Upper limb

• The upper limb contains 2 compartments of muscles contained within fascial sheath:

  • Anterior = flexor
  • Posterior = extensor
• Areas of transition = axilla, cubital fossa and carpal tunnel
• The axilla is important for the transition of nerves that supply the upper limb
• The brachial plexus supplies the upper limb and originates from C5-T1

  • Roots - arise from between the scalene muscles
  • Trunks - pass through posterior triangle of the neck
  • Divisions - pass under the clavicle
  • Cords - named in relation to the axillary artery
  • Terminal nerves - musculocutaneous, axillary, median, radial and ulnar
• The axillary and median nerves receive innervation from all the nerve roots C5-T1
• The musculocutaneous nerve supplies all muscles in the anterior compartment of the arm - flexors
• The radial nerve supplies all muscles in the posterior compartment of the arm and forearm - extensors
• The median nerve supplies most anterior (flexor) muscles in the forearm and the thenar muscles in the hand
• The ulnar nerve supplies small muscles in the hand and some forearm flexors
• The musculocutaneous nerve is also called the BBC nerve as it supplies all muscles in the anterior compartment of the arm:

  • Biceps brachii
  • Brachialis
  • Coracobrachialis

  Musculocutaneous nerve injury = unable to flex at the elbow
• Bones of the shoulder:

  • Clavicle and scapula = pectoral girdle
  • Head of humerus and pectoral girdle = shoulder joint
• The shoulder joint is formed by an articulation between the head of the humerus and the glenoid cavity (or fossa) of the scapula. This gives rise to the alternate name for the shoulder joint – the glenohumeral joint.
• The scapula:

  • Spine of the scapula
  • Supraspinous fossa
  • Infraspinous fossa
  • Glenoid cavity - where the humerus sits to create the glenohumeral joint
• The serratus anterior muscle rotates the scapular - allows the arm to be raised over 90 degrees

  Supplied by the long thoracic nerve - damage results in a winged scapula appearance
• The humerus has 2 different necks:

  • Anatomical neck - where the capsule of the shoulder joint will attach
  • Surgical neck - where fractures happen
  • Muscles attach to the neck of the humerus by the lesser and greater tubercles
• The glenohumeral joint is a synovial joint:

  • Articular capsule - fibrous capsule
  • Articular cartilage - hyaline cartilage
  • Synovial fluid
• Rotator cuff muscles = SITS

  • Supraspinatus = 0-15 degree abduction of the arm (completed by deltoid)
  • Infraspinatus - external rotation
  • Teres minor - external rotation
  • Subscapularis - internal rotation
• The supraspinatus muscle passes under the bony caraco-acromial arch

  Can rub against this arch during abduction = tendonitis

  Abduction of the arm is painless until 45-60 degrees
• The trapezius muscle allows us to shrug our shoulders

  It is supplied by the accessory nerve (CN XI) - also supplies the skin over the trapezius
• The deltoid muscle allows us to abduct our arms past 15 degrees

  The deltoid is supplied by the axillary nerve

  the axillary nerve wraps around the surgical neck of the humerus so can be damaged when there is a fracture
• The axillary nerve wraps around the surgical neck of the humerus
• The radial nerve supplies the posterior arm and forearm and runs through the radial groove of the humerus
• The ulnar nerve runs medially and passed through a groove in the medial epicondyle
• The median nerve descends down the arm lateral to the brachial artery. It then crosses over via the cubital fossa to become medial in the forearm
• Fracture of the surgical neck of the humerus = injury to the axillary nerve

  Unable to complete abduction of the arm and loss of sensation to the deltoid
• Midshaft fracture of the humerus = injury to the radial nerve

  Injury to the radial nerve results in a wrist drop - radial nerve is the extensor nerve
• Fracture above the epicondyle (distal humerus) is called a supracondylar fracture

  Supracondylar fracture = injury to the medial nerve

  Injury to the medial nerve = flexors and pronators in the forearm being paralyzed

  Flexion of the thumb is also prevented
• Fracture of the medial epicondyle = ulnar nerve injury

  Ulnar nerve injury = sensation loss and clawing of the 4th and 5th digit
• The shoulder is the most commonly dislocated large joint. Sacrifices the stability of the joint to achieve a wide range of movement
• Anterior dislocation of the shoulder is most common:

  • Elbow flexed
  • Internally rotated
• Posterior dislocation of the shoulder mainly occurs after an epileptic seizure - lightbulb appearance of head of humerus on an x-ray
• The ulnar is the medial bone of the forearm

  The radius is the lateral bone of the forearm
• The humero-ulnar and humero-radial joints allow flexion and extension of the elbow
• The proximal and distal radioulnar joints allow pronation and supination of the forearm
• Stabilising ligaments of the elbow:

  • Radial collateral ligament
  • Anular ligament of the radius encompasses the radius
  • Median collateral ligament
  • Ulnar collateral ligament
• Dislocation of the radial head commonly happens when a child is swung around by their arm

  Radius slips out of the anular ligament
• Flexor muscles of the elbow:

  • Biceps brachii - has a long head and short head
  • Brachialis
  • Brachioradialis - spans the humerus and radius
• The triceps muscle is the main extensor of the elbow
• Boundaries of the cubital fossa:

  • Laterally - brachioradialis muscle
  • Medially - pronator teres muscle
  • Line across lateral and medial epicondyle of the humerus
• Contents of the superficial cubital fossa:

  • Medial - basilic vein
  • Lateral - cephalic vein
  • Median cubital - venepuncture