2.1 Shoulder and arm: Bones and muscles

Question 1

Fracture of clavicle

Answer 1

Common when weight bearing, usually fractures between lateral 1/3 and medial 2/3.

Deltoid pulls lateral end down and sternomastoid pulls medial head up.
*put arm in sling to facilitate rejoining/repair of clavicle

Question 2

Clavicle

Answer 2

Possesses sternal end, acromial end and conoid tubercles.

Has characteristics of both long bones (sternal & acromial ends) and flat bones (shaft).

• Long bone = endochondral ossification (1 and 2 centres of ossification), presence of medullary cavity
• Flat bone = intramembranous ossification.

Question 3

Winging of scapula

Answer 3

Caused by the damage of nerve that supplies serratus anterior, which holds the scapula to the posterior thoracic wall. Usually nerve supply will lie deep to the muscle it supplies, however not the case here. The nerve lies just under the skin and is particularly susceptible to damage, leading to a loss of function for SA.

Question 4

Intrinsic shoulder muscles

Answer 4

• Deltoid
• Teres major
• Supraspinatus
• Infraspinatus
• Teres minor
• Subscapularis

Question 5

Fracture of humerus

Answer 5

Surgical neck - axillary nerve, post humeral circumflex artery

Midshaft - radial nerve, arm extensors compromised

Supracondylar - median nerve, brachial artery which can lead to ischemia, avascular necrosis

Medial epicondyle - avulsion fractures typical, ulnar nerve

Question 6

Upper limb muscles from spine

Answer 6

Superficial
*trapezius
*latissimus dorsi
T + LD + medial border of scapula form triangle of auscultation

Deep
*levator scapulae
*rhomboid minor
*rhomboid major
RM/RM retract scapula when contracting

Question 7

Rotator cuff muscles

Answer 7

SITS

• stabilise shoulder
• act as dynamic ligaments (tendinous point of insertion)
• fixators

Question 8

Rotator cuff injuries

Answer 8

Impingement of supraspinatus
-Tendon of supraspinatus lies just beneath coraco-acromial ligament

Frozen shoulder/’adhesive capsulitis’
-With buildup of calcium, synovial tissue lining can stick against shoulder joint

Question 9

Anterior compartment muscles of arm

Answer 9

Biceps (SH coracoid process to forearm on tuberosity on ulna; LH has intracapsular course)
Coracobrachialis (coracoid process to humerus)
Brachialis (midshaft of humerus to proximal shaft of ulna)

*all supplied by musculocutaneous nerve - passes b/w 2 heads of CB

Question 10

Biceps injury/’Pop Eye Syndrome’

Answer 10

Tendinitis
Dislocation of LH
Rupture of LH

*overextension of biceps

Question 11

Posterior compartment of arm

Answer 11

Triceps (3 heads: long, lateral, medial)

Anconeus (small triangular muscle from lateral epicondyle of humerus to olecranon process of ulna)
*prevents pinching of muscle during extension

• supplied by radial nerve, passes b/w medial & lateral heads
• susceptible to injury in mid-shaft of humerus

Question 12

Posterior apertures

Answer 12

Suprascapular notch
Quadrangular space
Triangular space
Triangular interval

Question 13

Suprascapular notch

Answer 13

Suprascapular nerve goes through the suprascapular notch

Ligament converted into foramen

Question 14

Quadrangular space

Answer 14

Lying superior: Teres minor
Inferior: Teres major
Medial: LH triceps
Lateral: humeral shaft

• axillary nerve
• post humeral circumflex artery (main bld supply of shoulder joint)

Question 15

Triangular space

Answer 15

Lying superior: Teres minor
Inferior: Teres major
Medial: -
Lateral: LH biceps

• circumflex scapular artery
• right next to quadrangular space

Question 16

Triangular interval

Answer 16

Lying superior: Teres major
Inferior: -
Medial: LH of triceps
Lateral: humeral shaft

*radial nerve
*profunda brachial artery
(these two are likely to be damaged with a humeral shaft fracture)