SCAPHOID FRACTURES - MOST COMMON CARPAL FRACTURE
Retrograde Blood Supply | High Nonunion Risk | Anatomic Snuffbox Tenderness
HERBERT CLASSIFICATION
Critical Must-Knows
- Retrograde blood supply - enters distally, proximal pole at risk
- Waist fractures are most common (70%) and highest AVN risk
- Proximal pole fractures have highest nonunion and AVN rates
- Anatomic snuffbox tenderness is key clinical finding
- If suspected but X-ray negative - treat as fracture or get MRI
Examiner's Pearls
- "Blood supply via dorsal carpal branch of radial artery - enters distally
- "Proximal pole has no direct blood supply - depends on intraosseous flow
- "Displacement over 1mm, angulation over 15°, or comminution = unstable = surgery
- "Herbert screw allows early motion without cast
Clinical Imaging
Imaging Gallery
Additional Imaging Examples
Critical Scaphoid Fracture Exam Points
Blood Supply
Retrograde blood supply via dorsal carpal branch of radial artery. Blood enters at the distal pole, flows proximally. Proximal pole fractures have highest AVN risk because they are distal to the blood entry.
X-ray Negative
10-20% of scaphoid fractures not visible on initial X-ray. If clinical suspicion high (snuffbox tenderness), either treat as fracture with cast/splint or MRI (most sensitive) to confirm. Don't dismiss.
Nonunion Risk Factors
Proximal pole location, displacement greater than 1mm, delay in treatment greater than 4 weeks, smoking, and comminution increase nonunion risk. These factors guide operative vs conservative decision.
Herbert Classification
Type A (stable) = cast. Type B (unstable) = surgery recommended. Type C (delayed) and Type D (nonunion) = surgery required. Know the subtypes.
Quick Decision Guide
| Pattern | Key Finding | Treatment |
|---|---|---|
| Herbert A1 (tubercle) | Extra-articular, very stable | Splint 4-6 weeks, excellent prognosis |
| Herbert A2 (waist, non-displaced) | Stable incomplete fracture | Scaphoid cast 8-12 weeks or consider screw |
| Herbert B1 (oblique distal) | Unstable distal fracture | Operative fixation recommended |
| Herbert B2 (displaced waist) | Displaced greater than 1mm | Operative fixation recommended |
| Herbert B3 (proximal pole) | High AVN and nonunion risk | Operative fixation strongly recommended |
| Herbert B4 (trans-scaphoid perilunate) | Complex carpal injury | Urgent operative fixation |
| Herbert D (nonunion) | Failed to heal, often with AVN | Surgery with bone graft +/- vascularized graft |
SCAPHOIDSCAPHOID - Key Features
Memory Hook:SCAPHOID fractures need careful assessment and often surgery
RETROGRADERETROGRADE - Blood Supply Pattern
Memory Hook:Blood flows RETROGRADE - enters distal, travels to proximal pole
HERBERTHERBERT - Classification
Memory Hook:HERBERT classification: A = stable, B = unstable, C = delayed, D = nonunion
PANDAPANDA - Surgical Indications
Memory Hook:Think of a PANDA - these fractures need surgery to avoid becoming extinct (nonunion)!
Overview and Epidemiology
Scaphoid fractures are the most common carpal fracture and the second most common wrist fracture (after distal radius). They are critical to diagnose and treat appropriately due to the high risk of nonunion and avascular necrosis.
Mechanism of injury:
- Fall on outstretched hand (FOOSH) - most common
- Wrist in dorsiflexion and radial deviation
- Axial load through thenar eminence
- Compresses scaphoid between radius and capitate
- Sports injuries - common in young males
- Motor vehicle accidents
Typical Patient
The typical scaphoid fracture patient is a young male (15-30 years) with a FOOSH injury playing sports or from a fall. This demographic has highest incidence. Be suspicious in any young person with wrist pain after fall.
Location distribution:
- Waist fractures: 70% (most common, highest absolute numbers of nonunion)
- Proximal pole: 20% (highest percentage nonunion and AVN)
- Distal pole/tubercle: 10% (excellent prognosis)
Anatomy and Blood Supply
Scaphoid anatomy:
- Boat-shaped carpal bone (Greek: skaphe = boat)
- Links proximal and distal carpal rows
- 80% covered by articular cartilage - limits blood entry points
- Oblique orientation in coronal and sagittal planes
- Tubercle palpable palmarly
Key relationships:
- Proximal: articulates with radius (scaphoid fossa)
- Distal: articulates with trapezium and trapezoid
- Medial: articulates with lunate and capitate
- Forms floor of anatomic snuffbox
Blood supply (Critical to understand):
Retrograde Blood Supply
The scaphoid has retrograde blood supply. The dorsal carpal branch of the radial artery provides 70-80% of blood supply via dorsal ridge. Blood enters distally and flows proximally. The proximal pole has no direct blood supply - entirely dependent on intraosseous flow.
Blood supply details:
- 70-80%: Dorsal carpal branch - enters at dorsal ridge (waist level)
- 20-30%: Palmar branch - enters at tubercle and distal pole
- Proximal pole: No direct blood supply, relies on intraosseous vessels
- This explains why proximal pole fractures have highest AVN risk
Implications:
- Waist fractures interrupt blood flow to proximal pole
- More proximal fractures = higher AVN risk
- Displaced fractures disrupt intraosseous vessels
- May take longer to heal than other carpal fractures
Classification Systems
Herbert Classification (most commonly used)
| Type | Subtype | Description |
|---|---|---|
| A | Stable acute fractures | |
| A1 | Fracture of tubercle | |
| A2 | Incomplete fracture through waist | |
| B | Unstable acute fractures | |
| B1 | Distal oblique fracture | |
| B2 | Complete fracture of waist | |
| B3 | Proximal pole fracture | |
| B4 | Trans-scaphoid perilunate dislocation | |
| B5 | Comminuted fractures | |
| C | Delayed union | |
| D | Established nonunion | |
| D1 | Fibrous nonunion | |
| D2 | Pseudarthrosis |
Herbert Key Points
Type A = stable = conservative treatment reasonable. Type B = unstable = operative treatment recommended. Type B criteria: displaced, proximal pole, oblique, or with perilunate dislocation.
Clinical Presentation and Assessment
History:
- Mechanism (FOOSH typical)
- Time since injury
- Hand dominance
- Occupation (manual worker implications)
- Smoking status (affects healing)
- Previous wrist injury
Physical examination:
Physical Examination Findings
| Finding | Test | Significance |
|---|---|---|
| Anatomic snuffbox tenderness | Palpate between EPL and EPB/APL | Classic sign, 90% sensitive |
| Scaphoid tubercle tenderness | Palpate palmarly at wrist crease | Equally sensitive, more specific |
| Pain with axial compression | Compress thumb metacarpal | Scaphoid compression test |
| Pain with resisted supination | Watson test component | Suggests scaphoid involvement |
| Reduced grip strength | Compare to contralateral | May indicate fracture |
| Swelling dorsal wrist | Observe/palpate | Less obvious than other wrist fractures |
Key clinical points:
Clinical Diagnosis
Anatomic snuffbox tenderness has high sensitivity (~90%) but low specificity. Scaphoid tubercle tenderness is equally sensitive and more specific. If both present with appropriate mechanism, treat as scaphoid fracture even if X-ray is negative.
Watson's test (for scaphoid instability):
- Pressure on scaphoid tubercle while moving wrist from ulnar to radial deviation
- Clunk or pain = positive
- Indicates scapholunate ligament injury or instability
Investigations
Radiographic assessment:
Standard scaphoid series (4 views):
- PA in ulnar deviation - elongates scaphoid
- Lateral - assess angulation, DISI
- 45° semi-pronated oblique - scaphoid profile
- AP with clenched fist - shows displacement
X-ray Limitations
10-20% of scaphoid fractures are NOT visible on initial X-ray. If clinical suspicion is high (snuffbox tenderness, appropriate mechanism), either treat as fracture or obtain MRI for definitive diagnosis. Do not dismiss based on normal X-ray alone.
Advanced imaging:
MRI (Gold standard for occult fractures):
- Sensitivity 100%, Specificity 99% for fractures
- Shows bone marrow edema before visible fracture line
- Detects associated soft tissue injuries
- Can assess vascularity (gadolinium enhancement)
CT scan:
- Best for fracture characterization
- Shows displacement and angulation precisely
- Assess healing (union vs nonunion)
- Surgical planning for complex fractures
Bone scan:
- High sensitivity, low specificity
- Positive within 72 hours (earlier than X-ray changes)
- Less used now with MRI availability
Approach to occult fracture:
- Clinical suspicion + negative X-ray
- Options:
- Treat as fracture: Cast, repeat X-ray 10-14 days (bone resorption shows fracture)
- MRI: Immediate definitive diagnosis (cost-effective if high clinical suspicion)
- CT: If fracture confirmed, characterize for treatment planning
Management
Conservative management indications:
- Herbert Type A fractures (tubercle, non-displaced waist)
- Non-displaced, stable fractures
- Patient preference (understanding risks)
- Medical contraindications to surgery
- Scaphoid (thumb spica) cast
- Thumb IP joint free
- Wrist in slight flexion and radial deviation
- Controversy: above vs below elbow (evidence mixed)
- Duration: 8-12 weeks minimum
- X-ray at 6 weeks
- If healing: continue cast to 8-12 weeks
- If not healed: CT to assess, consider surgery
- Prolonged immobilization for proximal fractures (up to 20 weeks)
Cast Immobilization Controversy
The position and extent of casting is debated. Evidence is mixed on above vs below elbow and thumb position. Key principles: stable fractures can heal in cast, but 8-12 weeks minimum and regular follow-up are essential.
Surgical Technique
Headless Compression Screw (Herbert Screw)
- Gold standard for acute fractures
- Variable pitch provides compression
- Buried entirely within bone
- Allows early motion without cast
Technique options:
- Volar approach (preferred for most)
- Access through thenar muscles
- Good for waist and distal fractures
- Screw placed perpendicular to fracture
- Dorsal approach (for proximal pole)
- Access between 3rd and 4th compartments
- Better for proximal pole fractures
- Screw enters at central axis
Other fixation:
- K-wires (temporary or adjunct)
- Mini-fragment screws (rarely now)
Screw Position
The ideal screw position is along the central axis of the scaphoid, perpendicular to the fracture. This provides best compression and lowest risk of screw cutout. Fluoroscopy or navigation helps achieve this.
Complications
Complications of Scaphoid Fractures
| Complication | Incidence | Management |
|---|---|---|
| Nonunion | 5-15% (higher proximal) | Surgery with bone graft |
| Avascular necrosis (AVN) | 13-50% proximal pole | Vascularized bone graft |
| Malunion (humpback) | Variable | Corrective osteotomy if symptomatic |
| Post-traumatic arthritis (SNAC) | Progressive with nonunion | Salvage procedures |
| Stiffness | 10-20% | Physiotherapy, rarely surgical |
| Hardware prominence | Variable | Screw removal |
| Missed diagnosis | Common | High index of suspicion, MRI |
Nonunion:
- Most common significant complication
- Risk factors: proximal pole, displacement, delay, smoking
- Leads to progressive arthritis if untreated
- Treatment: bone graft, +/- vascularized graft for AVN
Avascular necrosis:
- Proximal pole most at risk
- Appears sclerotic on X-ray
- MRI with gadolinium assesses vascularity
- Treatment: vascularized bone graft
SNAC Wrist Progression
Scaphoid nonunion advanced collapse (SNAC) wrist follows predictable arthritis pattern: Stage I (radial styloid), Stage II (radioscaphoid), Stage III (capitolunate), Stage IV (radiolunate/pancarpal). Treatment depends on stage.
Malunion - Humpback deformity:
- Scaphoid collapses into flexion
- Creates DISI pattern of carpus
- Affects carpal kinematics
- Treatment: wedge osteotomy to restore anatomy
Postoperative Care and Rehabilitation
Post-operative protocol:
- Bulky dressing and thumb spica splint
- Elevation
- Finger motion immediately
- Wound check at 10-14 days
- Convert to removable thumb spica splint
- Begin gentle wrist ROM
- Active finger motion
- May remove splint for exercises
- X-ray/CT to assess healing
- If united: progressive ROM and strengthening
- If not united: continue protection
- Wean from splint as comfort allows
- Full activity after confirmed union
- Grip strengthening
- Return to sport/work
- Final outcome assessment
Key rehabilitation principles:
- Early finger motion is critical
- Wrist motion after initial healing (2-4 weeks for operative)
- Confirm union before loading
- Grip strength returns over 6-12 months
Operative Advantage
A key advantage of operative fixation with a Herbert screw is the ability to begin early motion without prolonged casting. This is particularly valuable for athletes and manual workers who cannot tolerate 8-12 weeks in cast.
Outcomes and Prognosis
Outcomes by fracture type:
| Type | Conservative Union | Operative Union | Notes |
|---|---|---|---|
| Tubercle | Over 95% | N/A | Excellent prognosis |
| Distal waist, non-displaced | 90-95% | 95%+ | Cast reasonable |
| Waist, displaced | 60-70% | 90-95% | Surgery recommended |
| Proximal pole | 60-70% | 85-90% | Surgery strongly recommended |
Prognostic factors:
- Fracture location (proximal worse)
- Displacement (over 1mm = worse)
- Time to treatment (delay = worse)
- AVN present (much worse)
- Smoking (significant negative impact)
Time to Treatment
Delay in diagnosis/treatment over 4 weeks significantly increases nonunion risk. This is why treating suspected fractures (clinical signs, negative X-ray) is important. The mantra: "If in doubt, treat as a scaphoid fracture."
Evidence Base
- Described the Herbert screw - variable pitch, headless compression screw. Achieved high union rates (over 95%) and allowed early mobilization without cast.
- RCT comparing cast vs surgery for non-displaced scaphoid waist fractures. No significant difference in patient-reported outcomes at 1 year. Surgery had faster return to work/sport.
- Meta-analysis showed operative fixation has lower nonunion rate (0-5%) compared to cast (5-15%) for acute waist fractures. Time to union and return to activity faster with surgery.
- Described retrograde blood supply of scaphoid. 70-80% via dorsal carpal branch entering at dorsal ridge. Proximal pole has no direct blood supply.
- Immediate MRI for suspected scaphoid fracture was cost-effective compared to treating all suspected fractures and repeating X-rays. Reduced unnecessary treatment.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: X-ray Negative Suspected Scaphoid
"A 22-year-old man falls playing football, landing on his outstretched hand. He has anatomic snuffbox tenderness and scaphoid tubercle tenderness. X-rays are normal. How do you manage this patient?"
Scenario 2: Displaced Scaphoid Fracture
"A 28-year-old mechanic presents 2 days after a fall. X-rays show a displaced scaphoid waist fracture with 2mm displacement and carpal instability (DISI pattern). How do you manage this?"
Scenario 3: Scaphoid Nonunion
"A 35-year-old presents with chronic wrist pain. He recalls an injury 2 years ago that was never treated. X-rays show scaphoid nonunion with humpback deformity and sclerosis of the proximal pole. How do you assess and manage this patient?"
MCQ Practice Points
Blood Supply Question
Q: What is the blood supply pattern of the scaphoid? A: Retrograde - the dorsal carpal branch of the radial artery enters at the distal pole (dorsal ridge) and blood flows proximally. The proximal pole has no direct blood supply - it relies entirely on intraosseous vessels. This is why proximal pole fractures have highest AVN risk.
Classification Question
Q: In Herbert classification, what defines a Type B fracture? A: Unstable acute fractures. Subtypes: B1 (distal oblique), B2 (displaced waist), B3 (proximal pole), B4 (trans-scaphoid perilunate), B5 (comminuted). Type B fractures generally require operative fixation.
Imaging Question
Q: What is the best investigation for a clinically suspected scaphoid fracture with negative X-rays? A: MRI - sensitivity and specificity approaching 100%. It shows bone marrow edema before fracture line is visible on X-ray and can identify alternative diagnoses. CT is better for characterizing known fractures.
Location Question
Q: Which scaphoid fracture location has the highest nonunion and AVN rate? A: Proximal pole - due to the retrograde blood supply, the proximal pole is entirely dependent on intraosseous vessels. Fractures here interrupt this flow, leading to highest rates of nonunion (up to 30-40%) and AVN (up to 50%).
Treatment Question
Q: What is the indication for vascularized bone graft in scaphoid nonunion? A: Avascular necrosis of the proximal pole. Standard non-vascularized bone graft has high failure rate when the proximal pole is avascular. Vascularized grafts (1,2 ICSRA or medial femoral condyle) bring new blood supply to the dead bone.
Australian Context
Scaphoid Fractures in Australia
Epidemiology and Common Mechanisms:
- Most common carpal fracture in young males (15-30 years)
- Peak incidence in sports-active population: AFL, rugby league/union, skateboarding, cycling
- Significant incidence in manual workers (construction, trades)
- Fall on outstretched hand (FOOSH) is the classic mechanism
- Increasing recognition in elderly population (lower energy trauma)
Clinical Practice Patterns:
- Emergency departments see high volume of suspected scaphoid injuries
- Clinical examination with anatomic snuffbox tenderness is standard screening
- MRI access varies significantly between metropolitan and regional areas
- Where MRI unavailable, empiric treatment (thumb spica cast) with follow-up X-ray at 10-14 days remains common practice
- Herbert screw fixation widely available at major trauma centers
- Vascularized bone grafting typically performed at specialized hand surgery units
Medicolegal Considerations:
- Missed scaphoid fracture is one of the most common orthopaedic litigation cases in Australia
- Failure to diagnose or inadequate follow-up arrangements are key risk factors
- Standard of care requires:
- Documented clinical examination (snuffbox tenderness, scaphoid tubercle tenderness)
- Appropriate imaging (minimum 4 views: PA, lateral, scaphoid views, or dedicated scaphoid series)
- If clinical suspicion persists despite negative X-ray: either immobilize and follow-up OR arrange MRI
- Clear documentation of follow-up plan and safety-netting advice
- Patient education about risks of non-compliance
RACS Training Implications:
- Scaphoid fractures are core curriculum for orthopaedic SET training
- Expected knowledge for Part II clinical examination:
- Herbert classification system
- Blood supply anatomy (retrograde flow, AVN risk)
- Indications for operative vs conservative management
- Management of occult fractures
- Treatment algorithms for nonunion and AVN
Access and Equity Issues:
- MRI availability limited in rural/remote Australia
- Telemedicine consultations increasingly used for regional management
- Transfer to tertiary centers may be required for complex cases (nonunion, AVN requiring vascularized grafting)
- Cost considerations: MRI is bulk-billed under Medicare for appropriate indications
Workplace Implications:
- WorkCover claims common for industrial injuries
- Return-to-work timing critical for manual laborers
- Operative fixation often preferred to minimize time off work (vs 8-12 weeks casting)
- Functional outcomes and grip strength important for compensation assessments
PBS and Medication Considerations:
- Analgesia (simple + opioid short-term) PBS-subsidized
- Calcium and vitamin D supplementation for bone health
- Smoking cessation support essential (Quitline 13 7848) - smoking impairs fracture healing
FRACS Exam Focus
Be prepared to discuss retrograde blood supply anatomy, Herbert classification, management algorithm for X-ray negative but clinically suspected fractures, and nonunion treatment options (vascularized vs non-vascularized bone graft indications). Medicolegal aspects of missed diagnosis are frequently examined.
SCAPHOID FRACTURES
High-Yield Exam Summary
BLOOD SUPPLY
- •Retrograde - enters distally, flows proximally
- •Dorsal carpal branch of radial artery
- •Enters at dorsal ridge (waist level)
- •Proximal pole has NO direct blood supply
HERBERT CLASSIFICATION
- •Type A: Stable (A1=tubercle, A2=non-displaced waist)
- •Type B: Unstable (B1-B5, see subtypes)
- •Type C: Delayed union
- •Type D: Established nonunion
OPERATIVE INDICATIONS
- •Displacement greater than 1mm
- •Proximal pole fractures
- •Associated carpal instability
- •Nonunion
- •Relative: athlete, manual worker, patient choice
X-RAY NEGATIVE MANAGEMENT
- •10-20% not visible initially
- •Option 1: Treat as fracture, repeat X-ray 10-14 days
- •Option 2: MRI (gold standard, 100% sensitive)
- •Never dismiss with clinical findings
NONUNION TREATMENT
- •Assess proximal pole vascularity (MRI + gadolinium)
- •Viable: non-vascularized bone graft (Fisk-Fernandez)
- •AVN: vascularized bone graft (1,2 ICSRA, MFC)
- •SNAC wrist: salvage procedures
KEY NUMBERS
- •70% waist fractures (most common)
- •20% proximal pole (highest AVN risk)
- •10-20% X-ray negative initially
- •5-15% nonunion rate overall
- •greater than 1mm displacement = surgery