Anatomy: Upper Limb

Osteology of the Upper Limb

• The capsule of the elbow joint attaches to the coronoid process and the medial and lateral epicondyles of the humerus.
• The bicipital tuberosity is a bony projection on the proximal end of the radius.
• The supinator muscle attaches to the lateral epicondyle of the humerus.
• The flexor pollicis longus muscle attaches to the medial epicondyle of the humerus.
• The interosseous membrane is a fibrous sheet that connects the radius and ulna bones.

Muscular Attachments to the Radius and Ulna

• The flexor carpi radialis muscle attaches to the anterior surface of the radius.
• The extensor pollicis longus muscle attaches to the posterior surface of the radius.
• The abductor pollicis longus muscle attaches to the posterior surface of the radius.
• The pronator teres muscle attaches to the medial epicondyle of the humerus.
• The flexor pollicis brevis muscle attaches to the anterior surface of the ulna.
• The adductor pollicis muscle attaches to the medial epicondyle of the humerus.
• The extensor carpi ulnaris muscle attaches to the posterior surface of the ulna.

Muscular Attachments to the Hand

• The thenar muscles (opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis) attach to the anterior surface of the hand.
• The interosseous muscles attach to the palmar and dorsal surfaces of the hand.
• The flexor digitorum profundus muscle attaches to the palmar surface of the hand.
• The extensor digitorum communis muscle attaches to the dorsal surface of the hand.
• The extensor carpi ulnaris muscle attaches to the posterior surface of the hand.

Clinical Notes

• Fractures of the scaphoid bone can occur in young adults who fall on an outstretched hand.
• Fractures of the lunate bone can occur due to hyperextension of the wrist joint.
• Fractures of the metacarpal bone can occur as a result of a fall onto the hand.
• The coronoid process of the ulna is susceptible to injury in fractures of the humerus.
• The radial nerve can be damaged in fractures of the humerus.
• The median nerve can be involved in fractures of the lunate bone.
• Fractures of the distal end of the humerus can occur in children and adults.
• Supracondylar fractures are common in children and can result in damage to the median, radial, and ulnar nerves.
• The pronator quadratus muscle pronates and medially deviates the distal fragment of the radius in fractures.
• The brachioradialis and extensor carpi radialis longus and brevis muscles can shorten and angulate the forearm in fractures.

Upper Limb

• The breast consists of 15 to 20 lobes, which radiate out from the nipple.
• The main duct from each lobe opens separately on the summit of the nipple and possesses a dilated ampulla just before its termination.

Pectoral Region

• The pectoral region is the anterior aspect of the shoulder.
• The breast is situated in the pectoral region, and its blood supply and lymphatic drainage are largely related to the armpit.

Scapular Region

• The scapular region is the posterior aspect of the shoulder.
• The underlying bones of the back are shown in Figure 3.18 and are described in detail in Chapter 2.
• Several structures in the scapular region (e.g., trapezius and latissimus dorsi muscles) connect with and function as part of the upper limb.

Breast Development

• In the early embryo, a linear thickening of ectoderm appears, called the milk ridge, which extends from the axilla obliquely to the inguinal region.
• The ridge disappears except for a small part in the pectoral region, which thickens, becomes slightly depressed, and sends off 15 to 20 solid cords, which grow into the widely lying mesenchyme.

Embryology Notes

• Retracted or inverted nipple is a failure in the development of the nipple during its later stages.
• Micromastia is an excessively small breast on one side, resulting from a lack of development.
• Macromastia is an excessively large breast.

Axilla

• The axilla is a pyramid-shaped space between the upper part of the arm and the side of the chest.
• The axilla forms an important passage for nerves, blood vessels, and lymph channels as they travel between the root of the neck to the upper limb.

Quadrangular Space

• The quadrangular space is an intermuscular space located immediately below the glenohumeral (shoulder) joint.
• The axillary nerve and the posterior circumflex humeral vessels emerge through this space to reach their terminal destinations in the shoulder.

Axillary Walls

• The four walls of the axilla are constructed as follows:
  • Anterior wall: By the pectoralis major, subclavius, and pectoralis minor muscles.
  • Posterior wall: By the subscapularis and teres minor muscles.
  • Medial wall: By the chest wall.
  • Lateral wall: By the humerus.

Wrist

• The wrist (carpus) is a complex of the eight small carpal bones that connect the forearm and hand.
• The wrist is a common site for Injury.

Hand Anatomy

• The hand is located at the distal end of the upper limb and is a very important organ.
• The palmar surface is the anterior side of the hand, while the dorsal surface is the posterior aspect.

Palmar Fascial Spaces

• The fascial spaces of the palm are potential spaces filled with loose connective tissue.
• Their boundaries are important clinically as they may limit the spread of infection in the palm.

Palmar Aponeurosis

• The triangular palmar aponeurosis fans out from the distal border of the flexor retinaculum.
• A fibrous septum passes backward from its medial border and is attached to the anterior border of the fifth metacarpal bone.

Hand Skin

• The skin of the palm of the hand is thick and hairless.
• It is bound down to the underlying deep fascia by numerous fibrous bands.

Dupuytren Contracture

• Dupuytren contracture is a localized thickening and contracture of the palmar aponeurosis, which limits hand function.
• It commonly starts near the root of the ring finger and draws the finger into the palm, flexing it at the metacarpophalangeal joint.

Treatment of Dupuytren Contracture

• Surgical division of the fibrous bands followed by physiotherapy to the hand is the usual form of treatment.
• An alternative treatment is the injection of the enzyme collagenase into the contracted bands of fibrous tissue.

Forearm Compartment Syndrome

• Forearm compartments are tightly packed spaces with little extra room, making them prone to compression of blood vessels and nerves.
• Soft tissue injury is a common cause, and early diagnosis is crucial.
• Early signs include:
  • Altered skin sensation (caused by ischemia of sensory nerves)
  • Pain disproportionate to any injury (caused by pressure on nerves within the compartment)
  • Pain on passive stretching of muscles (caused by muscle ischemia)
  • Tenderness of the skin over the compartment (a late sign caused by edema)
  • Absence of capillary refill in the nail beds (caused by pressure on the arteries within the compartment)
• Delay in diagnosis can cause irreversible damage to the muscles, and surgical incision of the deep fascia is required to decompress the affected compartment.

Absent Palmaris Longus

• The palmaris longus muscle may be absent on one or both sides of the forearm in about 10% of people.
• Its absence produces no disability.

Tennis Elbow

• No specific details mentioned in this context.

Anatomy of the Hand

• Figure 3.44 shows the anterior view of the palm of the hand, with the long flexor tendons removed, but their method of insertion into the fingers is shown.
• Figure 3.45 shows the anterior view of the palm of the hand, with the deep palmar arch and the deep terminal branch of the ulnar nerve, as well as the interossei.

Tenosynovitis of Flexor Tendon Synovial Sheaths

• Tenosynovitis is an infection of a synovial sheath, commonly resulting from the introduction of bacteria into a sheath through a small penetrating wound.
• Infection of a digital sheath results in distension of the sheath with pus, causing the finger to be held semiflexed and swollen.
• Any attempt to extend the finger is accompanied by extreme pain due to the distended sheath being stretched.
• Compressive pressure within the sheath may cause rupture of the sheath or severe scarring of the tendons.
• Infection of the digital sheaths of the little finger and thumb can quickly involve the ulnar and radial bursae, and if neglected, pus may burst through the proximal ends of these bursae and enter the fascial space of the forearm.

Ulnar Nerve

• Originates from C8 and T1 roots
• Passes through the brachial plexus
• No branches in the axilla
• Divides into flexor carpi ulnaris and flexor digitorum profundus (medial half) in the forearm
• Gives off the ulnar artery
• Has a palmar cutaneous branch
• Has a dorsal cutaneous branch
• Innervates the medial side of the hand and the medial 1 1/2 fingers
• Controls the adductor pollicis, third and fourth lumbricals, and interossei muscles

Brachial Plexus Injuries

• Can be divided into upper and lower lesions
• Upper lesions: roots, trunks, and divisions of the brachial plexus are affected
• Incomplete injuries are common and usually caused by traction or pressure
• Lower lesions: cords and most of the branches of the plexus are affected
• Can result in a "waiter's tip" posture due to loss of supination and adduction

Lower Lesions of Brachial Plexus (Klumpke's Palsy)

• Usually caused by traction injuries, such as falling from a height
• Results in loss of sensation over the lower half of the deltoid and lateral side of the forearm

Dermatomes and Cutaneous Nerves

• Dermatomes for the upper cervical segments C3 to 6 are located along the lateral margin of the upper limb
• C7 dermatome is situated on the middle finger
• Dermatomes for C8, T1, and T2 are along the medial margin of the upper limb
• Nerve fibers from a particular segment of the spinal cord pass to the skin in two or more different cutaneous nerves

Long Thoracic Nerve

• Arises from the roots of the brachial plexus in the neck
• Passes down over the lateral border of the first rib deep to the axillary vessels and brachial plexus
• Descends over the superficial surface of the serratus anterior muscle, which it supplies
• Unusual in that it is a motor nerve that enters its target muscle on the muscle's superficial side rather than the deep side
• Places the nerve in a position of greater potential danger to trauma

Ulnar Nerve

• Originates from C8 and T1 roots
• Passes through the brachial plexus
• No branches in the axilla
• Divides into flexor carpi ulnaris and flexor digitorum profundus (medial half) in the forearm
• Gives off the ulnar artery
• Has a palmar cutaneous branch
• Has a dorsal cutaneous branch
• Innervates the medial side of the hand and the medial 1 1/2 fingers
• Controls the adductor pollicis, third and fourth lumbricals, and interossei muscles

Brachial Plexus Injuries

• Can be divided into upper and lower lesions
• Upper lesions: roots, trunks, and divisions of the brachial plexus are affected
• Incomplete injuries are common and usually caused by traction or pressure
• Lower lesions: cords and most of the branches of the plexus are affected
• Can result in a "waiter's tip" posture due to loss of supination and adduction

Lower Lesions of Brachial Plexus (Klumpke's Palsy)

• Usually caused by traction injuries, such as falling from a height
• Results in loss of sensation over the lower half of the deltoid and lateral side of the forearm

Dermatomes and Cutaneous Nerves

• Dermatomes for the upper cervical segments C3 to 6 are located along the lateral margin of the upper limb
• C7 dermatome is situated on the middle finger
• Dermatomes for C8, T1, and T2 are along the medial margin of the upper limb
• Nerve fibers from a particular segment of the spinal cord pass to the skin in two or more different cutaneous nerves

Long Thoracic Nerve

• Arises from the roots of the brachial plexus in the neck
• Passes down over the lateral border of the first rib deep to the axillary vessels and brachial plexus
• Descends over the superficial surface of the serratus anterior muscle, which it supplies
• Unusual in that it is a motor nerve that enters its target muscle on the muscle's superficial side rather than the deep side
• Places the nerve in a position of greater potential danger to trauma

Axillary Lymph Node Examination

• Axillary lymph nodes are examined as part of the clinical examination of the breast
• Posterior (subscapular) nodes are palpated by pressing backward against the anterior surface of the subscapularis muscle
• Lateral nodes are palpated against the medial side of the axillary vein
• Central nodes are palpated in the center of the axilla between the pectoralis major (anterior wall) and subscapularis (posterior wall)
• Apical nodes drain into the subclavian lymph trunk, which drains into the thoracic duct on the left side and the right lymph trunk on the right side

Elbow Joint Stability

• The elbow joint is stable due to the wrench-shaped trochlea of the humerus and strong medial and lateral ligaments
• In extension, the medial and lateral epicondyles and the top of the olecranon process are in a straight line
• In flexion, the bony points form the boundaries of an equilateral triangle
• The normal relations of the bony points must be remembered when examining the elbow joint

Elbow Joint Dislocation

• Elbow dislocations are common, and most are posterior
• Posterolateral dislocation usually follows falling on an outstretched hand

Ulnar Nerve Damage with Elbow Joint Injuries

• The ulnar nerve is closely related to the medial side of the joint and can become damaged in dislocations or fracture dislocations
• Nerve lesions can occur at the time of injury or weeks, months, or years later
• The nerve can become involved in scar tissue formation or become stretched due to lateral deviation of the forearm in a badly reduced supracondylar fracture of the humerus

Venipuncture and Blood Transfusion

• Superficial veins are clinically important for venipuncture, transfusion, and cardiac catheterization
• The median cubital or basilic veins are the veins of choice for central venous catheterization
• The basilic vein increases in diameter and is in direct line with the axillary vein, making it suitable for catheterization

Distal Radioulnar Joint

• Located between the rounded head of the ulna and the ulnar notch on the radius
• Type: Synovial pivot joint
• Capsule: Encloses the joint, but is deficient superiorly
• Ligaments: Weak anterior and posterior ligaments strengthen the capsule

Articular Disc

• Triangular in shape and composed of fibrocartilage
• Attached by its apex to the lateral side of the base of the styloid process of the ulna
• Attached by its base to the lower border of the ulnar notch of the radius
• Shuts off the distal radioulnar joint from the wrist

Joint Movement

• Pronation: hand rotates medially, palm faces posteriorly, and thumb lies on the medial side
• Supination: reversal of pronation movement, hand rotates laterally, and palm faces anteriorly

Distal Radioulnar Joint

• Located between the rounded head of the ulna and the ulnar notch on the radius
• Type: Synovial pivot joint
• Capsule: Encloses the joint, but is deficient superiorly
• Ligaments: Weak anterior and posterior ligaments strengthen the capsule

Articular Disc

• Triangular in shape and composed of fibrocartilage
• Attached by its apex to the lateral side of the base of the styloid process of the ulna
• Attached by its base to the lower border of the ulnar notch of the radius
• Shuts off the distal radioulnar joint from the wrist

Joint Movement

• Pronation: hand rotates medially, palm faces posteriorly, and thumb lies on the medial side
• Supination: reversal of pronation movement, hand rotates laterally, and palm faces anteriorly

Surface Anatomy

• The medial and lateral epicondyles of the humerus and the olecranon process of the ulna can be palpated in the elbow region.
• When the elbow joint is extended, these bony points lie on the same straight line; when the elbow is flexed, these three points form the boundaries of an equilateral triangle.
• The head of the radius can be palpated in a depression on the posterolateral aspect of the extended elbow, distal to the lateral epicondyle.
• The head of the radius can be felt to rotate during pronation and supination of the forearm.
• The cubital fossa is a skin depression in front of the elbow, and the boundaries can be seen and felt.
• The brachioradialis muscle forms the lateral boundary, and the pronator teres muscle forms the medial boundary.
• The tendon of the biceps muscle can be palpated as it passes downward into the fossa.
• The bicipital aponeurosis can be felt as it leaves the tendon to join the deep fascia on the medial side of the forearm.
• The ulnar nerve can be palpated where it lies behind the medial epicondyle of the humerus.
• The brachial artery can be felt to pulsate as it passes down the arm, overlapped by the medial border of the biceps muscle.

Scapula

• The inferior angle of the scapula can be palpated opposite the seventh thoracic spine.
• The superior angle of the scapula can be felt through the trapezius muscle and lies opposite the second thoracic spine.

Breast

• In children and men, the breast anatomy is rudimentary and the glandular tissue is confined to a small area beneath the pigmented areola.
• In young women, the breast is usually hemispherical and slightly pendulous, overlapping the second to the sixth ribs and their costal cartilages.
• The breast lies in the superficial fascia and can be moved freely in all directions.
• The upper lateral edge of the breast extends around the lower border of the pectoralis major and enters the axilla, where it comes into close relationship with the axillary vessels.
• The breast is soft because the fat contained within it is fluid.
• On careful palpation with the open hand, the breast has a firm, overall lobulated consistency, produced by its glandular tissue.

Wrist and Hand

• The stylold process of the radius can be palpated at the wrist.
• The dorsal tubercle of the radius is palpable on the posterior surface of the distal end of the radius.
• The head of the ulna is most easily felt with the forearm pronated.
• The pillform bone can be felt on the medial side of the anterior aspect of the wrist between the two transverse creases.
• The hook of the hamate bone can be felt on deep palpation of the hypothenar eminence, a fingerbreadth distal and lateral to the pisiform bone.
• The transverse creases seen in front of the wrist are important landmarks.
• The proximal transverse crease at the level of the wrist joint corresponds to the proximal border of the flexor retinaculum.

Arm

• The arm contains two osseofascial compartments, anterior and posterior.
• The muscles in the anterior compartment contribute to flexion of the shoulder and elbow and to power supination.
• The muscle in the posterior compartment acts in extension of the shoulder and elbow.

Forearm

• The forearm contains three osseofascial compartments, anterior, posterior, and lateral.
• The muscles in the anterior compartment contribute largely to flexion of the wrist and digits and to pronation.

Axilla

• The axilla is a pyramid-shaped space between the arm and side of the chest.
• It conveys major blood vessels (axillary artery and vein and their branches), nerves (brachial plexus), and lymph channels (axillary nodes).
• The pectoralis minor muscle divides the axilla into three subregions that are useful in describing the pathways of the arteries and lymph drainage.