Lucan · Conditions

Scaphoid fracture

Australian guidance: WA HealthPathways — Wrist Injury / Scaphoid Fracture pathway + RACGP / Australian Journal of General Practice clinical review on suspected scaphoid fracture + EMST (Early Management of Severe Trauma) primary/secondary survey principles for high-energy mechanisms

1. Definition and epidemiology

A scaphoid fracture is a break in the boat-shaped carpal bone that forms the radial link between the proximal and distal carpal rows. It is the most commonly fractured carpal bone by a wide margin, accounting for the large majority of all carpal fractures, and it is the injury that every clinician is taught to actively hunt for after a fall onto the hand because a missed diagnosis carries a disproportionate long-term cost. The typical patient is a young, active adult, most often a man in his teens to thirties, injured during sport (football codes, cycling, skateboarding) or a simple fall; scaphoid fracture is comparatively uncommon in young children, whose more cartilaginous, resilient carpal bones and looser wrist ligaments mean an equivalent fall is more likely to sprain the wrist or fracture the distal radius instead, and in older adults, who more often sustain a distal radius fracture from the same fall because of relatively weaker metaphyseal bone. This age distribution is itself a diagnostic clue: a young adult with snuffbox tenderness after a fall is treated as a scaphoid fracture until proven otherwise, regardless of the initial X-ray.

2. Pathophysiology

The scaphoid has a waist, a proximal pole, and a distal pole (tubercle), and roughly two-thirds to three-quarters of fractures occur through the waist, with the remainder split between the proximal and distal poles. Its blood supply is the single most important anatomical fact governing prognosis. The dominant supply enters through nutrient vessels, branches of the radial artery, at the dorsal ridge near the junction of the middle and distal thirds of the bone, and these vessels then run proximally within the bone to nourish the waist and, ultimately, the proximal pole. Because this intraosseous flow travels backwards relative to the direction a fracture line most often runs, from distal entry point toward the proximal pole, it is described as a retrograde blood supply: the proximal pole depends almost entirely on flow that has to travel the full length of the bone from a distal entry point, with little or no independent proximal vascular contribution.

A fracture through the waist or proximal pole can therefore sever the vessels before they reach the proximal fragment, leaving that fragment relying on collateral flow through the fracture site itself, or on no viable supply at all, to survive. This is why proximal pole fractures carry the highest rates of avascular necrosis and non-union, waist fractures carry an intermediate risk, and distal pole (tubercle) fractures, which sit distal to the point of vascular entry and retain a good independent blood supply, heal reliably and rarely progress to avascular necrosis. The mechanism of injury is a fall onto an outstretched hand (FOOSH) with the wrist forced into hyperextension and radial deviation; axial compressive load is transmitted through the thenar eminence and the base of the thumb along the long axis of the scaphoid, and because the scaphoid bridges the two carpal rows and is levered against the dorsal rim of the radius in this position, it concentrates and fails under a bending and shear force that the more centrally supported carpal bones are not exposed to in the same way.

3. Clinical presentation and diagnostic criteria

The history is a fall onto an outstretched, extended, radially deviated hand, with pain and swelling at the radial side of the wrist and reduced grip strength; many patients initially dismiss the injury as "just a sprain" because early swelling and bruising can be subtle compared with a displaced distal radius fracture. Examination is built around a well-recognised triad, and all three components are checked in every patient with a plausible mechanism. First, tenderness in the anatomical snuffbox, the triangular depression on the radial dorsum of the wrist bounded by the tendons of extensor pollicis brevis and abductor pollicis longus radially and extensor pollicis longus ulnarly, with the scaphoid and part of the trapezium, along with the radial styloid process proximally, forming its floor; this is the single most sensitive bedside sign, though it is not specific, since radial styloid and de Quervain-type tenderness can also localise here. Second, tenderness directly over the scaphoid tubercle, palpated at the base of the thenar eminence with the wrist held in slight extension. Third, pain reproduced by axial compression (telescoping) of the thumb along its long axis, which transmits load through the trapezium into the scaphoid. Reduced or painful range of wrist motion and reduced grip strength on the affected side support the diagnosis but are non-specific.

Because a high-energy mechanism (a fall from height, a motor vehicle or cycling collision at speed) can produce a scaphoid fracture alongside other injuries, assessment of these patients sits within a broader primary and secondary survey consistent with EMST principles, ensuring associated injuries, most importantly a concomitant distal radius fracture, perilunate or lunate dislocation, or other carpal injury, are not overlooked while attention is fixed on the wrist.

4. Investigations and AU-specific cutoffs

Initial imaging is a dedicated four-view scaphoid series (posteroanterior, lateral, both obliques, and a PA view with the wrist in ulnar deviation and slight supination, which elongates the scaphoid out of its normally foreshortened resting position and profiles the waist). The central diagnostic problem in this topic is that a genuine, non-displaced scaphoid fracture is radiographically occult on this initial series in a substantial minority of cases, commonly cited at around one in five to one in four, because an undisplaced fracture line can be extremely subtle or simply not yet visible before any bony resorption has occurred at its margins. Consistent with WA HealthPathways and RACGP guidance, the practical rule that follows is that clinical suspicion overrides a normal X-ray: any patient with a plausible FOOSH mechanism and snuffbox, tubercle, or axial-compression tenderness is managed as a "clinically suspected scaphoid fracture" regardless of the initial films, because failing to immobilise a true but occult fracture is precisely the pathway that leads to avascular necrosis and non-union.

Two accepted pathways then follow from this point, and the choice between them is increasingly guided by imaging access and the value of an early return to work or sport. The traditional pathway is immobilise-and-reimage: the wrist is splinted in a thumb spica for approximately ten to fourteen days and then reimaged, either with repeat plain films, which by then may show a fracture line as bony resorption at the fracture margins makes it visible, or with CT, which better defines fracture pattern and displacement once callus or resorption changes have developed but is not the most sensitive test in the truly acute occult setting. The alternative, increasingly favoured where access allows and reflected in current RACGP and WA HealthPathways commentary, is early MRI within the first few days of injury, which is the single most sensitive and specific test for an occult scaphoid fracture, can also detect bone bruising or an alternative diagnosis (a ligamentous injury or an occult fracture of another carpal bone), and allows patients who are MRI-negative to be released from immobilisation and back to work or sport far sooner than the wait-and-reimage approach. CT scanning has a particular role once a fracture is confirmed, for defining displacement, comminution, and fracture geometry to guide operative planning, and for assessing suspected non-union later in the course, rather than as the first-line test for excluding an occult fracture. Isotope bone scanning was historically used for this same occult-fracture problem but has been superseded by MRI and is now rarely used.

5. Management

An undisplaced or minimally displaced fracture, most commonly through the waist or distal pole, is managed non-operatively in a cast. Below-elbow immobilisation is now standard, in a thumb spica configuration that immobilises the wrist and the thumb metacarpophalangeal joint (leaving the thumb interphalangeal joint free) with the wrist in a neutral or slightly extended, radially deviated position; trial evidence has not shown any advantage of extending the cast above the elbow, and a below-elbow cast is better tolerated and does not compromise union rates for stable, undisplaced fractures. Duration of immobilisation is guided by fracture location and healing, since this tracks directly back to the retrograde blood supply: a distal pole fracture typically unites within around six weeks, a waist fracture usually needs roughly six to ten weeks, and a proximal pole fracture may need ten to twelve weeks or longer, with serial imaging (repeat X-ray or, where available, CT) used to confirm bony union before the cast is removed and rehabilitation begun, rather than relying on a fixed calendar duration alone.

A displaced fracture is not managed in a cast alone. Displacement of more than about one millimetre of step-off or gap, an abnormal scapholunate angle, angulation producing a "humpback" deformity of the scaphoid, or any associated carpal instability or perilunate injury are indications for referral to an orthopaedic or hand surgeon for operative fixation, most commonly percutaneous or open reduction and internal fixation with a headless compression screw placed down the long axis of the bone.

Proximal pole fractures are also frequently treated operatively even when minimally displaced, both because their vascular vulnerability makes reliable cast union less certain and because early rigid fixation allows earlier mobilisation. Any fracture with a delayed or missed presentation, evidence of established non-union, or avascular necrosis on imaging likewise warrants specialist referral, as does any patient in whom cast immobilisation is impractical (a young child, a manual worker unable to tolerate prolonged immobilisation, an elite athlete) where surgical fixation may be offered even for an undisplaced fracture to shorten time off activity.

6. Pharmacology and AU PBS notes

Analgesia is simple and supportive rather than disease-modifying. Paracetamol, with a short course of an NSAID such as ibuprofen where not contraindicated, is first-line for pain in the acute injury and after cast application or surgical fixation; a brief course of a weak opioid such as codeine, or occasionally a stronger opioid such as low-dose oxycodone, is sometimes used for the first day or two after high-energy injury or surgery but is not routinely required and is minimised given standard Australian opioid stewardship principles. There is no PBS-listed pharmacological therapy that alters fracture union or reduces the risk of avascular necrosis; smoking cessation advice is appropriate wherever relevant, since smoking impairs bone healing generally, but this is a general principle rather than a scaphoid-specific pharmacological intervention. Routine antibiotic prophylaxis is not required for a closed fracture managed in a cast, and standard clean-procedure prophylaxis principles apply if operative fixation is undertaken.

7. Complications and monitoring

Non-union is the complication that defines long-term outcome in this topic and follows directly from the retrograde blood supply described above: an occult or inadequately immobilised fracture, particularly of the waist or proximal pole, can fail to unite, leaving a persistent fibrous or ununited gap at the fracture site. Un-united fragments progressively collapse into a flexed, foreshortened "humpback" deformity, with the proximal fragment tilting into a dorsal intercalated segment instability (DISI) pattern as the surrounding carpal ligaments lose their normal alignment. Over years this altered carpal mechanics produces a predictable, progressive degenerative cascade known as scaphoid non-union advanced collapse (SNAC wrist), beginning at the radial styloid, extending to involve the whole radioscaphoid joint, and finally to the capitolunate (midcarpal) joint, while the radiolunate joint is characteristically spared until very late disease. Avascular necrosis of the proximal pole, visible on MRI as reduced marrow signal or on plain films as increased radiodensity of the fragment relative to its neighbours, similarly predisposes to collapse and accelerates the same arthritic sequence.

Clinically, established non-union or SNAC wrist presents with chronic radial wrist pain, progressive stiffness, reduced grip strength, and eventually visible deformity, and by the time arthritic change is established, treatment shifts from attempting to achieve union to salvage procedures such as proximal row carpectomy or scaphoidectomy with four-corner fusion, and ultimately total wrist fusion in advanced disease. This entire cascade, from occult fracture through non-union to SNAC wrist, is the clinical argument for the low threshold to immobilise a clinically suspected but radiographically normal scaphoid fracture, for early MRI where it is available, and for timely surgical referral of displaced or proximal pole fractures rather than a trial of casting alone.

Written for Australian practice and grounded in the guidance named above. Study material only — not medical advice. Always check against current guidelines.