High Yield Overview

CAPITATE FRACTURES

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

Examiner's 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 - Fracture Features

Central location

Protected by surrounding carpals - high energy needed

AVN risk

Retrograde blood supply like scaphoid

Proximal pole vulnerable

Most at risk for avascular necrosis

Imaging with CT

Plain films often miss - CT essential

Transscaphoid variant

Scaphocapitate syndrome classic pattern

Associated injuries

50% have other carpal injuries

Turned fragment

Proximal fragment may rotate 180 degrees

Early fixation

ORIF to reduce AVN and nonunion risk

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

Mnemonic

FENTON - Scaphocapitate Syndrome

Fenton's syndrome

Eponymous name for scaphocapitate fracture

Extension mechanism

Hyperextension injury to wrist

Neck of capitate

Fracture through capitate waist

Two bones fractured

Scaphoid waist + capitate neck

One-eighty rotation

Proximal capitate rotates 180 degrees

Need ORIF

Surgical reduction and fixation required

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

Mnemonic

RARE - Why Capitate Fractures Are Uncommon

Recessed position

Sits deep in carpal concavity

Adjacent protection

Surrounded by other carpals

Requires high energy

Protected location needs significant force

Easily missed

Overlapping bones obscure on X-ray

Memory 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 often non-specific; maintain high index of suspicion after high-energy wrist trauma.

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
AVN risk 10-30%
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
Higher nonunion and AVN rates

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

Body fractures: 5-10%
Neck fractures: 15-30%
Scaphocapitate: 20-40%

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:

First description of scaphocapitate syndrome
180-degree rotation of proximal capitate fragment
Mechanism is hyperextension with axial load
Both bones must be fixed surgically

Clinical Implication: The classic description of scaphocapitate syndrome established the importance of recognizing fragment rotation.

Source: J Bone Joint Surg Am 1956

Level V

📚 Stein F, Siegel MW. Naviculocapitate Fracture Syndrome: A Case Report

Key Findings:

Confirmed Fenton's mechanism
Rotation occurs as wrist returns to neutral
Early surgery improves outcomes
Delayed treatment associated with complications

Clinical Implication: Early surgical intervention for scaphocapitate syndrome reduces complication rates.

Source: J Bone Joint Surg Am 1969

Level IV

📚 Rand JA et al. Isolated Fractures of the Capitate

Key Findings:

Isolated capitate fractures are rare
AVN rate 10-15% for neck fractures
Conservative treatment possible for undisplaced body fractures
ORIF recommended for displaced fractures

Clinical Implication: Fracture location determines treatment approach and prognosis.

Source: Clin Orthop Relat Res 1982

Level IV

📚 Panagis JS et al. The Arterial Anatomy of the Capitate

Key Findings:

Retrograde blood supply to proximal pole
Similar pattern to scaphoid
Neck fractures disrupt proximal blood supply
Explains high AVN rate for neck fractures

Clinical Implication: Understanding capitate blood supply explains AVN risk pattern and guides surgical technique.

Source: J Hand Surg Am 1983

Level V

📚 Viegas SF et al. Capitate Fractures and Injuries

Key Findings:

Over 50% associated with other carpal injuries
CT essential for diagnosis and planning
Scaphocapitate syndrome often missed initially
Early ORIF improves outcomes

Clinical Implication: High rate of associated injuries requires systematic evaluation and early surgical intervention.

Source: Hand Clin 2000

The evidence supports early recognition and surgical treatment for most capitate fractures.

Viva Scenarios

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

High-Energy Wrist Injury Evaluation

EXAMINER

"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?"

EXCEPTIONAL ANSWER

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 POINTS TO SCORE

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 TRAPS

✗Accepting normal plain films as excluding injury

✗Missing associated carpal fractures

✗Not obtaining CT for high-energy wrist trauma

LIKELY FOLLOW-UPS

"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?"

VIVA SCENARIOChallenging

Scaphocapitate Syndrome Management

EXAMINER

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

EXCEPTIONAL ANSWER

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 are reasonable, but there is still a 20-40% AVN rate. The patient must understand this risk and the need for follow-up.

KEY POINTS TO SCORE

Fenton's syndrome = scaphocapitate with rotation

Proximal capitate rotates 180 degrees

Must derotate before fixation

Fix both bones with headless screws

COMMON TRAPS

✗Fixing capitate without correcting rotation

✗Only addressing one of the two fractures

✗Underestimating AVN risk

LIKELY FOLLOW-UPS

"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?"

VIVA SCENARIOChallenging

Capitate AVN Management

EXAMINER

"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?"

EXCEPTIONAL ANSWER

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 POINTS TO SCORE

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 TRAPS

✗Not adequately staging the AVN

✗Rushing to fusion when salvage possible

✗Not counseling about progressive nature

LIKELY FOLLOW-UPS

"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.

Australian Context

Capitate fractures are uncommon injuries seen across Australian trauma centers. High-energy mechanisms such as motorcycle accidents and workplace falls in construction and mining industries represent common etiologies.

Given the rarity of isolated capitate fractures, many Australian orthopaedic surgeons may see only a few in their careers. This reinforces the importance of maintaining a high index of suspicion after high-energy wrist trauma and obtaining CT when clinical concern exists.

Major trauma centers in Australian capital cities have the expertise for complex carpal surgery including scaphocapitate syndrome management. Regional patients may require transfer for definitive care, with initial stabilization and imaging at the presenting hospital.

Hand surgery subspecialists provide advanced care for complex patterns and complications such as AVN. The Australian Hand Surgery Society provides resources and continuing education for managing these challenging injuries.

The Australian healthcare system supports comprehensive care pathways for capitate fractures through both public and private sectors, with access to CT imaging and specialist hand surgery consultation.