Superficial Back, Shoulder, and Scapular Region

Question 1

What muscles connect the upper limb to the vertebral column?

Answer 1

Trapezius.
Rhomboideus major.
Latissimus dorsi.
Rhomboideus minor.

Question 2

trapezius

Answer 2

innervation:
Spinal accessory nerve (CN XI) (motor fibers) and C3, C4 spinal nerves (pain and proprioceptive fibers)

action:
Descending part elevates; ascending part depresses; and middle part (or all parts together) retracts scapula; descending and ascending parts act together to rotate glenoid cavity superiorly

Question 3

Rhomboideus major and minor

Answer 3

innervation:
Dorsal scapular nerve (C4, C5)

action:
Retract scapula and rotate it to depress glenoid cavity; fix scapula to thoracic wall

Question 4

Latissimus dorsi.

Answer 4

innervation:
Thoracodorsal nerve (C6, C7, C8)

action:
Extends, adducts, and medi- ally rotates humerus; raises body toward arms during climbing

Question 5

Levator scapulae

Answer 5

innervation:
Dorsal scapular (C5) and cervical (C3, C4) nerves

action:
Elevates scapula and tilts its glenoid cavity inferiorly by rotating scapula

Question 6

What muscle of the back connects the upper limb with the thoracic wall? What is its nerve supply?

Answer 6

Trapezius
innervation:
Spinal accessory nerve (CN XI) (motor fibers) and C3, C4 spinal nerves (pain and proprioceptive fibers)

Question 7

What functions are associated with the deltoid muscle? What nerve supplies the deltoid and when would this nerve likely be injured? How would one clinically test the function of the deltoid?

Answer 7

action:
Clavicular (anterior) part: flexes and medially rotates arm
Acromial (middle) part: abducts arm
Spinal (posterior) part: extends and laterally rotates arm

innervation:
Axillary nerve (C5, C6)

likely injury:
the axillary nerve is usually injured during fracture of this part of the humerus. It may also be damaged during dislocation of the glenohumeral joint and by compression from the incorrect use of crutches.

test:
the arm is abducted, starting from approximately 15°, against resistance. If acting normally, the del- toid can easily be seen and palpated. The influence of gravity is avoided when the person is supine.

Question 8

What muscles form the posterior axillary fold? What is their nerve supply?

Answer 8

latissimus dorsi and teres major

Lower subscapular nerve (C5, C6) Thoracodorsal nerve (C6, C7, C8)

Question 9

What muscles connect the scapula with the humerus?

Answer 9

deltoid, supraspinatus, infraspinatus. teres minor, teres major, subscapularis

Question 10

What muscles form the rotator cuff?

Answer 10

supraspinatus, infraspinatus, teres minor, and subscapularis

Question 11

What are the attachments of the omohyoid muscle? How is the omohyoid innervated and what is it’s function?

Answer 11

scapula to the hyoid

ansa cervicalis from cervical plexus (C1–C3)

Fixes or depresses hyoid bone

Question 12

What vessels are involved in establishing collateral circulation in the shoulder region?

Answer 12

transverse cervical artery
suprascapular artery
subscapular artery

Question 13

What is the most common site of clavicular fracture?

Answer 13

The weak- est part of the clavicle is the junction of its middle and lateral thirds.

Question 14

Why does the shoulder droop following clavicular fracture?

Answer 14

After fracture of the clavicle, the sternocleidomastoid mus- cle elevates the medial fragment of bone (Fig. B6.1). Because of the subcutaneous position of the clavicles, the end of the superiorly directed fragment is prominent—readily palpa- ble and/or apparent. The trapezius muscle is unable to hold the lateral fragment up owing to the weight of the upper limb, and thus the shoulder drops.

Question 15

What is a ‘greenstick’ fracture?

Answer 15

The slender clavicles of newborn infants may be fractured during delivery if the neonates are broad shouldered; however, the bones usually heal quickly. A fracture of the clavicle is often incomplete in younger children—that is, it is a greenstick fracture, in which one side of a bone is broken and the other
is bent. This fracture was so named because the parts of the bone do not separate; the bone resembles a tree branch (green- stick) that has been sharply bent but not disconnected.

Question 16

What is “winged scapula” and how does it usually occur?

Answer 16

When the serratus anterior is paralyzed owing to injury to the long thoracic nerve, the medial border of the scapula moves laterally and
posteriorly away from the thoracic wall, giving the scapula the appearance of a wing, especially when the person leans on the upper limb may not be able to be abducted above the
horizontal position because the serratus anterior is unable to rotate the glenoid cavity superiorly to allow complete abduction of the limb. Remember, the trapezius also helps raise the arm above the horizontal. Although protected when the limbs are at one’s sides, the long thoracic nerve is exceptional in that it courses on the superficial aspect of the serratus anterior, which it supplies. Thus when the limbs are elevated, as in a knife fight, the nerve is especially vulnerable. Weapons, including bullets directed toward the thorax, are a common source of injury.

Question 17

What is the triangle of auscultation? When using a stethoscope and listening for lung sounds, what intercostal space would the triangle expose?

Answer 17

Near the inferior angle of the scapula is a small tri- angular gap in the musculature. The superior hori- zontal border of the latissimus dorsi, the medial
border of the scapula, and the inferolateral border of the trapezius form a triangle of auscultation. This gap in the thick back musculature is a good place to examine posterior segments of the lungs with a stethoscope. When the scapulae are drawn anteriorly by folding the arms across the chest and the trunk is flexed, the auscultatory triangle enlarges and parts of the 6th and 7th ribs and 6th intercostal space are subcutaneous.

Question 18

What clinical deficit would be apparent with injury to the thoracodorsal nerve? What happens with respect to “chinning” one’s self and the use of crutches with paralysis of the latissimus dorsi?

Answer 18

Surgery in the inferior part of the axilla puts the tho- racodorsal nerve (C6–C8) supplying the latissimus dorsi at risk of injury. This nerve passes inferiorly
along the posterior wall of the axilla and enters the medial surface of the latissimus dorsi close to where it becomes tendinous (Fig. B6.6). The thoracodorsal nerve is also vulner- able to injury during mastectomies when the axillary tail of the breast is removed. The nerve is also vulnerable during surgery on scapular lymph nodes because its terminal part lies anterior to them and the subscapular artery (Fig. B6.7).
The latissimus dorsi and the inferior part of the pectoralis major form an anteroposterior muscular sling between the trunk and the arm; however, the latissimus dorsi forms the more powerful part of the sling. With paralysis of the latissimus dorsi, the person is unable to raise the trunk with the upper limbs, as occurs during climbing. Furthermore, the person cannot use an axillary crutch because the shoulder is pushed superiorly by it. These are the primary activities for which active depression of the scapula is required; the passive depres- sion provided by gravity is adequate for most activities.

Question 19

How would injury to the dorsal scapular nerve effect the position of the scapula?

Answer 19

Injury to the dorsal scapular nerve, the nerve to the rhomboids, affects the actions of these muscles. If the rhomboids on one side are paralyzed, the
scapula on the affected side is located farther from the mid- line than that on the normal side.

Question 20

When is injury to the axillary nerve most likely to occur? What would be the appearance of the patient’s shoulder sometime following axillary nerve injury?

Answer 20

The deltoid atrophies when the axillary nerve (C5 and C6) is severely damaged. Because it passes inferior to the humeral head and winds around the surgical neck of the humerus (Fig. B6.8A), the axillary nerve is usually injured during fracture of this part of the humerus. It may also be damaged during dislocation of the glenohumeral joint and by compression from the incorrect use of crutches. As the deltoid atrophies, the rounded contour of the shoul- der is flattened compared to the uninjured side. This gives the shoulder a flattened appearance and produces a slight hollow inferior to the acromion. In addition to atrophy of the deltoid, a loss of sensation may occur over the lateral side of the proximal part of the arm, the area supplied by the supe- rior lateral cutaneous nerve of the arm, the cutaneous branch of the axillary nerve.
The deltoid is a common site for the intramuscular injection of drugs. The axillary nerve runs transversely under cover of the deltoid at the level of the surgical neck of the humerus (Fig. B6.8A). Awareness of its location also avoids injury to it during surgical approaches to the shoulder.

Question 21

supraspinatus

Answer 21

origin:
Supraspinous fossa of scapula

termination:
Superior facet of greater tubercle of humerus

innervation:
Suprascapular nerve (C4, C5, C6)

Question 22

infraspinatus

Answer 22

origin:
infraspinous fossa of scapula

termination:
Middle facet of greater tubercle of humerus

innervation:
Suprascapular nerve (C5, C6)

Question 23

teres minor

Answer 23

origin:
Middle part of lateral border of scapula

termination:
Inferior facet of greater tubercle of humerus

innervation:
Axillary nerve (C5, C6)

Question 24

subscapularis

Answer 24

origin:
Subscapular fossa (most of anterior surface of scapula)

termination:
Lesser tubercle of humerus

innervation:
Upper and lower sub- scapular nerves (C5, C6, C7)

Question 25

What muscle serves to initiate abduction of the arm?

Answer 25

supraspinatus

Question 26

What is the function of the rotator cuff?

Answer 26

Their primary function during all movements of the glenohumeral (shoulder) joint is to hold the humeral head in the glenoid cavity of the scapula.

Question 27

Which muscle of the rotator cuff is most commonly torn?

Answer 27

The supraspinatus tendon is most commonly ruptured

Question 28

When is dislocation of the shoulder joint most likely to occur? Where would the head of the humerus usually move with a shoulder dislocation?

Answer 28

Because of its freedom of movement and instability, the glenohumeral joint is commonly dislocated by direct or indirect injury. Because the presence of the coraco-acromial arch and the support of the rotator cuff are effective in preventing upward dislocation, most disloca- tions of the humeral head occur in the downward (inferior) direction. However, they are described clinically as anterior or (more rarely) posterior dislocations, indicating whether the humeral head has descended anterior or posterior to the infraglenoid tubercle and the long head of the triceps. The head ends up lying anterior or posterior to the glenoid cavity. Anterior dislocation of the glenohumeral joint occurs most often in young adults, particularly athletes. It is usu- ally caused by excessive extension and lateral rotation of thehumerus (Fig. B6.33). The head of the humerus is driven inferoanteriorly, and the fibrous layer of the joint capsule and glenoid labrum may be stripped from the anterior aspect of the glenoid cavity in the process. A hard blow to the humerus when the glenohumeral joint is fully abducted tilts the head of the humerus inferiorly onto the inferior weak part of the joint capsule. This may tear the capsule and dislocate the shoulder so that the humeral head comes to lie inferior to the glenoid cavity and anterior to the infraglenoid tubercle. The strong flexor and adductor muscles of the glenohumeral joint usu- ally subsequently pull the humeral head anterosuperiorly into a subcoracoid position. Unable to use the arm, the per- son commonly supports it with the other hand. Inferior dislocation of the glenohumeral joint often occurs after an avulsion fracture of the greater tubercle, owing to the absence of the upward and medial pull pro- duced by the muscles attaching to the tubercle.

Question 29

When would a patient most likely experience shoulder pain (subacromial bursitis)?

Answer 29

Inflammation and calcification of the subacromial bursa result in pain, tenderness, and limitation of movement of the glenohumeral joint. This condition is also known as calcific scapulohumeral bursitis. Deposition of calcium in the supraspinatus tendon is common. This causes increased local pressure that often causes excruciating pain during abduction of the arm; the pain may radiate as far as the hand. The calcium deposit may irritate the overlying sub- acromial bursa, producing an inflammatory reaction known as subacromial bursitis. As long as the glenohumeral joint is adducted, no pain usu- ally results because in this position the painful lesion is away from the inferior surface of the acromion. In most people, the pain occurs during 50–130° of abduction (painful arc syn- drome) because during this arc the supraspinatus tendon is in intimate contact with the inferior surface of the acromion. The pain usually develops in males 50 years of age and older after unusual or excessive use of the glenohumeral joint.