T2 L3 Anatomy of the shoulder region Flashcards
What are the skeletal components of the shoulder?
Pectoral girdle - clavicle and scapula
Humerus
What are the 2 joints in the shoulder?
Glenohumeral joint
Acromioclavicular joint
What are the 4 ligaments of the shoulder region?
Coracoclavicular
Acromoclavicular
Coracoacromial
Glenohumeral
What is the coracoclavicular ligament between?
Clavicle and coracoid process of scapula
What is the function of the acromoclavicular ligament?
Forms a capsule around the acromoclavicular joint to strength and stabilise the joint
What is the coracoacromial ligament between?
Between coracoid process and acromion
What is the function of the coracoacromial ligament?
Forms coraco-acromial arch over top of glenohumeral joint
Provides support for head of humerus to prevent superior dislocation
What are the movements of the glenohumeral joint?
Abduction / adduction
Flexion / extension
Lateral / medial rotation
Circumduction
What parts is the glenohumeral joint split into?
Superior
Middle
Inferior
What is abduction mainly performed by?
Deltoid
What is the origin, insertion, function and innervation of the deltoid muscle?
Origin: spine of scapula, acromion, clavicle
Insertion: deltoid tuberosity
Innervation: axillary nerve
Function: abduction
- anterior fibres: flexion and medial rotation
- posterior fibres: extension and lateral rotation
What is adduction performed by?
Latissimus dorsi
Pectoralis major
What is the origin, insertion, function and innervation of latissimus dorsi?
Origin: thoracolumbar fascia, spinous process T6-T12, iliac crest, inferior 3 ribs
Insertion: bicipital groove of humerus
Function: adduction and medial rotation
Innervation: dorsal scapular nerve
What is the origin, insertion, function and innervation of pectoralis major?
Origin: sternum, medial part clavicle, costal cartilage
Insertion: lateral lip bicipital groove
Function: adduction, flexion, medial rotation
Innervation: pectoral nerves
What helps abduction above 90 degrees?
Upper fibres trapezius
Lower fibres trapezius
Serratus anterior
What helps adduction above 90 degrees?
Most of it is gravity
Levator scapulae
Rhomboids
What muscles are involved in flexion of the arm?
Short head of biceps
Long head of biceps
Coracobrachialis
Anterior fibres deltoid
What muscles are involved in extension of the arm?
Long head of triceps
Lateral and medial heads of triceps
Posterior fibres of deltoid
Latissimus dorsi
Why is the glenohumeral joint unstable?
Large humeral head
Shallow glenoid fossa
What is the most frequently dislocated joint?
Glenohumeral joint
Anterior dislocation where humeral head descends inferior to end up anterior
What 5 factors increase the stability of the glenohumeral joint to prevent dislocation?
Coracoacromial arch Glenohumeral ligaments Deepening of glenoid fossa by glenoid labrum Long heads of biceps and triceps Tendons of rotator cuff muscles
Why does the coracoacromial arch prevent glenohumeral dislocation?
Prevents superior displacement of humeral head to prevent superior dislocation
How do the glenohumeral ligaments prevent dislocation?
Supports the joint anteriorly
Between rim of glenoid fossa and anatomical neck of humerus
What is the glenoid labrum?
Fibrocartilaginous ridge surrounding glenoid cavity
Creates a seal with the head of the humerus to reduce the risk of dislocation
What are the 4 rotator cuff muscles?
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
What is the origin, insertion and function of supraspinatus
Sits superior over joint
Origin: supraspinous fossa
Insertion: greater tubercle
Function: initiate abduction
What is the origin, insertion and function of infraspinatus?
Sits posterior over joint
Origin: infraspinous fossa
Insertion: greater tubercle
Function: lateral rotation
What is the origin, insertion and function of teres minor?
Sits posterior over joint
Origin: infraspinous fossa
Insertion: greater tubercle
Function: lateral rotation
What is the origin, insertion and function of subscapularis?
Sits anterior over joint
Origin: subscapular fossa of scapula
Insertion: lesser tubercle of humerus
Function: medial rotation
Why is the most common route for dislocation inferiorly?
There is no inferior rotator cuff muscle
What is the function of the subacromial bursa?
Reduces friction beneath deltoid to promote free motion of rotator cuff tendons
Where does teres major sit?
Inferior to teres minor
Why is teres major not a true rotator cuff muscle?
It doesn’t cuff the joint
What is the origin, insertion and function of teres major?
Origin: inferior angle of scapula
Insertion: medial lip bicipital groove
Function: medial rotation, stabilises humerus during abduction - eccentric contraction
Why is the supraspinatus commonly injured?
Limited space for tendon under coracoacromial arch
Impingement due to repetitive overhead activities
Describe the scapula anastomosis
Couple of branches from subclavian and one from axillary
Subscapular artery comes from 3rd part axillary
Suprascapular artery comes from thyrocervical trunk which comes from subclavian artery
Dorsal scapular artery comes from subclavian and runs along medial edge of scapula
Where is the nerve supply to the shoulder from?
Brachial plexus
What does the suprascapular nerve supply?
Supraspinatus and infraspinatus
What are the terminal branches of the posterior division?
Axillary
Radial
What does the axillary nerve supply?
Deltoid
Teres major
Badge area of skin
What does the radial nerve supply?
Extensors such as triceps brachii
What other branches come from the posterior cord?
Upper / lower subscapular nerves
Thoracodorsal nerves
What do the subscapular nerves supply?
Subscapularis
Teres major
What does the thoracodorsal nerve supply?
Latissimus dorsi
What are the borders of the quadrangular space?
Teres minor
Teres major
Long head of triceps
Humerus
What is the consequence of a fracture to the cervical neck?
Can damage axillary artery so deltoid can’t work so can’t abduct arm
What are the terminal branches of the lateral cord?
Musculocutaneous
Median
What does the musculocutaneous nerve supply?
Arm flexors
What is another branch of the lateral cord?
Lateral pectoral nerve which supplies pectoralis major
What are the terminal branches of the medial cord?
Median
Ulnar
What are some other branches of the medial cord?
Medial pectoral nerve
Medial cutaneous nerves
What does the medial pectoral nerve supply?
Pectoralis major / minor
