High-yield overview

Rare Carpal Injury | Scaphocapitate Syndrome | High AVN Risk

1-2%Of all carpal fractures

NeckMost common fracture site

50%Associated with other injuries

AVN RiskProximal pole vulnerable

CAPITATE FRACTURE PATTERNS

Neck Fracture

PatternThrough waist of capitate

TreatmentORIF if displaced, high AVN risk

Body Fracture

PatternThrough capitate body

TreatmentCast if undisplaced, ORIF if displaced

Scaphocapitate

PatternCombined scaphoid and capitate

TreatmentORIF both bones, assess rotation

Critical Must-Knows

Rarest of common carpals to fracture - only 1-2% of carpal injuries
Scaphocapitate syndrome is classic pattern - both bones fractured
Proximal fragment rotates 180 degrees in scaphocapitate syndrome
High AVN risk due to retrograde blood supply to proximal pole
50% have associated injuries - always examine entire carpus

Clinical Pearls

"
Capitate is protected centrally - fracture implies significant force
"
Scaphocapitate syndrome = scaphoid waist + capitate neck fractures
"
Look for 180-degree rotation of proximal capitate fragment
"
AVN risk similar to scaphoid proximal pole fractures

High-Yield Capitate Fracture Exam Points

Scaphocapitate Syndrome

The classic exam topic: Combined fracture of scaphoid waist AND capitate neck. The proximal capitate fragment rotates 180 degrees so its articular surface faces the fracture site. This must be recognized and corrected surgically.

Central Protection

The capitate is centrally located and protected by surrounding carpals. Fracture therefore implies high-energy mechanism. Always assess for associated injuries including perilunate instability.

AVN Risk

Similar to scaphoid, the capitate has retrograde blood supply. The proximal pole is vulnerable to AVN, especially with displacement or rotation. Early recognition and fixation may reduce AVN risk.

Imaging Strategy

Plain radiographs often miss capitate fractures. The overlapping carpals obscure detail. CT is essential for diagnosis and surgical planning. MRI assesses vascularity if AVN is a concern.

At a Glance: Capitate Fracture Management

Fracture Pattern	Displacement	Management	Key Consideration
Isolated body	Undisplaced	Cast 6-8 weeks	Monitor for displacement
Isolated body	Displaced	ORIF with screws	Restore articular surface
Neck fracture	Any	ORIF recommended	High AVN risk to proximal pole
Scaphocapitate	Rotated fragment	ORIF both bones	Derotate proximal capitate
Perilunate-associated	Variable	Address entire injury	Comprehensive carpal stabilization

Mnemonic

CAPITATE - FCAPITATE - Fracture Features

C	Central location Protected by surrounding carpals - high energy needed
A	AVN risk Retrograde blood supply like scaphoid
P	Proximal pole vulnerable Most at risk for avascular necrosis
I	Imaging with CT Plain films often miss - CT essential
T	Transscaphoid variant Scaphocapitate syndrome classic pattern
A	Associated injuries 50% have other carpal injuries
T	Turned fragment Proximal fragment may rotate 180 degrees
E	Early fixation ORIF to reduce AVN and nonunion risk

C	Central location Protected by surrounding carpals - high energy needed	I	Imaging with CT Plain films often miss - CT essential	T	Turned fragment Proximal fragment may rotate 180 degrees
A	AVN risk Retrograde blood supply like scaphoid	T	Transscaphoid variant Scaphocapitate syndrome classic pattern	E	Early fixation ORIF to reduce AVN and nonunion risk
P	Proximal pole vulnerable Most at risk for avascular necrosis	A	Associated injuries 50% have other carpal injuries

Hook:CAPITATE - Central bone with AVN risk requiring CT and early Treatment

Mnemonic

FENTON - SFENTON - Scaphocapitate Syndrome

F	Fenton's syndrome Eponymous name for scaphocapitate fracture
E	Extension mechanism Hyperextension injury to wrist
N	Neck of capitate Fracture through capitate waist
T	Two bones fractured Scaphoid waist + capitate neck
O	One-eighty rotation Proximal capitate rotates 180 degrees
N	Need ORIF Surgical reduction and fixation required

F	Fenton's syndrome Eponymous name for scaphocapitate fracture	N	Neck of capitate Fracture through capitate waist	O	One-eighty rotation Proximal capitate rotates 180 degrees
E	Extension mechanism Hyperextension injury to wrist	T	Two bones fractured Scaphoid waist + capitate neck	N	Need ORIF Surgical reduction and fixation required

Hook:FENTON syndrome - scaphoid and capitate fractured with 180-degree rotation

Mnemonic

RARE - WRARE - Why Capitate Fractures Are Uncommon

R	Recessed position Sits deep in carpal concavity
A	Adjacent protection Surrounded by other carpals
R	Requires high energy Protected location needs significant force
E	Easily missed Overlapping bones obscure on X-ray

R	Recessed position Sits deep in carpal concavity	R	Requires high energy Protected location needs significant force
A	Adjacent protection Surrounded by other carpals	E	Easily missed Overlapping bones obscure on X-ray

Hook:RARE fracture - Recessed position needs high energy and is Easily missed

Overview and Epidemiology

Definition

Capitate fractures are fractures of the capitate bone, the largest carpal bone located centrally in the distal carpal row. Due to its protected position, isolated capitate fractures are rare, but when they occur, they carry significant implications including AVN risk.

Epidemiology

Incidence: 1-2% of all carpal fractures (very rare)
Ranking: Among the least common carpal fractures
Age distribution: Young adults predominantly
Gender: Male predominance
Mechanism: High-energy axial loading with hyperextension

Associated Injuries

Over 50% of capitate fractures occur with other carpal injuries:

Scaphoid fracture: Scaphocapitate syndrome (most common association)
Perilunate injury: Part of greater arc pattern
Other carpal fractures: Hamate, lunate
Ligamentous injuries: Scapholunate, lunotriquetral

Clinical Significance

The capitate's central position and size make it critical to wrist function:

Keystone of distal carpal row
Articulates with multiple carpals and metacarpals
Transmits force from 2nd and 3rd metacarpals
Essential for wrist stability and motion

Understanding the capitate's anatomy explains why fractures are rare but significant.

Anatomy/Biomechanics

Osseous Anatomy

Shape and Configuration

Largest carpal bone: Occupies central position
Head: Proximal, rounded, articulates with lunate concavity
Neck: Constricted waist region - common fracture site
Body: Larger distal portion

Articular Surfaces

Proximal (head): Articulates with lunate
Radial: Articulates with scaphoid
Ulnar: Articulates with hamate
Distal: Articulates with 2nd, 3rd, and 4th metacarpal bases

Surface Features

Smooth proximal convexity for lunate
Flat distal surface for metacarpals
Waisted neck region

Blood Supply

Vascular Pattern (Critical)

The capitate has a retrograde blood supply similar to the scaphoid:

Dorsal Vessels (Primary)

Enter through dorsal non-articular surface
Supply proximal two-thirds of bone
Retrograde flow to proximal pole

Volar Vessels (Secondary)

Smaller contribution
Enter distal body
Limited anastomosis with dorsal vessels

AVN Implications

Proximal pole fractures have highest AVN risk
Neck fractures can disrupt blood supply to head
Similar vulnerability pattern to scaphoid proximal pole

AVN Risk Pattern

The capitate's retrograde blood supply means the proximal pole (head) is vulnerable to AVN when fracture occurs through the neck, similar to scaphoid waist fractures affecting the proximal pole.

Biomechanics

Load Transmission

Central location transmits axial load
Force from 2nd and 3rd metacarpals
Distributes to proximal row through lunate

Carpal Kinematics

Part of distal row (moves as unit)
Limited independent motion
Follows scaphoid and lunate motion

Protection Mechanism

Surrounded by other carpals
Recessed in carpal concavity
Requires significant force to fracture

Understanding the anatomy is essential for surgical planning and prognosis.

Classification Systems

Anatomical Classification

Based on fracture location within the capitate:

Head (Proximal Pole) Fractures

Least common pattern
Highest AVN risk
May be isolated or with other injuries
Treatment: ORIF to preserve blood supply

Neck Fractures

Most common location
Through waisted region
Prone to displacement
Treatment: ORIF recommended due to AVN risk

Body Fractures

Through distal capitate
Lower AVN risk
May be undisplaced
Treatment: Cast if undisplaced, ORIF if displaced

Avulsion Fractures

Small fragments from ligament insertions
Usually minimal clinical significance
Treatment: Conservative unless large or symptomatic

Location determines prognosis and treatment approach.

Classification Summary

Pattern	Location	AVN Risk	Treatment
Head fracture	Proximal pole	Highest	ORIF
Neck fracture	Waist region	High	ORIF recommended
Body fracture	Distal portion	Moderate	Cast or ORIF
Scaphocapitate	Neck + scaphoid	High	ORIF both bones

Classification guides treatment decisions and prognostic counseling.

Clinical Assessment

History

Mechanism of Injury

High-energy trauma: Motor vehicle accident, motorcycle crash, fall from height
Sports injury: Contact sports, gymnastics with axial load
FOOSH: Fall onto outstretched hand with hyperextension
Direct trauma: Rare due to protected position

Key History Points

Energy of injury (significant force required)
Position of wrist at impact
Associated symptoms suggesting other injuries
Immediate disability and swelling pattern
Hand dominance and occupation

Physical Examination

Inspection

Swelling over central wrist (may be diffuse)
Less localized than scaphoid or triquetrum
Compare to contralateral side

Palpation

Capitate tenderness: Difficult to isolate due to deep location
Palpate through 3rd metacarpal axis
Dorsal central wrist tenderness
Assess for tenderness over other carpals

Range of Motion

Limited by pain
Test flexion, extension, deviation
Compare to contralateral

Neurovascular Assessment

Usually preserved
Document baseline

Special Tests

Axial Compression Test

Load through 3rd metacarpal
Pain suggests capitate pathology

Watson Test

Assess for associated scapholunate injury
Important given frequent scaphoid association

General Carpal Assessment

Examine all carpals systematically
High rate of associated injuries

Finger Cascade

Ensure no metacarpal malrotation
Assess grip strength (limited by pain)

Clinical examination is often non-specific; maintain a high index of suspicion after high-energy wrist trauma.

Differential Diagnosis

Central dorsal wrist pain after trauma has several mimics. Because the capitate is hard to isolate clinically and is frequently missed on plain films, the differential drives the imaging strategy.

Differential Diagnosis of Central Dorsal Wrist Pain After Trauma

Diagnosis	Distinguishing features	Key investigation
Capitate fracture	Central dorsal tenderness, pain on axial loading of the 3rd metacarpal, high-energy mechanism	CT (plain films frequently negative)
Scaphoid fracture	Anatomical snuffbox and scaphoid tubercle tenderness, pain on thumb axial load	Dedicated scaphoid views; MRI/CT if occult
Scaphocapitate syndrome	Combined scaphoid and capitate signs after hyperextension; rotated proximal capitate fragment	CT showing both fractures and 180-degree fragment rotation
Perilunate / lunate dislocation	Gross swelling, deformity, median nerve symptoms, disrupted Gilula arcs	Lateral radiograph (capitolunate malalignment); CT
Scapholunate ligament injury	Dorsal SL tenderness, positive Watson (scaphoid shift) test, SL gap	Clenched-fist PA; dynamic/stress views; MRI
Distal radius fracture	Diffuse wrist tenderness, deformity, more distal/radial focus	PA and lateral radiographs
Wrist sprain (no fracture)	Diffuse mild tenderness, full passive motion, low-energy mechanism	Diagnosis of exclusion after negative imaging

Investigations

Plain Radiographs

Standard Views

PA view: May show fracture line through capitate
Lateral view: Assess carpal alignment, displacement
Oblique views: Additional perspective

Radiographic Challenges

Overlapping carpals obscure capitate
Fracture often not visible on initial films
Scaphocapitate syndrome frequently missed
Carpal alignment assessment important

Signs to Look For

Fracture line through capitate (often subtle)
Disruption of carpal arcs (Gilula's lines)
Associated scaphoid fracture
DISI or VISI pattern on lateral

CT Scanning (Essential)

Indications

Any suspected capitate injury
High-energy wrist trauma
Surgical planning
Assessment of fragment rotation

Key CT Findings

Fracture line orientation
Fragment displacement and rotation
Associated carpal fractures
Articular surface involvement

Scaphocapitate Syndrome on CT

Both fractures visible
180-degree rotation of proximal capitate
Articular surface facing fracture site

MRI

Indications

Vascularity assessment
Occult fracture detection
Ligamentous injury evaluation
AVN monitoring

Findings

Bone marrow edema in acute fracture
Signal changes suggesting AVN
Associated soft tissue injuries

Bone Scan

Limited Role

Rarely needed with CT and MRI availability
May detect occult injuries

Investigations summary is provided below.

Imaging Strategy for Capitate Fractures

Modality	Primary Role	Advantage	Limitation
Plain X-ray	Initial screening	Available, quick	Often misses fracture
CT scan	Definitive diagnosis	Fracture detail, rotation	Essential for planning
MRI	Vascularity, ligaments	AVN assessment	Cost, availability
Bone scan	Rarely needed	Sensitive	Non-specific

CT is essential for diagnosis and surgical planning in capitate fractures.

Management Algorithm

Scaphocapitate syndrome imaging showing X-rays and CT with 180-degree rotated proximal capitate fragment — Scaphocapitate (Fenton) Syndrome Imaging. (A) PA and lateral radiographs showing carpal injury (red circles). (B) CT imaging: coronal view shows scaphoid waist fracture, sagittal view demonstrates the pathognomonic 180-degree rotation of proximal capitate fragment with articular surface facing the fracture site instead of the lunate.Credit: Pedrazzini et al., Acta Biomed 2019, PMC7233705, CC BY 4.0

Conservative Management

Indications

Undisplaced body fractures (rare)
Small avulsion fragments
Elderly or low-demand patients with undisplaced fractures
Medical contraindications to surgery

Protocol

Immobilization

Short arm cast including thumb
Wrist in neutral position
Duration: 6-8 weeks minimum
May need longer for neck fractures

Follow-Up

Week 2: Clinical review, assess comfort
Week 4: Repeat radiographs, assess for displacement
Week 6-8: CT to assess healing
Continue immobilization until union confirmed

Red Flags for Surgery

Secondary displacement on follow-up imaging
Persistent pain suggesting nonunion
Development of AVN signs

Expected Outcomes

Undisplaced body fractures generally heal
Neck fractures have higher failure rate with conservative treatment
Close monitoring for AVN essential

Conservative treatment is reserved for select undisplaced fractures.

Most capitate fractures require surgical treatment due to displacement and AVN risk.

Surgical Technique

Dorsal Approach for Capitate ORIF

Intraoperative images showing capitate fragment before and after derotation in scaphocapitate syndrome — Intraoperative reduction of scaphocapitate syndrome via dorsal approach. (A) Before reduction: proximal capitate fragment is rotated 180 degrees with articular surface (white, smooth) facing the fracture site. (B) After reduction: fragment has been derotated and now articulates normally with lunate. Note the fractured scaphoid visible alongside.Credit: Pedrazzini et al., Acta Biomed 2019, PMC7233705, CC BY 4.0

Patient Positioning

Supine with arm table
Tourniquet on upper arm
May use traction tower for exposure

Incision and Exposure

Skin Incision

Dorsal longitudinal over central wrist
4-5 cm centered on Lister's tubercle
May extend for associated injuries

Deep Dissection

Incise extensor retinaculum between 3rd and 4th compartments
Retract EDC ulnarly, EPL radially
Capsulotomy - ligament-sparing if possible
Expose capitate fully

Fracture Reduction

Isolated Capitate

Direct visualization of fracture
Reduce with dental pick or small elevator
Assess articular surface reduction
Provisional K-wire fixation

Scaphocapitate Syndrome

Identify rotated proximal fragment
Insert K-wire into fragment as joystick
Derotate 180 degrees
Confirm articular surface now proximal
Provisional K-wire across fracture

Fixation

Headless Compression Screw

2.0-2.4mm diameter
Retrograde (distal to proximal) or antegrade
Countersink beneath cartilage
Confirm position with fluoroscopy

Technical Pearls

Central placement in capitate
Avoid articular penetration
Consider second screw for rotational control
Check screw length carefully

Closure

Repair capsule
Close retinaculum loosely
Standard skin closure
Splint in neutral

Dorsal approach provides excellent access to the capitate.

Surgical technique requires attention to fragment rotation and careful fixation.

Complications

Intraoperative Complications

Iatrogenic Fracture

Risk during fragment manipulation
Capitate is small and may fragment
Prevention: Gentle technique
Management: Additional fixation

Screw Malposition

Joint penetration
Inadequate purchase
Prevention: Careful measurement, fluoroscopy
Management: Revise if intra-articular

Failure to Recognize Rotation

Scaphocapitate syndrome
Fragment left in wrong orientation
Prevention: Careful preoperative CT review
Management: Recognize and correct intraoperatively

Early Complications

Wound Complications

Infection: Rare
Dehiscence: May expose hardware
Management: Antibiotics, debridement if needed

Hardware Problems

Screw prominence
K-wire migration
Management: Remove once healed

Stiffness

Common due to prolonged immobilization
Prevention: Early finger motion
Management: Hand therapy, patience

Late Complications

Avascular Necrosis (Major Concern)

Most significant complication
Risk highest for neck fractures
May present months to years later
Treatment: Stage-dependent, may need salvage

Nonunion

Related to AVN, inadequate fixation, or biology
May require bone grafting
Consider vascularized graft if AVN present

Post-Traumatic Arthritis

Consequence of AVN or malreduction
Progressive wrist pain
Treatment: Activity modification to fusion

Carpal Instability

May develop if ligaments injured
DISI or VISI pattern
Treatment: May require carpal fusion

Complication Management Summary

Complication	Risk Factors	Prevention	Management
AVN	Neck fracture, rotation	Early fixation, preserve blood supply	Stage-dependent salvage
Nonunion	AVN, inadequate fixation	Stable fixation, bone graft	Revision with vascularized graft
Malunion	Missed rotation	Recognize scaphocapitate	Corrective osteotomy
Arthritis	Malreduction, AVN	Anatomic reduction	Fusion if severe

AVN is the primary concern in capitate fracture management.

Postoperative Care

Immediate Postoperative (0-2 Weeks)

Immobilization

Volar resting splint with thumb
Wrist neutral, thumb in functional position
Allow immediate finger motion
Elevate above heart level

Pain Management

Multimodal analgesia
Ice application
Elevation critical for swelling

Monitoring

Neurovascular checks
Watch for signs of infection
Swelling assessment

Wound Care

Dressing Changes

First change at 48-72 hours
Assess wound healing
K-wire sites need attention if used

Suture Removal

10-14 days postoperatively
Apply steri-strips
Transition to cast

Rehabilitation Phases

Phase 1: Protection (0-6 Weeks)

Thumb spica cast
Active finger motion throughout
Shoulder and elbow ROM
Edema control

Phase 2: Early Motion (6-8 Weeks)

If CT shows healing, begin wrist ROM
Removable splint between exercises
Gentle, progressive range
No loading

Phase 3: Progressive Loading (8-12 Weeks)

Progressive strengthening
Light grip activities
Continue splint protection as needed
Hand therapy guidance

Phase 4: Return to Function (12+ Weeks)

Full ROM and strength focus
Sport-specific activities
Work conditioning
Monitor for late complications

Follow-Up Schedule

Timepoint	Assessment	Imaging
Week 2	Wound, comfort	None
Week 6	Healing assessment	CT scan
Week 8	ROM, K-wire removal	Radiographs
Week 12	Function	As needed
Month 6	Final outcome	Consider MRI
Year 1	AVN surveillance	If symptomatic

Rehabilitation is prolonged due to AVN concerns and need for confirmed healing.

Outcomes and Prognosis

Functional Outcomes

Isolated Body Fractures

Generally good outcomes when appropriately treated
ROM recovery 80-90% of contralateral
Grip strength recovery variable
Return to previous activities expected

Neck Fractures

Higher complication rate than body fractures
Meaningful avascular necrosis risk given retrograde proximal-pole supply (rates uncertain owing to rarity and small series)
Outcomes depend on AVN development
May have residual stiffness

Scaphocapitate Syndrome

Outcomes depend on recognition and treatment
Delayed or missed diagnosis worsens prognosis
If properly treated, reasonable outcomes are reported in small series
Higher nonunion and AVN risk than isolated body fractures

Prognostic Factors

Favorable Factors

Body fracture location
Undisplaced pattern
Early diagnosis
Anatomic reduction achieved
Isolated injury

Unfavorable Factors

Neck fracture
Fragment rotation
Delayed diagnosis
Scaphocapitate pattern
Associated carpal injuries
High-energy mechanism

AVN Development

Risk by Pattern

Precise AVN rates are not reliably established because capitate fractures are rare and reported only in small series. The relative risk gradient, however, is consistent across the literature:

Body fractures: lowest risk (fracture is distal to the watershed)
Neck fractures: higher risk (interrupts retrograde supply to the proximal pole)
Scaphocapitate syndrome: highest risk (rotated, devascularised proximal fragment)

The anatomical basis is the proximal pole's exclusive retrograde intraosseous supply across the waist, analogous to the proximal scaphoid (PMID 6386955, 6886331).

Timeline

May develop months to years after injury
Progressive once established
Require salvage procedures if symptomatic

Return to Activity

Conservative Treatment

Light activities: 8-12 weeks
Full activities: 12-16 weeks if healed

Surgical Treatment

Light activities: 8-12 weeks
Full activities: 12-16 weeks
Contact sports: 4-6 months

Long-Term Considerations

Patients should be counseled about:

Risk of late AVN development
Need for surveillance imaging if symptomatic
Potential for salvage procedures
Generally good outcomes with appropriate treatment

Prognosis depends on fracture pattern and AVN development.

Evidence Base

Level V

Fenton RL. The naviculo-capitate fracture syndrome

Key Findings:

Original description of the naviculo-capitate (scaphocapitate) fracture syndrome
Combined scaphoid waist and capitate neck fractures with rotation of the proximal capitate fragment
Proposed hyperextension with axial load as the mechanism
Established that the rotated proximal fragment must be recognised and reduced

Clinical Implication: The founding description of scaphocapitate syndrome; recognising rotation of the proximal capitate fragment remains the defining diagnostic and operative challenge. (No DOI: pre-DOI-era 1956 publication.)

Source: J Bone Joint Surg Am 1956;38-A(3):681-684

Verify on PubMed (PMID 13319423)

Level IV

Vander Grend R, Dell PC, Glowczewskie F, Leslie B, Ruby LK. Intraosseous blood supply of the capitate and its correlation with aseptic necrosis

Key Findings:

Cadaveric injection study plus five patients with proximal-pole aseptic necrosis
The proximal pole is supplied exclusively in retrograde fashion across the capitate waist, analogous to the proximal scaphoid
Palmar vessels contribute the majority of the capitate blood supply
Aseptic necrosis without collapse was managed with curettage and bone grafting; collapse with arthrosis required intercarpal fusion

Clinical Implication: Provides the anatomical basis for retrograde proximal-pole vascularity and the resulting avascular necrosis risk after waist/neck fractures, and stages salvage by collapse.

Source: J Hand Surg Am 1984;9(5):677-683

Verify on PubMed (PMID 6386955)

Level IV

Rand JA, Linscheid RL, Dobyns JH. Capitate fractures: a long-term follow-up

Key Findings:

Capitate fractures should be treated as aggressively as scaphoid fractures
Anatomic reduction is required to restore carpal kinematics, with open reduction if needed
Even a proximal-pole fragment free of soft-tissue attachments can unite with adequate reduction and immobilisation
Some post-traumatic carpal arthrosis may still be seen at long-term follow-up

Clinical Implication: Supports anatomic reduction and adequate immobilisation/fixation and warns that arthrosis can develop even with optimal treatment.

Source: Clin Orthop Relat Res 1982;(165):209-216

Verify on PubMed (PMID 7075062)

Level IV

Panagis JS, Gelberman RH, Taleisnik J, Baumgaertner M. The arterial anatomy of the human carpus. Part II: the intraosseous vascularity

Key Findings:

Twenty-five cadaver limbs studied by injection and Spalteholz clearing
The capitate, scaphoid and 20% of lunates form Group I, with large areas dependent on a single intraosseous vessel
Group I bones are at greatest risk of avascular necrosis after fracture
Trapezoid/hamate (Group II) and trapezium/triquetrum/pisiform (Group III) carry lower AVN risk

Clinical Implication: Classifies the capitate among the carpal bones most vulnerable to post-traumatic avascular necrosis, explaining the AVN risk pattern.

Source: J Hand Surg Am 1983;8(4):375-382

Verify on PubMed (PMID 6886331)

Level IV

Gelberman RH, Gross MS. The vascularity of the wrist: identification of arterial patterns at risk

Key Findings:

Seventy-five cadaver limbs studied for intra- and extraosseous vascularity
Scaphoid and capitate share a vascular pattern most vulnerable to post-traumatic avascular necrosis
In the capitate a pure intraosseous disruption is sufficient to produce avascular necrosis
Defines at-risk arterial patterns correlated with the clinical incidence of AVN

Clinical Implication: Corroborates that an intraosseous vascular interruption alone can cause capitate avascular necrosis, reinforcing meticulous, soft-tissue-preserving fixation. (No DOI: pre-DOI-era 1986 publication.)

Source: Clin Orthop Relat Res 1986;(202):40-49

Verify on PubMed (PMID 3514029)

Level V

Moneim MS. Management of greater arc carpal fractures

Key Findings:

Reviews greater arc perilunate fracture-dislocations, of which the scaphocapitate syndrome is part
Recommends open reduction and Kirschner-wire/screw fixation of the displaced capitate fragment through a dorsal approach
If the scaphoid is displaced it is also openly reduced and fixed
A dorsal midline approach stabilises the midcarpal joint in transscaphoid perilunate patterns

Clinical Implication: Frames capitate fractures within the greater arc spectrum and supports dorsal open reduction and fixation of the displaced capitate fragment, with the scaphoid addressed when displaced.

Source: Hand Clin 1988;4(3):457-467

Verify on PubMed (PMID 3049639)

The evidence supports early recognition and anatomic surgical treatment for most displaced capitate fractures, with the retrograde proximal-pole blood supply explaining the avascular necrosis risk.

Viva Scenarios

Clinical Decision Scenarios

Use these scenarios to practise clinical reasoning and management decisions

CLINICAL SCENARIOStandard

High-Energy Wrist Injury Evaluation

CLINICAL PROMPT

"A 25-year-old motorcyclist presents after a crash with central wrist pain and swelling. Initial PA radiograph shows no obvious fracture. How do you approach this patient?"

PRACTICAL APPROACH

This is a high-energy wrist injury that requires thorough evaluation given the mechanism. **Initial Assessment:** I would first ensure this patient has been assessed for other injuries given the motorcycle mechanism. After completing the trauma workup, I would focus on the wrist. **Clinical Examination:** I would examine for point tenderness, which may be difficult to localize due to swelling. Central dorsal wrist tenderness after high-energy trauma raises concern for capitate or other carpal injuries. I would also assess for scaphoid tenderness, as scaphocapitate syndrome is a possibility. **Imaging Strategy:** A normal PA radiograph does not exclude significant carpal injury. The capitate is difficult to visualize due to overlapping bones. I would ensure we have a true lateral radiograph to assess carpal alignment. Given the high-energy mechanism and persistent symptoms, I would obtain a CT scan, which is essential for diagnosing occult carpal fractures including capitate injuries. **What I Would Look For on CT:** - Capitate fracture, particularly through the neck - Associated scaphoid fracture (scaphocapitate syndrome) - Fragment rotation - Carpal alignment and ligament integrity **If CT Confirms Capitate Fracture:** I would classify the fracture by location and assess for rotation. Most capitate fractures, especially neck fractures, require surgical fixation due to the high AVN risk. If scaphocapitate syndrome is present, both bones need ORIF with careful attention to derotating the proximal capitate fragment.

KEY CLINICAL POINTS

High-energy mechanism requires thorough evaluation

Normal PA X-ray does not exclude capitate fracture

CT is essential for diagnosis

Look for scaphocapitate syndrome

COMMON PITFALLS

Accepting normal plain films as excluding injury

Missing associated carpal fractures

Not obtaining CT for high-energy wrist trauma

FURTHER QUESTIONS

"What findings on CT would indicate scaphocapitate syndrome?"

"How would you differentiate capitate fracture from other central wrist pain causes?"

"What is the urgency of surgical intervention?"

CLINICAL SCENARIOChallenging

Scaphocapitate Syndrome Management

CLINICAL PROMPT

"CT confirms a scaphoid waist fracture and capitate neck fracture. The proximal capitate fragment appears rotated 180 degrees. How do you manage this injury?"

PRACTICAL APPROACH

This is scaphocapitate syndrome, also known as Fenton's syndrome. This classic injury pattern requires surgical management. **Understanding the Injury:** The mechanism involves hyperextension with axial load. The dorsum of the capitate head impacts the radius, fracturing the capitate neck. The scaphoid waist fractures from bending forces. As the wrist returns to neutral, the proximal capitate fragment rotates 180 degrees, so its articular surface now faces the fracture site instead of the lunate. **Treatment Goals:** 1. Derotate the proximal capitate fragment to restore normal anatomy 2. Reduce and fix both fractures 3. Achieve stable fixation allowing early motion 4. Minimize AVN risk by preserving blood supply **Surgical Technique:** I would use a dorsal approach through the 3rd and 4th extensor compartments. After capsulotomy: First, I would address the capitate: 1. Identify the rotated proximal fragment 2. Insert a K-wire as a joystick 3. Carefully derotate 180 degrees until the articular surface faces proximally 4. Reduce to the distal fragment and provisionally K-wire 5. Fix with a headless compression screw Then the scaphoid: 1. Reduce the waist fracture 2. Fix with a headless compression screw **Postoperative Care:** Thumb spica cast for 6-8 weeks. CT at 6-8 weeks to assess healing before mobilization. Long-term surveillance for AVN of both bones is essential. **Prognosis:** With proper treatment, outcomes can be reasonable, but the avascular necrosis risk is real and is highest in this rotated-fragment pattern. Exact rates are uncertain given the rarity of the injury, so the patient must understand the AVN risk and the need for follow-up.

KEY CLINICAL POINTS

Fenton's syndrome = scaphocapitate with rotation

Proximal capitate rotates 180 degrees

Must derotate before fixation

Fix both bones with headless screws

COMMON PITFALLS

Fixing capitate without correcting rotation

Only addressing one of the two fractures

Underestimating AVN risk

FURTHER QUESTIONS

"How do you recognize that the fragment is rotated 180 degrees?"

"What is your preferred fixation for the scaphoid component?"

"What is your postoperative surveillance protocol for AVN?"

CLINICAL SCENARIOChallenging

Capitate AVN Management

CLINICAL PROMPT

"A patient returns 8 months after ORIF of a capitate neck fracture. Despite initial healing, they now have worsening wrist pain. MRI shows AVN of the proximal capitate. How do you manage this complication?"

PRACTICAL APPROACH

This patient has developed avascular necrosis of the proximal capitate, which is the most significant complication of capitate fractures. **Assessment:** I would take a detailed history regarding pain severity, location, and functional impact. I would examine for range of motion, which is likely reduced, and point tenderness over the capitate. **Imaging Review:** I would review the MRI to assess the extent of AVN and any early collapse. I would also obtain updated radiographs to look for carpal collapse or arthritis. CT can help assess bony architecture. **Staging:** Similar to Kienbock's disease for the lunate, AVN severity determines treatment: - Early: Bone preserved, no collapse - Intermediate: Beginning collapse - Advanced: Collapse with secondary arthritis **Treatment Options:** For early AVN without collapse: - Trial of conservative treatment with splinting, activity modification - Consider core decompression with or without bone grafting - Vascularized bone graft may promote revascularization For intermediate disease with collapse: - Proximal row carpectomy if lunate and capitate head cartilage acceptable - Limited intercarpal fusion (scaphoid-trapezium-trapezoid) - Consider capitate excision with interposition For advanced disease with arthritis: - Total wrist fusion provides reliable pain relief - Wrist arthroplasty in selected patients - Proximal row carpectomy if articular surfaces permit **My Recommendation:** Given this is 8 months post-injury with established AVN, I would counsel the patient that conservative management may provide temporary relief but the condition typically progresses. I would discuss surgical options based on the extent of disease and their functional requirements. For a young patient, I would try to preserve motion as long as possible before proceeding to fusion.

KEY CLINICAL POINTS

AVN is the major late complication of capitate fractures

Treatment depends on stage and articular surfaces

Try to preserve motion in young patients

Fusion is reliable for advanced disease

COMMON PITFALLS

Not adequately staging the AVN

Rushing to fusion when salvage possible

Not counseling about progressive nature

FURTHER QUESTIONS

"When would you consider vascularized bone grafting?"

"What are the contraindications to proximal row carpectomy?"

"How do you counsel about return to work expectations?"

MCQ Practice Points

Fracture Frequency

Q: What percentage of carpal fractures involve the capitate? A: Capitate fractures account for only 1-2% of all carpal fractures, making them among the rarest carpal injuries. Their central, protected location requires significant force to fracture.

Scaphocapitate Syndrome

Q: What is the characteristic feature of scaphocapitate (Fenton's) syndrome? A: The proximal capitate fragment rotates 180 degrees so its articular surface faces the fracture site instead of the lunate. This occurs as the wrist returns to neutral after hyperextension injury.

Blood Supply Pattern

Q: Why is the capitate proximal pole vulnerable to AVN? A: The capitate has a retrograde blood supply similar to the scaphoid. Vessels enter through the dorsal non-articular surface and supply the proximal pole in retrograde fashion. Neck fractures disrupt this supply.

Imaging Modality

Q: What is the imaging modality of choice for diagnosing capitate fractures? A: CT scanning is essential. Plain radiographs often miss capitate fractures due to overlapping carpal bones. CT also reveals fragment rotation in scaphocapitate syndrome.

Associated Injuries

Q: What percentage of capitate fractures have associated carpal injuries? A: Over 50% of capitate fractures occur with other carpal injuries, most commonly scaphoid fractures (scaphocapitate syndrome), perilunate injuries, or other carpal fractures.

Treatment Priority

Q: In scaphocapitate syndrome, which bone should be addressed first surgically? A: The capitate should be reduced and fixed first. The rotated proximal fragment must be derotated 180 degrees before fixation. Then the scaphoid is reduced and fixed.

Understanding these key concepts will help with exam success.

Guidelines, Registries & Global Practice

Global Epidemiology

Capitate fractures are among the rarest carpal injuries worldwide, classically quoted at roughly 1-2% of carpal fractures, with the great majority occurring in young men after high-energy axial loading and hyperextension. Because the scaphoid alone accounts for the large majority of carpal fractures, robust population data for the capitate are scarce and most evidence comes from case series.

Carpal Fracture Epidemiology in Context

Metric	Figure / Finding	Source population
Scaphoid as share of carpal fractures	Most common carpal fracture; scaphoid approx 2.4% of all wrist fractures	US NEISS database (Van Tassel/Wolf, PMID 20684922)
Scaphoid fracture incidence	Approx 12.4 per 100,000/year; peak in males 15-19 years	UK regional cohort (Garala/Dias, PMID 27143737)
Demographic of capitate fracture	Young adult male predominance, high-energy mechanism	Case series (Rand/Linscheid/Dobyns, PMID 7075062)
Capitate AVN vulnerability	Group I carpal bone (single dominant intraosseous vessel)	Cadaveric vascular studies (PMID 6886331, 3514029)

Guidance Across Major Bodies

No society publishes a capitate-specific guideline; management is extrapolated from carpal/perilunate injury principles and the historical case-series literature. The table summarises how the major bodies' frameworks apply.

Guideline Frameworks Applied to Capitate Fractures

Body / region	Relevant guidance	Evidence level
AO Foundation (global)	Anatomic reduction and stable fixation of displaced carpal fractures; address perilunate/greater-arc components	Expert consensus / Level V
BOA / BOAST (UK)	High-energy wrist injuries follow open-fracture and major-trauma standards; CT where plain films are inconclusive	Consensus standard
AAOS (US)	No capitate-specific clinical practice guideline; managed under general carpal fracture principles	Not graded
EFORT / European	Maintain suspicion of occult carpal injury after high-energy trauma; cross-sectional imaging for diagnosis and planning	Consensus / Level V

Registry Evidence

Capitate fractures are not tracked by the national arthroplasty registries (NJR, AJRR, AOANJRR, SHAR, Norwegian, NZJR), which capture joint replacements rather than carpal trauma. The evidence base therefore rests on case series and cadaveric vascular studies rather than registry data. Registries become relevant only at the salvage end of the spectrum (for example total wrist arthroplasty for post-AVN arthritis), where implant survival data inform the choice between arthrodesis and arthroplasty.

Global Practice Variation

Imaging access: In high-resource settings CT is the default for diagnosis and planning, and MRI is added for vascularity; where cross-sectional imaging is limited, diagnosis depends on a high index of suspicion, repeat radiographs and clinical follow-up, so missed scaphocapitate syndrome is more likely.
Fixation hardware: Headless compression screws are standard where available; K-wire fixation remains a wholly acceptable and widely used alternative in resource-limited environments and for small fragments.
Referral pathways: Complex perilunate and scaphocapitate patterns are concentrated in units with hand/wrist expertise globally; initial stabilisation and imaging are performed at the presenting hospital with onward referral for definitive reconstruction.