Metacarpal Fractures
METACARPAL FRACTURES
Boxer's Fracture | Rotation vs Angulation | Fight Bites | 10-10-30-50 Rule
Critical Must-Knows
- Cardinal rule: NO degree of rotation is acceptable - fingers must converge to scaphoid tubercle on flexion without scissoring
- 10-10-30-50 rule for acceptable neck angulation: 2nd=10°, 3rd=10°, 4th=30°, 5th=50° (increases ulnarly due to CMC mobility)
- Interossei cause apex dorsal angulation (head drops volar, shaft points dorsally)
- Fight bite (laceration over MCP) = human bite until proven otherwise - Eikenella corrodens - requires formal washout + Augmentin
- Shortening greater than 5mm causes extensor lag (loss of extensor tension)
Examiner's Pearls
- "Jahss manoeuvre: Flex MCP + PIP to 90°, push dorsally on proximal phalanx to reduce neck fracture
- "Why 4th/5th tolerate more angulation? CMC joints have 20-30° flexion-extension arc to compensate
- "X-ray CANNOT assess rotation - must check clinically (nail planes, finger cascade, scissoring)
- "Never suture a fight bite wound tightly - leave open for drainage
Clinical Imaging
Imaging Gallery




Exam Warning
The cardinal rule of metacarpal fractures: No degree of rotation is acceptable. Fingers must converge to the scaphoid tubercle on flexion. If they cross (scissoring), surgical correction is needed. Angulation is tolerated progressively from radial to ulnar (2nd < 3rd < 4th < 5th) due to CMC mobility. Boxer's fracture can tolerate up to 40-50 degrees neck angulation.
Anatomy
Deforming Forces
Interossei Muscles:
- Origin from shafts
- Flex MCP, Extend IPJ
- In fractures: Flex the distal fragment
- Result: Apex Dorsal Angulation (Head drops volar)
Acceptable Angulation (Neck Fractures):
- Index (2nd): less than 10-15° (Rigid CMC)
- Middle (3rd): less than 10-15° (Rigid CMC)
- Ring (4th): less than 30-40° (Mobile CMC)
- Little (5th): less than 50-60° (Mobile CMC) - Boxer's
Why the Difference?
- 4th/5th CMC joints have 20-30° flexion/extension arc
- Allows compensation for fixed deformity (pseudoclawing)
- 2nd/3rd CMC joints are rigid pillars
At a Glance
Metacarpal fractures account for 40% of all hand fractures, with the 5th metacarpal neck (Boxer's fracture) being the most common pattern in young males. The cardinal rule is that no degree of rotation is acceptable - fingers must converge to the scaphoid tubercle on flexion without scissoring. Acceptable angulation increases from radial to ulnar (10° for 2nd/3rd, 30° for 4th, 50° for 5th) due to progressive CMC joint mobility. The interossei cause apex dorsal angulation, and any laceration over the MCP joint should be treated as a human "fight bite" requiring washout and antibiotics covering Eikenella corrodens.
10-10-30-50Acceptable Angulation
Memory Hook:Increases ulnarly due to mobile CMCs - 1-1-3-5 easy to remember
ROMISurgical Indications
Memory Hook:ROMI goes to theatre - Rotation, Open, Multiple, Intra-articular
WASHFight Bite Management
Memory Hook:WASH the fight bite properly - don't believe the glass story
Clinical Assessment
Fracture Patterns
Metacarpal Fracture Overview
Epidemiology:
- 40% of all hand fractures
- Most common: 5th metacarpal neck (Boxer's fracture)
- Peak incidence: Young males (10-29 years)
- Common mechanisms: Punch, fall, crush
Key Principles:
- Rotation is NEVER acceptable (cardinal rule)
- Angulation tolerance increases from radial to ulnar
- Mobile 4th/5th CMC joints compensate for apex dorsal angulation
Fracture Location Overview
| Location | Pattern | Treatment |
|---|---|---|
| Neck | Apex dorsal angulation (Boxer's) | Usually conservative |
| Shaft | Transverse, oblique, spiral | Assess rotation carefully |
| Base | Intra-articular (CMC joint) | May need surgery if displaced |
| Head | Intra-articular (MCP joint) | Often need ORIF |
Anatomy
Metacarpal Anatomy
Structure:
- Five metacarpals (1st = thumb, 2nd-5th = fingers)
- Each has head, neck, shaft, and base
- 2nd and 3rd CMC joints are rigid (fixed pillars)
- 4th and 5th CMC joints are mobile (20-30° arc)
Key Structures:
- Interossei muscles originate from shafts
- Extensor tendons run dorsally over MCP joint
- Sagittal bands stabilise extensor over metacarpal head
CMC Joint Mobility
| Ray | CMC Mobility | Angulation Tolerance |
|---|---|---|
| 2nd (Index) | Rigid | 10-15° |
| 3rd (Middle) | Rigid | 10-15° |
| 4th (Ring) | Mobile | 30-40° |
| 5th (Little) | Mobile | 50-70° |
Fracture Types
Classification by Location
Anatomic Classification:
- Head fractures (intra-articular MCP)
- Neck fractures (most common = Boxer's)
- Shaft fractures (transverse, oblique, spiral, comminuted)
- Base fractures (intra-articular CMC or extra-articular)
By Fracture Pattern:
- Transverse: Prone to angulation, stable in rotation
- Oblique: Intermediate stability
- Spiral: Prone to rotation and shortening
- Comminuted: Unstable, often need surgery
Pattern and Implications
| Pattern | Deformity Risk | Fixation Preference |
|---|---|---|
| Transverse | Apex dorsal angulation | Plate or IM screws |
| Oblique (greater than 2x diameter) | Shortening, rotation | Lag screws |
| Spiral | Rotation, shortening | Lag screws or plate |
| Comminuted | Shortening, instability | Plate +/- bone graft |
Examination
Inspection:
- Swelling (dorsal hand)
- Loss of knuckle prominence (depressed head)
- Rotational Alignment:
- Ask patient to make a fist
- Fingertips should all point to Scaphoid Tubercle
- Look for scissoring/overlap
- Compare fingernail planes (should be parallel)
Neurovascular:
- Sensation (Digital nerves)
- Perfusion
Skin:
- "Fight Bite": Laceration over MCP joint from tooth
- Assume infected human bite (Eikenella corrodens)
- Needs washout + antibiotics (Augmentin)
Fight Bites
Any laceration over an MCP joint in a young male is a human bite until proven otherwise. The tooth penetrates the joint capsule in flexion, dragging bacteria in. When the finger extends, the tract seals. These require formal washout (often in theatre) and antibiotics covering Eikenella.
Clinical Context: Never suture a fight bite wound tightly.
Management
Management Algorithm

Indications:
- Stable fractures
- Acceptable angulation
- No rotation
Technique:
- Buddy Strapping: For stable shaft fractures
- Ulnar Gutter Splint: For 4th/5th Metacarpal
- Radial Gutter Splint: For 2nd/3rd Metacarpal
- Position of Safety (Not for fractures!): Intrinsic plus position usually used for immobilisation, BUT:
- Some evidence suggests buddy taping alone allows earlier return to work for Boxer's fractures.
Duration:
- 3-4 weeks immobilisation
- X-ray check at 1 week for position
Radiographic Assessment
Imaging Assessment
Plain Radiographs:
- PA (posteroanterior) of hand
- Lateral of hand
- Oblique of hand
- Assess all 5 metacarpals systematically
What to Assess:
- Fracture location (head, neck, shaft, base)
- Angulation (apex dorsal = most common)
- Shortening (compare to adjacent metacarpal)
- Rotation (cannot assess on X-ray - clinical only)

Special Views
| View | Indication | What It Shows |
|---|---|---|
| Brewerton | MCP collateral ligament injury | Collateral ligament avulsions |
| Skyline | Metacarpal head assessment | Articular surface fractures |
| CT scan | Complex base fractures | CMC joint involvement |
Management Algorithm
Surgical Management
Indications:
- Rotational deformity (ANY)
- Unacceptable angulation (e.g., greater than 50° in 5th neck)
- Shortening greater than 5mm (relative)
- Open fractures
- Multiple metacarpal fractures
- Intra-articular displacement
Techniques:
-
K-wire Fixation:
- Retrograde (intramedullary) or Transverse (pinning to adjacent bone)
- Minimally invasive, wire removal later
-
ORIF (Plate/Screws):
- For shaft fractures, unstable patterns
- Anatomical reduction
- Risk: Tendon adhesions, prominent hardware
-
Intramedullary Screw:
- Newer technique for neck/shaft
- Headless compression screw
Poolman et al. Cochrane Review
- Conservative treatment for Boxer's fractures yields good results
- No significant difference between splintering vs wrapping/buddy taping
- Surgery has higher complication rate without clear functional benefit for typical neck fractures
Rotational Malunion Impact
- Each 5° of rotational malunion = 1.5cm fingertip overlap
- Rotational malunion poorly tolerated functionally
- Causes scissoring and weak grip
- Derotational osteotomy at MC shaft required for correction
Fight Bite Infections
- Eikenella corrodens primary pathogen in human bites
- Polymicrobial infection common
- High rate of septic arthritis if treatment delayed
- Amoxicillin-clavulanate provides appropriate coverage
Intramedullary Screw Fixation
- Headless compression screw for MC neck fractures
- Minimally invasive, no hardware removal needed
- Comparable outcomes to K-wires with fewer complications
- Allows early mobilisation
Complications
Complications of Metacarpal Fractures
Complications
Potential Complications
Malunion:
- Apex dorsal angulation: Loss of knuckle, pseudoclawing
- Rotational malunion: Scissoring, poor grip (NOT acceptable)
- Treatment: Corrective osteotomy if symptomatic
Stiffness:
- Most common complication after surgery
- Caused by tendon adhesions, joint contracture
- Prevention: Early mobilisation, stable fixation
Infection:
- Fight bite: High risk if not treated properly
- Pin site infection with K-wires
- Deep infection requires washout
Complication Management
| Complication | Cause | Treatment |
|---|---|---|
| Rotational malunion | Missed rotation, inadequate reduction | Derotation osteotomy |
| Extensor lag | Shortening greater than 5mm | Accept or lengthening osteotomy |
| Stiffness | Prolonged immobilisation | Hand therapy, tenolysis |
| Septic arthritis | Fight bite | Urgent washout, IV antibiotics |
Postoperative Care
Rehabilitation Protocol
Immobilisation Phase (0-3 weeks):
- Splint protection (ulnar or radial gutter)
- Elevation to reduce swelling
- Active finger ROM if fixation stable
- Avoid heavy loading
Mobilisation Phase (3-6 weeks):
- K-wire removal at 4-6 weeks
- Wean from splint
- Active ROM exercises
- Hand therapy referral
Strengthening Phase (6-12 weeks):
- Progressive grip strengthening
- Return to light activities
- Functional exercises
Timeline by Treatment
| Treatment | Immobilisation | Return to Work |
|---|---|---|
| Buddy taping | Immediate ROM | 1-2 weeks light duties |
| Splinting | 3-4 weeks | 4-6 weeks |
| K-wires | 4-6 weeks to removal | 6-8 weeks |
| ORIF plate | 1-2 weeks splint | 8-12 weeks manual |
Outcomes
Functional Outcomes
Overall:
- Excellent outcomes for most metacarpal fractures
- 95% union rate with appropriate treatment
- Stiffness is main complication, especially after surgery
Boxer's Fracture:
- Excellent function even with radiographic malunion
- Loss of knuckle prominence is cosmetic only
- Surgery not superior to conservative for typical patterns
Shaft Fractures:
- Good outcomes if rotation corrected
- Stiffness risk higher with plate fixation
- K-wires associated with less stiffness but less rigid fixation
Outcome by Pattern
| Pattern | Union Rate | Main Concern |
|---|---|---|
| Boxer's (conservative) | Greater than 95% | Cosmetic only |
| Shaft (K-wire) | Greater than 95% | Pin complications |
| Shaft (plate) | Greater than 95% | Stiffness, adhesions |
| Head fracture | 90-95% | MCP arthritis |
Evidence Base
Key Studies
Cochrane Review (Poolman 2005):
- Conservative treatment effective for Boxer's fractures
- No difference between immobilisation methods
- Surgery adds risk without clear benefit for standard patterns
Biomechanical Studies:
- Rotation tolerance: Zero degrees acceptable
- 5° rotation = 1.5cm fingertip overlap
- Shortening greater than 5mm causes extensor lag
Evidence Summary
| Study | Key Finding | Clinical Impact |
|---|---|---|
| Poolman 2005 | Conservative = surgical for Boxer's | Avoid unnecessary surgery |
| Ali 2005 | K-wire biomechanics effective | K-wires are reasonable fixation |
| Kollitz 2014 | Review of treatment options | Algorithm-based approach |
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Boxer's Fracture
"A 22-year-old rugby player presents with a swollen right hand after punching a wall. X-ray shows a 5th metacarpal neck fracture with 40 degrees of volar angulation. There is no rotational deformity clinically. How do you manage this?"
Scenario 2: Third Metacarpal Shaft Fracture with Rotation
"A 30-year-old presents 5 days after a fall onto his hand. X-rays show a short oblique fracture of the third metacarpal shaft with minimal displacement and approximately 15 degrees of apex dorsal angulation. However, on clinical examination, when he makes a fist, you notice that the middle finger crosses over the index finger and the fingernail plane is rotated compared to the adjacent fingers. What is your management?"
Scenario 3: Fight Bite with Septic Arthritis
"A 24-year-old presents to the emergency department 3 days after 'cutting his hand on glass' at a bar. He has a 1cm laceration over the dorsum of his right 3rd MCP joint that he cleaned himself. The wound now has purulent discharge, the MCP joint is swollen and erythematous, and he has pain and restricted motion. He is febrile at 38.5 degrees. X-rays show soft tissue swelling but no fracture or gas. What is your assessment and management?"
MCQ Practice Points
Exam Pearl
Q: What is the maximum acceptable angulation for a fifth metacarpal neck fracture (boxer's fracture) treated non-operatively?
A: Up to 70 degrees of apex dorsal angulation is acceptable for fifth metacarpal neck fractures due to the compensatory motion at the 4th and 5th CMC joints (30-40 degrees of flexion-extension). The fourth metacarpal accepts up to 40 degrees, the third metacarpal 15 degrees, and the second metacarpal (index) only 10-15 degrees because the 2nd and 3rd CMC joints have minimal motion. Rotational deformity is never acceptable and always requires correction.
Exam Pearl
Q: What is the indication for surgical fixation of metacarpal shaft fractures?
A: Surgical indications include: Rotational malrotation (any degree - clinical scissoring), angulation exceeding acceptable limits (varies by ray), multiple metacarpal fractures, open fractures, intra-articular fractures with displacement, and shortening greater than 5mm (causes extensor lag). Spiral fractures are prone to rotational deformity while transverse fractures are prone to angular deformity. Lag screws are ideal for long oblique/spiral patterns; plates for transverse/short oblique/comminuted patterns.
Exam Pearl
Q: How do you clinically assess for rotational malalignment in metacarpal fractures?
A: Finger cascade test: With the MCP joints flexed, all fingers should point toward the scaphoid tubercle. Scissoring: Overlapping of fingers during flexion indicates malrotation. Each 5 degrees of rotational deformity at the metacarpal level results in approximately 1.5cm of digital overlap at the fingertip. Compare tenodesis effect (passive wrist extension causes finger flexion) to the contralateral hand. Rotational deformity is the most poorly tolerated malunion and requires correction.
Exam Pearl
Q: What is the difference between a Bennett's fracture and a Rolando's fracture?
A: Bennett's fracture: Intra-articular fracture-dislocation at the thumb CMC joint with a single volar-ulnar fragment attached to the AOL while the metacarpal shaft subluxates radially and proximally due to APL pull. Rolando's fracture: Comminuted intra-articular fracture at the same location with T or Y pattern (at least 3 fragments). Both require anatomic reduction. Bennett's is typically fixed with K-wires or screw, while Rolando's may need plate fixation or external fixation for severe comminution.
Exam Pearl
Q: What is the reverse Bennett fracture and how is it managed?
A: Reverse Bennett fracture is an intra-articular fracture-dislocation at the fifth CMC joint with a volar-ulnar fragment remaining attached to the hamate while the metacarpal base displaces dorsally and proximally (pulled by ECU). Also called a baby Bennett. Treatment follows similar principles to thumb Bennett's: closed reduction and percutaneous pinning if anatomic reduction achieved, or ORIF for irreducible or significantly displaced fractures. Maintain reduction with splinting in slight flexion.
Australian Context
Australian Healthcare Considerations
Medicare (MBS) Item Numbers:
- 47726: Closed reduction and K-wire fixation
- 47729: Open reduction and internal fixation
- Separate items for multiple fractures
Setting:
- Most Boxer's fractures managed in ED/fracture clinic
- Surgery typically day case procedure
- Hand therapy widely available
Australian Pathway
| Presentation | Setting | Management |
|---|---|---|
| Boxer's (stable) | ED/Fracture clinic | Buddy tape, early review |
| Rotational deformity | Theatre (day case) | K-wires or ORIF |
| Fight bite | Theatre (urgent) | Washout + IV antibiotics |
Metacarpal Fractures Quick Reference
High-Yield Exam Summary
Acceptable Angulation
- •Index/Middle: less than 10-15 degrees (Rigid)
- •Ring: less than 30-40 degrees
- •Little: less than 50-70 degrees (Mobile)
Operation Indications
- •ANY Rotation (fingers scissor)
- •Open fracture
- •Multiple fractures
- •Intra-articular step-off
Fight Bite
- •Laceration over MCP joint
- •Eikenella corrodens
- •Formal washout required
References
- Ali A, et al. Biomechanical stability of intramedullary K-wire fixation of metacarpal neck fractures. J Hand Surg Br. 2005.
- Kollitz KM, et al. Metacarpal fractures: treatment and complications. Hand (NY). 2014.