Shoulder, Axilla and Posterior Triangle (Week 2--Miller) Flashcards
Axial skeleton
Bones of head (skull), neck (hyoid bone and cervical vertebrae), and trunk (ribs, sternum, vertebrae, sacrum)
Appendicular skeleton
Bones of the limbs (extremities, appendages), including those forming the pectoral (shoulder) and pelvic girdles
Pectoral (shoulder) girdle
Clavicle and scapula
Joints of the shoulder
Glenohumoral joint
Acromioclavicular joint
Sternoclavicular joint
Articulations that are not true joints
Suprahumeral“joint”
Scapulothoracic“joint”
Glenohumoral joint
Synovial joint (ball and socket)
Allows flexion, extension, abduction, adduction, medial and lateral rotation, circumduction of humerus
Reinforced by rotator cuff tendons and anteriorly by glenohumeral ligaments (thickenings of joint capsule)
Often dislocated
Innervated by suprascapular, lateral pectoral and axillary nerves
Foramen of Weitbrecht is weakness between superior and middle glenohumeral ligaments
Glenoid labrum is fibrocartilagenous ring that surrounds glenoid fossa
Foramen of Weitbrecht
Part of glenohumeral joint
Weakness in joint capsule between superior and middle glenohumeral ligaments
In anterior dislocation, head of the humerus penetrates through this weak area
Tendon of the long head of the biceps
Invaginates the joint capsule (is intracapsular) but does not enter synovial cavity (is extrasynovial)
Tendon held in bicipital groove by transverse humeral ligament
Glenoid labrum
Fibrocartilagenous ring that surrounds glenoid fossa and helps deepen socket of the shoulder joint
Fibrous joint capsule attaches to labrum, so any injury of the joint capsule can potentially involve the labrum
Normal abduction and adduction
Normal range of abduction: 180 degrees overhead
Normal range of adduction: 45 degrees across the front of the body
Normal range of external (lateral) and internal (medial) rotation
Normal range of external rotation: 40 - 45 degrees
Normal range of internal rotation: 55 degrees before motion interrupted by body
Normal range of flexion and extension
Normal range of flexion: 90 degrees
Normal range of extension: 45 degrees posterior to vertical axis of body
Circumduction
Motion where distal aspect of appendage goes in circle and proximal aspect remains relatively stationary
Sternoclavicular joint
Synovial joint (saddle-type, but functions like ball and socket)
Articular disk divides joint into 2 separate joint cavities
Very strong, dislocation is rare
Mobile, to allow movements of pectoral girdle
Only joint between pectoral girdle and axial skeleton
Innervated by supraclavicular nerves and nerve to subclavius muscle
Acromioclavicular joint
Synovial joint (plane-type)
Allows gliding movements
Weak and has incomplete articular disk
Protected by strong superior and inferior acromioclavicular ligaments
This joint involved in shoulder separation injuries
Innervated by supraclavicular, lateral pectoral, axillary nerves
Coracoclavicular ligament
Provides means by which scapula and free limb are suspended from clavicular strut
Suprahumeral “joint” space
Not a true joint
Space between head of humerus and the acromion and coracoacromial ligament
Contains biceps long head tendon, rotator cuff tendons, subacromial/subdeltoid bursa, gleno-humeral joint capsule
Frozen shoulder syndrome
The result (sequelae) of shoulder tendinitis, bursitis, or partial tear
Shoulder injury initially painful but gradually becomes more restricted in motion in all directions (“frozen”)
Exact mechanism unknown but many tissues of suprahumeral “joint” space may be involved (subdeltoid bursa synovium, glenohumeral capsule synovium, conjoined tendon tenosynovium, biceps long head tendon synovial lining)
Subdeltoid/subacromial bursa
Synovial-lined sac that has 2 parts that may be fused or separated: subacromial bursa and subdeltoid bursa
Bursa lies between supraspinatus tendon and deltoid muscle in suprahumeral “joint” space
Reduces friction during abduction so if inflamed, will have pain during abduction
Extrinsic muscles of the shoulder
In general, act on scapula (except pec major and lat dorsi), which is important because scapula must move in order to place the hand in functional position
Anterior group: pectoralis major, pectoralis minor, subclavius, seratus anterior
Posterior group = superficial “back” muscles: trapezius, levator scapulae, rhomboids, latissimus dorsi
In addition to latissimus dorsi, what other shoulder muscles attach to the bicipital groove of the humerus?
Pectoralis major, teres major, latissimus dorsi all attach to bicipital groove of the humerus
Thus, have similar actions on humerus as latissimus dorsi (lat dorsi adducts, medially rotates and extends at shoulder; pec major adducts and medially rotates; teres major adducts and medially rotates at shoulder)
Movements of scapula
Retract: trapezius middle fibers, rhomboids
Protract: serratus anterior
Elevate: trapezius superior fibers, levator scapulae
Depress: trapezius inferior fibers
Superiorly (upwardly) rotate: trapezius superior and inferior fibers, serratus anterior (glenoid cavity pointed superiorly)
Inferiorly rotate: levator scapulae, rhomboids (glenoid cavity pointed inferiorly)
Note: in order to position the hand, the scapula and humerus must move in a smoothly coordinated and integrated fashion (this is called scapulohumeral rhythm)
Scapulohumeral rhythm
Integrated movement of scapula and humerus together; involved in any movement of upper limb which places hand in functional position
Simultaneous movement of humerus at glenohumeral joint and rotation of scapula
For every secondary abduction at glenoheral joint, there is primary rotation of scapula
When arm abducted 90 degrees, 60 degrees occurs at glenohumeral joint and 30 degrees is from scapular rotation
Intrinsic muscles of the shoulder
Deltoid muscle
Teres major muscle
Supraspinatus (rotator cuff)
Infraspinatus (rotator cuff)
teres minor (rotator cuff)
Subscapularis (rotator cuff)
Conjoined tendon of rotator cuff
This IS the rotator cuff itself
Rotator cuff muscles’ tendons (at the ends) form common tendon (“cuff”)/conjoined tendon which is contained within suprahumeral “joint” space
Tendons cover fibrous capsule of shoulder joint and reinforce it, however note that shoulder joint NOT reinforced by cuff inferiorly, so is weak inferiorly
Within the rotator cuff is a “critical zone” which is potential site of tears and Ca2+ deposit buildup
Abduction of the humerus
Initiated by supraspinatus muscle and then deltoid muscle takes over (and is major abduction of humerus)
Rotator cuff muscles
SItS
Supraspinatus: posterior, greater tubercle of humerus
Infraspinatus: posterior, greater tubercle of humerus
Teres minor: posterior, greater tubercle of humerus
Subscapularis: anterior, lesser tubercle of humerus
Critical Zone
Area of vascular anastomoses within the rotator cuff
Is alternately ischemic of hyperemic depending on whether there is tension on the cuff
This is often the site of degeneration, Ca2+ deposits, tears
Neurovascular structures and spaces of the shoulder
Quadrangular space: transmits axillary nerve, posterior circumflex humeral artery (these also wrap around surgical neck of humerus so if you fracture that, could affect that artery and nerve)
Triangular space: transmits branches of circumflex scapular artery
Scapular anastomosis: network of interconnecting arteries formed by branches of the subclavian artery, 3rd part of axillary artery, and intercostal arteries
Quadrangular space boundaries
Lateral: lateral head of triceps
Medial: long head of triceps
Superior: teres minor
Inferior: teres major
Remember, transmits axillary nerve and posterior circumflex humeral artery which also wrap around surgical neck of humerus
Suprascapular nerve and artery
Suprascapular nerve and artery are both found deep to supraspinatus and infraspinatus muscles
From supraspinous fossa to scapular spine to infraspinous fossa
Suprascapular nerve is a branch of the upper trunk of the brachial plexus
Arteries of the Scapular Anastomosis
Dorsal scapular goes toward spine (if this isn’t present, transverse cervical artery takes its place)
Suprascapular artery in upper area
Subscapular artery in lower area
Circumflex scapular artery closes the loop
Brachial plexus
Somatic nerve plexus formed by ventral rami of C5-T1 spinal cord segments (innervates skeletal muscle, bone, joints, skin, and NOT blood vessels)
Located across two different anatomical regions: posterior triangle (supraclavicular part) and axilla (infraclavicular part)
5 roots –> 3 trunks (visible in posterior neck)–> 6 divisions (under clavicle, not visible) –> 3 cords (visible in axilla) –> 5 terminal branches (also have non-terminal branches that originate from different regions of the brachial plexus)
How are the 3 cords named?
All in relation to the axillary artery
Posterior cord is posterior to axillary artery
Lateral cord is lateral to axillary artery
Medial cord is medial to axillary artery
What does the classic M of the brachial plexus include?
Musculocutaneous nerve
Median nerve
Ulnar nerve
Which spinal levels do fibers of the 5 terminal branches of the brachial plexus predominantly originate from?
Axillary: C5-6
Musculocutaneous: C5-7
Median: C5-T1
Radial: C5-T1
Ulnar: C8, T1
Memorize these!!
What non-terminal branches arise from the roots of the brachial plexus?
Dorsal scapular nerve (levator scapulae and rhomboids)
Long thoracic nerve (serratus anterior)
What non-terminal branches arise from the upper trunk of the brachial plexus?
Nerve to the subclavius (subclavius)
Suprascapular nerve (supraspinatus and infraspinatus)
What non-terminal branches arise from the medial cord of the brachial plexus?
Medial pectoral nerve (pec major and pec minor)
Medial brachial cutaneous nerve
Medial antebrachial cutaneous nerve
What non-terminal branches arise from the lateral cord of the brachial plexus?
Lateral pectoral nerve (pec major)
What non-terminal branches arise from the posterior cord of the brachial plexus?
Upper subscapular nerve (subscapularis)
Thoracodorsal nerve (latissimus dorsi)
Lower subscapular nerve (subscapularis and teres major)
The axilla
The pyramidal-shaped region or space inferior to shoulder joint; the armpit
Has apex, base, anterior (pec major, pec minor, clavicle, subclavius muscle), posterior (lat dorsi, teres major, subscapularis), medial (thorax and serratus anterior) and lateral walls (conceptually by bicipital groove of humerus)
Contains axillary artery, axillary vein, distal part of brachial plexus, axillary lymph nodes
Axillary lymph nodes
Receive lymph from upper limb but also 75% of lymph drainage from breast (so important in diagnosing breast cancer)
What part of the brachial plexus does the axilla contain?
Infraclavicular part (cords and terminal branches)
Also contains tendons of biceps (long head tendon and short head tendon) and coracobrachialis
This is where you see the “M”
Relationship of axillary artery/vein with cords of brachial plexus
Cords of brachial plexus surround the axillary artery
Brachial plexus and axillary artery are contained within fascial sheath called axillary sheath
Branches of the axillary artery
Subclavian artery passes 1st rib –> axillary artery has 3 branches –> passes teres major to become brachial artery
1st part (medial; medial to pec minor): supreme thoracic artery (supplies 1st intercostal space)
2nd part (deep; deep to pec minor): thoraco-acromial artery (related to superior margin of pec minor, has pectoral deltoid, acromial and clavicular branches) and lateral thoracic artery (runs along border of pec minor and supplies the breast)
3rd part (lateral; lateral to pec minor): anterior circumflex humeral artery (goes lateral and anterior to neck of humerus; anastomoses w/posterior), posterior circumflex humeral artery (goes lateral and posterior to neck of humerus; anastomoses w/anterior), subscapular artery (medial and divides into circumflex scapular and thoracodorsal arteries)
Posterior triangle of the neck
Supraclavicular part of the brachial plexus, phrenic nerve, accessory nerve, subclavian artery all course through it
Important for control of upper limb, diaphragm and trapezius
Boundaries: anterior margin of trapezius, posterior margin of SCM, clavicle
Cervical fascia
Investing fascia: roof of posterior triangle and surrounds SCM and trapezius
Prevertebral fascia: covers muscular floor of triangle and surrounds prevertebral and true (deep) back muscles
Pretracheal fascia: surrounds thyroid gland, trachea, esophagus
Roof (investing fascia) of posterior triangle
Contains cutaneous branches of cervical plexus: lesser occipital, great auricular, transverse cervical, supraclavicular nerves (these are all sensory nerves)
Cervical plexus
Somatic nerve plexus with cutaneous (sensory) and motor branches
Formed by C1-4 ventral rami nerves
Cutaneous branches
Phrenic nerve
Ansa cervicalis
Motor branches to prevertebral muscles
Contributions to accessory nerve
Note: hypoglossal and accessory nerves are NOT part of cervical plexus
External jugular vein
Descends inferiorly across external surface of SCM muscle
Drains into subclavian vein or junction of internal jugular and subclavian veins
Floor of posterior triangle
Splenius capitis, levator scapulae, middle and anterior scalene muscles
Brachial plexus (supraclavicular part; roots/trunks) is between anterior and middle scalene muscles and deep to the clavicle
Subclavian artery is inferior to brachial plexus roots/trunks
Phrenic nerve (C3,4,5) goes over anterior scalene muscle
Accessory nerve travels on levator scapulae as is dives deep to trapezius to innervate it
Transverse cervical artery (to trapezius) is superior to suprascapular artery and suprascapular artery (to supraspinatus) is deep to clavicle; both are branches of thyrocervical trunk (which comes off 1st part of subclavian artery)
Prevertebral fascia covers structures on floor of posterior triangle
