Session 3: Elbow, forearm and wrist

Question 1

Describe the anatomy of the elbow joint.

Answer 1

Bones articulating to form the Elbow Joint:

1. —Humerus
2. —Radius
3. —Ulna

Radius: (LATERAL)

—Important to identify:

—Proximally:

• —Head
• —Neck
• —Radial tuberosity

—Distally:

• —Radial styloid process

Ulna (MEDIAL):

—Important bony landmarks:

• —Olecranon and coronoid processes
• —Trochlear notch
• —Ulnar tuberosity

—Distally:

• —Ulnar head
• —Ulnar styloid process

Elbow Joint:

• Synovial hinge joint which allows
  
  • —Flexion and extension only
• The trochlea articulates with ulna
• The capitulum articulates with the radius
• In addition to the elbow joint there is a proximal radio-ulnar joint which allows supination

Question 2

Which are the three ligaments that stabilise the elbow joint

Answer 2

There are 3 ligaments which stabilise the elbow joint:

1. —Radial collateral ligament (lateral)
2. —Ulnar collateral ligament (medial)
3. —Annular ligament (Strictly part of the proximal radio-ulnar joint)

Question 3

Demonstrate the bone anatomy of the hand

Answer 3

The majority of the function of the upper limb is devoted to the hand.

—Carpal bones:

Some Lovers Try Positions That They Can’t Handle

Carpals – Proximal:

—Scaphoid

• —Most lateral
• —Boat shaped
• Articulates with radius
• Has an anteriorly projecting tubercle

—Lunate

• Crescent shaped, also articulates with radius

—Triquetrum

• —3 sided bone

—Pisiform

• —Sesamoid bone existing in the tendon of the flexor carpi ulnaris

Carpals – Distal:

Lateral to Medial:

—Trapezium (has a tubercle and is next to the thumb)

—Trapezoid

—Capitate (largest of all carpal bones)

—Hamate (has a hook on palmar surface)

Question 4

Identify the muscles responsible for flexion & extension (at the elbow).

Answer 4

Anterior compartment: Brachialis, Brachioradialis & Biceps Brachii

—Posterior compartment: Triceps, anconeus

Question 5

Coracobrachialis

Answer 5

• —Anterior arm compartment
• Proximal attachment:
  
  • Coracoid process
• Distal attachment:
  
  • Humeral shaft
• Function:
  
  • Flexion at the gleno-humeral join
• Innervation:
  
  • Musculocutaneous

Question 6

Biceps brachii

Answer 6

• —Anterior arm compartment
• Proximal attachments(two heads):

1. —Short: Coracoid process
2. —Long: Supraglenoid tubercle

• —Distal attachments:

1. —Radial tuberosity
2. —Bicipital aponeurosis

—Functions:

• —Flexion at the gleno-humeral joint
• —Flexion at the elbow joint
• —Supination of the forearm at the proximal radio-ulnar joint.

—Innervation:

• —Musculocutaneous

Question 7

Brachialis

Answer 7

• —Anterior arm compartment
• —Proximal attachment:

1. —Anterior humeral shaft
   * —Distal attachment:
2. —Ulnar tuberosity

—Function:

• —Flexion at the elbow joint (main flexor)

—Innervation:

• —Musculocutaneous

Question 8

Triceps

Answer 8

—Posterior arm compartment

—Proximal attachments (3 heads):

—Long: Infraglenoid tubercle

—Medial and later: Posterior humeral shaft

• —Distal attachments:
  1. —Olecranon

—Functions:

• —Extension of the elbow joint
• —Long head extends the gleno-humeral joint

—Innervation:

• —Radial

Cubital Fossa:

—Borders:

—Line between the medial epicondyles

—Brachioradialis

—Pronator teres

—Roof*:

—Aponeurosis of the biceps brachii and deep fascia of the forearm

—Contains:

—Median cubital vein

—Medial and lateral cutaneous nerves of the forearm

—Most things passing from arm to forearm go through the cubital fossa

1. —Median nerve
2. —Radial nerve: Passes anterior to lateral epicondyle*
3. Brachial artery (divides in the cubital fossa)
4. Biceps tendon

—Important exception:

—Ulnar nerve, passes posteriorly to medial epicondyle

Question 9

Proximal Radio-Ulnar Joint

Answer 9

• —This is a pivot joint which allows pronation and supination of the forearm
• —The radius is held over the ulna by the annular ligament but is allowed free rotation
• —Commonly dislocated in children
• —Pivot type joint which allows the radius to move around the ulna in rotation
• —Pronation and supination
• —Distal Radio-Ulnar Joint: Ligaments

Question 10

Compartments of the Forearm

Answer 10

—The compartments of the forearm are separated by the interosseous membrane, which lies between the radius and ulna

• —Anterior forearm compartment

1. —Superficial
2. —Intermediate
3. —Deep

• —Posterior (extensor) forearm compartment
• —Can be more easily remembered through function:

—-Wrist extensors

—-Digit extensors

—-Thumb extensors (and more)

—Also supinator and brachioradialis

Question 11

Anterior forearm - Superficial

Answer 11

—Four of these have the same proximal attachment, the common flexor origin

1. —Pronator teres
2. —Flexor carpi radialis
3. —Palmaris longus

—Pronator teres: (thumb - lateral @anat pos)

—Distal: Radius

—Function: Wrist pronation + flexion

—Innervation: Median

—Flexor carpi radialis:

—Distal: metacarpals (II & III)

—Function: Wrist abduction* + flexion

—Innervation: Median

—Palmaris longus:

—Distal: Palmar aponeurosis of the hand

—Function: Wrist flexion

—Innervation: Median

—Flexor carpi ulnaris (pinky - medial @anat pos)

—Distal: Carpal and metacarpals

—Function: Wrist adduction* + flexion

—Innervation: Ulnar

—

—

Question 12

Anterior forearm - intermediate

Answer 12

—Flexor digitorum superficialis:

• —Large muscle inferior to the common wrist flexors
• —Proximal*
  
  • —Radial and ulnar heads
  • Partial attachment to the humerus
• —Distal
  
  • Middle phalanx

—Functions:

• —Flexion at the proximal interphalangeal, MCP and wrist joints

—Innervation

• —Median nerve

Question 13

Anterior forearm - Deep

Answer 13

—All innervated by median nerve except for FDP to ring and little fingers (ulnar nerve)

—Flexor digitorum profundus:

• —Proximal: Ulna and interosseous membrane*
• —Distal: Anterior aspect of distal phalanges
• —Function: Flexion of interphalangeal joints and wrist
• —Innervation?

—Flexor pollicus longus

• —Proximal: Radius*
• —Distal: Distal phalanx of thumb*
• —Function: Flexes interphalangeal joints of thumb

—Pronator quadratus

• —Proximal: Distal ulna*
• —Distal: Distal radius*
• —Function: Pronation

Question 14

Posterior forearm

Answer 14

—Extension of the wrist

1. —Extensor carpi radialis longus
2. —Extensor carpi radialis brevis
3. —Extensor carpi ulnaris

—Extension of the digits

1. —Extensor digitorum (all 4 digits)
2. —Extensor indicis (index digit)
3. —Extensor digiti minimi (little finger)

—Innervation:

• —The entire posterior forearm is innervated by the posterior interosseous nerve, which is a continuation of the deep motor branch of the radial nerve.

—Extension of the thumb

1. —Extensor pollicis brevis
2. —Extensor pollicis longus
3. —Abductor pollicis longus
4. —Mostly thumb abduction

—Supinator

• —Proximal: Lateral epicondyle of humerus*
• —Distal: Proximal 1/3 of radius*
• —Function: Wrist supination

—Brachioradialis

• —Proximal: Distal humerus*
• —Distal: Lateral distal radius*
• —Function: Elbow flexion

—

—

Question 15

Arterial supply

Answer 15

Brachial artery has many branches:

• —It is lateral to the median nerve
• —Most important branch: the profunda brachii
• —The profunda brachii runs alongside the radial nerve
• —Gives off the nutrient artery to the humerus
• —Divides at the elbow into the radial and ulnar arteries
• —The common interosseous artery branches off the ulnar artery, this splits into the:
• —Anterior interosseous artery
• —Supplies anterior compartment of the forearm
• —Posterior interosseous artery
• —Supplies posterior compartment of the forearm
• —These anastomose on the posterior of the hand with the dorsal carpal branches of the radial and ulnar arteries to form the dorsal carpal arch*
• —Ulnar artery runs into hand over flexor retinaculum
• —Crosses the floor of the anatomical snuff box to enter the hand
• —Here, it forms the palmar arches

Radial artery also gives off a dorsal carpal branch which will anastomose with the dorsal carpal branch of the ulnar artery and the interosseous arteries to form the dorsal carpal arch

Question 16

Venous Drainage

Answer 16

—Superficial

—Basilic – draining medial part

—Cephalic – draining lateral part

—Deep

—The venae comitantes of the brachial artery (brachial vein)

—Basilic pierces deep fascia midway up arm to become deep and joins the brachial vein to form the axillary vein at the inferior border of the teres major

—This is the same landmark as?

—Cephalic dives in to join the axillary vein

—At the delto-pectoral triangle*

—Superficial drainage is to the cephalic and basilic veins

—The dorsal venous arch forms the cephalic vein laterally and the basilic vein medially.

—The median cubital vein connects the cephalic and basilic vein at the level of the elbow

—This is a common site for venepuncture

Deep venous drainage

—The palmar venous arches form the venae comitantes of the radial and ulnar arteries

—These flow to the “brachial veins” (venae comitantes of the brachial artery)

Question 17

Innervation

Answer 17

Median Nerve:

—Medial to the brachial artery at the level of the elbow

• —Can be damaged by supracondylar elbow fractures or dislocations
• —Enters forearm below head of pronator teres
• —It gives off the anterior interosseous nerve* which supplies the anterior compartment, except for?
  
  • —Flexor carpi ulnaris
  • —Medial flexor digitorum profundi
• —Also gives off a palmar cutaneous branch prior to the wrist
• —Enters wrist through carpal tunnel

Ulnar Nerve:

• —Enters forearm below head of flexor carpi ulnaris
• —Supplies FCU and medial FDP
• —Proximal to the wrist it gives off the
• —Palmar cutaneous branch
• —Dorsal cutaneous branch
• —At the wrist, it is medial to the FCU and lateral to the ulnar artery

Radial Nerve:

—Anterior to the lateral epicondyle it divides into

—Sensory: Superficial radial nerve

—Motor: Posterior interosseous nerve (deep branch)

—Posterior interosseous passes through head of supinator to supply the extensor compartment

——NOTE: The “deep branch of the radial nerve” is the true division, it is this nerve which becomes the posterior interosseous nerve*.