatus muscle, subacromial bursa, coracoacromial ligament, and deltoid muscle Inferiorly: The long head of the triceps muscle, the axillary nerve, and the posterior circumflex humeral vessels

Stability of the Shoulder Joint shallow glenoid +weak ligaments = unstable

Strength SItS

Inferior = unprotected

The shallowness of the glenoid fossa of the scapula and the lack of support provided by weak ligaments make this joint an unstable structure. Its strength almost entirely depends on the tone of the short muscles that bind the upper end of the humerus to the scapulanamely, the subscapularis in front, the supraspinatus above, and the infraspinatus and teres minor behind. The tendons of these muscles are fused to the underlying capsule of the shoulder joint. Together, these tendons form the rotator cuff. The least supported part of the joint lies in the inferior location, where it is unprotected by muscles.

Anterior Inferior Dislocation Dislocates in abduction= weak inferiorly

acromion has acted as a fulcrum

humeral head = inferior to the glenoid fossa

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 movement, 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 Rare

Direct violence to the front of the joint

quadrangular space -damage to the axillary nerve

Radial nerve- downward displacement of humerus

Posterior dislocations are rare and are usually caused by direct violence to the front of the joint. On inspection of the patient with shoulder dislocation, the rounded appearance of the shoulder is seen to be lost because the greater tuberosity of the humerus is no longer bulging laterally beneath the deltoid muscle. A subglenoid displacement of the head of the humerus into the quadrangular space can cause damage to the axillary nerve, as indicated by paralysis of the deltoid muscle and loss of skin sensation over the lower half of the deltoid. Downward displacement of the humerus can also stretch and damage the radial nerve.

Testing axillary nerve function

Motor- deltoid

Sensory- sensation to the lateral aspect of the upper arm (posterior terminal branch)

Technique for testing axillary nerve function. With the arm adducted and stabilized by the examiner, the patient is asked to actively abduct the arm. The motor component (A) of the axillary nerve is documented by observing or palpating deltoid muscle contraction. The sensory component (B) of the axillary nerve is documented by testing the sensation to the lateral aspect of the upper arm.

Shoulder Pain

synovial membrane, capsule, ligaments = axillary nerve and the suprascapular

pain, pressure, excessive traction, and distention.

Muscle = reflex spasm = immobilize the joint = reduce pain.

diaphragmatic pleura or peritoneum: referred pain via the phrenic and supraclavicular nerves.

Shoulder Pain The synovial membrane, capsule, and ligaments of the shoulderjoint are innervated by the axillary nerve and the suprascapular nerve. The joint is sensitive to pain, pressure, excessive traction, 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. Injury to the shoulder joint is followed by pain, limitation of 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 example, diseases of the spinal cord and vertebral column and the pressure of a cervical rib can cause shoulder pain. Irritation of the diaphragmatic pleura or peritoneum can produce referred pain via the phrenic and supraclavicular nerves.

The

Sca

pu

lar

Hu

me

ral

Me

chan

ism

scapula and upper limb are suspended from the clavicle by the strong coracoclavicular ligament

Axis of rotation = coracoclavicular ligament.

Abduction (3) = scapula (1) + shoulder joint (2)

120 = greater tuberosity hits acromion

Further elevation = rotation of scapula

The scapula and upper limb are suspended from the clavicle by the strong coracoclavicular ligament assisted by the tone of muscles. When the scapula rotates on the chest wall so that the position of the glenoid fossa is altered, the axis of rotation may be considered to pass through the coracoclavicular ligament. Abduction of the arm involves rotation of the scapula as well as movement at the shoulder joint. For every 3 ofabduction of the arm, a 2 abduction occurs in the shoulderjoint and a 1 abduction occurs by rotation of the scapula. At about 120 of abduction of the arm, the greater tuberosity of the humerus comes into contact with the lateral edge of the acromion. Further elevation of the arm above the head is accomplished by rotating the scapula

Superficial Sensory Nerves

supraclavicular nerves - halfway down the deltoid muscle (3 4 cervical nerve)

upper lateral cutaneous nerve of the arm- Axillary nerve

lower lateral cutaneous nerve of the arm- radial nerve

Armpit and medial side- medial cut N (medial cord) , intercostobrachial N

Back of the arm- posterior cutaneous nerve of the arm (radial nerve)

Skin

Fascial Compartments

The Upper Arm

The sensory nerve supply (Fig. 9.38) to the skin over the point of the shoulder to halfway down the deltoid muscle is from the supraclavicular nerves (C3 and 4). --arise from the third and fourth cervical nerves The skin over the lower half of the deltoid is supplied by the upper lateral cutaneous nerve of the arm, a branch of the axillarynerve (C5 and 6). The skin over the lateral surface of the arm below the deltoid is supplied by the lower lateral cutaneous nerve of the arm, a branch of the radial nerve (C5 and 6). The skin of the armpit and the medial side of the arm is supplied by the medial cutaneous nerve of the arm (T1) and the intercostobrachial nerves (T2). The skin of the back of the arm (Fig. 9.38) is supplied by the posterior cutaneous nerve of the arm, a branch of the radial nerve (C8).

Superficial Veins

Superficial (superficial fascia) cephalic vein - lateral side of the

biceps axillary vein.

basilic - medial side of the biceps venae comitantes of the brachial artery

the axillary vein

Deep Venae comitantes

axillary vein

Superficial Veins The veins of the upper limb can be divided into two groups: superficial and deep. The deep veins comprise the venae comitantes, which accompany all the large arteries, usually in pairs, and the axillary vein. The superficial veins of the arm (Fig. 9.39) lie in the superficial fascia. The cephalic vein ascends in the superficial fascia on the lateral side of the biceps and, on reaching the infraclavicular fossa, drains into the axillary vein. The basilic vein ascends in the superficial fascia on the medial side of the biceps (Fig. 9.39). Halfway up the arm, it pierces the deep fascia and at the lower border of the teres major joins the venae comitantes of the brachial artery to form the axillary vein.

Venipuncture and Blood Transfusion

cephalic vein- posterior to the styloid process of the radius

median cubital vein = cubital fossa

separated from the underlying brachial artery by the bicipital aponeurosis

cephalic vein = frequently communicates with the external jugular vein (hematoma in clavicular fx)

The superficial veins are clinically important and are used for venipuncture, transfusion, and cardiac catheterization. Every clinical professional, in an emergency, should know where to obtain blood from the arm. When a patient is in a state of shock,the superficial veins are not always visible. The cephalic vein lies fairly constantly in the superficial fascia, immediately posterior to the styloid process of the radius. In the cubital fossa, the median cubital vein is separated from the underlying brachial artery by the bicipital aponeurosis. This is important because it protects the artery from the mistaken introduction into its lumen of irritating drugs that should have been injected into the vein. The cephalic vein, in the deltopectoral triangle, frequently communicates with the external jugular vein by a small vein that crosses in front of the clavicle. Fracture of the clavicle can result in rupture of this communicating vein, with the formation of a large hematoma.

Anatomy of Basilic and Cephalic Vein Catheterization

median basilic or basilic veins = veins of choice for central venous catheterization increases in diameter

direct line with the axillary vein

cephalic vein does not increase in size

divides into small branches

joins the axillary vein at a right angle

Anatomy of Basilic and Cephalic Vein Catheterization The median basilic or basilic veins are the veins of choice for central venous catheterization, because from the cubital fossa until the basilic vein reaches the axillary vein, the basilic vein increases in diameter and is in direct line with the axillary vein (Fig. 9.39). The valves in the axillary vein may be troublesome, but abduction of the shoulder joint may permit the catheter to move past the obstruction. The cephalic vein does not increase in size as it ascends the arm, and it frequently divides into small branches as it lies within the deltopectoral triangle. One or more of these branches may ascend over the clavicle and join the external jugular vein. In its usual method of termination, the cephalic vein joins the axillary vein at a right angle. It may be difficult to maneuver the catheter around this angle.

Nerve Supply of the Veins

sympathetic postganglionic nerve

Like the arteries, the smooth muscle in the wall of the veins is innervated by sympathetic postganglionic nerve fibers that provide vasomotor tone.

Lymph Vessels Superficial

lateral side = follow the cephalic vein to the infraclavicular group of nodes

medial side = follow the basilic vein to the lateral group of axillary nodes.

The deep lymph

lateral group of

axillary nodes.

Superficial Lymph Vessels The superficial lymph vessels draining the superficial tissues of the upper arm pass upward to the axilla (Fig. 9.40). Those from the lateral side of the arm follow the cephalic vein to the infraclavicular group of nodes; those from the medial side follow the basilic vein to the lateral group of axillary nodes. The deep lymphatic vessels draining the muscles and deep structures of the arm drain into the lateral group of axillary nodes.

thumb and index finger and the lateral part of the hand cephalic-infraclavicular group of axillary nodes

3-4-5 fingers- basilic vien supratrochlear node lateral group of axillary nodes

The lymph vessels from the thumb and index finger and the lateral part of the hand follow the cephalic vein to the infraclavicular group of axillary nodes; those from the middle, ring, and little fingers and from the medial part of the hand follow the basilic vein to the supratrochlear node, which lies in the superficial fascia just above the medial epicondyle of the humerus, and thence to the lateral group of axillary nodes.

Lymphangitis- Infection of the lymph vessels

Red streaks along the course of the lymph vessels

Lymphadenitis- Once the infection reaches the lymph nodes

Lymphangitis Infection of the lymph vessels (lymphangitis) of the arm is common. Red streaks along the course of the lymph vessels are characteristic of the condition. Lymphadenitis Once the infection reaches the lymph nodes, they become enlarged and tender, a condition known as lymphadenitis.

lymph vessels from the fingers and palm pass to the dorsum of the hand edema/abscess @ dorsum of hand

Most of the lymph vessels from the fingers and palm pass to the dorsum of the hand before passing up into the forearm. This explains the frequency of inflammatory edema, or even abscess formation, which may occur on the dorsum of the hand after infection of the fingers or palm.

Fascial Compartments of the Upper Arm

Anterior Fascial Compartment

Muscles: Biceps, coracobrachialis, and brachialis

Blood supply: Brachial artery

Nerve supply : Musculocutaneous nerve

Structures passing through the compartment: Musculocutaneous, median, and ulnar nerves; brachial artery and basilic vein.

radial nerve is present in the lower part of the compartment

Note that the biceps brachii is a powerful supinator, and this action is made use of in twisting the corkscrew into the cork or driving the screw into wood with a screwdriver. The biceps also is a powerful flexor of the elbow joint and a weak flexor of the shoulder joint.

Brachial Artery

begins at the lower border of the teres major

terminates opposite the neck of the radius by dividing into the radial and ulnar arteries

The brachial artery begins at the lower border of the teres major muscle as a continuation of the axillary artery. It provides the main arterial supply to the arm (Fig. 9.42). It terminates opposite the neck of the radius by dividing into the radial and ulnar arteries.

Brachial Artery Anteriorly: overlapped coracobrachialis and biceps

Posteriorly: triceps, coracobrachialis insertion ,brachialis

Medially:

Upper: ulnar nerve, basilic vein

lower part :the median nerve

Laterally:

Above: median nerve and the coracobrachialis and biceps muscles

lower part :tendon of the biceps

Anteriorly: The vessel is superficial and is overlapped from the lateral side by the coracobrachialis and biceps. The medial cutaneous nerve of the forearm lies in front of the upper part; the median nerve crosses its middle part; and the bicipital aponeurosis crosses its lower part Posteriorly: The artery lies on the triceps, the coracobrachialis insertion, and the brachialis Medially: The ulnar nerve and the basilic vein in the upper part of the arm; in the lower part of the arm, the median nerve lies on its medial side (Fig. 9.43). Laterally: The median nerve and the coracobrachialis and biceps muscles above; the tendon of the biceps lies lateral to the artery in the lower part of its course

Branches: Brachial Artery

Muscular branches

The nutrient artery

profunda - follows the radial nerve into the spiral groove

superior ulnar collateral artery - follows the ulnar nerve

inferior ulnar collateral artery anastomosis around the elbow joint

Branches Muscular branches to the anterior compartment of the upper arm The nutrient artery to the humerus The profunda artery arises near the beginning of the brachial artery and follows the radial nerve into the spiral groove of the humerus (Fig. 9.45). The superior ulnar collateral artery arises near the middle of the upper arm and follows the ulnar nerve (Fig. 9.45). The inferior ulnar collateral artery arises near the termination of the artery and takes part in the anastomosis around the elbow joint (Fig. 9.45).

Musculocutaneous Nerve

lateral cord of the brachial plexus

pierces the coracobrachialis muscle

between the biceps and brachialis

muscles

The origin of the musculocutaneousnerve from the lateral cord of the brachial plexus (C5, 6, and 7) in the axilla. It runs downward and laterally, pierces the coracobrachialis muscle (Fig. 9.15), and then passes downward between the biceps and brachialis muscles (Fig. 9.43).

Musculocutaneous Nerve Elbow- lateral margin of the biceps tendon

lateral aspect of the forearm as the lateral cutaneous nerve of the forearm

It appears at the lateral margin of the biceps tendon and pierces the deep fascia just above the elbow. It runs down the lateral aspect of the forearm as the lateral cutaneous nerve of the forearm (Fig. 9.38).

Branches lateral cutaneous nerve of the

forearm = front and lateral aspects of the forearm down as far as the root of the thumb

Articular branches to the elbow joint

Branches Muscular branches to the biceps, coracobrachialis, and brachialis (Fig. 9.22) Cutaneous branches; the lateral cutaneous nerve of the forearm supplies the skin of the front and lateral aspects of the forearm down as far as the root of the thumb. Articular branches to the elbow joint

Median Nerve

Lat side of brachial art medial side

Elbow- crossed by the bicipital aponeurosis

no branches in the upper arm (small vasomotor nerve to the brachial Artery)

It runs downward on the lateral side of the brachial artery (Fig. 9.43). Halfway down the upper arm, it crosses the brachial artery and continues downward on its medial side. The nerve, like the artery, is therefore superficial, but at the elbow, it is crossed by the bicipital aponeurosis The median nerve has no branches in the upper arm (Fig. 9.22), except for a small vasomotor nerve to the brachial artery.

Median nerve from the medial and lateral cords of the brachial plexus

Ulnar Nerve

origin of the ulnar nerve = medial cord of the brachial plexus

Ulnar Nerve

Medial side of the art

@ coracobrachialis insertion pierce medial fascial septum (with superior ulnar collateral artery) post compartment post to medial epicondyle

ULNAR NERVE It runs downward on the medial side of the brachial artery as far as the middle of the arm (Fig. 9.43). Here, at the insertion of the coracobrachialis, the nerve pierces the medial fascial septum, accompanied by the superior ulnar collateral artery, and enters the posterior compartment of the arm; the nerve passes behind the medial epicondyle of the humerus. The ulnar nerve has no branches in the anterior compartment of the upper arm (Fig. 9.23).

Radial Nerve

On leaving the axilla, the radial nerve immediately enters the posterior compartment of the arm and enters the anterior compartment just above the lateral epicondyle

Contents of the Posterior Fascial Compartment of the Upper Arm

Muscle: The three heads of the triceps muscle

Nerve supply to the muscle: Radial nerve

Blood supply: Profunda brachii and ulnar collateral arteries

Structures passing through the compartment: Radial nerve and ulnar nerve

Structures Passing through the Posterior Fascial Compartment

Radial Nerve

Ulnar Nerve

Profunda Brachii Artery

Superior and Inferior Ulnar Collateral Arteries

Radial Nerve

From posterior cord

Branches of Radial Nerve Axilla

long and medial heads of the triceps

the posterior cutaneous nerve of the arm

Branches of Radial Nerve

spiral groove

lateral and medial heads of the triceps

Anconeus

lower lateral cutaneous nerve

posterior cutaneous nerve nerve of the forearm

In the spiral groove (Fig. 9.46), branches are given to the lateral and medial heads of the triceps and to the anconeus. lower lateral cutaneous nerve of the arm supplies the skin over the lateral and anterior aspects of the lower part of the arm. The posterior cutaneous nerve of the forearm runs down the middle of the back of the forearm as far as the wrist.

Branches of Radial Nerve: anterior compartment of the arm

Brachialis

Brachioradialis

extensor carpi radialis longus muscles

Articular branches to the elbow joint

In the anterior compartment of the arm, after the nerve has pierced the lateral fascial septum, it gives branches to the brachialis, the brachioradialis, and the extensor carpi radialis longus muscles (Fig. 9.47). It also gives articular branches to the elbow joint.

Ulnar Nerve pierced the medial fascial

septum halfway down the upper arm, the ulnar nerve descends behind the septum

covered posteriorly by the medial head of the triceps

accompanied by the superior ulnar collateral vessels

Elbow = lies behind the medial epicondyle

Ulnar Nerve Having pierced the medial fascial septum halfway down the upper arm, the ulnar nerve descends behind the septum, covered posteriorly by the medial head of the triceps. The nerve is accompanied by the superior ulnar collateral vessels. At the elbow, it lies behind themedial epicondyle of the humerus (Fig. 9.46) on the medial ligament of the elbow joint. It continues downward to enter the forearm between the two heads of origin of the flexor carpi ulnaris (see page 390).