Anatomy of the Arm and Shoulder Flashcards
When someone falls with their arms straight out what are the two most common bones to break?
Scaphoid
Clavicle
As a general rule with the brachial plexus what do the higher trunks tend to supply compared to the lower trunks?
Higher trunk -> tends to supply arm and shoulder
Lower trunk generally hand and forearm
What is the action of the serratus anterior on the scapula?
What are its attachments?
Serratus anterior is a ventrolateral muscle arising from the chest wall which attaches to the medial border of the scapula and protracts and stabilises the pectoral girdle
What can cause winging of the scapula?
Weakness of the serratus anterior
Palsy of Long Thoracic Nerve (of bell)
-supplies serratus anterior
Name the 3 posterior group short scapular muscles.
What is their action?
Hold the glenohumeral joint together (also called the rotator cuff muscles)
Supraspinatus
-abduction
Infraspinatus and teres minor
-External lateral rotation
What muscle is in the anterior group of the short scapular muscles?
What is its action?
Subscapularis
-internal medial rotation
What rotator cuff muscles (short scapular muscles) attach to the greater tuberosity and which attach to the lesser tuberosity?
Greater tuberosity
- Supraspinatus
- Infraspinatus
- Teres Minor
Lesser Tuberosity
-Subscapularis
Give some functions of the clavicle
how does it aid movement? what structures are around it?
Strut to support the shoulder and keep shoulder girdle out to length for function
Protects the brachial plexus and vessels
Attachment for muscles
What muscles attach to the clavicle?
Trapezius Deltoid Pectoralis Major Subclavus Sternocleidomastoid Sternohyoid
What is cleidocranial dysostosis?
Cleidocranial dysostosis, is a hereditary congenital disorder, where there is delayed ossification of midline structures.
Clavicle may only have medial section of may be missing
What 3 ligaments attach to the coracoid process?
Coracoacromial
2 coracoclavicular
-conoid and trapeziod
What 3 muscles originate from the coracoid process?
Coracobrachialis
Short head of biceps
Important structures lie on which side of the coracoid process?
Medial side
“2 sides to the coracoid process -> lateral side and suicide”
What is the most mobile joint in the body?
What is the trade off for this?
Glenohumeral joint
-Most commonly dislocated large joint in the body (45% of dislocations)
What are the static and dynamic stabilisers of the glenohumeral joint?
Static stabilisers -> labrum, capsule and ligaments
Dynamic stabilisers -> muscles (intrinsic -> rotator cuff) and extrinsic (large)
What are the 2 openings in the glenohumeral joint capsule for?
Tendon of long head of biceps
Subscapular bursa
What is the weakest part of the glenohumeral joint capsule and why?
Inferior part of the capsule
Only part not reinforced by the rotator cuff muscles
(long loose redundant fold hanging down into axilla when arm by the side (need that capsule for when arm fully abducted))
Why is shoulder effusion commonly seen anteriorly?
Glenohumeral joint capsule very thin anteriorly so if muscle is wasted and there is effusion you will see swelling anteriorly