Brachial plexus and shoulder Flashcards
What is the origin of the brachial plexus?
Ventral rami C5-T1
What are the sections of the brachial plexus?
Randy texans drink cold beer
(roots, trunks, divisions, cords, branches)
Where are the roots of the brachial plexus located?
Pass between scalenus anterior and medius
Where are the trunks of the brachial plexus located?
-upper and middle trunk are superior to subclavian
-Lower trunk runs posterior to subclavian
Edit:
-Run from base of posterior triangle
-Over first rib
-Behind first part of subclavian
Where are the divisions of brachial plexus located?
Apex of axilla, lie behind middle 1/3rd of clavicle
Where are the cords of the brachial plexus located?
My there names related to axillary artery
–> posterior
–> lateral
–> medial
Draw out the brachial plexus
Upper roots:
-Long thoracic: C5-C7-serratus anterior
-Dorsal scapular: C5, rhomboids and levator scapulae
Upper trunk
-Nerve to subclavius: C5-C6, subclavius
-Suprascapular: C5,C6
Lateral cord:
-Lateral pectoral nerve (C5-C7)
Posterior cord
–> upper subscapular (upper part subscapularis)
–> lower subscapular (lower part subscapularis, teres major)
–> Thoracodorsal (LD)
Medial cord
-Medial pectoral nerve (part of pec major), pec minor
-Medial cutaneous nerve of arm
-Medial cutaneous nerve of forearm
Describe Erb’s palsy
Causes
-During newborn delivery
-Traumatic force downwards on arm and shoulder
-Damage to upper nerve roots C5,C6
Motor
–> Adduction: denervation arm abductors (deltoid, supraspinatus)
–> Internal rotation: denervation arm external rotators (teres minor, infraspinatus)
–> pronationand extension: denervation elbow flexors and supinators (biceps, brachialis, coracobrachialis)
Sensory
–> loss of sensation radial side of arm and forearm
Describe Klumpke’s palsy
Injury to lower trunk (C8, T1)
Hyperabduction/birth trauma
Motor (claw hand deformity)
–> Denervation all intrinsic muscles of hand
–> paralysis of wrist flexors (except flexor carpi radialis-innervated by C6+7)
–> hyperextension MCP joints
–> flexion IP joints
Label posterior scapula
Label lateral scapula
label anterior scapula
left scapula and clavicle articulation from above
What is the origin and insertion of the pec major?
Origin
Clavicular head:
–> Medial half anterior clavicle
Sternocostal head
–> Anterior sternum
—> upper 6 costal cartilages
–> external oblique aponeurosis
Insertion
–> lateral intertrochanteric groove
–> Lateral lip of bicipital groove
Pec major action
Whole muscle:
–> adduction and medial rotation of the arm
Clavicular head
–> Flexion of the humerus
Sternocostal head
–> extension of the flexed humerus
–> acts as accessory muscle of respiration by elevating the ribs
What is the innervation of pec major?
-Medial (C8-T1) pectoral nerve
-Lateral (C5-C7) pectoral nerve
What is the origin/insertion/innervation/action of trapezius?
Origin:
–> Spinous process T6-T12
–> Occipital protuberance
–> ligamentum nuchae
Insertion
–> Spine/acromion of scapula
–> clavicle
Action
–> rotates scapula
Innervation:
–> spinal accessory nerve (12th cranial nerve)
What is origin/insertion/action/innervation of serratus anterior?
Origin
–> Ribs 1-9
Insertion
–> Scapula (ventral medial)
Action
–> prevents winging
Innervation
–> long thoracic nerve
Deltoid origin/insertion
Origin:
–> spine of scapula, acromion
–> clavicle
Insertion
–> Humerus (deltoid tuberosity)
Deltoid action/innervation
Action:
Anterior fibres
–> Flexion and internal rotation
Posterior fibres
–> Extension and external rotation
Middle fibres
–> major abductor of arm (after 15 degrees)
Innervation
–> axillary nerve
Origin/insertion/action/innervation subscapularis
Origin:
–> Subscapular fossa
Insertion
–> Humerus (LT)
Action
–> internally rotates arm
–> provides anterior stability
Innervation:
–> upper and lower subscapular nerves (posterior cord of brachial plexus)
Origin/insertion/action/innervation of supraspinatus/infraspinatus/teres minor
Origin:
-Supraspinatus–> supraspinatus fossa
-Infraspinatus–> infraspinatus fossa
-Teres minor: –> dorsolateral scapula
Insertion
–> GT of humerus
Action
-Supraspinatus –> abducting, providing stability, externally rotating arm
-Infraspinatus + teres minor –> external rotating, providing stability
Innervation:
-Supraspinatus and infraspinatus –> suprascapular nerve
-Teres minor–> axillary nerve
What are the borders and contents of the triangular space?
Superior: teres minor
Inferior: teres major
Lateral: Long head of triceps
Contents
-Circumflex scapular artery
What are the borders and contents of the triangular interval?
Borders:
-Medial: long head of triceps
-Lateral: Lateral head of triceps/humerus
-superior: Teres major
Contents
-Profunda brachii artery
-Radial nerve
What are the borders and contents of the quadrangular space
-Medial: long head of triceps
-Lateral: humerus
-Superior: Teres minor
-Inferior: teres major
Contents
-Axillary nerve
-Posterior circumflex humeral artery
What are the branches of the axillary artery?
Semen tastes like sweet apple pie
1st part (above pec minor)
–> Superior thoracic artery
2nd part (posterior to pec minor)
–> Thoracoacromial
–> Lateral thoracic
3rd part (inferior to pec minor)
–> Subscapular (largest branch)
–> Anterior circumflex humeral
–> posterior circumflex humeral
What is the surface marking of the coracoid process?
2cm inferior to junction between middle and lateral 1/3rd of the clavicle
What structures attach to the coracoid process?
-Ligaments:
–> Coracoclavicular
–> coracohumeral
–> coracoacromial
Muscles
–> pec minor (insertion)
–> Coracobrachialis (origin)
–> short head of biceps (origin)
What muscles are inserted into the bicipital groove?
-A lady between two majors
Lateral: Pec major
Medial: teres major
Floor: LD
Tendon of long head of biceps lies within the groove
Muscles involved in shoulder abduction
Supraspinatus 0-15
Middle fibres deltoid 15-90
>90 trapezius and serratus anterior, which will require upward rotation of the scapula with lateral rotation of the humerus
What factors reduce the stability of the shoulder joint?
-Shallow glenoid cavity
-Lax capsule with few ligaments
-Inferior aspect not supported due to presence of quadrangular space
What factors stabilise the shoulder?
Static restraints:
-Glenoid labrum
-Capsule
-Glenohumeral ligaments
Dynamic restraints
-Rotator cuff
—> joint cavity depression produced by synchronised contraction of rotator cuff
—> Increased capsular tension due to attachments of rotator cuff to the capsule
What is a synovial joint?
-Articulating surfaces covered in hyaline cartilage
-Separated by film of synovial fluid that acts as a lubricant
-Joint stability is provided by fibrous capsule and accessory ligaments
-Synovial fluid is produced by synovial membrane that lines the joint capsule
Describe axillary nerve motor and sensory supply, and deficit
Motor:
-Deltoid
-Teres minor
Sensory
-Skin to lower half deltoid (regimental badge)
Injury
-Inability to abduct arm beyond 15 degrees
-sensory deficit over regimental badge area
1,6,10,11,14
1,6,10,11,14
What are the upper limb myotomes?
C5: elbow flexion
C6: wrist extension
C7: elbow extension
C8: finger flexion
T1: finger abduction
What are the reflexes?
1,2 buckle my shoe (ankle)
3,4 kick the door (knee)
5,6 pick up sticks (biceps and brachioradialis)
7,8 lay them straight (triceps)
Dermatomes
C4: lateral neck and shoulder
C5: lateral upper arm and elbow
C6: lateral forearm and thumb
C7: Middle finger
C8: little finger and medial palm
T1: Medial forearm and elbow
What are the findings in upper limb nerve root compressions?
What is the main stabiliser of the shoulder joint?
-Rotator cuff muscles
