Orthopaedic Surgery - Hand Anatomy and Examination

Basics

The hand is a highly specialized organ that provides strength, precision, sensation, grasp, and fine motor control, allowing complex activities ranging from heavy manual work to delicate manipulation.

Anatomically, the hand can be divided into volar (palmar) and dorsal surfaces.

Volar Anatomy

The volar aspect contains many of the major structures responsible for hand function, including the digital nerves, major vascular structures, flexor tendons, and intrinsic muscles.

Because these structures are closely packed together, even relatively small palmar lacerations may injure several important tissues simultaneously.

Bony Anatomy

The hand and wrist contain a complex arrangement of bones.

There are:

8 carpal bones, 5 metacarpals, and 14 phalanges.

Each finger contains a proximal, middle, and distal phalanx.

The thumb has only two phalanges: proximal and distal.

History

A thorough history should precede the physical examination.

Important information includes:

Hand dominance, occupation, previous hand injuries or operations, mechanism of trauma, duration of symptoms, and location and character of pain.

Functional complaints such as weakness, loss of grip, numbness, locking, instability, or difficulty with specific activities should also be documented.

General Examination Principles

Understanding normal hand anatomy and biomechanics is essential for identifying injury.

The examiner should use a consistent, systematic examination sequence so that important structures are not overlooked.

The opposite hand provides an extremely useful comparison with the patient’s normal anatomy, strength, motion, and joint laxity.

Inspection

The hand should first be observed at rest.

Resting Posture

The natural posture of the fingers should be assessed.

Abnormal finger position may indicate tendon rupture, nerve injury, fracture, dislocation, or joint contracture.

The normal flexor cascade should also be observed.

Deformity

The examiner should identify any gross angular, rotational, or joint deformity.

Rotational malalignment may become more obvious when the patient makes a fist.

Soft-Tissue Changes

Look for:

Swelling, bruising, erythema, wounds, scars, masses, muscle wasting, and skin abnormalities.

Nail and Fingertip Examination

The nail plate, nail folds, pulp, and surrounding soft tissues should be inspected for:

Subungual hematoma, nail-bed injury, infection, fingertip trauma, vascular compromise, or deformity.

Vascular Examination

Adequate perfusion should be confirmed in the hand and each individual digit.

Radial and Ulnar Arteries

The radial and ulnar arteries should be palpated at the wrist.

Doppler examination can be used if pulses are difficult to detect.

Digital Arteries

The digital arteries can be assessed with handheld Doppler when vascular injury is suspected.

Capillary Refill

Capillary refill should be tested in each finger.

Normal refill is generally less than approximately 2 seconds in a warm, well-perfused hand.

Additional Perfusion Assessment

When necessary, finger temperature and pulse oximetry may provide additional information about digital perfusion.

These measurements are particularly useful when vascular compromise is subtle.

Allen Test

The Allen test assesses patency of the radial and ulnar arteries and the completeness of the palmar arterial arch.

The patient repeatedly opens and closes the hand while the examiner compresses both the radial and ulnar arteries.

The hand is then opened and one artery is released.

Rapid return of color indicates adequate flow through that artery and the palmar arch.

The test is then repeated for the opposite artery.

Delayed or absent reperfusion suggests arterial obstruction or incomplete collateral circulation.

Neurologic Examination

Neurologic assessment should include both sensory and motor testing.

The median, ulnar, and radial nerves should be evaluated systematically.

Sensory Examination

Sensation can initially be tested with light touch.

Two-point discrimination provides a more detailed evaluation of digital nerve function.

Two-Point Discrimination

Normal static two-point discrimination at the fingertip is generally approximately 6 mm or less, while moving two-point discrimination is normally somewhat finer.

The result should be compared with the opposite hand and adjacent digits.

A bent paperclip or formal discriminator can be used when dedicated instruments are unavailable.

Motor Examination

Both the extrinsic muscles, originating in the forearm, and the intrinsic muscles, originating within the hand, should be tested.

Extrinsic Flexors

The flexor digitorum superficialis and flexor digitorum profundus tendons should be tested individually in each finger.

Flexor Digitorum Profundus

To test the FDP, hold the PIP joint in extension and ask the patient to flex the DIP joint.

Active DIP flexion indicates continuity of the profundus tendon.

Flexor Digitorum Superficialis

To isolate the FDS, hold the other fingers in extension and ask the patient to flex the finger being tested at the PIP joint.

Extrinsic Extensors

Finger extension at the MCP joints should be tested individually.

Thumb extension should also be assessed.

Weakness may reflect tendon injury or radial nerve dysfunction proximal to the hand.

Intrinsic Muscles

The intrinsic muscles can be assessed by asking the patient to flex the MCP joints while extending the interphalangeal joints.

Finger abduction and adduction should also be tested with the MCP joints extended.

Asking the patient to cross adjacent fingers can further assess intrinsic muscle function.

Median Nerve

Sensory Examination

Median nerve sensation should be tested over the palmar aspect of the thumb, index finger, middle finger, and radial half of the ring finger.

Thenar Eminence

Sensation over the thenar eminence is supplied by the palmar cutaneous branch of the median nerve, which branches proximal to the carpal tunnel.

This area should be tested separately.

Preserved thenar sensation despite numbness in the median-innervated digits can support localization of compression to the carpal tunnel.

Motor Examination

Palmar abduction of the thumb assesses the abductor pollicis brevis and is an important test of recurrent motor branch function of the median nerve.

Ulnar Nerve

Sensory Examination

Sensation should be tested over the little finger and ulnar half of the ring finger, including the volar fingertip.

Motor Examination

The ulnar nerve supplies most of the intrinsic muscles of the hand.

Motor function can be tested by asking the patient to abduct and adduct the fingers or cross the fingers.

Radial Nerve

Sensory Examination

Radial nerve sensation is best assessed over the dorsal first web space.

Motor Examination

The radial nerve does not provide meaningful intrinsic motor innervation within the hand itself.

Motor function is assessed through muscles in the forearm by testing wrist extension, MCP joint extension of the fingers, and thumb extension.

Bones, Tendons, and Ligaments

Every bone and major joint should be palpated systematically when trauma or localized pain is present.

Range of Motion

Both active and passive range of motion should be assessed.

Approximate normal values include:

Thumb IP joint: approximately 0–80° of flexion.

Thumb MCP joint: approximately 0–50° of flexion.

Finger DIP joints: approximately 0–70 to 90°.

Finger PIP joints: approximately 0–100° or slightly greater.

Finger MCP joints: approximately 0–90°.

Wrist flexion: approximately 80°.

Wrist extension: approximately 70°.

Normal motion varies among individuals, so comparison with the opposite side is valuable.

Joint Examination

Each joint should be assessed for:

Tenderness, swelling, effusion, bogginess, instability, crepitus, loss of motion, or hypermobility.

Collateral Ligaments

Excessive side-to-side laxity may indicate injury to a collateral ligament.

Stress testing should be performed carefully and compared with the opposite side.

Important Wrist Structures

Two common sources of wrist pathology are the scapholunate ligament and the triangular fibrocartilage complex (TFCC).

Scapholunate Ligament

The scapholunate interval should be palpated dorsally for tenderness, particularly after wrist trauma.

TFCC

The TFCC lies on the ulnar side of the wrist and contributes to distal radioulnar and ulnocarpal stability.

Tenderness in this region may indicate a TFCC injury.

Special Tests

Tinel Sign at the Carpal Tunnel

Percussion over the median nerve at the volar wrist may produce tingling, numbness, or electric sensations in the median nerve distribution.

A positive test supports median nerve irritation and may be seen in carpal tunnel syndrome.

Flexion-Compression Test

The examiner applies direct pressure over the carpal tunnel while the wrist is held in flexion.

Reproduction of numbness, tingling, or pain in the median distribution within approximately 30 seconds supports the diagnosis of carpal tunnel syndrome.

Phalen Test

The patient holds the wrists in maximal flexion, usually by placing the dorsal surfaces of the hands together.

Development of paresthesias in the median nerve distribution within approximately 60 seconds is considered a positive test.

Wrist Aspiration

Wrist aspiration may be performed when infection, crystal arthropathy, hemarthrosis, or another joint process is suspected.

Dorsal Approach

A common dorsal entry point is between the third extensor compartment, containing extensor pollicis longus, and the fourth compartment, containing extensor digitorum communis and extensor indicis proprius.

Lister’s tubercle can be used as a palpable landmark.

The radiocarpal joint is entered just distal to this region, with slight wrist flexion facilitating access.

Eichhoff Test

The Eichhoff maneuver is frequently, although inaccurately, referred to as the Finkelstein test.

The patient places the thumb within the fist, and the examiner then passively deviates the wrist toward the ulna.

Pain over the first dorsal extensor compartment, containing the abductor pollicis longus and extensor pollicis brevis, supports the diagnosis of de Quervain tenosynovitis.

The true Finkelstein maneuver is performed somewhat differently, but both tests stress the first extensor compartment.

Thumb CMC Grind Test

The thumb carpometacarpal joint is assessed by applying axial compression through the thumb metacarpal while rotating or grinding the joint.

Reproduction of pain, particularly with crepitus, is consistent with trapeziometacarpal or thumb CMC osteoarthritis.

Imaging

Plain Radiographs

The standard hand radiographic series includes:

AP or PA, oblique, and lateral views.

These films help identify fractures, dislocations, joint-space abnormalities, malalignment, and degenerative changes.

Lateral View

For evaluation of individual digits, the fingers may be splayed or separated on the lateral projection to prevent overlap and allow clearer visualization of each phalanx and joint.

General Examination Approach

A complete hand assessment should proceed systematically through:

Inspection, vascular examination, sensory testing, motor testing, tendon assessment, joint range of motion, ligament stability, palpation, special tests, and appropriate imaging.

Because the structures of the hand are small and closely related, comparison with the opposite hand and careful documentation are especially important for detecting subtle abnormalities.