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
What is adhesive capsulitis of shoulder?
What causes it
What are some of the symptoms?
Adhesive capsulitis (also known as Frozen shoulder) is a painful and disabling disorder of unclear cause in which the shoulder capsule, the connective tissue surrounding the glenohumeral joint of the shoulder, becomes inflamed and stiff, greatly restricting motion and causing chronic pain.
Pain is usually constant, worse at night, and with cold weather. Certain movements or bumps can provoke episodes of tremendous pain and cramping. The condition is thought to be caused by injury or trauma to the area and may have an autoimmune component.
What is the labrum?
What is its function and what is it made of?
Fibrocartilaginous lip
Elevated the glenoid edge
-Doubles the glenoid depth and increases the surface area
acts ad the “chock block” limiting glenohumeral translation
What is the most common dislocation of the shoulder and why?
Anterior disloaction of the shoulder (90%)
Glenohumeral capsule weak here
What is a Bankart lesion?
A Bankart lesion is an injury of the anterior (inferior) glenoid labrum of the shoulder due to anterior shoulder dislocation.
When this happens, a pocket at the front of the glenoid forms that allows the humeral head to dislocate into it. It is an indication for surgery and often accompanied by a Hill-Sachs lesion, damage to the posterior humeral head
(Shoulder dislocates pushing labrum across creating cavity for humeral head to slip into)
Where deos the sabacromial bursa sit?
Sits on top/front/side of shoulder
looks like a Frenchmen’s beret
What is the action of the subacromial bursa?
Allows free movement of:
- Supraspinatus tendon between humeral head and acromion
- Humeral head under acromion
- Deltoid over humeral head
Where does the subacromial bursa start?
Superiorly in tunnel formed by acromion (roof and posterior border), coracoacromial ligament (anterior) and humeral head (floor)
What is the most common rotator cuff muscle to tear?
Supraspinatus
What 4 joints integrate to provide total shoulder function?
Sternoclavicular joint
Acromioclavicular joint
Glenohumeral joint
Scapulothoracic articulation
(delocate interaction of 30 muscles)
What muscles cause shoulder flexion?
Pectoralis major
Coracobrachialis
Biceps
Deltoid (ant part)
What muscles cause shoulder extension?
Teres major
Latissimus dorsi
Deltoid (post. part)
What muscles cause shoulder abduction?
Deltoid (middle part)
Supraspinatus
What muscles cause shoulder adduction?
Pectoralis major
Latissimus dorsi
What muscles cause medial rotation of the shoulder?
Teres major
Subscapularis
What muscles cause lateral rotation of the shoulder?
Teres minor
Infraspinatus
Which two bones does the biceps bracii attach to?
What is its action?
Scapula to the radius
Flexion and supination of the forearm
Which two bones does the triceps bracii attach to?
What is its action?
Humerus to the ulnar
Extends the arm and forearm
What is the most powerful flexor of the elbow?
Brachialis muscle
Acts in all positions for flexion
-biceps only acts in some
What is the function of the brachioradialis muscle?
Weaker synergist muscle for flexion of the elbow
Supernation AND pronation
- WOW
- Brings arm back to resting position
What two muscles are the antagonists to the supination of the biceps bracii?
Pronator Teres
Pronator Quadratus
What is the elbow carrying angle also called?
Physiological valgus
What are the 3 flexor muscles of the elbow joint?
Brachialis
Biceps brachii
Brachioredialis
What are the extensors of the elbow joint?
Triceps
Anconeus
Gravity
What type of joints are the superior and inferior radioulnar joints?
Uniaxial pivot
synovial
What type of joint is the middle radioulnar joint?
Syndesmosis
-interosseus membrane
(fibres run obliquely)
What is the annular ligament?
What is its structure? What does it do etc
Strong fibrous band
Encircles radial head
Proximal part blends with the elbow joint capsule
What can elevation of the fat pads of the elbow joint on x-ray show?
Fluid in the elbow joint
-usually blood
What is the function of the olecranon bursa?
Where does it lie?
Lies on the posterior aspect of elbow, over olecranon process.
Small “envelope” with synovial membrane lining, secreting synovial fluid for lubrication to allow movement of skin over bone
What is olecranon bursitis?
what causes it? what other name does it have? what is it?
Inflamed -> Swollen, red, hot, painful olecranon bursa
Also called students elbow
Most usually from trauma or infection
