3. Anatomy of the shoulder region Flashcards
Skeletal components of shoulder region
Pectoral girdle - clavicle and scapula
humerus
Two joints: glenohumeral joint and acromioclavicular joint
Important aspects: acromion, coricoid, greater tubercle of humerus, lesser tubercle of humerus, bicepital groove
ligaments of shoulder
stabilise/support shoulder region
coracoclavicular
acromioclavicular
coracoacromial
glenohumeral (superior, middle, inferior)
Coracoclavicular ligament
two parts
major stabilising ligament
Coracoacromial ligament
- Forms arch
- Provides support for head of humerus
- Prevents superior dislocation
Glenohumeral joint
Highly mobile ball and socket joint
- Abduction/adduction
- Flexion/extension
- Lateral/medial rotation
- Circumduction
between head of humerus and glenoid fossa
Abduction of arm
Performed by deltoid
Origin: spine of scapula & acromion & clavicle
Insert: deltoid tuberosity
Innervation: axillary nerve (from posterior chord of brachial plexus)
Posterior fibres: extension and lateral rotation
Anterior fibres: flexion and medial rotation
Adduction of arm
lattisimus dorsi
- origin spinal processes of T6-T12
- inserts into bicepital groove
pectoralis major
- origin sternum, clavicle, costal cartilages
- inserts into bicepital groove’s lateral lip
What components accommodate abduction/adduction of arm
Glenohumeral joint accommodates parts of movement
Rotation of scapula increases range of movement
Which muscles move the scapula during abduction of the arm and in what direction?
Upper fibres of trapezius moves acromion medially superiorly
lower fibres of trapezius moves spine inferiomedially
serratus anterior moves lower angle superiorly distally
Which muscle(s) move the scapula during adduction of the arm and in what direction?
levator scapular moves top of scapula medially and upright
Rhomboids move medial border medially and upright
Flexion of the arm
Short head of biceps, long head of biceps, coracobrachialis
also anterior fibres of deltoid
Brachialis flexes forearm
Extension of arm
Long head of triceps
Posterior fibres of deltoid
Lattisimus dorsi
Lateral head of triceps and medial head of triceps extend forearm
Forearm flexion
Brachialis
Forearm extension
lateral head of triceps and medial head of triceps
Glenohumeral joint stability
Between large humeral head and shallow glenoid fossa
unstable structure
most frequently dislocated joint - anterior dislocation common (humeral head descends inferiorly and ends up anterior
Factors increasing glenohumeral joint stability
- Coracoacromial arch
- Glenohumeral ligaments
- Deepening of glenoid fossa by glenoid labrum
- Long heads of biceps (above) and triceps (below)
- Tendons of rotator cuff muscles
Glenohumeral arch
prevents superior dislocation of joint
Glenohumeral ligaments
Supports anterior of joint
Glenoid labrum
Deepens the glenoid fossa
Long head of biceps and triceps
Splint joint - prevent movement of head of humerus out of glenoid fossa
Long head of biceps origin in supraglenoid tubercle, passes through joint capsule
Origin of long head of triceps in infraglenoid tubercle
Tendons of rotator cuff muscles
Four muscles
Insert on humerus close to joint
Fuse with the joint capsule
Forms cuff around joint
Rotator cuff muscles origin
supraspinatus - origin from supraspinous fossa
Intraspinatus - origin from infraspinatus fossa
Teres minor - posterior of scapula near lateral border
Rotator cuff muscles - insertion
Supraspinatus, infraspinatus and teres minor insert into the greater tubercle
SIT - upper, middle and lower facets of greater tubercle
Subscapularis
Originates from subscapular fossa, forms a tendon, passes across anterior of joint to insert into lesser tubercle
Rotator cuff function
Supraspinatus - initiate abduction
Infraspinatus - lateral rotation
Teres minor - lateral rotation
Subscapularis - medial rotation
Teres major
Should also be considered with the rotator cuff muscles
Performs medial rotation
Stabilises the humerus during abduction - Eccentric contraction
Originates: inferior angle of scapula
Insertion: medial lip of bicepital groove
Rotator cuff injuries
Supraspinatus impingement:
Supraspinatus most commonly injured
Limited space for tendon under coracoacromial arch
- Impingement due to repetitive overhead activities
- Common in athletes (throwers)
Blood supply
Rich blood supply
Scapula anastomosis
Allows continuous supply of blood to shoulder region during movement
From subclavian and axillary arteries
Scapula anastomosis
From subclavian and axillary
Subclavian -> thyrocervical trunk -> suprascapular -> subscapular subscapula -> dorsal scapula -> subclavian
Nerve supply to the shoulder
From brachial plexus
Suprascapular nerve -> supraspinatus and infraspinatus
from posterior cord
Cords of brachial plexus
Within axilla
below pectoralis major
Posterior cord
Deltoid and teres minor - axillary
triceps brachii - radial
subscapularis, teres major - upper/lower subscapular nerves
Thoracodorsal nerve - lattisimus dorsi
Quadrangular space
Formed by teres minor (superior), humerus (lateral), teres major (inferior), long head of triceps (medial)
What is found in the quadrangular space?
Nerve supply to :
deltoid
teres minor
badge area
Axillary nerve and posterior circumflex humeral artery
Clinical significance of quadrangular space
Fracture of surgical neck can damage axillary nerve and posterior circumflex humeral artery
Lateral cord
lateral pectoral nerve -> pectoralis major
Musculocutaneous - arm flexors
Medial cord
Medial pectoral nerve - Pectoralis major/minor
Medial cutaneous nerves to arm and forearm
