Anatomy Atlas

Scaphoid

Os scaphoideum
Also: Navicular of the hand
BoneHigh-yielddraftMSK

Boat-shaped bone of the proximal carpal row. It is the most commonly fractured carpal bone and its proximal pole is prone to avascular necrosis.

Core anatomy

Location

Lateral part of the proximal carpal row, forming the floor of the anatomical snuffbox.

Classification

Short bone (carpal).

Key features & landmarks
  • Proximal pole, waist, distal pole
  • Tubercle: palpable at the base of the thenar eminence; attachment of the flexor retinaculum
  • Articulates with the radius proximally; with the lunate, capitate, trapezium and trapezoid
Relations

Forms the floor of the anatomical snuffbox, with the radial artery crossing over it. It links the proximal and distal carpal rows, which is part of why it is so often fractured.

Notes

Blood supply is retrograde: the main vessels (from the radial artery, mainly dorsal carpal branches) enter at the waist and distal pole and supply the proximal pole by flowing backward. A fracture through the waist can cut off the proximal pole, causing avascular necrosis and nonunion.

Joints

Mentioned in

Generated automatically from links in other entries.

Carpal bones (right hand, palmar view)Palmar view of the right wrist with the thumb on the left. The proximal row, from lateral to medial, is the scaphoid, lunate, triquetrum and pisiform; the distal row is the trapezium, trapezoid, capitate and hamate. The radius articulates with the scaphoid and lunate; the ulna is separated from the carpus by the triangular fibrocartilage complex. The flexor retinaculum spans from the scaphoid tubercle and trapezium to the pisiform and hook of hamate, roofing the carpal tunnel, through which the median nerve passes. The ulnar nerve passes through Guyon canal, between the pisiform and the hook of hamate, superficial to the retinaculum.SLTPTTCHScaphoidmost fractured carpal; snuffboxtenderness; proximal pole AVN riskTrapeziumTrapezoidMedian nerve (in the tunnel)Flexor retinaculum(roof of the carpal tunnel)Radiusradial styloid is the more distalLunatemost dislocated carpal (palmar);AVN = Kienböck diseaseTriquetrumPisiform (sesamoid in FCU)CapitateHamateHook of hamate: fractures ingolf, baseball; Guyon canal edgeTFCC (triangular fibrocartilage)UlnaUlnar nerve (Guyon canal,between pisiform and hook)Right hand, palmar view · thumb ←Not to scaleLateral → medial: proximal row S L T P,distal row T T C H ("Some Lovers TryPositions That They Can't Handle")

Swipe sideways to see the whole diagram →

Carpal bones (right hand, palmar view). Thumb on the left. The flexor retinaculum (dashed) is anchored to the scaphoid tubercle and trapezium laterally and to the pisiform and hook of hamate medially, forming the roof of the carpal tunnel. Highlighted bones are the high-yield ones: scaphoid (fracture), lunate (dislocation) and hamate (hook fracture).
Original schematic, created for this atlas.
Palmar view of the carpal bones, metacarpals and phalanges of the left hand
Bones of the left hand, palmar (volar) surface. The scaphoid is the lateral bone of the proximal carpal row.
Henry Vandyke Carter, Gray's Anatomy of the Human Body, 20th ed. (1918), Fig. 219. Source · Public domain (Public domain in the US: published before January 1, 1931 (per Wikimedia Commons))

Clinical correlations

Scaphoid fracture PANCE

Mechanism / lesion

Fall on an outstretched hand with the wrist dorsiflexed and radially deviated. The waist is the most common site. Typically young adults.

Classic presentation

Radial-sided wrist pain with anatomical snuffbox tenderness, scaphoid tubercle tenderness, and pain with axial loading of the thumb. Initial radiographs can be normal. With clinical suspicion, immobilize in a thumb spica splint and repeat imaging in 10–14 days, or obtain MRI (or CT) early.

Avascular necrosis and nonunion PANCE

Mechanism / lesion

Interrupted retrograde blood flow to the proximal pole, especially in proximal pole or displaced fractures, or from delayed diagnosis.

Classic presentation

Persistent wrist pain. Radiographs show sclerosis and collapse of the proximal pole. Long-term, the result is scaphoid nonunion advanced collapse (SNAC) arthritis.

Scapholunate ligament injury

Mechanism / lesion

Fall on an outstretched hand. The most common carpal instability.

Classic presentation

Dorsal wrist pain and weakness. On PA radiograph, a widened scapholunate gap ("Terry Thomas" sign). verify Positive Watson scaphoid shift test.

High-yield PANCE pearls

  • Most commonly fractured carpal bone. Snuffbox tenderness + normal X-ray → thumb spica splint and repeat imaging (or MRI).
  • Retrograde blood supply → proximal pole AVN and nonunion.
  • Anatomical snuffbox: floor = scaphoid (and trapezium); contains the radial artery.

Imaging anatomy

X-ray

PA, lateral, oblique, plus a dedicated scaphoid view (PA with ulnar deviation), which elongates the scaphoid and shows the waist. Fractures can be radiographically occult at first. Late signs: sclerosis of the proximal pole (AVN), nonunion, collapse.

CT

Shows fracture displacement, union and nonunion. Useful for surgical planning.

MRI

The most sensitive modality for occult scaphoid fracture (marrow edema, fracture line). Also assesses proximal pole viability.

Key views & landmarks
  • Scaphoid series: PA, lateral, oblique, PA in ulnar deviation
  • MRI wrist if radiographs are negative and suspicion persists

Physical exam

Surface landmarks

Anatomical snuffbox: a depression on the dorsolateral wrist when the thumb is extended, bounded by the EPL tendon (medial/ulnar) and the APL and EPB tendons (lateral/radial). The scaphoid lies in its floor. The scaphoid tubercle is palpable on the volar wrist at the distal wrist crease, at the base of the thenar eminence.

Palpation

Palpate the snuffbox and scaphoid tubercle for tenderness; compare with the other side.

Scaphoid compression (axial load) test

Technique

The examiner applies axial compression along the long axis of the thumb metacarpal.

Positive test

Pain at the radial wrist.

Significance

Suggests scaphoid fracture. Sensitivity is higher when combined with snuffbox and tubercle tenderness.

Watson scaphoid shift test

Technique

The examiner presses the scaphoid tubercle volarly with a thumb while moving the wrist from ulnar to radial deviation.

Positive test

Pain and/or a clunk as the scaphoid subluxes dorsally and then reduces.

Significance

Scapholunate instability.

Self-quiz

Q1.

A 22-year-old man fell on his outstretched hand while skateboarding. He has tenderness in the anatomical snuffbox. Wrist radiographs, including a scaphoid view, show no fracture. What is the most appropriate next step?

Show answer

B

Scaphoid fractures are often occult on initial films. With snuffbox tenderness, immobilize in a thumb spica and re-image, or get an MRI, to avoid missing a fracture that could progress to nonunion or AVN.

Q2.

Which portion of the scaphoid is most at risk of avascular necrosis after a waist fracture?

Show answer

C

Blood enters distally and flows retrograde, so a waist fracture can leave the proximal pole without a blood supply.

Q3.

Which tendons form the boundaries of the anatomical snuffbox?

Show answer

B

The snuffbox is bounded by EPL on the ulnar (medial) side and APL/EPB on the radial (lateral) side. The scaphoid and trapezium form the floor, and the radial artery crosses it.

Q4.

After a fall on an outstretched hand, a PA wrist radiograph shows an abnormally wide gap between the scaphoid and lunate. Which injury does this sign indicate?

Show answer

B

A widened scapholunate gap on the PA view (the "Terry Thomas" sign) indicates scapholunate ligament injury, the most common carpal instability. The Watson scaphoid shift test may be positive.

Q5.

A scaphoid fracture goes undiagnosed and progresses to nonunion. What is the long-term consequence?

Show answer

D

Delayed diagnosis and interrupted retrograde blood supply lead to proximal pole AVN and nonunion, which progresses to SNAC wrist arthritis. This is why snuffbox tenderness is immobilized and reimaged even when the first radiographs are normal.

Flashcards

See also