Scaphoid Fracture for NEET PG: Snuffbox Tenderness, the Imaging Pathway and AVN Risk

A young adult falls on an outstretched hand. The wrist is sore on the thumb side, the anatomical snuffbox is tender, and the first X-ray looks normal. That pattern is managed as a scaphoid fracture until imaging says otherwise.

The caution comes from the blood supply. Vessels enter distally and flow toward the proximal pole, so a break can strand the proximal fragment and lead to avascular necrosis (AVN), nonunion and wrist arthritis. Where sources disagree, the figures below appear as ranges with the source named.

Key Takeaways

• The scaphoid is the most commonly fractured carpal bone. Its blood supply runs retrograde, so the proximal pole carries the highest risk of AVN and nonunion.

• Snuffbox tenderness is sensitive but not specific: absence makes a fracture unlikely, while presence justifies imaging.

• The scaphoid view is a PA film in ulnar deviation. Plain films miss up to roughly 30% of fractures, yet only 4-20% of suspected cases with normal films prove to be fractures. MRI is increasingly favoured over repeat films at 10-14 days.

• Herbert classification runs A (stable), B (unstable), C (delayed union), D (nonunion). Displacement thresholds of 1 mm, 1.5 mm and 2 mm all appear. AVN is reported in 13-50% of fractures.

• For waist fractures displaced by 2 mm or less, the SWIFFT trial found no significant difference in function between a cast and early surgery.

Scaphoid Fracture Anatomy and Blood Supply

The scaphoid is a boat-shaped carpal bone (the name comes from the Greek for boat, per Rhemrev 2011). It links the proximal and distal carpal rows and articulates with the radius, capitate, lunate, trapezium and trapezoid (Rhemrev 2011). About 80% of its surface is cartilage, so few vessels can enter.

The dorsal branch of the radial artery enters at the dorsal ridge near the waist and supplies roughly the proximal 70-80% of the bone. Volar branches enter at the distal tubercle and supply the distal 20-30% (Kawamura 2008). Flow is therefore retrograde, from distal to proximal, and the proximal pole depends entirely on intraosseous flow (Steinmann 2006).

Shares are drawn from Clementson 2020, Kawamura 2008 and Rhemrev 2011. No source reports AVN rates site by site, so the last column is qualitative.

Mechanism and Epidemiology of Scaphoid Fracture

The typical mechanism is a fall on an outstretched hand with the wrist extended and radially deviated. A fall with the wrist abducted raises the chance of a proximal pole fracture (Rhemrev 2011). In older people the same fall can produce distal radius or other carpal fractures (Rhemrev 2011), so scaphoid fracture is classically a young-adult injury; the distal radius case is covered in the note on Colles fracture.

The scaphoid is the most commonly fractured carpal bone. Reported shares of carpal fractures run from about 60% (Clementson 2020) to 82-89% (Rhemrev 2011). Young active men are typical patients, with age bands of 15-25, 15-30 and 15-40 years quoted, and young children rarely sustain it (Kawamura 2008).

Snuffbox Tenderness and Other Clinical Signs of Scaphoid Fracture

The anatomical snuffbox is a triangular depression at the base of the thumb on the radial side of the wrist (Hadjivassiliou 2021), with the radial styloid as its proximal landmark (the 2019 snuffbox technical note). The extensor pollicis brevis and abductor pollicis longus tendons form its radial (lateral) border, the extensor pollicis longus tendon forms its ulnar (medial) border, and the floor is the scaphoid and trapezium; the radial artery and the superficial branch of the radial nerve lie within it, so the artery sits over the scaphoid and trapezium (Hadjivassiliou 2021). Because the scaphoid lies in the floor, pressure here reaches the bone, which is why tenderness in the snuffbox is tested.

Three bedside tests are standard: snuffbox tenderness, scaphoid tubercle tenderness and pain on axial compression of the thumb, each compared with the other wrist (Clementson 2020). Reported accuracy varies:

Table sources: Rhemrev 2011, Shehab 2013 and Phillips 2004; Clementson 2020 is linked above.

Despite the spread, the message is steady: these signs are sensitive and poorly specific, and no single test confirms or excludes the fracture. Absent tenderness at both the snuffbox and the tubercle makes a fracture very unlikely, while swelling or grip strength more than 50% below the other side raises suspicion. Axial compression performs worst and should not be used alone (Phillips 2004; Rhemrev 2011; Clementson 2020).

Memory aid (this post's own, not from the sources): a sensitive sign is useful when negative, and a specific sign is useful when positive. Snuffbox tenderness belongs to the first group, so use it to decide who needs imaging, not to name the diagnosis. The note on sensitivity and specificity shows the 2x2 logic.

Separate it from De Quervain tenosynovitis (radial styloid tenderness, positive Finkelstein test), scapholunate injury (widened gap on films) and distal radius or first metacarpal fracture (Phillips 2004).

Imaging a Suspected Scaphoid Fracture: Scaphoid View, MRI and CT

Initial radiographs and the scaphoid view

Standard views are a PA, a lateral and two 45-degree obliques, plus the scaphoid view: a PA film with the wrist in ulnar deviation (Kawamura 2008). Ulnar deviation stretches the bone out and separates unstable fragments, and some descriptions add a clenched fist (Stecher's view) (Clementson 2020). Non-displaced fractures are hardest to see (Phillips 2004).

Why a normal film does not settle the question

Plain films can miss up to about 30% of fractures at first (Shehab 2013), in line with sensitivities near 70% or lower in other reviews (Clementson 2020; Steinmann 2006). One trial quoted by Phillips 2004 reported 86%.

Yet only 4-20% of suspected cases with normal films prove to have a fracture (Clementson 2020), and the Cochrane review gives a median of 20%. Traditional immobilisation therefore casts an estimated 75-80% unnecessarily, while an unrecognised, unprotected fracture risks nonunion in up to 12% (Kawamura 2008).

MRI, CT and bone scan compared

Pooled figures come from the Cochrane review, whose search ended in 2012 and whose confidence intervals are wide. The other column draws on Clementson 2020, Steinmann 2006, Rhemrev 2011 and Shehab 2013. A fracture on MRI appears as marrow oedema on T2 with a focal low T1 signal (Wong and Peh 2019), but studies define an MRI fracture differently (2026 review).

Choosing an imaging pathway

The traditional route is a thumb spica, then review and repeat films at 10-14 days (Shehab 2013), though one review finds repeat films add little (Rhemrev 2011). NICE guideline NG38 advises considering MRI as first-line imaging after a thorough clinical examination (NICE), and the American College of Radiology is described as preferring MRI after normal radiographs (Wong and Peh 2019).

A working sequence:

1. Examine, comparing both wrists.
2. X-ray with the scaphoid view; add CT if displacement or instability is suspected.
3. Normal films but persistent suspicion: thumb spica.
4. Early MRI (CT if MRI is unavailable), or review with repeat films at 10-14 days.
5. Negative MRI: mobilise, but look for scapholunate ligament injury (Clementson 2020).

Scaphoid Fracture Classification: Herbert, Mayo and Russe

Herbert and Fisher sort fractures by stability (Kawamura 2008; Steinmann 2006). The note on types of fractures covers general terms such as displacement and union.

Another memory aid of this post's own: the letters run in order of trouble, A stable, B unstable, C slow, D nonunion. Comminution is B5, not C.

Displacement thresholds differ, so attribute each one:

• Herbert: more than 1 mm in any view marks instability (Kawamura 2008).
• Clementson 2020: instability signs are displacement over 1 mm, a scapholunate angle above 60 degrees (dorsal intercalated segment instability, DISI), a lateral intrascaphoid angle above 35 degrees, comminution and perilunate injury; their institution advocates fixation from 1.5 mm.
• SWIFFT: included waist fractures displaced by up to 2 mm (Dias 2020).

Mayo classifies by location and Russe by the plane of the fracture line, where vertical oblique lines are unstable. Reliability of all three systems is limited (Steinmann 2006), and Clementson 2020 argues that Herbert invites overtreatment.

Avascular Necrosis, Nonunion and SNAC After Scaphoid Fracture

AVN is reported in 13-50% of scaphoid fractures, higher when the proximal fifth is involved (Kawamura 2008; Steinmann 2006). Without surgery, proximal pole nonunion occurs in 10-14% of non-displaced and up to about 50% of displaced fractures (Clementson 2020).

AVN also changes surgical odds. In a Mayo Clinic series of nonunions treated with vascularised grafts, union was 48% with AVN and 91% without. A meta-analysis cited in the same review found 88% union with vascularised grafts against 47% with standard grafts when AVN was present (Steinmann 2006).

Overall nonunion is put at 5-10% by Steinmann 2006 and at about 12% by Maris 2024. By the conventional definition, a scaphoid unhealed at 6 months is a nonunion (Kawamura 2008). In humpback deformity, shortening of the palmar cortex increases the lateral intrascaphoid angle, and the lunate rotates dorsally with the proximal fragment, producing DISI (Kawamura 2008).

Untreated nonunion can progress to scaphoid nonunion advanced collapse (SNAC), with an intact scapholunate ligament. Maris 2024 summarises Vender's three stages:

Texts word these stages slightly differently, so remember the spread from the radial styloid to the midcarpal joints. Salvage options include proximal row carpectomy and four-corner fusion (Maris 2024; Kawamura 2008).

Scaphoid Fracture Treatment: Cast, Surgery and the SWIFFT Trial

Cast immobilisation is the usual treatment for suspected or stable fractures (Rhemrev 2011). About 90% of waist fractures displaced by 0.5 mm or less unite by 6 weeks (Clementson 2020), and 88-95% of non-displaced waist fractures unite if casting starts within 3 weeks (Kawamura 2008). Sources disagree on cast type and duration:

Table sources: Steinmann 2006 and AO Surgery Reference; Clementson 2020 and Kawamura 2008 are linked above.

The thumb spica is the traditional teaching, but thumb inclusion is unproven. Surgery is generally advised for displaced waist fractures, displaced proximal pole fractures, unstable patterns such as perilunate injury, and nonunion. The standard implant is a headless compression screw, placed palmar for waist and distal fractures and dorsal for the proximal pole (Kawamura 2008). For minimally displaced fractures, fixation carries a higher complication rate than casting, up to 30% in one review (Clementson 2020).

SWIFFT randomised 439 adults at 31 UK hospitals with a bicortical waist fracture displaced by 2 mm or less to a cast or early surgery (Dias 2020; abstract on Europe PMC). At 52 weeks the Patient-Rated Wrist Evaluation score had adjusted means of 11.9 after surgery and 14.0 after casting (adjusted difference -2.1, 95% CI -5.8 to 1.6, p=0.27), which was not significant.

Potentially serious complications occurred in 14% of the surgery group (31 of 219) and 1% of the cast group (3 of 220), and cast-related complications in 2% and 18% respectively. The authors recommend an initial cast, with early fixation for confirmed nonunion. For established nonunion, surgery is preferred: non-vascularised grafting generally suffices without AVN, and vascularised grafting is considered with AVN (Kawamura 2008).

Common Mistakes to Avoid With Scaphoid Fracture

• Treating a normal first film as proof of no fracture. Think "immobilise, then image" when the snuffbox is tender.
• Reading snuffbox tenderness as diagnostic. It triages; it does not confirm.
• Quoting one displacement figure for every purpose. Keep 1 mm, 1.5 mm and 2 mm attached to Herbert, Clementson 2020 and SWIFFT.
• Reversing the blood supply. Draw it from memory: entry at the dorsal ridge and distal tubercle, flow running proximally.
• Mixing the Herbert letters. C is delayed union, D is nonunion, comminution is B5.

Conclusion: Scaphoid Fracture in One Pass

A scaphoid fracture is the story of one bone with a one-way blood supply. Snuffbox tenderness says look harder, the scaphoid view and MRI decide whether a fracture exists, displacement and site decide between cast and surgery, and AVN and SNAC describe what follows when healing fails. To test the pattern, redraw the blood supply and the Herbert table from memory, then try the hand and wrist practice questions.