yeditepeanatomy1.files.wordpress.com€¦ · Web viewThe glenohumeral joint (shoulder joint) is...

SHOULDER 19. 12. 2012

Kaan Yücel

M.D., Ph.D.

http://yeditepeanatomy1.org

A TOTAL OF 8 FIGURES IN THE TEXT

Dr.Kaan Yücel http://yeditepeanatomy1.org Shoulder

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The shoulder is the region of upper limb attachment to the trunk. Shoulder is the proximal segment of the limb that overlaps parts of the trunk (thorax and back) and lower lateral neck. It includes the pectoral, scapular, and deltoid regions of the upper limb, and the lateral part (greater supraclavicular fossa) of the lateral cervical region. It overlies half of the pectoral girdle.The bone framework of the shoulder consists of: • the clavicle and scapula, which form the pectoral girdle (shoulder girdle); and • the proximal end of the humerus.

The superficial muscles of the shoulder consist of the trapezius and deltoid muscles, which together form the smooth muscular contour over the lateral part of the shoulder. These muscles connect the scapula and clavicle to the trunk and to the arm, respectively.The three joints in the shoulder complex are the sternoclavicular, acromioclavicular, and glenohumeral joints.The two most superficial muscles of the shoulder are the trapezius and deltoid muscles. Together, they provide the characteristic contour of the shoulder: • trapezius attaches the scapula and clavicle to the trunk;• deltoid attaches the scapula and clavicle to the humerus.

The superficial posterior axioappendicular (extrinsic shoulder) muscles are the trapezius and latissimus dorsi. The deep posterior thoracoappendicular (extrinsic shoulder) muscles are the levator scapulae and rhomboids. These muscles provide direct attachment of the appendicular skeleton to the axial skeleton.

The six scapulohumeral muscles (deltoid, teres major, supraspinatus, infraspinatus, subscapularis, and teres minor) are relatively short muscles that pass from the scapula to the humerus and act on the glenohumeral joint. All the intrinsic muscles but the deltoid and the subscapularis are muscles of the posterior scapular region.

The deltoid muscle is large and triangular in shape, with its base attached to the scapula and clavicle and its apex attached to the humerus. It originates along a continuous U-shaped line of attachment to the clavicle and the scapula, mirroring the adjacent insertion sites of the trapezius muscle. The major function of the deltoid muscle is abduction of the arm beyond the initial 15° accomplished by the supraspinatus muscle.

The subscapularis is the primary medial rotator of the arm and also adducts it. It joins the other rotator cuff muscles in holding the head of the humerus in the glenoid cavity during all movements of the glenohumeral joint (i.e., it helps stabilize this joint during movements of the elbow, wrist, and hand).

The posterior scapular region occupies the posterior aspect of the scapula and is located deep to the trapezius and deltoid muscles. It contains four muscles, which pass between the scapula and proximal end of the humerus: supraspinatus, infraspinatus, teres minor, and teres major muscles.

The supraspinatus, infraspinatus, and teres minor muscles are components of the rotator cuff, which stabilizes the glenohumeral joint.

The suprascapular nerve passes through the suprascapular foramen; the suprascapular artery and the suprascapular vein follow the same course as the nerve, but normally pass immediately superior to the superior transverse scapular ligament and not through the foramen. Quadrangular space, triangular space and triangular interval are other gateways in the posterior scapular region.

The two major nerves of the posterior scapular region are the suprascapular and axillary nerves, both of which originate from the brachial plexus in the axilla.

Three major arteries are found in the posterior scapular region: the suprascapular, posterior circumflex humeral, and circumflex scapular arteries. These arteries contribute to an interconnected vascular network around the scapula. Veins in the posterior scapular region generally follow the arteries and connect with vessels in the neck, back, arm, and axilla.

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The shoulder is the region of upper limb attachment to the trunk. Shoulder is the proximal segment of

the limb that overlaps parts of the trunk (thorax and back) and lower lateral neck. It includes the pectoral,

scapular, and deltoid regions of the upper limb, and the lateral part (greater supraclavicular fossa) of the

lateral cervical region. It overlies half of the pectoral girdle. The pectoral (shoulder) girdle is a bony ring,

incomplete posteriorly, formed by the scapulae and clavicles and completed anteriorly by the manubrium of

the sternum (part of the axial skeleton).

The bone framework of the shoulder consists of:

• the clavicle and scapula, which form the pectoral girdle (shoulder girdle); and

• the proximal end of the humerus.

The superficial muscles of the shoulder consist of the trapezius and deltoid muscles, which together

form the smooth muscular contour over the lateral part of the shoulder. These muscles connect the scapula

and clavicle to the trunk and to the arm, respectively.

The three joints in the shoulder complex are the sternoclavicular, acromioclavicular, and glenohumeral

joints.

The sternoclavicular joint and the acromioclavicular joint link the two bones of the pectoral girdle to

each other and to the trunk. The combined movements at these two joints enable the scapula to be

positioned over a wide range on the thoracic wall, substantially increasing "reach" by the upper limb.

The glenohumeral joint (shoulder joint) is the articulation between the humerus of the arm and the

scapula.

The two most superficial muscles of the shoulder are the trapezius and deltoid muscles. Together, they

provide the characteristic contour of the shoulder:

• trapezius attaches the scapula and clavicle to the trunk;

• deltoid attaches the scapula and clavicle to the humerus.

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1. INTRODUCTION

2. JOINTS

3. MUSCLES


The superficial posterior axioappendicular (extrinsic shoulder) muscles are the trapezius and latissimus

dorsi.

The deep posterior thoracoappendicular (extrinsic shoulder) muscles are the levator scapulae and

rhomboids. These muscles provide direct attachment of the appendicular skeleton to the axial skeleton.

SCAPULOHUMERAL (INSTRINSIC SHOULDER) MUSCLESThe six scapulohumeral muscles (deltoid, teres major, supraspinatus, infraspinatus, subscapularis, and

teres minor) are relatively short muscles that pass from the scapula to the humerus and act on the

glenohumeral joint. All the intrinsic muscles but the deltoid and the subscapularis are muscles of the posterior

scapular region.

The deltoid muscle is large and triangular in shape, with its base attached to the scapula and clavicle

and its apex attached to the humerus. It originates along a continuous U-shaped line of attachment to the

clavicle and the scapula, mirroring the adjacent insertion sites of the trapezius muscle. The major function of

the deltoid muscle is abduction of the arm beyond the initial 15° accomplished by the supraspinatus muscle.

Clavicular part: flexes and medially rotates arm

Acromial part: abduction of arm

Spinal part: extends and laterally rotates arm

Figure 1. Deltoid musclehttp://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/sporting-edge/sci-media/images/deltoid-muscles/14542-15-eng-NZ/Deltoid-

muscles_full_size_portrait.jpg

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http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/sporting-edge/sci-media/images/deltoid-muscles/14542-15-eng-NZ/Deltoid-muscles_full_size_portrait.jpg

http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/sporting-edge/sci-media/images/deltoid-muscles/14542-15-eng-NZ/Deltoid-muscles_full_size_portrait.jpg


The subscapularis is a thick, triangular muscle that lies on the costal surface of the scapula and forms

part of the posterior wall of the axilla.

The subscapularis is the primary medial rotator of the arm and also adducts it. It joins the other rotator

cuff muscles in holding the head of the humerus in the glenoid cavity during all movements of the

glenohumeral joint (i.e., it helps stabilize this joint during movements of the elbow, wrist, and hand).

Figure 2. Subscapularishttp://www.coretherapy.com/images/fig_4.gif

The posterior scapular region occupies the posterior aspect of the scapula and is located deep to the

trapezius and deltoid muscles. It contains four muscles, which pass between the scapula and proximal end

of the humerus: supraspinatus, infraspinatus, teres minor, and teres major muscles.

The posterior scapular region also contains part of one additional muscle, the long head of the triceps

brachii, which passes between the scapula and the proximal end of the forearm. This muscle, along with other

muscles of the region and the humerus, participates in forming a number of spaces through which nerves and

vessels enter and leave the region.


4. POSTERIOR SCAPULAR REGION

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The supraspinatus, infraspinatus, and teres minor muscles are components of the rotator cuff, which

stabilizes the glenohumeral joint.

The supraspinatus and infraspinatus muscles originate from two large fossae, one above and one

below the spine, on the posterior surface of the scapula. They form tendons that insert on the greater

tubercle of the humerus. The supraspinatus initiates abduction of the arm. The infraspinatus laterally rotates

the humerus.

Figure 3. Supraspinatus and infraspinatushttp://www.daviddarling.info/images/rotator_cuff.jpg

The teres minor muscle is a cord-like muscle that originates from a flattened area of the scapula

immediately adjacent to its lateral border below the infraglenoid tubercle. Its tendon inserts on the inferior

facet of the greater tubercle of the humerus. The teres minor laterally rotates the humerus and is a

component of the rotator cuff.

The teres major muscle originates from a large oval region on the posterior surface of the inferior

angle of the scapula. This broad cord-like muscle ends as a flat tendon that attaches to the medial lip of the

intertubercular sulcus on the anterior surface of the humerus. The teres major medially rotates and extends

the humerus.

Figure 4. Teres major & teres minor muscleshttp://www.saddleback.edu/faculty/charrison/smmuscles.html


http://www.saddleback.edu/faculty/charrison/smmuscles.html

http://www.daviddarling.info/images/rotator_cuff.jpg


The long head of triceps brachii muscle originates from the infraglenoid tubercle and passes somewhat

vertically down the arm to insert, with the medial and lateral heads of this muscle, on the olecranon of the

ulna. The triceps brachii is the primary extensor of the forearm at the elbow joint. Because the long head

crosses the glenohumeral joint, it can also extend and adduct the humerus.

Four of the scapulohumeral muscles (intrinsic shoulder muscles)—supraspinatus, infraspinatus,

teres minor, and subscapularis (referred to as the SITS muscles)—are called rotator cuff muscles because they

form a musculotendinous rotator cuff around the glenohumeral joint. The rotator muscles are short muscles

which covers and blends with all bu the inferior aspect of the shoulder joint. The supraspinatus, infraspinatus

and teres minor are inserted from above down into the humeral greater tubercle, and the subscapularis is

inserted into the lesser tubercle. All originate from scapula. All except the supraspinatus are rotators of the

humerus; the supraspinatus, besides being part of the rotator cuff, initiates and assists the deltoid in the first

15° of abduction of the arm (See “Movements of the shoulder girdle” on page 15).

Figure 5. Rotator cuff muscleshttp://assets2.medhelp.org/adam/graphics/images/en/19622.jpg


5. ROTATOR CUFF MUSCLES

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The tendons of the SITS muscles blend with and reinforce the fibrous layer of the joint capsule

of the glenohumeral joint, thus forming the rotator cuff that protects the joint and gives it stability. The tonic

contraction of the contributing muscles holds the relatively large head of the humerus in the small, shallow

glenoid cavity of the scapula during arm movements.

Suprascapular foramenThe suprascapular foramen is the route through which structures pass between the base of the neck

and the posterior scapular region. It is formed by the suprascapular notch of the scapula and the superior

transverse scapular (suprascapular) ligament, which converts the notch into a foramen.

The suprascapular nerve passes through the suprascapular foramen; the suprascapular artery and the

suprascapular vein follow the same course as the nerve, but normally pass immediately superior to the

superior transverse scapular ligament and not through the foramen.

Figure 6. Suprascapular foramenhttp://www.e-algos.com/wp-content/uploads/2011/05/84611-91895-92672-92768.jpg


6. GATEWAYS TO THE POSTERIOR SCAPULAR REGION

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Quadrangular space The quadrangular space provides a passageway for nerves and vessels passing between the axilla and the

more posterior scapular and deltoid regions. When viewed from anteriorly, its boundaries are formed by:

inferior margin of the subscapularis muscle;

surgical neck of the humerus;

superior margin of the teres major muscle; and

lateral margin of the long head of the triceps brachii muscle.

Passing through the quadrangular space are the axillary nerve and the posterior circumflex humeral artery

and vein.

Triangular space [Medial triangular space]

The triangular space is an area of communication between the axilla and the posterior scapular region. When

viewed from anteriorly, it is formed by:

medial margin of the long head of the triceps brachii muscle;

superior margin of the teres major muscle; and

inferior margin of the subscapularis muscle.

The circumflex scapular artery and vein pass into this space.

Triangular interval [Lateral triangular space]

This triangular interval is formed by:



lateral margin of the long head of the triceps brachii muscle;

shaft of the humerus; and

inferior margin of the teres major muscle.

The radial nerve passes out of the axilla traveling through this interval to reach the posterior compartment of

the arm. The profunda brachii artery (deep artery of arm) and associated veins also pass through the

triangular interval.

Figure 7. Gateways in the posterior wall of the axillahttp://t2.gstatic.com/images?q=tbn:ANd9GcRxwzEGsoXMzYwMw7O_4GXA0TsYYKwURRH9iSQDkT-yTFLLZMzP

Because this space is below the inferior margin of the teres major, which defines the inferior boundary

of the axilla, the triangular interval serves as a passageway between the anterior and posterior compartments

of the arm and between the posterior compartment of the arm and the axilla. The radial nerve, the profunda

brachii artery (deep artery of arm), and associated veins pass through it.

The two major nerves of the posterior scapular region are the suprascapular and axillary nerves, both

of which originate from the brachial plexus in the axilla.

Suprascapular nerveThe suprascapular nerve originates in the base of the neck from the superior trunk of the brachial

plexus. It passes through the suprascapular foramen to reach the posterior scapular region, where it lies in the

plane between bone and muscle. It innervates the supraspinatus muscle, then terminates in and innervates

the infraspinatus muscle. Generally, the suprascapular nerve has no cutaneous branches.

Axillary nerveThe axillary nerve originates from the posterior cord of the brachial plexus. It exits the axilla by passing

through the quadrangular space in the posterior wall of the axilla, and enters the posterior scapular region.

Together with the posterior circumflex humeral artery and vein, it is directly related to the posterior surface http://www.youtube.com/yeditepeanatomy 10

7. NERVES OF THE POSTERIOR SCAPULAR REGION

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of the surgical neck of the humerus.The axillary nerve innervates the deltoid and teres minor muscles. In

addition, it has a cutaneous branch, the superior lateral cutaneous nerve of the arm, which carries general

sensation from the skin over the inferior part of the deltoid muscle.

Three major arteries are found in the posterior scapular region: the suprascapular, posterior circumflex

humeral, and circumflex scapular arteries. These arteries contribute to an interconnected vascular network

around the scapula. Veins in the posterior scapular region generally follow the arteries and connect with

vessels in the neck, back, arm, and axilla.

ANASTOMOSIS IN THE SHOULDERFormation of anastomosis around the surgical neck of humerus

(See for more info @ http://www.slideshare.net/ananthatiger/3-anastomosis-around-the-surgical-

neck-of-humerus1)

Anterior circumflex humeral artery and posterior circumflex humeral artery are both branches of the

third part of the axillary artery.The posterior circumflex humeral artery anastomoses with anterior circumflex

humeral artery and also with branches from profunda brachii (a branch of brachial artery), suprascapular (a

branch of subclavian artery) and thoracoacromial (a branch of axillary artery) arteries.

The scapular anastomosis system: is a system connecting each subclavian artery and the

corresponding axillary artery, forming an anastomosis around the scapula. It allows blood to flow past the

joint regardless of the position of the arm. It includes:

• transverse cervical artery (subclavian artery)

• transverse scapular artery (subclavian artery)

• subscapular artery (axillary artery)

• branches of thoracic aorta

The subscapular artery gives off a circumflex scapular branch that enters the infraspinous fossa on the

dorsal surface of the bone, grooving the axillary border.


8. ARTERIES & VEINS OF THE POSTERIOR SCAPULAR REGION


All these vessels anastamose or join to connect the first part of the subclavian with the third part of

the axillary, providing a collateral circulation. This collateral circulation allows for blood to continue circulating

if the subclavian is obstructed.

Figure 8. Anastomosis in the shoulder

http://en.wikipedia.org/wiki/File:Gray521.png

TESTING THE DELTOID MUSCLETo test the deltoid (or the function of the axillary nerve that supplies it), the arm is abducted, starting

from approximately 15°, against resistance. If acting normally, the deltoid can easily be seen and palpated.

The influence of gravity is avoided when the person is supine.

QUADRANGULAR SPACE SYNDROMEQuadrilateral space syndrome is a clinical syndrome resulting from compression of the axillary nerve

and posterior circumflex humeral artery in the quadrilateral space. The quadrilateral space is an anatomic

space in the upper arm bounded by the long head of the triceps, the teres minor and teres major muscles,

and the cortex of the humerus. The passage of the axillary nerve backward from the axilla through the

quadrangular space makes it particularly vulnerable here to downward displacement of the humeral head in

shoulder dislocations or fractures of the surgical neck of the humerus. Paralysis of the deltoid and teres minor

muscles results. The cutaneous branches of the axillary nerve, including the upper lateral cutaneous nerve of

the arm, are functionless, and consequently there is a loss of skin sensation over the lower half of the deltoid

muscle.


CLINICAL ANATOMY

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RUPTURE OF THE SUPRASPINATUS TENDONIn advanced cases of rotator cuff tendinitis, the necrotic supraspinatus tendon can become calcified or

rupture. 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 the humerus in the glenoid fossa at

the commencement of abduction. The patient with a ruptured supraspinatus tendon is unable to

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 movement to a right angle.

ROTATOR CUFF TENDINITISThe rotator cuff, consisting of the tendons of the subscapularis,supraspinatus, infraspinatus, and teres

minor muscles, which are fused to the underlying capsule of the shoulder joint, plays an important role in

stabilizing the shoulder joint. Lesions of the cuff are a common cause of pain in the shoulder region. Excessive

overhead activity of the upper limb may be the cause of tendinitis, although many cases appear

spontaneously. During abduction of the shoulder joint, the supraspinatus tendon is exposed to friction against

the acromion. Under normal conditions, the amount of friction is reduced to a minimum by the large

subacromial bursa, which extends laterally beneath the deltoid. 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. Clinically, the condition is known as subacromial bursitis, supraspinatus

tendinitis, or pericapsulitis. 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.

MOVEMENTS OF THE SHOULDER GIRDLEThe movements of the shoulder joint itself cannot be divorced from those of the whole shoulder

girdle. Even if the shoulder joint is fused, a wide range of movement is still possible by elevation, depression,

rotation and protraction of the scapula, leverage occuring at the sternoclavicular joint, the pivot being the

costoclavicular ligament.

Abduction of the shoulder is initiated by the supraspinatus; the deltoid can then abduct to 90 degrees.

Further movement to 180 degrees (elevation) is brought about by rotation of the scapula upwards by the

trapezius and serratus anterior. Shoulder and shoulder girdle movements combine into one smooth action. As

soon as abduction commences at the shoulder joint, so the rotation of the scapula begins. Movements of the

scapula occur with reciprocal movements at the sternoclavicular joint.



Of the rotator cuff musles, the supraspinatus is of the greatest practical importance. It passes over the

apex of the shoulder beneath the acromion process and coracoacromial ligament, from which it is separated

by the subacromial bursa. This bursa is continued beneath the deltoid as the subdeltoid bursa, forming,

together, the largest bursa in the body.

The supraspinatus initiates the abduction of humerus on the scapula; if the tendon is torn as a result of

injury, active initation of abduction becomes impossible and the patient has to develop the trick movement of

tilting his body towards the injured side so that gravity passively swings the arm from his trunk. Once this

occurs, the deltoid and the scapular rotators can then come into play.

Principal muscles acting on the shoulder joint

AbductorsSupraspinatusDeltoid

AdductorsPectoralis majorLattisimus dorsi

ExtensorsTeres majorLattisimus dorsiDeltoid (posterior fibres)

FlexorsPectoralis majorCoracobrachialisDeltoid (anterior fibres)

Medial rotatorsPectoralis majorLattisimus dorsiTeres majorDeltoid (anterior fibres)Subscapularis

Lateral rotatorsInfraspinatusTeres minorDeltoid (posterior fibres)

Table 1. Movements of scapula

Movement of Scapula Muscles Producing Movementa

Nerve to Muscles Range of Movement (AngularRotation; Linear Displacement)

Elevation Trapezius, descending part Levator scapulae

Spinal accessory (CN XI) Dorsal scapular

10-12 cm



Rhomboids

Depression Gravity Pectoralis major, inferior sternocostal head Latissimus dorsi Trapezius, ascending part Serratus anterior, inferior part Pectoralis minor

Pectoral nervesThoracodorsalSpinal accessory (CN XI)Long thoracicMedial pectoral

Protraction Serratus anterior Pectoralis major Pectoralis minor

Long thoracicPectoral nervesMedial pectoral

40-45°; 15 cm

Retraction Trapezius, middle part Rhomboids Latissimus dorsi

Spinal accessory (CN XI)Dorsal scapularThoracodorsal

Upward rotationa Trapezius, descending part Trapezius, ascending part Serratus anterior, inferior part

Spinal accessory (CN XI)Long thoracic 60°; inferior angle: 10-12

cm, superior angle: 5-6 cm

Downward rotationb Gravity Levator scapulae Rhomboids Latissimus dorsi Pectoralis minor Pectoralis major, inferior sternocostal head

Dorsal scapularThoracodorsal Medial pectoral Pectoral nerves

Boldface indicates prime or essential mover(s). aThe glenoid cavity moves superiorly, as in abduction of the arm.b The glenoid cavity moves inferiorly, as in adduction of the arm

Table 2. Scapulohumeral (Intrinsic) shoulder muscles



Muscle Origin Insertion Nerve FunctionDeltoid Lateral third of clavicle;

acromion and spine of scapula

Deltoid tuberosity of humerus

Axillary nerve Clavicular (anterior) part: flexes and medially rotates armAcromial (middle) part: abducts armSpinal (posterior) part: extends and laterally rotates arm

Supraspinatus Supraspinous fossa of scapula

Superior facet of greater tubercle of humerus

Suprascapular nerve

Initiates and assists deltoid in abduction of arm and acts with rotator cuff muscles

Infraspinatus Infraspinous fossa of scapula

Middle facet of greater tubercle of humerus

Suprascapular nerve

Laterally rotates arm; and acts with rotator cuff muscles

Teres minor Middle part of lateral border of scapula

Inferior facet of greater tubercle of humerus

Axillary nerve Laterally rotates arm; and acts with rotator cuff muscles

Teres major Posterior surface of inferior angle of scapula

Medial lip of intertubercular sulcus of humerus

Inferior subscapular nerve

Adducts and medially rotates arm

Subscapularis Subscapular fossa (most of anterior surface of scapula)

Lesser tubercle of humerus Sup. & Inf. subscapular nerves

Medially rotates arm; as part of rotator cuff, helps hold head of humerus in glenoid cavity

Supraspinatus Supraspinous fossa of scapula

Superior facet of greater tubercle of humerus

Suprascapular nerve

Initiates and assists deltoid in abduction of arm and acts with rotator cuff muscles

Collectively, the supraspinatus, infraspinatus, teres minor, and subscapularis muscles are referred to as the rotator cuff, or SITS, muscles. Their primary function during all movements of the glenohumeral (shoulder) joint is to hold


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