Scaphoid Fractures

The scaphoid is the most common carpal fracture, about 70% of them, and the second most common fracture at the wrist after the distal radius. It matters out of proportion to its frequency because of its high risk of nonunion and avascular necrosis, and a nonunion eventually costs the whole wrist.

Mechanism. A fall on the outstretched hand with the wrist dorsiflexed and radially deviated. The load passes through the thenar eminence and compresses the scaphoid between the radius and the capitate.

• FOOSH - by far the most common
• Sports injuries - young males
• Motor vehicle accidents

Who. A young man aged 15-30, hurt playing sport or in a fall. In one large UK series 365 of 415 fractures were in males, peaking at 15-19 years. Be suspicious of any young person with radial-sided wrist pain after a fall.

Where. Location predicts prognosis:

• Waist - 70%. Most common, and the largest absolute number of nonunions simply because there are so many.
• Proximal pole - 20%. Highest nonunion and AVN rates. The blood supply explains why.
• Distal pole and tubercle - 10%. Almost always heal.

The bone. Boat-shaped (Greek skaphe, a boat), set obliquely in both the coronal and sagittal planes, and about 80% covered by articular cartilage, which leaves few places for blood to enter. It links the proximal and distal carpal rows, so a scaphoid that shortens or fails to unite changes the mechanics of the whole carpus.

• Proximal: radius (scaphoid fossa)
• Distal: trapezium and trapezoid
• Ulnar side: lunate and capitate
• Forms the floor of the anatomic snuffbox; the tubercle is palpable on the palmar side

The blood supply. Branches of the radial artery enter through the dorsal ridge near the waist and supply 70-80% of the bone and the entire proximal pole. Palmar branches enter at the tubercle and feed only the distal 20-30%. The proximal pole has no vessel of its own: its blood arrives through the waist, flowing from distal to proximal, the reverse of most bones, which is what "retrograde" means.

Why it matters. A waist fracture lies across the only route into the proximal pole, so the proximal fragment is the one stranded, and the one that dies.

• The more proximal the fracture, the smaller the fragment downstream and the higher the risk of nonunion and AVN
• Displacement tears the intraosseous vessels as well, so displaced fractures heal less reliably
• The scaphoid takes longer to unite than its neighbours
• Collateral flow from the anterior interosseous artery is why many proximal pole fractures do not go on to necrosis (Gelberman): the retrograde supply raises the risk, it does not seal the fate

Herbert's classification is the shared language. The letter tells you the treatment: A is stable and can be cast, B is unstable and is fixed, C has failed to unite on time, D has failed altogether. It was published by the designer of the screw it was used to justify, without reliability testing, and observers disagree about exactly the A-versus-B boundary that drives the operative decision. Use it to describe the fracture, then decide on the fracture in front of you.

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History. The mechanism is usually a fall on the outstretched hand. The answers that change management:

• Time since injury - delay costs union
• Hand dominance and occupation - decides what a long cast will cost the patient
• Smoking - impairs healing
• Previous wrist injury

Examination. Swelling is often slight, far less than a distal radius fracture produces, and the diagnosis rests on where it hurts. Snuffbox tenderness is the classic sign and about 90% sensitive, but the snuffbox is tender after many wrist injuries; tubercle tenderness is as sensitive and more specific. A patient with the right mechanism who is tender in both the snuffbox and over the tubercle has a scaphoid fracture until imaging says otherwise, whatever the first radiograph shows.

Watson's test looks for scapholunate ligament injury or instability. Press on the scaphoid tubercle while bringing the wrist from ulnar to radial deviation; a clunk or pain is positive.

Radiographs. Request a scaphoid series, not a wrist series. The fracture line moves in and out of view as the projection changes, which is why one view is never enough:

• PA in ulnar deviation - elongates the scaphoid
• Lateral - angulation and the DISI pattern
• 45° semi-pronated oblique - profiles the bone
• AP with clenched fist - shows displacement

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The occult fracture. Between 10 and 20% of scaphoid fractures are not visible on the first films. That fact shapes the whole pathway. When the mechanism and examination are convincing and the radiographs are normal, there are two honest options:

1. Treat as a fracture: thumb spica, repeat films at 10-14 days, by which time resorption at the fracture edges has usually made the line visible
2. Image now: MRI, or CT once a fracture is confirmed, to characterise it for treatment

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MRI is the practical first-line test for the occult fracture. It shows marrow oedema before any line appears, picks up the ligament injuries and other carpal fractures that mimic a scaphoid fracture, and with gadolinium can assess the vascularity of the proximal pole.

CT characterises a fracture you already know is there: displacement and angulation measured precisely, union or nonunion judged, and the planning study before surgery.

Bone scintigraphy is the most sensitive of the three and the least specific. It turns positive within about 72 hours, earlier than radiographic change, but that means it cannot be done at once, and it needs a radiotracer injection and carries a radiation dose.

Cost. Modelling favours immediate MRI or CT over empiric casting with repeat radiographs: advanced imaging was cheaper overall and produced better outcomes, and empiric casting only won if the scan cost more than about $2000 or its sensitivity fell below 25-32%. Where advanced imaging is not readily available, thumb-spica immobilisation with re-imaging at 10-14 days remains common and acceptable practice.

The decision. Stability, location and the patient. A stable fracture (Herbert A) heals in a cast; an unstable one heals unreliably in a cast and is fixed. The difficult middle ground is the undisplaced or minimally displaced waist fracture, and here the evidence has moved:

• The classic instability threshold is displacement over 1mm
• SWIFFT randomised 439 adults with bicortical waist fractures displaced 2mm or less to early screw fixation or a below-elbow cast with fixation of any confirmed nonunion, and found no difference in patient-rated wrist function at a year
• Surgery brought a 14% rate of potentially serious complications against 18% cast-related complications: a trade of one complication profile for another, not a choice between risk and safety
• For that group, cast first and fix the few that fail is the modern position. Displacement over 2mm, proximal pole, comminution and fracture-dislocation were not randomised, and the classic criteria still apply there

The point of fixing a scaphoid is to be able to move it, so rehabilitation after a screw is built around early motion under protection. Fingers move from day one; the wrist starts gentle motion once initial healing allows, at 2-4 weeks; nothing is loaded until union is confirmed.

Principles

• Early finger motion is critical
• Confirm union before loading
• Grip strength returns over 6-12 months

Union rates fall as the fracture moves proximally and as it displaces, and they rise with fixation in exactly the groups where cast treatment does worst.

What worsens the prognosis

• Proximal location
• Displacement over 1mm
• Delay to treatment - over 4 weeks significantly increases nonunion, which is the reason the radiograph-negative wrist is immobilised rather than reassured
• AVN
• Smoking

If in doubt, treat it as a scaphoid fracture.

Global Epidemiology

Scaphoid fractures are the most common carpal fracture, occurring predominantly in young, active males. In a large UK regional study the annual incidence was 12.4 per 100,000, with the highest rate in males aged 15-19 years; 64% were at the waist and 18% at the tubercle, and incidence was higher in more socially deprived groups and peaked in summer (Garala et al., Bone Joint J 2016 — DOI). The classic mechanism is a fall on the outstretched hand; sport and manual occupations dominate the risk profile, though low-energy injuries are increasingly recognised in older adults. The true prevalence among clinically suspected fractures is low — roughly 16% in consecutive suspected presentations, which is why over-treatment of the radiograph-negative wrist is a recognised problem (Jenkins et al., Injury 2008 — DOI).

Guidance & Evidence by Region

Cost-effectiveness modelling supports immediate MRI or CT over empiric casting plus repeat radiographs for the occult fracture, as advanced imaging was the dominant strategy on both cost and outcome (Karl, Swart, Strauch, JBJS Am 2015 — DOI).

Global Practice Variation

• Casting configuration: No RCT evidence favours above- versus below-elbow casting or thumb inclusion (Doornberg, Buijze et al., J Trauma 2011 — DOI); below-elbow casting excluding the thumb is increasingly standard, though practice remains heterogeneous.
• Surgery vs cast for minimally displaced fractures: Rates of early fixation rose internationally before SWIFFT; the trial has shifted high-resource practice back toward cast-first with selective fixation, but operative thresholds still vary by surgeon and patient (athlete, manual worker) preference.
• Imaging access: In high-resource settings MRI/CT is used early for occult fractures; in limited-resource or remote settings empiric thumb-spica immobilisation with delayed re-imaging at 10-14 days remains common and acceptable.
• Reconstruction: Vascularised bone grafting and salvage procedures are typically concentrated in specialist hand units worldwide.

Registry Note

There is no dedicated international scaphoid-fracture registry; population-level epidemiology derives from national administrative and regional datasets (e.g. UK and German fracture surveillance), which consistently show a young-male predominance and a majority of waist fractures.