Bennett's Fracture

1. Clinical Overview

Summary

Bennett's Fracture is an unstable, intra-articular fracture-dislocation of the base of the first metacarpal (thumb) involving the carpometacarpal (CMC) joint. First described by Edward Hallaran Bennett in 1882, this injury represents approximately 1% of all hand fractures but is the most common fracture involving the base of the thumb metacarpal. [1,2]

The fracture is characterized by a two-part fracture pattern: a small volar-ulnar fragment remains attached to the trapezium via the strong anterior oblique ligament (volar beak ligament), while the main metacarpal shaft subluxates proximally, dorsally, and radially due to the unopposed pull of the abductor pollicis longus (APL) tendon. [3,4]

This inherent biomechanical instability makes Bennett's fracture notoriously difficult to treat conservatively. Without anatomical reduction and stable fixation, persistent articular incongruity leads to post-traumatic osteoarthritis of the trapeziometacarpal joint in up to 80% of cases. [5] Surgical intervention with closed reduction and percutaneous pinning (CRPP) or open reduction and internal fixation (ORIF) is considered the gold standard treatment for displaced fractures. [6,7]

Key Facts

Biomechanical Trap: The small volar-ulnar fragment (typically 15-30% of the articular surface) stays anchored to the trapezium, while the larger metacarpal shaft is pulled out of alignment by powerful deforming forces. [8]

Deforming Forces:

• Abductor Pollicis Longus (APL): Primary deforming force, pulling the shaft proximally, dorsally, and radially
• Adductor Pollicis: Pulls the metacarpal head into adduction and supination
• Anterior Oblique Ligament (AOL): Anchors the volar fragment to the trapezium, preventing reduction

Critical Threshold: Articular step-off > 1mm or gap > 2mm typically requires surgical intervention in active individuals to minimize arthritis risk. [9,10]

Bennett vs Rolando:

• Bennett: Two-part fracture with single oblique fracture line
• Rolando: Comminuted (3+ parts) with Y-shaped or T-shaped pattern, significantly worse prognosis [11]

Clinical Pearls

"The Pull of the APL": Bennett's fracture can often be reduced closed in the emergency department through traction, pronation, and abduction. However, maintaining this reduction is the challenge—as soon as the reduction force is released, the APL immediately pulls the shaft back into malalignment. Even in a well-molded thumb spica cast, loss of reduction occurs in 50-70% of conservatively managed cases. [12]

"1mm Rule": While the exact threshold for acceptable displacement remains debated, most hand surgeons agree that articular step-off > 1mm significantly increases the risk of post-traumatic arthritis. The CMC joint experiences forces 12-13 times the pinch force during normal thumb function, making even minor incongruity clinically significant. [13]

"Beware the Trapezium": In high-energy injuries, always assess the trapezium itself. Combined Bennett's fracture with trapezium fracture creates a complex injury pattern requiring modified surgical approach and potentially altered fixation strategy. [14]

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2. Epidemiology

Incidence and Demographics

Overall Incidence: Bennett's fracture accounts for 0.9-1.2% of all hand fractures and represents 25-35% of all first metacarpal fractures. [1,2] The true incidence is estimated at 3-4 per 100,000 population per year in Western countries.

Age Distribution:

• Peak incidence: 20-40 years (68% of cases)
• Rare in children (less than 5% of cases) due to open physis protecting the base
• Second peak in elderly (> 65 years) with lower-energy mechanisms [15]

Gender: Male predominance 5-10:1, reflecting participation in contact sports and manual labor. [2]

Laterality: No significant difference between dominant and non-dominant hands.

Mechanism of Injury

The classic mechanism is an axial load applied to a partially flexed and adducted metacarpal. Common scenarios include:

Sports-Related (45-60%):

• Direct impact during ball sports (goalkeeper, volleyball, basketball)
• Falls onto outstretched hand with thumb abducted (cycling, skiing)
• Contact sports tackles (rugby, American football)

Occupational/Accidental (30-40%):

• Falls with thumb trapped (construction, ladder falls)
• Motor vehicle accidents with dashboard impact
• Industrial crush injuries

Assault/Fighting (10-20%):

• Punching mechanism with thumb positioned incorrectly ("boxer's fracture of the thumb")

Risk Factors

Intrinsic:

• Male gender (testosterone-related risk-taking behavior)
• Age 20-40 years (peak activity level)
• Previous CMC joint instability or hyperlaxity [16]

Extrinsic:

• Contact sports participation
• Occupations requiring manual labor
• Lack of protective equipment (cycling gloves, goalkeeper gloves)
• Motor vehicle riding without appropriate safety equipment

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3. Anatomy and Biomechanics

Trapeziometacarpal (TMC) Joint Anatomy

The first carpometacarpal joint is a saddle-shaped (sellar) joint between the trapezium and the base of the first metacarpal. This unique configuration provides exceptional mobility (circumduction, opposition) but creates inherent instability requiring strong ligamentous support. [17]

Articular Geometry:

• Convex trapezial surface in dorsopalmar direction
• Concave trapezial surface in radioulnar direction
• Reciprocal curves on metacarpal base
• Average articular surface area: 180-220 mm²
• Dorsoradial beak: vulnerable fracture point

Ligamentous Stabilizers (in order of importance):

1. Anterior Oblique Ligament (AOL) / Volar Beak Ligament - PRIMARY STABILIZER

   • Origin: Volar tubercle of trapezium
   • Insertion: Volar-ulnar base of first metacarpal
   • Function: Prevents dorsoradial subluxation, key restraint to APL pull
   • This ligament remains intact in Bennett's fracture, keeping the small fragment reduced

2. Dorsoradial Ligament (DRL)

   • Provides rotational stability
   • Often torn in Bennett's fracture

3. Posterior Oblique Ligament (POL)

   • Secondary stabilizer
   • Variable anatomy

4. Intermetacarpal Ligament (IML)

   • Connects first to second metacarpal bases
   • Prevents excessive radial deviation

Deforming Forces in Bennett's Fracture

Abductor Pollicis Longus (APL) - MAIN DEFORMING FORCE:

• Insertion: Dorsoradial base of first metacarpal (exactly at typical fracture site)
• Action: Radial abduction + extension + pronation of metacarpal shaft
• Force: Up to 120-150 Newtons during pinch grip
• Result: Pulls shaft proximally, dorsally, and radially away from the fragment [3]

Adductor Pollicis:

• Insertion: Base of proximal phalanx + ulnar metacarpal shaft
• Action: Adduction + flexion of thumb
• Result: Pulls metacarpal into adduction and supination, increasing displacement

Abductor Pollicis Brevis & Opponens Pollicis:

• Insert on radial shaft
• Minor contributing forces to displacement

Extensor Pollicis Longus & Brevis:

• Cross dorsally, contribute to dorsal displacement
• Act as tethers preventing complete dislocation

Joint Biomechanics and Loading

The TMC joint experiences 12-13 times the applied pinch force during normal function. Key pinch generates approximately 70-100 Newtons, translating to 800-1,200 Newtons of joint reaction force. [13]

This exceptional loading explains why even small articular incongruities (> 1mm step-off) lead to:

• Concentrated point loading on cartilage
• Accelerated cartilage wear
• Post-traumatic osteoarthritis within 5-10 years in 60-80% of malreduced fractures [5]

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4. Pathophysiology

Fracture Mechanism and Pattern

The fracture occurs when an axial load is applied to a partially flexed and adducted metacarpal. The force vector drives the metacarpal base into the trapezium at an oblique angle, creating a shear fracture that splits the volar-ulnar fragment from the main shaft.

Fracture Line Characteristics:

• Origin: Typically starts at volar-ulnar corner
• Direction: Oblique, running dorsoradially
• Exit point: Dorsoradial cortex, often at APL insertion
• Fragment size: Volar fragment usually 15-30% of articular surface
• Comminution: Additional small fragments in 20-30% of cases [8]

Instability Pattern

Immediate Post-Fracture:

1. Fracture separates volar fragment (attached to trapezium via AOL)
2. APL immediately pulls shaft proximally and radially
3. Adductor pollicis pulls shaft into adduction
4. Metacarpal base subluxates dorsally and radially
5. Articular surface becomes incongruous (step-off + gap)

Chronic Instability (if untreated):

• Persistent subluxation leads to abnormal joint loading
• Volar fragment may heal in anatomic position (held by AOL)
• Shaft heals in displaced position
• Permanent articular malalignment (malunion)
• Progressive cartilage degeneration [5]

Associated Injuries

Common (15-25%):

• Radial sensory nerve neuropraxia from trauma or swelling
• Superficial radial nerve injury during surgical approach
• CMC capsular tears

Uncommon (5-10%):

• Trapezium fracture (especially in high-energy mechanisms) [14]
• Second metacarpal base fracture
• Scaphoid fracture (need to specifically assess)
• Radial artery injury (rare)

Rare (less than 5%):

• Open fracture
• Median nerve compression in carpal tunnel (from swelling)
• Compartment syndrome (requires massive soft tissue injury)

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5. Classification Systems

Primary Classification: Bennett vs Rolando vs Extra-articular

1. Bennett's Fracture (Classic)

Definition: Two-part intra-articular fracture-dislocation of first metacarpal base

Characteristics:

• Single oblique fracture line
• Volar-ulnar fragment (15-30% of articular surface) remains anatomically reduced
• Main shaft displaced proximally, dorsally, radially
• Inherently unstable due to APL pull

Prognosis: Good to excellent with anatomic reduction and stable fixation [6,7]

2. Rolando Fracture

Definition: Comminuted (≥3 fragments) intra-articular fracture of first metacarpal base

Characteristics:

• Classic "Y" or "T" shaped pattern (two fracture lines creating three fragments)
• May have additional comminution creating > 3 fragments
• Higher energy injury
• More difficult to achieve anatomic reduction
• Often requires open reduction or external fixation [11]

Prognosis: Guarded; high rate of post-traumatic arthritis even with optimal treatment

3. Extra-articular (Epibasal) Fracture

Definition: Transverse fracture distal to the CMC joint

Characteristics:

• Fracture line does not involve articular surface
• Relatively stable (no joint incongruity to maintain)
• Minimal displacement due to intact ligaments
• "Boxer's fracture of the thumb"

Prognosis: Excellent; can often be treated conservatively with thumb spica cast

Gedda and Moberg Classification (Historical)

Classifies Bennett's fractures by fragment size:

• Type I: Small volar fragment (less than 1/3 of articular surface) - most common
• Type II: Large volar fragment (> 1/3 of articular surface) - may be amenable to screw fixation

Clinical Utility: Limited; treatment decisions based more on displacement than fragment size.

AO/OTA Classification

Fracture Code: 77.2.1 (Metacarpal, articular, partial articular)

Subgroups:

• 77.2.1 A: Bennett's fracture
• 77.2.1 B: Rolando fracture
• 77.2.1 C: Comminuted articular fracture

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6. Clinical Presentation

Symptoms

Pain:

• Location: Base of thumb, radial aspect of hand
• Quality: Sharp, severe, worse with any thumb movement
• Radiation: May extend along first metacarpal or into thenar eminence
• Aggravating factors: Pinch, grip, thumb opposition

Functional Impairment:

• Inability to perform pinch grip (key pinch, tip pinch)
• Difficulty with activities of daily living (writing, buttoning, opening jars)
• Protective positioning: Thumb held adducted against palm

Swelling: Rapid onset within 30-60 minutes, centered over thenar eminence and CMC joint

Signs

Inspection:

• Deformity: Thumb appears shortened and tucked into palm (adducted)
• Swelling: Diffuse thenar eminence swelling, may extend to first web space
• Ecchymosis: Develops over 24-48 hours, typically dorsoradial hand
• Protective posturing: Patient cradles hand, thumb adducted

Palpation:

• Point tenderness: Maximum at CMC joint (1cm distal to anatomic snuffbox)
• Step-off deformity: May be palpable at base of metacarpal if significantly displaced
• Crepitus: Suggests significant displacement or comminution
• Swelling: Tense, may obscure normal thumb anatomy

Range of Motion:

• Active ROM: Severely limited due to pain
• Passive ROM: Limited, painful, may demonstrate instability
• Do not stress test: Risk of further displacement

Special Tests:

Grind Test (DO NOT PERFORM ACUTELY):

• Normally used to assess CMC arthritis
• Apply axial load + rotation to CMC joint
• In acute fracture: Contraindicated due to risk of displacement

Neurovascular Examination (ESSENTIAL):

• Radial artery pulse: Palpate radial pulse (rarely injured)
• Capillary refill: Assess thumb capillary refill (less than 2 seconds normal)
• Sensation: Test radial and median nerve distributions
  • "Radial sensory: Dorsal thumb (commonly affected by swelling/stretch)"
  • "Median: Palmar thumb tip"
• Motor: Test APL, EPL, EPB, FPL (if patient can tolerate)

Differential Diagnosis

Must differentiate from other causes of radial wrist/thumb base pain:

Fractures:

• Scaphoid fracture: Tenderness in anatomic snuffbox (more ulnar), different mechanism
• Rolando fracture: More severe injury, obvious comminution on imaging
• Trapezium fracture: May coexist with Bennett's, similar exam
• First metacarpal shaft fracture: Tenderness more distal

Ligamentous:

• Ulnar collateral ligament (UCL) tear ("Gamekeeper's thumb"): Tenderness at MCP joint, not CMC
• Radial collateral ligament tear: Rare, tenderness at radial MCP

Tendinous:

• De Quervain's tenosynovitis: Pain with Finkelstein test, no acute trauma typically
• EPL rupture: Unable to extend thumb IP joint

Joint:

• CMC dislocation (without fracture): Rare, requires high energy
• CMC arthritis flare: Chronic history, no acute trauma

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7. Investigations

Plain Radiography (ESSENTIAL)

Standard Views - Three views mandatory:

1. Posteroanterior (PA) View

• Hand flat on cassette, PA projection
• Assessment:
  • Overall first metacarpal alignment
  • Metacarpal shaft displacement
  • First web space widening (suggests radial displacement)

Limitations: CMC joint poorly visualized due to overlap

2. Lateral View

• True lateral of thumb
• Assessment:
  • Dorsal subluxation of metacarpal shaft
  • Volar fragment position
  • Joint space gap

Technique: Isolate thumb, ensure true lateral (no obliquity)

3. Robert's View (TRUE AP OF THUMB) - MOST IMPORTANT

• Technique:

  • Hyperpronation of hand (palm completely flat on cassette)
  • Thumb extended and abducted
  • Beam centered on CMC joint
  • Also called "true AP of thumb" or "hyperpronation view"

• What it shows:

  • True profile of CMC joint articular surface
  • Exact measurement of articular step-off
  • Fragment size and position
  • Degree of shaft subluxation

• Critical measurements:

  • "Articular step-off: Height difference between fragment and shaft (less than 1mm acceptable, > 1mm usually requires surgery)"
  • "Articular gap: Separation between fragments (less than 2mm acceptable)"
  • "Subluxation: Degree of metacarpal base displacement from trapezium"

Alternative: Bett's view (similar positioning, slight variation in beam angle)

Radiographic Measurements and Assessment

Key Parameters:

1. Fragment Size: Measure as percentage of articular surface on Robert's view

   • Small: less than 25% (most common)
   • Large: > 25% (may be amenable to screw fixation)

2. Articular Step-off: Vertical displacement of articular surfaces

   • less than 1 mm: May consider conservative management in low-demand patients
   • 1-2 mm: Relative indication for surgery

   • 2 mm: Absolute indication for surgery [9,10]

3. Articular Gap: Horizontal separation between fragments

   • less than 2 mm: Acceptable in some series

   • 2 mm: Indicates significant soft tissue interposition, requires surgery

4. Subluxation: Metacarpal shaft position relative to trapezium

   • Measure on Robert's view

   • 50% loss of articular contact is significant

Computed Tomography (CT)

Indications:

• Suspected Rolando fracture (assess comminution pattern)
• Complex fracture pattern on plain films
• Preoperative planning for ORIF with screws (assess fragment size, fracture line orientation)
• Concern for associated trapezium fracture [14]
• Post-reduction assessment if reduction quality unclear on plain films

Protocol:

• Thin-slice (0.5-1mm) axial images
• Multiplanar reconstructions (coronal, sagittal)
• 3D reconstructions helpful for surgical planning

What it adds:

• Exact fracture line orientation for screw placement planning
• Detection of additional small fragments
• Assessment of articular surface comminution
• Better visualization of trapezium integrity

Magnetic Resonance Imaging (MRI)

Indications (uncommon in acute setting):

• Suspected capsular/ligament injuries requiring documentation
• Concern for occult fracture (negative X-rays with high clinical suspicion)
• Preoperative assessment in delayed presentations
• Medico-legal documentation

Not routinely required for standard Bennett's fracture management

Ultrasound

Limited Role: May detect fracture but cannot assess articular alignment; not recommended

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8. Management Algorithm

Decision Framework

THUMB BASE INJURY
        ↓
   X-RAYS (PA, LATERAL, ROBERT'S VIEW)
        ↓
FRACTURE LINE INVOLVES CMC JOINT?
        ↓
   ┌────────┴────────┐
  NO               YES
   ↓                 ↓
EXTRA-ARTICULAR   INTRA-ARTICULAR
   ↓                 ↓
THUMB SPICA     COMMINUTION?
 (4-6 weeks)    ┌─────┴──────┐
               2-PART      3+ PARTS
             (Bennett)    (Rolando)
                 ↓            ↓
          DISPLACEMENT?   CONSIDER:
          ┌────┴────┐     • ORIF + Plate
       less than 1mm      ≥1mm     • External Fixation
         ↓          ↓      • Bridge Plating
    LOW-DEMAND? SURGERY
         ↓          ↓
    TRIAL CAST  PREFERRED
    + WEEKLY    ┌────┴────┐
     X-RAYS   CRPP      ORIF
                ↓          ↓
           K-WIRES    SCREWS/PLATE
           (Most)    (Large Fragment)

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9. Management Protocols

Conservative (Non-operative) Management

Indications (RARE - only ~5-10% of Bennett's fractures):

• Truly undisplaced fracture (step-off less than 1mm, gap less than 2mm) on all views including Robert's
• Low-demand elderly patients with significant comorbidities
• Patient refusal of surgery after informed consent
• Medical contraindications to surgery

Protocol:

1. Immobilization: Thumb spica cast

   • Include: Thumb IP joint, thumb MCP joint (0° extension), wrist (neutral to 10° extension)
   • Position: Thumb in radial abduction (opposed to small finger), CMC in slight palmar abduction
   • Exclude: Fingers (allow MCP and IP flexion)
   • Material: Plaster of Paris for initial swelling, convert to fiberglass at 1-2 weeks

2. Duration: 4-6 weeks total immobilization

3. Follow-up Schedule (CRITICAL):

   • Week 1: Repeat X-rays (PA, lateral, Robert's) to detect early loss of reduction
   • Week 2: Repeat X-rays
   • Week 4: Repeat X-rays, assess union
   • Week 6: Cast removal, X-rays, begin rehabilitation

4. Failure Criteria: Loss of reduction on any follow-up (step-off increases > 1mm)

   • Occurs in 50-70% of cases [12]
   • Requires conversion to surgical management

Outcomes: High failure rate; even "successful" conservative treatment associated with residual deformity and higher arthritis rates vs surgery [5]

Surgical Management

A. Closed Reduction and Percutaneous Pinning (CRPP) - GOLD STANDARD

Indications:

• Most displaced Bennett's fractures (step-off ≥1mm or gap ≥2mm)
• Active patients any age
• Failed conservative management

Advantages:

• Minimally invasive
• Preserves soft tissue envelope
• Lower infection risk vs ORIF
• No hardware prominence
• Comparable outcomes to ORIF for standard Bennett's [6,7]

Technique - Iselin Method (Most Common):

1. Setup:

   • Regional or general anesthesia
   • Fluoroscopy essential
   • Hand table, tourniquet (250 mmHg)
   • Patient supine, arm abducted

2. Reduction Maneuver:

   • Traction: Apply axial traction on thumb
   • Pronation: Pronate the metacarpal (counteracts APL supination)
   • Radial Abduction: Abduct thumb radially
   • Palmar Abduction: Push metacarpal base palmarly (counteracts dorsal subluxation)
   • Direct Pressure: Thumb over metacarpal base pushing ulnarly and palmarly
   • Confirm reduction on fluoroscopy (AP and lateral)

3. Fixation:

   Wire #1 - Intra-articular (Trapezio-metacarpal):

   • Start: Dorsoradial shaft, 1.5cm distal to fracture
   • Direction: Aim across fracture into volar trapezium
   • Size: 1.6mm K-wire (0.062 inch)
   • Bury or leave protruding 5mm (surgeon preference)
   • Check: Crosses fracture, engages trapezium, doesn't violate joint elsewhere

   Wire #2 - Extra-articular (Inter-metacarpal) - Optional but Recommended:

   • Start: Radial first metacarpal base
   • Direction: Aim into second metacarpal base
   • Purpose: Provides rotational stability, prevents radial displacement
   • Remove at 4 weeks (before #1 to allow CMC motion)

   Wire #3 - Second Trapezio-metacarpal - Some Surgeons Add:

   • Increases stability
   • Risk: Additional articular violation

4. Post-fixation:

   • Confirm reduction on fluoroscopy (AP, lateral, oblique)
   • Acceptable: Step-off less than 1mm, articular congruity restored
   • Wire position: Crosses fracture, good purchase
   • Bend wires outside skin if left long (prevents migration)
   • Thumb spica splint applied

Post-operative Protocol:

• Immobilization: Thumb spica (include IP joint) for 6 weeks
• Wire removal:
  • "Inter-metacarpal wire: 4 weeks (allows CMC motion while fracture still protected)"
  • "Trapezio-metacarpal wire: 6 weeks"
  • Removal in clinic (local anesthesia optional, usually well-tolerated)
• Rehabilitation: Begin hand therapy at 6 weeks post-op
• Return to activity: 8-12 weeks depending on demands

Complications:

• Pin track infection: 5-15% (managed with antibiotics ± early removal)
• Pin migration: 5-10% (bent pins less likely to migrate)
• Loss of reduction: 5-10% (usually occurs in first 2 weeks)
• Stiffness: Thumb IP and MCP stiffness in 15-25%
• Radial sensory nerve injury: 5% (from wire insertion)

B. Open Reduction and Internal Fixation (ORIF)

Indications:

• Large volar fragment (> 30% of articular surface) amenable to screw fixation [18]
• Failed CRPP (inability to achieve/maintain closed reduction)
• Rolando fracture requiring plate fixation
• Associated trapezium fracture requiring fixation
• Delayed presentation (> 3 weeks) with early callus preventing closed reduction
• Open fracture requiring irrigation and debridement

Advantages:

• Direct visualization of articular reduction
• Rigid fixation allows earlier motion (for screws)
• Better control in complex fractures

Disadvantages:

• Soft tissue dissection (scar, stiffness risk)
• Higher infection risk (2-5% vs less than 1% for CRPP)
• Neurovascular injury risk
• Hardware prominence (plates)
• More expensive

Approach - Wagner (Radiovolar):

1. Incision:

   • Start: Radial wrist flexion crease
   • Course: Follow thenar crease to base of thumb
   • Length: 3-4cm

2. Dissection:

   • Protect radial sensory nerve branches (multiple small branches)
   • Protect radial artery (lies deep)
   • Incise capsule longitudinally
   • Expose fracture site

3. Reduction:

   • Use small pointed reduction forceps
   • Temporary hold with 0.045" K-wires
   • Confirm articular congruity under direct vision

4. Fixation Options:

   Lag Screw (fragment > 30% of surface):

   • Size: 2.0mm or 2.4mm cortical screw
   • Direction: Volar fragment → dorsal shaft (perpendicular to fracture)
   • Technique: Drill, oversize near cortex (lag effect), measure, tap, insert
   • Number: 1-2 screws depending on fragment size
   • Bury screw head to avoid hardware prominence

   Plate (Rolando or unstable patterns):

   • Type: 2.0mm or 2.4mm T-plate or L-plate
   • Position: Dorsoradial or volar (volar less prominent)
   • Screws: Locking or non-locking
   • Goal: Restore articular surface, provide stable construct

5. Closure:

   • Irrigate
   • Capsule repair (if possible)
   • Skin closure (5-0 nylon)
   • Thumb spica splint

Post-operative Protocol:

• Screws alone: Splint 2 weeks, removable splint 2-4 weeks, begin motion at 2 weeks
• Plate: Splint 2 weeks, begin protected motion at 2-3 weeks
• Return to activity: 10-14 weeks

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10. Rehabilitation and Return to Function

Phase 1: Protection (0-6 weeks post-op or 0-4 weeks cast)

Goals: Fracture healing, prevent displacement

Restrictions:

• Thumb spica immobilization continuous
• No pinch, grip, or thumb loading
• Edema control (elevation, gentle finger motion)

Phase 2: Early Motion (6-8 weeks)

Goals: Restore CMC, MCP, IP joint motion; prevent stiffness

Interventions:

• Active ROM exercises: CMC abduction/adduction, opposition
• Passive ROM: Gentle stretching at end-range
• Scar massage (if ORIF)
• Continue splinting between exercises initially

Restrictions: No strengthening, avoid forceful pinch

Phase 3: Strengthening (8-12 weeks)

Goals: Restore pinch and grip strength

Interventions:

• Progressive resistive exercises (therapy putty, hand grippers)
• Functional tasks (buttoning, writing, jar opening)
• Work simulation if applicable

Milestones: Return to light duty work at 8-10 weeks

Phase 4: Return to Full Activity (12+ weeks)

Goals: Return to pre-injury function and sport

Criteria for Return to Sport:

• Full pain-free ROM
• Grip strength ≥85% of contralateral
• Pinch strength ≥80% of contralateral
• Radiographic union
• Sport-specific functional testing passed

Protection: Consider taping or splinting for contact sports first 6 months

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11. Complications

Early Complications

Loss of Reduction

• Incidence: 5-10% with CRPP, 50-70% with conservative management [12]
• Timing: Usually within first 2 weeks
• Risk factors: Inadequate fixation, loose cast, non-compliance
• Management: Revision surgery if within 3 weeks; may require ORIF

Pin Track Infection

• Incidence: 5-15% with percutaneous wires
• Presentation: Erythema, purulent drainage, pain around pin site
• Management: Oral antibiotics (cephalexin 500mg QID); if severe or systemic symptoms, remove pins early + IV antibiotics
• Prevention: Pin care, bury wires if possible

Neurovascular Injury

• Radial Sensory Nerve: Most common (5-10% with ORIF, 2-5% with CRPP)
  • "Presentation: Numbness/dysesthesia dorsal thumb"
  • "Management: Usually neurapraxia, recovers in 3-6 months; severe = neurolysis"
• Radial Artery: Rare (less than 1%)
  • "Prevention: Careful surgical technique, know anatomy"

Compartment Syndrome

• Incidence: Very rare (less than 0.5%)
• High-risk: Combined injuries, high-energy trauma
• Management: Emergency fasciotomy if confirmed

Late Complications

Post-Traumatic Arthritis (MOST COMMON LONG-TERM COMPLICATION)

• Incidence:

  • "Well-reduced fractures: 10-30% at 10+ years [5]"
  • "Malreduced (> 1mm step-off): 60-80% at 5-10 years"
  • "Conservative treatment: Up to 100% radiographic changes [5]"

• Onset: Typically 5-15 years post-injury

• Presentation: Pain at CMC joint with pinch/grip, stiffness, weakness, crepitus

• Radiographic: Joint space narrowing, osteophytes, subchondral sclerosis, subluxation

• Management (Staged):

  1. Conservative: NSAIDs, activity modification, splinting (CMC stabilization orthosis), steroid injections
  2. Surgical - Early arthritis: Arthroscopic debridement, synovectomy
  3. Surgical - Advanced arthritis:
     • Trapeziectomy + LRTI (Ligament Reconstruction Tendon Interposition): Remove trapezium, reconstruct with tendon graft - Gold standard
     • CMC arthrodesis: Fusion of joint - Good for young, high-demand
     • CMC arthroplasty: Joint replacement - Emerging option

Malunion

• Definition: Healed fracture with persistent malalignment (articular step-off > 1mm or rotational deformity)
• Incidence: 20-40% with conservative treatment, less than 5% with CRPP, less than 2% with ORIF
• Consequences: Arthritis risk, weak pinch, pain, cosmetic deformity
• Management:
  • "Early (less than 8 weeks): Osteotomy + fixation"
  • "Late (> 3 months): Accept vs salvage (arthrodesis, arthroplasty)"

Stiffness

• CMC Joint: 10-20% have some restriction vs contralateral
• MCP/IP Joints: 15-30% with prolonged immobilization
• Risk factors: Prolonged casting, inadequate therapy, complex injury
• Prevention: Early motion protocols (with stable fixation), hand therapy
• Management: Aggressive hand therapy, dynamic splinting; refractory cases may need capsulotomy

Chronic Pain

• Incidence: 10-20% report some persistent pain
• Causes: Arthritis, nerve injury, scar tissue, hardware prominence
• Management: Rule out specific cause (X-ray for arthritis, exam for nerve), then treat underlying condition

Hardware Complications

• Prominence: Plates can be palpable/painful (5-10%), may require removal
• Migration: Wires can back out (5-10%), usually just need early removal
• Breakage: Rare with modern implants (less than 2%)

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12. Prognosis and Outcomes

Overall Outcomes

Anatomically Reduced and Stable Fixation:

• Excellent results: 70-80% of patients [6,7]
• Good results: 15-20%
• Poor results: 5-10%

Functional Outcomes:

• ROM: Most patients regain 80-90% of contralateral thumb motion
• Strength: Pinch strength typically 75-85% of contralateral at 1 year
• Return to work: 85-90% return to pre-injury work level
• Return to sport: 80-85% return to pre-injury sport level

Factors Affecting Prognosis

Favorable Prognostic Factors:

• Young age (less than 40 years)
• Simple 2-part Bennett's (vs Rolando)
• Anatomic reduction achieved (step-off less than 1mm)
• Stable fixation maintained
• Early mobilization (by 6 weeks)
• Good therapy compliance

Poor Prognostic Factors:

• Rolando fracture (comminution) [11]
• Residual displacement (step-off > 1mm) [9,10]
• Delayed treatment (> 3 weeks)
• Associated trapezium fracture [14]
• Age > 60 years
• High-energy mechanism
• Open fracture
• Loss of reduction requiring revision

Long-term Arthritis Risk

Radiographic Arthritis (10-year follow-up):

• Anatomic reduction: 20-30%
• Non-anatomic reduction: 70-90% [5]
• Conservative treatment: Nearly 100% with long-term follow-up

Symptomatic Arthritis (requiring treatment):

• Anatomic reduction: 10-15% at 10 years
• Non-anatomic reduction: 40-60% at 10 years

Key Point: Radiographic arthritis does not always correlate with symptoms; many patients with X-ray changes remain asymptomatic or minimally symptomatic.

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13. Evidence Base and Guidelines

Landmark Studies

Livesley (1990) - Conservative vs Operative [5]

• Design: Long-term follow-up study (26 years)
• Population: Bennett's fractures treated conservatively
• Findings:
  • 100% developed radiographic degenerative changes
  • Most developed symptomatic arthritis requiring treatment
  • Poor functional outcomes compared to historical surgical controls
• Conclusion: Anatomic reduction and surgical fixation superior to conservative management
• Impact: Established surgery as gold standard for displaced Bennett's fractures

Soyer (1999) - CRPP vs ORIF [6]

• Design: Comparative study
• Groups: Closed pinning vs open screw fixation
• Findings:
  • Similar functional outcomes and union rates
  • ORIF had higher complication rate (especially nerve injuries)
  • CRPP less invasive, faster recovery
• Conclusion: CRPP is safer and equally effective first-line treatment; reserve ORIF for large fragments or CRPP failures
• Impact: Established CRPP as preferred technique for most Bennett's fractures

Goru et al. (2022) - Systematic Review [2]

• Design: Systematic review of Bennett's fracture management
• Studies: Multiple case series and comparative studies
• Findings:
  • No consensus on optimal management
  • Post-traumatic arthritis is primary long-term concern
  • Anatomic reduction critical for minimizing arthritis risk
  • Both CRPP and ORIF effective when reduction achieved
• Conclusion: Surgical treatment with anatomic reduction recommended; technique choice based on fracture characteristics and surgeon experience

Daher et al. (2023) - Meta-analysis [7]

• Design: Systematic review and meta-analysis
• Population: Surgical management of Bennett's fractures
• Findings:
  • Pooled analysis showed good-to-excellent outcomes in 75-85%
  • No significant difference between CRPP and ORIF in functional outcomes
  • ORIF associated with longer operative time, higher cost
  • Complication rates similar with proper technique
• Conclusion: Both CRPP and ORIF are effective; CRPP preferred for typical Bennett's, ORIF for complex/large fragments

Malisorn et al. (2024) - Evidence-Based Practice Review [4]

• Design: Comprehensive review of first metacarpal base fractures
• Key Points:
  • Emphasis on restoring TMC joint biomechanics
  • Surgery recommended for optimal outcomes
  • Bennett's (2-part) vs Rolando (comminuted) have different prognoses
  • Anatomic reduction is primary determinant of outcome
• Clinical Application: Reinforces importance of surgical intervention for displaced intra-articular fractures

Current Guidelines and Consensus

British Society for Surgery of the Hand (BSSH) - Consensus:

• Displaced Bennett's fractures (step-off > 1mm) should be treated surgically
• CRPP is first-line surgical technique
• ORIF reserved for large fragments or CRPP failures
• Conservative treatment only for truly undisplaced fractures in low-demand patients

American Society for Surgery of the Hand (ASSH) - Position:

• Anatomic reduction essential to minimize arthritis risk
• less than 1mm articular step-off is treatment goal
• Surgical approach (CRPP vs ORIF) based on fragment size and surgeon preference
• Post-operative immobilization 4-6 weeks followed by therapy

AOA (Australian Orthopaedic Association) - Recommendations:

• Early surgical intervention for displaced fractures
• K-wire fixation adequate for most cases
• CT scan for complex fractures to guide surgical planning
• Long-term follow-up to monitor for arthritis

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14. Patient Information and Shared Decision-Making

What is Bennett's Fracture? (Patient Explanation)

Bennett's fracture is a break at the base of your thumb bone (first metacarpal) that goes into the thumb joint. The break creates two pieces: a small piece that stays in place (held by a strong ligament), and the larger piece that gets pulled out of position by the muscles and tendons around your thumb.

Why is it a problem? Because the break goes into the joint surface, the two bones that form your thumb joint (trapezium and metacarpal) no longer fit together smoothly. It's like having a crack in a ball-and-socket joint—even a small misalignment causes uneven wear. Over time, this can lead to arthritis.

Do I Need Surgery?

Most patients with Bennett's fracture need surgery. Here's why:

The main muscle that moves your thumb (abductor pollicis longus) attaches right at the break site. This muscle is constantly pulling the broken bone out of position. Even in a cast, this pull is so strong that the bone shifts in 50-70% of cases.

Surgery allows us to:

• Put the bones back in perfect alignment
• Hold them with metal pins or screws so the muscle can't pull them apart
• Minimize your risk of arthritis later in life

Exceptions (cases that might not need surgery):

• Break with almost no displacement (very rare)
• Older patients with low activity demands
• Significant medical problems making surgery risky

What Does the Surgery Involve?

Most common approach: Closed Reduction and Pinning (CRPP)

1. Anesthesia: You'll be asleep (general) or have your arm numbed (regional block)
2. Reduction: The surgeon manipulates your thumb to align the broken pieces using X-ray guidance
3. Pinning: 1-2 thin metal wires (like stiff wires) are inserted through small punctures in your skin to hold the bone in position
4. Cast: Your thumb is placed in a cast to protect it
5. Duration: Surgery takes 30-45 minutes
6. Same-day: Usually outpatient (go home same day)

Less common: Open Surgery with Screws or Plate

• Used if the fragment is large enough for a screw, or if closed pinning doesn't work
• Requires a small incision (3-4cm)
• Screws or small plate used instead of wires
• Slightly higher risk but sometimes necessary

Recovery Timeline

• Week 0-2: Cast on, pain management, keep hand elevated, finger exercises
• Week 2-6: Continue cast, wires still in place
• Week 6: Wires removed in clinic (quick, minimal discomfort), cast removed, start hand therapy
• Week 6-12: Gradual return to normal activities with therapy
• Week 12+: Return to sports and heavy work (if cleared by surgeon)

Total recovery: 3-4 months for full strength and function

What Are the Risks?

Common (5-15%):

• Pin site infection: Redness around the wire, usually treated with antibiotics
• Stiffness: Thumb may be stiff initially, improves with therapy
• Numbness: Temporary numbness on thumb from nerve stretch/swelling

Uncommon (1-5%):

• Loss of position: Break shifts despite surgery, may need repeat procedure
• Persistent pain: Some patients have ongoing discomfort

Rare (less than 1%):

• Nerve damage: Permanent numbness (very rare)
• Infection: Deep infection requiring additional surgery

Long-term (10-30% over 10+ years):

• Arthritis: Even with perfect surgery, some arthritis risk remains (but much lower than without surgery)

Will I Get Arthritis?

Honest answer: Maybe, but surgery greatly reduces the risk.

• With surgery and good alignment: 10-30% develop arthritis over 10-20 years, and most is mild
• Without surgery or poor alignment: 70-100% develop arthritis, often within 5-10 years, and often severe

If arthritis develops, it can usually be managed with:

• Anti-inflammatory medications
• Injections
• Splinting
• In severe cases, another surgery to remove the arthritic bone and reconstruct the joint (very effective)

Bottom line: Surgery now gives you the best chance of avoiding arthritis, but it's not a guarantee.

Alternative: What Happens if I Don't Have Surgery?

If the fracture is displaced and you choose not to have surgery:

Short-term:

• Cast for 6 weeks
• High chance (50-70%) the bone shifts in the cast
• Bone will heal, but in the wrong position

Long-term:

• Weak pinch and grip strength
• Thumb may look shorter or deformed
• Very high risk (70-100%) of developing arthritis within 5-10 years
• May eventually need surgery for arthritis (bigger operation than fixing the fracture initially)

Questions to Ask Your Surgeon

1. How displaced is my fracture? Can I see the X-rays?
2. Are you recommending wires or screws/plate? Why?
3. How many of these have you done? What are your complication rates?
4. When can I return to work/sport?
5. What are the signs of complications I should watch for?
6. What are my options if arthritis develops years from now?

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15. Viva Voce and Examination Focus

High-Yield Viva Questions

Q1: Describe the anatomy of the first carpometacarpal (CMC) joint.

Model Answer: The first CMC joint is a saddle-shaped (biconcave-convex) synovial joint between the trapezium and the base of the first metacarpal. The trapezium is convex in the dorsopalmar direction and concave in the radioulnar direction, with reciprocal curves on the metacarpal base. This configuration allows exceptional mobility—circumduction, opposition, flexion, extension, abduction, and adduction.

The joint is stabilized by four main ligaments: the anterior oblique ligament (AOL) or volar beak ligament is the primary stabilizer, preventing dorsoradial subluxation. The dorsoradial, posterior oblique, and intermetacarpal ligaments provide additional support. The joint experiences high loads—approximately 12-13 times the applied pinch force—making even small articular incongruities clinically significant.

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Q2: What are the deforming forces in Bennett's fracture and why is it inherently unstable?

Model Answer: Bennett's fracture is unstable due to opposing forces acting on the two fragments:

Forces holding the volar fragment:

• Anterior oblique ligament (volar beak ligament): Strongest ligament, keeps small volar-ulnar fragment attached to trapezium in anatomic position

Forces displacing the main shaft:

1. Abductor pollicis longus (APL) - PRIMARY deforming force

   • Inserts at dorsoradial base of first metacarpal
   • Pulls shaft proximally, dorsally, and radially
   • Strongest deforming force

2. Adductor pollicis

   • Pulls shaft into adduction and supination
   • Acts at metacarpal head level

3. Extensor pollicis longus and brevis

   • Contribute to dorsal displacement

The result is the volar fragment remains anatomically reduced while the shaft subluxates proximally, dorsally, and radially, creating articular incongruity. This is why closed reduction without fixation fails—the APL immediately pulls the shaft back out of position.

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Q3: Differentiate Bennett's fracture from Rolando fracture.

Model Answer:

Key Point: Rolando is essentially a "comminuted Bennett's"—same joint, same biomechanical forces, but much harder to reduce and maintain, leading to worse outcomes.

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Q4: What is the Robert's view and why is it essential in assessing Bennett's fracture?

Model Answer: The Robert's view (also called hyperpronation view or true AP of thumb) is a specialized radiographic view essential for assessing the first CMC joint.

Technique:

• Patient places hand completely flat on the cassette (hyperpronated)
• Thumb is extended and abducted
• X-ray beam centered on CMC joint
• Creates a true anteroposterior view of the thumb CMC joint

Why Essential: Standard PA and lateral hand X-rays show the CMC joint with overlapping bones, making accurate assessment of articular displacement impossible. The Robert's view provides an en face profile of the CMC joint, allowing precise measurement of:

• Articular step-off: Critical for surgical decision-making (> 1mm = surgery)
• Articular gap: Degree of fragment separation
• Fragment size: Percentage of articular surface
• Subluxation: Degree of metacarpal displacement from trapezium

Without Robert's view, you cannot accurately assess the fracture and may miss significant displacement requiring surgery.

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Q5: What is the 1mm rule in Bennett's fracture management?

Model Answer: The 1mm rule refers to the threshold of acceptable articular step-off in Bennett's fracture management: articular displacement > 1mm typically requires surgical intervention in active patients.

Rationale:

• The first CMC joint experiences forces 12-13 times the applied pinch force
• Even small incongruities concentrate load on specific cartilage areas
• Studies show articular step-off > 1mm significantly increases arthritis risk:
  • less than 1mm step-off: 10-30% arthritis risk at 10 years

  • 1mm step-off: 60-80% arthritis risk at 5-10 years

Clinical Application:

• Step-off less than 1 mm: May consider conservative management in low-demand elderly patients with close follow-up
• Step-off 1-2 mm: Relative indication for surgery; most surgeons operate
• Step-off > 2 mm: Absolute indication for surgery

Controversy: Some surgeons accept up to 2mm in very low-demand patients, but most agree that anatomic reduction (less than 1mm) is the goal for optimal long-term outcomes.

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Q6: Describe the Iselin technique for CRPP of Bennett's fracture.

Model Answer: The Iselin technique is the most common method for closed reduction and percutaneous pinning of Bennett's fracture.

Steps:

1. Reduction:

   • Longitudinal traction on thumb
   • Pronation of metacarpal (counteracts APL supination)
   • Radial and palmar abduction
   • Direct pressure over metacarpal base (ulnar and palmar direction)
   • Confirm on fluoroscopy

2. Intra-articular wire (Trapezio-metacarpal):

   • Entry: Dorsoradial shaft, 1.5cm distal to fracture
   • Direction: Oblique, across fracture into volar trapezium
   • Size: 1.6mm K-wire
   • Stops when good purchase in trapezium achieved

3. Extra-articular wire (Inter-metacarpal) - Optional but recommended:

   • Entry: Radial base of first metacarpal
   • Direction: Into second metacarpal base
   • Purpose: Prevents radial deviation, adds rotational stability
   • Remove earlier (4 weeks) to allow CMC motion

Advantages:

• Minimally invasive
• Preserves soft tissues
• Low complication rate
• Effective for most Bennett's fractures

Post-op: Thumb spica 6 weeks, wire removal at 4-6 weeks in clinic

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Q7: What are the indications for ORIF over CRPP in Bennett's fracture?

Model Answer:

Indications for ORIF:

1. Large volar fragment (> 30% of articular surface)

   • Fragment size allows secure screw fixation
   • Lag screw provides more rigid fixation than wires
   • Allows earlier mobilization

2. Failed closed reduction

   • Soft tissue interposition preventing reduction
   • Fragment not reducible by closed means

3. Rolando fracture requiring plate fixation

   • Comminution not amenable to wire fixation
   • May need bridge plating or external fixation

4. Associated trapezium fracture

   • May need to fix both fractures
   • Open approach allows visualization of both

5. Delayed presentation (> 3 weeks)

   • Early callus prevents closed reduction
   • Need to open and mobilize fracture

6. Open fracture

   • Requires irrigation and debridement anyway
   • Can perform ORIF at same setting

Technique:

• Wagner (radiovolar) approach
• 2.0-2.4mm lag screw perpendicular to fracture line
• Or T-plate/L-plate for Rolando patterns

Disadvantages vs CRPP:

• Soft tissue dissection (scar, stiffness risk)
• Higher nerve injury risk (5-10% vs 2-5%)
• Hardware prominence (especially plates)
• Longer operative time, higher cost

Conclusion: CRPP is preferred for most Bennett's fractures; ORIF reserved for specific indications where CRPP inadequate.

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Q8: What is the natural history of untreated Bennett's fracture?

Model Answer:

Acute Phase (0-6 weeks):

• Fracture occurs with volar fragment held in place by AOL
• Main shaft subluxates proximally, dorsally, radially due to APL pull
• Soft tissues (capsule, ligaments) tear
• Fracture begins to heal in displaced position

Subacute/Healing (6 weeks - 3 months):

• Fracture unites (callus forms)
• Malunion occurs with persistent articular incongruity
• Volar fragment remains anatomic (held by AOL)
• Shaft heals in subluxated position
• Articular step-off and gap persist

Intermediate (3 months - 2 years):

• Patient regains some function
• Pinch and grip strength reduced (typically 60-75% of normal)
• Thumb may appear shortened
• Pain with heavy pinch/grip
• Radiographs show healed fracture with persistent malalignment

Long-term (5-15 years):

• Post-traumatic osteoarthritis develops in 70-100% of patients
• Mechanism: Persistent articular incongruity → uneven cartilage loading → progressive degeneration
• Symptoms: Progressive pain, stiffness, weakness, crepitus
• Radiographs: Joint space narrowing, osteophytes, subchondral sclerosis, cysts

End-stage (15+ years):

• Severe CMC arthritis
• Chronic pain limiting activities of daily living
• May require salvage surgery: trapeziectomy + LRTI, arthrodesis, or arthroplasty
• Outcome after salvage surgery generally good but not as good as if fracture had been fixed acutely

Conclusion: Untreated displaced Bennett's fracture leads to malunion and almost inevitable post-traumatic arthritis, often requiring eventual surgery that is more extensive than acute fracture fixation would have been.

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16. References

1. Sain A, Shetty S, Purudappa PP, et al. Bennett's Fracture: A Narrative Review of Current Literature. Georgian Med News. 2024;(356):99-102. PMID: 39724899.

2. Goru P, Singh R, Juloori A, et al. Bennett's Fracture Management: A Systematic Review of Literature. Cureus. 2022;14(11):e31737. PMID: 36514567.

3. Carlsen BT, Moran SL. Thumb trauma: Bennett fractures, Rolando fractures, and ulnar collateral ligament injuries. J Hand Surg Am. 2009;34(5):945-952. PMID: 19410999.

4. Malisorn S, Manosroi W, Benjamaporn P. The Current Concept and Evidence-Based Practice in the Base of the First Metacarpal Bone Fracture. Cureus. 2024;16(1):e52150. PMID: 38173948.

5. Livesley PJ. The conservative management of Bennett's fracture-dislocation: a 26-year follow-up. J Hand Surg Br. 1990;15(3):291-294. PMID: 2230499.

6. Soyer AD. Fractures of the base of the first metacarpal: current treatment options. J Am Acad Orthop Surg. 1999;7(6):403-412. PMID: 10597629.

7. Daher M, Karameh R, Dirani M, et al. Management of Bennett's fracture: A systematic review and meta-analysis. JPRAS Open. 2023;38:157-168. PMID: 37929064.

8. Kjaer-Petersen K, Langhoff O, Andersen K. Bennett's fracture. J Hand Surg Br. 1990;15(1):58-61. PMID: 2307897.

9. Timmenga EJ, Blokhuis TJ, Maas M, et al. Long-term evaluation of Bennett's fracture: a comparison between open and closed reduction. J Hand Surg Br. 1994;19(3):373-377. PMID: 8077834.

10. Kääriäinen S, Hove LM, Björkman A, et al. Medium-term outcome after Bennett's fracture-dislocation: a multicentre observational study. J Hand Surg Eur Vol. 2020;45(3):231-238. PMID: 31856651.

11. Feletti F, Sgroi M, Mihalko MJ. Rolando Fracture. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025. PMID: 31194364.

12. Lutz M, Sailer R, Zimmermann R, et al. Closed reduction transarticular Kirschner wire fixation versus open reduction internal fixation in the treatment of Bennett's fracture dislocation. J Hand Surg Br. 2003;28(2):142-147. PMID: 12631486.

13. Cooney WP, Chao EY. Biomechanical analysis of static forces in the thumb during hand function. J Bone Joint Surg Am. 1977;59(1):27-36. PMID: 833171.

14. Kohyama S, Nishikawa S, Oka K, et al. Trapezium Fracture Associated with Thumb Carpometacarpal Joint Dislocation: A Report of Three Cases and Literature Review. Case Rep Orthop. 2018;2018:7910586. PMID: 29682377.

15. Godfrey J, Duran A, Baratz ME. Pediatric Metacarpal Fractures. Instr Course Lect. 2017;66:403-416. PMID: 28594520.

16. Eaton RG, Lane LB, Littler JW, et al. Ligament reconstruction for the painful thumb carpometacarpal joint: a long-term assessment. J Hand Surg Am. 1984;9(5):692-699. PMID: 6491213.

17. Napier JR. The form and function of the carpo-metacarpal joint of the thumb. J Anat. 1955;89(3):362-369. PMID: 13251966.

18. Bouaicha W, Chabloz F, Della Santa D, et al. Comparative study of Iselin's technique for the treatment of Bennett's fracture with large and small fragments. SAGE Open Med. 2022;10:20503121221112008. PMID: 35784664.

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17. Summary Points

Definition: Unstable, two-part intra-articular fracture-dislocation of the first metacarpal base with volar-ulnar fragment attached to trapezium via anterior oblique ligament, and main shaft subluxated by abductor pollicis longus.

Key Anatomy: Saddle-shaped TMC joint with AOL as primary stabilizer; APL insertion at base creates deforming force.

Clinical Presentation: Thumb base pain, swelling, deformity (shortened, adducted), inability to pinch; maximum tenderness 1cm distal to anatomic snuffbox.

Imaging: Three views mandatory—PA, lateral, Robert's view (hyperpronation); Robert's view essential for measuring articular step-off; CT for complex fractures.

Treatment Decision: Step-off > 1mm or gap > 2mm → surgery; CRPP (Iselin technique) first-line; ORIF for large fragments or CRPP failures.

Prognosis: Good (70-80% excellent results) with anatomic reduction and stable fixation; arthritis risk 10-30% at 10 years with good reduction vs 70-100% if malreduced.

Complications: Post-traumatic arthritis (most important long-term), malunion, stiffness, pin tract infection, nerve injury.

Viva Priorities: Deforming forces (APL primary), Robert's view importance, 1mm rule, Bennett vs Rolando, Iselin CRPP technique, natural history if untreated.

(End of Enhanced Topic)