Gross Anatomy
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FUNCTIONAL ANATOMY OF THE ELBOW,
RADIO-ULNAR AND WRIST JOINTS

Required Reading - 330 - 335; 342 - 377

I. INTRODUCTION

  1. The axilla or armpit is a pyramidal shaped space that provides passage for the axillary artery and brachial plexus from the posterior triangle;e of the neck into the arm.
  2. The elbow joint is a hinge joint between the distal portion of the humerus and the ulna. Two movements can occur at this joint - flexion and extension. The muscles responsible for these movements , their nerve supply and vascular supply are contained within the compartments of the arm. The arm is that region of the upper limb between the shoulder joint and the elbow joint. It is divided into 2 compartments: an anterior or flexor compartment and a posterior or extensor compartment. Muscles in the former compartment flex the elbow joint and are involved in supination of the proximal radioulnar joint. Muscles in the latter compartment extend the elbow joint.
  3. The proximal and distal radioulnar joints are pivot joints between the respective portions of the radius and ulnar. Movements of pronation and supination take place at these joints. In addition, the radius and ulnar are connected by a fibrous interosseous membrane that forms and non moveable joint between these 2 bones called a syndesmosis.
  4. The wrist joint is a very complex type of joint between the distal end of the radius, a fibrocartilaginous disc at the distal end of the ulna, the carpal (wrist ) bones and the proximal portion of the metacarpal bones. These complex articulations form and ellipsoidal type synovial joint at which the movements of flexion-extension and abduction or radial deviation - adduction or ulnar deviation can occur. The forearm connects the elbow with the wrist an can also be divided into 2 compartments: an anterior or flexor compartment and a posterior or extensor compartment. Muscles in the former compartment pronate the radioulnar joints, flex the wrist and also flex the digits. Muscles in the latter compartment help supinate the radioulnar joints, extend the wrist and help extend the digits.

The anatomy of these regions is covered in the required readings and outlined below. You will need to understand the anatomy of this region in order to appreciate how the elbow, radioulnar and wrist joints function and how to use your knowledge to examine these joints.

II. The Axilla ( 330 - 335)

  1. Boundaries
    1. Anterior Wall
      1. Pectoralis major and pectoralis minor muscles
      2. Anterior axillary fold = lower portion of pectoralis major
    2. Posterior Wall
      1. Latissimus dorsi, subscapularis and teres major muscles
      2. Posterior axillary fold = portion of the latissimus dorsi muscle
    3. Medial Wall
      1. Serratus anterior muscle and the ribs to which it is attached
    4. Lateral wall
      1. Coracobrachialis muscle and shaft of the humerus
    5. Apex
      1. Clavicle, scapula, 1st. rib
    6. Floor
      1. Skin and axillary fascia extending between anterior and posterior axillary folds
  2. Spaces
    1. Quadrangular
      1. Lateral border - surgical neck of humerus
      2. Medial border - long head of triceps brachii muscle
      3. Superior border - teres minor muscle
      4. Inferior border - teres major muscle
      5. Contents
      6. Axillary nerve
      7. Posterior humeral circumflex artery
    2. Triangular
      1. Lateral border - long head of triceps brachii muscle
      2. Superior border - teres minor muscle
      3. Inferior border - teres major muscle
      4. Contents
      5. Circumflex scapular branch of subscapular artery
  3. Contents
    1. Axillary sheath
      1. Fascial sheath derived from fascia covering scalene muscles in neck
      2. Contains
        1. Proximal position of axillary artery
        2. Cords of brachial plexus
        3. Terminal portion of axillary vein
  4. Vasculature
    1. Axillary Artery (Fig. 1)
      1. Continuation of subclavian artery into axilla
        1. Name changes as subclavian passes distal to 1st rib
      2. Becomes brachial artery after passing distal to teres major muscle
      3. Branches (read text for distribution of arterial branches)
        1. Thoracoacromial trunk
        2. Lateral thoracic
        3. Anterior and Posterior humeral circumflex arteries
        4. Subscapular
          1. Muscular
          2. Circumflex scapular
    2. Axillary Vein
      1. Continuation of brachial vein into axilla
        1. Name changes after passing proximal to teres major muscle
      2. Drains into subclavian vein
        1. Name changes as it passes proximal to 1st rib
      3. Receives cephalic vein
    3. Axillary lymph nodes
      1. Drain upper limb, breast , and skin of chest wall
      2. Enlargement could indicate infections & / or tumors from these areas
    4. Scapular anastomosis
      1. Brings axillary artery into connection with the subclavian artery
        1. Collateral route should blockage occur in subclavian artery
      2. Branches
        1. Subclavian artery
          1. Transverse cervical
          2. Suprascapular arteries
          3. Arteries supply dorsal scapular muscles
        2. Axillary
          1. Circumflex scapular

III. The Arm (pgs.342 - 347)

  1. Bones
    1. Humerus
      1. Student should be able to identify the parts of the humerus
      2. Student should be able to distinguish the right humerus from the left humerus
  2. Flexor ( Anterior ) Compartment
      1. Muscles ( see text for attachments of muscles)
        1. Biceps brachii
        2. Brachialis
        3. Coracobrachialis
      2. Muscle Function(s) See Chart I
      3. Nerve Supply
        1. Musculocutaneous ( diagram)
          1. Motor to muscles in anterior brachial compartment
          2. Sensory to lateral portion of forearm
      4. 4. Blood Supply
        1. Brachial artery
          1. Muscular branches
          2. Superior ulnar collateral
          3. Inferior ulnar collateral
  3. Extensor ( Posterior) Compartment
    1. Muscles ( see text for attachments of muscles)
      1. Triceps brachii
      2. Anconeus
    2. Muscle Function(s) See Chart I
    3. Nerve Supply
      1. Radial
        1. Motor to triceps brachii
        2. Sensory to posterior and lateral regions of arm
    4. Blood Supply
      1. Deep ( profunda ) brachial
        1. Muscular branches
        2. Middle collateral
        3. Radial Collateral

IV. THE FOREARM (348 - 368)

  1. Bones
    1. The student should be able to identify the components of the radius and ulna
    2. The student should be able to distinguish the right radius and ulna from the left radius and ulna.
  2. Alignment
    1. Carry Angle
      1. Forearm is in valgus ( abducted) position with respect to arm
  3. Flexor ( Anterior ) Compartment
    1. Muscles ( refer to the text for specific attachments and actions of the muscles in this compartment)
      1. Superficial Group
        1. Pronator teres
        2. Flexor carpi radialis
        3. Palmaris longus
        4. Flexor carpi ulnaris
      2. Intermediate Group
        1. Flexor digitorum superficialis
      3. Deep group
        1. Flexor digitorum Profundus
        2. Flexor pollicis longus
        3. Pronator quadratus
    2. Muscle Function(s)See Chart I
    3. Nerve Supply
      1. Median
        1. Motor to all muscles except Flexor carpi ulnaris and ulnar half of Flexor digitorum profundus
        2. Sensory to palmar surface of 3 1/2 digits and corresponding area of palm
      2. Ulnar
        1. Motor to Flexor carpi ulnaris and ulnar portion of Flexor digitorum profundus
        2. Sensory to of 1 1/2 digits and corresponding area of hand
    4. Cutaneous Innervation
      1. Lateral Side
        1. Lateral antebrachial cutaneous ( C 6)
          1. Branch of musculocutaneous
      2. Medial side
        1. Medial antebrachial cutaneous ( T 1)
        2. Branch from medial cord
    5. 5. Blood Supply
      1. Radial Artery
        1. Muscular branches
        2. Recurrent branch
      2. Ulnar Artery
        1. Muscular branches
        2. Recurrent branches
        3. Common Interosseous
          1. Anterior interosseous - supplies deep structures in flexor compartment
          2. Posterior interosseous - supplies deep structures in extensor compartment
  4. Extensor ( Posterior) Compartment
    1. 1. Muscles ( refer to the text for specific attachments and actions of the muscles in this compartment)
      1. "Snuff Box" - Thumb Muscles
        1. Abductor pollicis longus
        2. Extensor pollicis brevis
        3. Extensor pollicis longus
      2. Wrist Extensors
        1. Extensor carpi radialis longus ii) Extensor carpi radialis brevis
        2. Extensor carpi ulnaris
      3. Finger Extensors
        1. Extensor digitorum
        2. Extensor digiti minimi
        3. Extensor indicis
      4. Deep
        1. i) Supinator
        2. ii) Brachioradialis
    2. Muscle Function(s)See Chart I
    3. Nerve Supply
      1. Radial
      2. Superficial - cutaneous to dorsum of hand and thumb
      3. Deep - motor to muscles in extensor compartment
    4. Blood Supply
      1. Posterior Interosseous Artery

V. THE ELBOW JOINT ( pgs 349 -352)

  1. A. Bones
    1. Humerus
      1. Capitulum
      2. Trochlea
    2. Radius
      1. Head
    3. Ulna
      1. Olecranon
  2. B. Ligaments
    1. Radial ( Lateral) Collateral
    2. Ulnar (Medial) Collateral
      1. anterior, posterior and intermediate bands
    3. Annular ligament of radius
      1. Binds head of radius to radial notch of ulnar
      2. Can be responsible for elbow dislocation in children
  3. C. Movements (Chart 1)
    1. Flexion
      1. Bringing anterior surface of forearm to anterior surface of arm
    2. Extension
      1. Moving forearm away from arm
  4. D. Muscle Actions
    1. Flexion
      1. Brachialis
        1. Palm in prone position
      2. Biceps brachii
        1. more active when forearm is supinated
      3. Brachioradialis
        1. active when palm in between prone and supine position
    2. Extension
      1. Anconeus
        1. Helps stabilize elbow joint
      2. Triceps brachii

VII. RADIOULNAR JOINT (352 -55)

  1. Bones and Ligaments
    1. Proximal joint
      1. Head of radius
      2. Coronoid process of ulna
    2. Annular Ligament
      1. binds head of radius
    3. Distal joint
      1. Distal radius
      2. Ulna head
    4. Interosseous membrane
      1. Binds shaft of radius to shaft of ulnar
  2. Movements (Chart 1)
    1. Pronation
      1. Radius rotates on ulna allowing the palm to face downward
    2. Supination
      1. Radius moves on ulna enabling palm to face upwards
  3. Muscle Actions
    1. Pronation
      1. Pronator teres
      2. Pronator quadratus
    2. 2. Supination
      1. Biceps brachii
        1. Very strong
      2. Supinator
        1. (1) Weak

VIII. THE WRIST JOINT (369 - 377)

  1. Articulations
    1. Radiocarpal Joint
      1. Distal radius
      2. Articular disk
        1. binds radius to ulna and carpal bones
        2. separates distal ulna from carpal bones
      3. Proximal carpal bones
        1. scaphoid
        2. lunate
        3. triquetrum
    2. Intercarpal Joints
      1. Midcarpal joint
        1. Between proximal and distal rows of carpal bones
    3. Carpometacarpal Joints
      1. Distal row of carpal bones
      2. Metacarpal bones
  2. Ligaments
    1. Radial collateral ligament
      1. Passes from styloid process of radius to scaphoid bone
    2. Ulnar collateral ligament
      1. Passes from styloid process of ulna to triquetral and pisiform bones
    3. Pisohamate ligament
      1. Insertion of the Fl. carpi ulnaris tendon on pisiform bone and hook of hamate bone
    4. Palmar and Dorsal radiocarpal ligament
      1. binds styloid process of radius to carpal bones
  3. Flexor Retinaculum
    1. Continuation of deep fascia of forearm that attaches to carpal bones
    2. Carpal Tunnel
      1. Space between carpal bones and flexor retinaculum
      2. Contains
        1. Digital flexor tendons
        2. Median nerve
    3. Attachments
      1. Pisiform bone & hook of hamate bone medially
      2. Scaphoid and trapezium bones laterally
  4. Movements
    1. Joints involved
      1. Radiocarpal
        1. Flexion
        2. Abduction
      2. Midcarpal
        1. Extension
        2. Adduction
    2. Types of Movements
      1. Flexion (Palmar Flexion)
        1. Brings palm of hand to anterior surface of forearm
      2. Extension ( Dorsiflexion - Hyperextension)
        1. Brings wrist to neutral position
        2. Dorsum of hand moves close to posterior surface of forearm ( hyperextension)
      3. Abduction ( Radial deviation)
        1. Hand moves towards radial side of forearm
      4. Adduction ( Ulnar deviation)
        1. Hand moves towards ulna side of forearm
    3. Muscle Actions See Chart I
  5. Elbow Anastomosis
    1. Medial Epicondyle
      1. Brachial Artery
        1. Superior ulnar collateral
        2. Inferior ulnar collateral
      2. Ulnar Artery
        1. Anterior ulnar recurrent
        2. Posterior ulnar recurrent]
    2. Lateral Epicondyle
      1. Deep ( Profunda ) Brachial Artery
        1. Radial collateral
        2. Middle collateral
      2. Radial Artery
        1. Radial recurrent
      3. Posterior Interosseous Artery
        1. Interosseous recurrent

IX. CLINICAL CONSIDERATIONS

  1. Dislocation of elbow in children - occurs as a result of a forearm being pulled away from arm. The head of the radius is held against the ulna by the annular ligament. The head and shaft of the radius do not fuse with each other until about 16 years of age. Traction applied to the forearm can result in the head of the radius being separated from the shaft.
  2. Epicondylitis - is an inflammation of either the lateral or medial epicondyle of the humerus. Inflammation is usually brought about from overuse of the muscles attached to either of these bony prominence. The area around the epicondyle becomes very painful especially after performing resisted movements using the appropriate muscles . Most of the forearm flexors arise from the medial epicondyle while lateral epicondylitis ( tennis elbow) comes from over use of the wrist extensors.
  3. Nerve lesions - resulting from trauma, entrapment or disease. Trauma to a peripheral nerve could result in loss of nerve function and paralysis of the affected muscles. Entrapment and nerve root damage usually leads to muscle weakness especially when trying to perform resisted movements.
    1. Musculocutaneous Nerve - the most common type of injury to this nerve is entrapment within the coracobrachialis muscle. Symptoms include pain along the lateral aspect of the forearm and weak elbow flexion and supination of the forearm. Traumatic lesion of the musculocutaneous nerve would result in loss of sensation from the radial portion of the forearm and a pronounced weakness of ability elbow flexion and supination of the forearm
    2. Radial Nerve - can be affected by trauma such as compression within the axilla "Saturday Night Palsy" , fracture of the shaft of the humerus or entrapment as the deep branch passes through the supinator muscle.
      1. "Saturday Night Palsy" results from compression of the radial nerve in the axilla. The patient experiences paraesthesia along the posterior lateral arm and dorsum of hand. There is also a pronounced drop wrist when the forearm is in the supine position because of weakness of the wrist extensors.
      2. Fractures of the humerus, especially the shaft, can damage the radial nerve. Elbow extension is usually not affected because the triceps brachii is innervated before the nerve winds around the humeral shaft. Again , drop wrist results because of the loss of function of the wrist extensors. There is also loss of sensation from the dorsum of the hand.
      3. Entrapment of the deep branch of the radial nerve can occur as it passes through the supinator muscle. No sensory loss accompanies this condition because the deep branch is a pure motor nerve. Drop writs is the primary symptom.
    3. Lesions of the medial and ulnar will be studied in the Hand section.


Chart I -PRIME MOVERS OF THE ELBOW, RADIOULNAR and WRIST JOINTS

JOINT ACTION MUSCLES NERVE SEGMENT
Elbow Flexion Brachialis Musculocutaneous C 5,6
Biceps brachii Musculocutaneous C 5,6
Brachioradialis Radial C 5,6
Extension Anconeus Radial C 7 ,8
Triceps brachii Radial C 6, 7 ,8
Radioulnar Supination Biceps brachii Musculocutaneous C 5,6
Supinator Radial C 5,6
Pronation Pronator teres Median C 6,7
Pronator quadratus Median( Anterior Interosseous) C 8, T 1
Wrist Flexion Flexor carpi radialis Median C 6,7
Palmaris longus Median C 7,8
Flexor carpi ulnaris Ulnar C 8, T 1
Extension Extensor carpi radialis longus Radial C 6, 7
Extensor carpi radialisbrevis Radial C 6, 7
Extensor carpi ulnaris Radial C 7, 8
Abduction Abductor pollicis longus Radial C 6, 7
Extensor pollicis brevis Radial C 6, 7
Adduction Flexor carpi ulnaris Ulnar C 8, T 1
Extensor carpi ulnaris Radial C 7, 8



Figure 5 - Arterial Supply
1. Name the artery branches to which each arrow points

2. Name the branches the participate in the elbow anastomosis



Figure 6 Carry Angle of Forearm
Note that the forearm is in a valgus (abducted) position with respect to the arm


Figure 7 - The Elbow Joint
Name the numbered bony portions of the elbow joint in both the anterior and posterior views


Figure 8 - Wrist Joint
1. Identify the bones and portions of bones indicated at each number.

2. What type of structure is found a X?

3. Correctly identify each of the carpal bones

4. Distinguish between the radiocarpal and midcarpal copmponents of the wrist joint



OBJECTIVES

  1. Correlate the important surface anatomical features of the wrist , hand and fingers, with the bony and or muscles forming each feature.
  2. Know the bones that comprise the hand and fingers.
  3. Know the shape and types of movements that take place at the metacarpophalangeal and interphalangeal articulations of the fingers and thumb .
    1. Understand the mechanism of action for muscles that act as prime movers for each type of motion
  4. Be able to describe the anatomy of the extensor expansion.
    1. Understand how the muscles whose tendons participate in the formation of the extensor expansion function in finger movement.
    2. Understand how the extensor expansion can "uncouple" flexion & extension.
  5. Understand the attachments, innervation and function(s) of the intrinsic muscles of the hand.
    1. Be able to localize the site(s) of peripheral nerve lesions by the functional deficits produced by such lesion
    2. Correlate deformities of the hand with the nerve lesion that produced the deformity.
    3. Know how to test from the individual functions of the intrinsic muscles of the hand.
  6. Understand the dermatome pattern of the hand and fingers.
    1. Be able to determine the location of a peripheral nerve lesion from the sensory deficits that result from such a lesion.
  7. Be familiar with the blood supply and venous drainage of the hand. Know the components that comprise the superficial and deep palmar arches.
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