Surface Anatomy of the Upper Limbs Flashcards

Introduction to Surface Anatomy

• Definition: Surface anatomy of the upper limbs is defined as the study of external features and landmarks of the shoulder, arm, forearm, wrist, and hand in relation to deeper structures including muscles, bones, blood vessels, nerves, and joints.

• Methodology: It utilizes observation and palpation of visible or tactile structures to map deeper anatomical components.

• Primary Surface Landmarks:

  • Bony Landmarks: Clavicle, acromion process, scapula, humerus, olecranon process, and the styloid processes of the radius and ulna.

  • Soft Tissue Landmarks: Tendons and muscles visible during active movement.

  • Neurovascular Structures: Arteries (brachial, radial, ulnar) and superficial veins (cephalic, basilic).

Special Anatomical Regions

1. Cubital Fossa (Anterior Elbow)

• Shape: A triangular depression located at the anterior aspect of the elbow joint.

• Boundaries:

  • Lateral: Brachioradialis muscle.

  • Medial: Pronator teres muscle.

  • Superior: An imaginary line connecting the medial and lateral humeral epicondyles.

• Key Contents:

  • Biceps Brachii Tendon: Easily palpable during elbow flexion.

  • Brachial Artery: Found medial to the biceps tendon; it bifurcates here into the radial and ulnar arteries.

  • Median Nerve: Positioned medial to the brachial artery.

• Clinical Utility: This is the preferred site for venipuncture, intravenous cannulation, and blood sampling because it is superficial, relatively fixed, and distinct from major nerves and arteries.

2. Anatomical Snuffbox

• Definition: A triangular depression on the dorsum of the wrist, most prominent when the thumb is extended.

• Boundaries:

  • Lateral: Tendons of the abductor pollicis longus ($\text{APL}$) and extensor pollicis brevis ($\text{EPB}$).

  • Medial: Tendon of the extensor pollicis longus ($\text{EPL}$).

• Floor: Formed by the scaphoid bone (proximally) and the trapezium bone (distally).

• Contents:

  • Radial Artery: Passes through the floor.

  • Cephalic Vein and Superficial Branch of the Radial Nerve: Run through the roof.

3. Palmar Surface of the Hand

• Thenar Eminence: The fleshy mound at the thumb base, formed by short thumb muscles.

• Hypothenar Eminence: The fleshy mound at the base of the little finger, formed by short little finger muscles.

• Palmar Flexion Creases: Skin folds utilized as surface guides to deeper structures like the flexor retinaculum.

The Shoulder Region

Regional Boundaries

• Superior: Clavicle and acromioclavicular joint (connecting the limb to the axial skeleton).

• Inferior/Medial: Inferior angle of the scapula, bounded by the latissimus dorsi and serratus anterior.

• Anterior: Pectoralis major and minor muscles (forming the anterior axillary wall).

• Posterior: Scapula, supraspinatus, infraspinatus, and teres muscles.

• Lateral: Deltoid muscle (forming the rounded contour) and the proximal humerus.

Key Bony Landmarks

• Clavicle: Subcutaneous throughout its length.

  • Sternoclavicular Joint: The only bony articulation with the axial skeleton.

  • Clinical Note: Subclavian vessels and the brachial plexus pass posterior to it; they are vulnerable during clavicular fractures.

  • Cephalic Vein Location: Runs inferior to the lateral clavicle in the deltopectoral groove.

• Acromion: The highest lateral bony prominence; forms the roof of the shoulder joint. It is a reference point for shoulder dislocation (where the humeral head may palpate inferiorly).

• Scapula: Situated on ribs $2-7$.

  • Spine of Scapula: Corresponds roughly to the level of $\text{T3}$ vertebrae.

  • Inferior Angle: Corresponds roughly to the level of $\text{T7}$ vertebrae.

  • Medial Border: Parallel to the spine; becomes prominent in "scapular winging" (serratus anterior weakness).

• Coracoid Process: Palpable inferior to the lateral clavicle. It provides attachment for the pectoralis minor, coracobrachialis, and the short head of the biceps brachii.

Soft Tissue and Spaces

• Deltoid Region: Covers the glenohumeral joint and axillary nerve. It is a "safe area" for intramuscular injections.

• Axilla (Armpit/Oxter): Area under the shoulder joint containing the axillary artery, axillary vein, and brachial plexus cords.

• Deltopectoral Groove: Indentation between the deltoid and pectoralis major; contains the cephalic vein.

• Clavipectoral Triangle: Junction of the clavicle, pectoralis major, and deltoid. It contains the cephalic vein, deltopectoral fascia, and the deltoid branch of the thoracoacromial artery. Deeper structures include the subclavian vein and artery.

• Quadrangular Space: Passageway for the axillary nerve and posterior circumflex humeral artery.

  • Boundaries: Teres minor (superior), teres major (inferior), long head of triceps (medial), surgical neck of humerus (lateral).

  • Sensory Note: Axillary nerve provides sensation to the "regimental badge" area.

The Arm Region (Brachium)

Proximal Landmarks

• Greater Tubercle: Most lateral bony prominence; palpable with arm at side but moves under the acromion during abduction.

• Lesser Tubercle: Anteriorly located; palpable $1\,cm$ lateral and slightly inferior to the coracoid process.

• Intertubercular Sulcus (Bicipital Groove): Contains the long head of the biceps brachii tendon.

• Head of Humerus: Not directly palpable but felt deeply in the axilla if the arm is abducted.

Distal Landmarks

• Medial Epicondyle: Prominent projection where the ulnar nerve passes posteriorly (the "funny bone").

• Lateral Epicondyle: Attachment for extensor muscles; site of pain in "tennis elbow."

• Epicondylar-Olecranon Relationship:

  • In full extension: Medial epicondyle, lateral epicondyle, and olecranon lie in a straight line.

  • In flexion: They form a triangular arrangement.

The Elbow and Forearm Regions

Elbow Landmarks and Nerves

• Olecranon Process of Ulna: Pointed posterior projection.

• Head of Radius: Distal to the lateral epicondyle; rotates during pronation and supination.

• Ulnar Nerve: Palpable in the cubital tunnel behind the medial epicondyle. Compression leads to Cubital Tunnel Syndrome.

• Radial Nerve: Located laterally in the cubital fossa.

• Median Nerve: Located medially in the cubital fossa.

Forearm Landmarks

• Compartmental Muscles:

  • Anterior: Pronator teres, flexor carpi radialis ($\text{FCR}$), palmaris longus ($\text{PL}$), flexor carpi ulnaris ($\text{FCU}$).

  • Posterior: Brachioradialis, extensor digitorum.

• Neurovascular: Cephalic, basilic, and median cubital veins; radial and ulnar arterial pulsations.

• Cutaneous Innervation: Musculocutaneous (lateral), medial cutaneous (medial), and radial (posterior).

The Wrist Region (Carpus)

Skin Creases

• Proximal Wrist Crease: Level of proximal carpal bones; $2\,cm$ proximal to radiocarpal joint.

• Distal Wrist Crease: Surgical landmark; overlies the proximal border of the radiocarpal joint and distal edge of the flexor retinaculum.

• Thenar/Hypothenar Creases: Delineate the eminences.

Palpable Bony Points

• Radial Styloid Process: Most lateral point; extends $1.0-1.5\,cm$ more distally than the ulnar styloid.

• Ulnar Styloid Process: Posteromedial aspect; proximal attachment for the triangular fibrocartilage complex.

• Scaphoid Tubercle: Base of thenar eminence; tenderness suggests scaphoid fracture (risk of avascular necrosis).

• Pisiform: Rounded, movable bone in the $FCU$ tendon; medial boundary of Guyon's canal.

• Hook of Hamate: Palpable $1\,cm$ distal and radial to the pisiform; lateral wall of Guyon's canal.

Tendons and Neurovascular Projections

• Flexor Tendons: FCU (most medial), Palmaris Longus (absent in $14\%$ of individuals, used for grafts), and FCR.

• Extensor Tendons: EPL (rupture risk in distal radius fractures), Extensor digitorum communis ($\text{EDC}$), and ECU.

• Radial Pulse: Felt between FCR and brachioradialis, $1\,cm$ proximal to radial styloid.

• Median Nerve: Midpoint of distal wrist crease; deep to palmaris longus.

• Guyon's Canal: Fibro-osseous tunnel on medial wrist containing ulnar nerve/artery.

• Superficial Branch of Radial Nerve ($\text{SBRN}$): Emerges $7-9\,cm$ proximal to radial styloid; injury causes Wartenberg's syndrome.

The Hand Region

Osteology

• Carpal Bones: $8$ total (Proximal: scaphoid, lunate, triquetrum, pisiform; Distal: trapezium, trapezoid, capitate, hamate).

• Metacarpals: $5$ total; heads form the knuckles.

• Phalanges: $14$ total (thumb has only proximal and distal).

Palm and Digits

• Simian Crease: A single transverse palmar crease associated with Down syndrome.

• Palmar Aponeurosis: Shortening causes Dupuytren’s contracture.

• Nerve Distribution Clinical Pearls:

  • Median Nerve Injury: Thenar wasting, loss of opposition, "Ape hand."

  • Ulnar Nerve Injury: Interosseous wasting, weak grip, "Claw hand."

• Arteries: Superficial palmar arch (primarily ulnar) and Deep palmar arch (primarily radial).

Examination Methods

Inspection and Palpation

• Inspection: Visualizing limb posture, symmetry, muscle bulk, and deformities (e.g., ulnar deviation in rheumatoid arthritis).

• Palpation: Testing for temperature, tenderness, and position of bony landmarks (e.g., triangle of epicondyles/olecranon at $90^{\circ}$ flexion).

Joint Movements and Range of Motion ($\text{ROM}$)

• Shoulder Flexion/Abduction: $\approx 180^{\circ}$.

• Shoulder Extension: $\approx 45-60^{\circ}$.

• Elbow Flexion: $\approx 150^{\circ}$.

• Forearm: Supination and pronation.

Muscle Power (MRC Scale 0-5)

• Deltoid: Arm abduction (Axillary nerve).

• Biceps: Elbow flexion with supination (Musculocutaneous nerve).

• Triceps: Elbow extension (Radial nerve).

• Interossei: Finger abduction/adduction (Ulnar nerve).

• Thenar: Thumb opposition (Median nerve).

Special Clinical Tests

• Phalen's Test: Maximal wrist flexion for $60\,seconds$; positive if tingling occurs (Carpal Tunnel Syndrome).

• Tinel's Sign: Tapping over median nerve; positive if "pins and needles" occurs.

• Allen's Test: Assessing arterial patency by compressing and releasing radial/ulnar arteries.

• Cozen's Test: Resisted wrist dorsiflexion; positive for Tennis Elbow.

• Empty Can Test: Resistance applied to abducted arm with thumb down; tests Supraspinatus tendon.

Introduction to Surface Anatomy

• Definition: Surface anatomy of the upper limbs is defined as the study of external features and landmarks of the shoulder, arm, forearm, wrist, and hand in relation to deeper structures including muscles, bones, blood vessels, nerves, and joints.

• Methodology: It utilizes observation and palpation of visible or tactile structures to map deeper anatomical components.

• Primary Surface Landmarks:

  • Bony Landmarks: Clavicle, acromion process, scapula, humerus, olecranon process, and the styloid processes of the radius and ulna.

  • Soft Tissue Landmarks: Tendons and muscles visible during active movement.

  • Neurovascular Structures: Arteries (brachial, radial, ulnar) and superficial veins (cephalic, basilic).

Special Anatomical Regions

1. Cubital Fossa (Anterior Elbow)

• Shape: A triangular depression located at the anterior aspect of the elbow joint.

• Boundaries:

  • Lateral: Brachioradialis muscle.

  • Medial: Pronator teres muscle.

  • Superior: An imaginary line connecting the medial and lateral humeral epicondyles.

• Key Contents:

  • Biceps Brachii Tendon: Easily palpable during elbow flexion.

  • Brachial Artery: Found medial to the biceps tendon; it bifurcates here into the radial and ulnar arteries.

  • Median Nerve: Positioned medial to the brachial artery.

• Clinical Utility: This is the preferred site for venipuncture, intravenous cannulation, and blood sampling because it is superficial, relatively fixed, and distinct from major nerves and arteries.

2. Anatomical Snuffbox

• Definition: A triangular depression on the dorsum of the wrist, most prominent when the thumb is extended.

• Boundaries:

  • Lateral: Tendons of the abductor pollicis longus ($ext{APL}$) and extensor pollicis brevis ($ext{EPB}$).

  • Medial: Tendon of the extensor pollicis longus ($ext{EPL}$).

  • Floor: Formed by the scaphoid bone (proximally) and the trapezium bone (distally).

• Contents:

  • Radial Artery: Passes through the floor.

  • Cephalic Vein and Superficial Branch of the Radial Nerve: Run through the roof.

3. Palmar Surface of the Hand

• Thenar Eminence: The fleshy mound at the thumb base, formed by short thumb muscles.

• Hypothenar Eminence: The fleshy mound at the base of the little finger, formed by short little finger muscles.

• Palmar Flexion Creases: Skin folds utilized as surface guides to deeper structures like the flexor retinaculum.