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OrthoVellum

© 2026 OrthoVellum. For educational purposes only.

Not affiliated with the Royal Australasian College of Surgeons.

Metacarpal Fractures

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Contents
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Hand & Upper LimbHand & Wrist

Metacarpal Fractures

Comprehensive guide to metacarpal fractures for Orthopaedic examination

complete
Updated: 2025-01-15

Metacarpal Fractures

High Yield Overview

METACARPAL FRACTURES

Boxer's Fracture | Rotation vs Angulation | Fight Bites | 10-10-30-50 Rule

40%Of all hand fractures
0°Acceptable rotation (NONE)
5°Rotation = 1.5cm fingertip overlap
50°Max angulation for 5th MC (Boxer's)

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

Preoperative X-ray of the first fracture event. The X-ray shows the fracture of the fifth metacarpal bone shaft of the left hand (red circle).
Click to expand
Preoperative X-ray of the first fracture event. The X-ray shows the fracture of the fifth metacarpal bone shaft of the left hand (red circle).Credit: Choi JS et al. via Arch Plast Surg via Open-i (NIH) (Open Access (CC BY))
Preoperative X-ray of the second fracture event. The X-ray shows refracture and hole-defects of the fifth metacarpal bone shaft of the left hand (red circle).
Click to expand
Preoperative X-ray of the second fracture event. The X-ray shows refracture and hole-defects of the fifth metacarpal bone shaft of the left hand (red Credit: Choi JS et al. via Arch Plast Surg via Open-i (NIH) (Open Access (CC BY))
(a) X-ray of the hand showing fractures involving the shaft of the 1st and base of the 2nd metacarpal of right hand following a blast injury (b) Postoperative X-ray of same patient showing composite f
Click to expand
(a) X-ray of the hand showing fractures involving the shaft of the 1st and base of the 2nd metacarpal of right hand following a blast injury (b) PostoCredit: Kamath JB et al. via Indian J Orthop via Open-i (NIH) (Open Access (CC BY))
Radiograph demonstrating the adjacent second metacarpal fracture post removal of K-wires
Click to expand
Radiograph demonstrating the adjacent second metacarpal fracture post removal of K-wiresCredit: Loh CY et al. via Indian J Plast Surg via Open-i (NIH) (Open Access (CC BY))

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.

Mnemonic

10-10-30-50Acceptable Angulation

1
10°
Index (2nd): 10 degrees - rigid CMC
2
10°
Middle (3rd): 10 degrees - rigid CMC
3
30°
Ring (4th): 30 degrees - mobile CMC
4
50°
Little (5th): 50 degrees - Boxer's fracture, mobile CMC

Memory Hook:Increases ulnarly due to mobile CMCs - 1-1-3-5 easy to remember

Mnemonic

ROMISurgical Indications

R
Rotation
ANY rotational deformity (cardinal rule) - scissoring
O
Open fracture
Open fractures including fight bites
M
Multiple
Multiple metacarpal fractures (unstable)
I
Intra-articular
Displaced intra-articular fractures (head/base)

Memory Hook:ROMI goes to theatre - Rotation, Open, Multiple, Intra-articular

Mnemonic

WASHFight Bite Management

W
Washout
Formal surgical washout in theatre
A
Augmentin
Amoxicillin-clavulanate covers Eikenella + oral flora
S
Stay open
Never primarily close - leave wound open
H
History
Often false ('cut on glass') - assume bite

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

LocationPatternTreatment
NeckApex dorsal angulation (Boxer's)Usually conservative
ShaftTransverse, oblique, spiralAssess rotation carefully
BaseIntra-articular (CMC joint)May need surgery if displaced
HeadIntra-articular (MCP joint)Often need ORIF

Exam Viva Point

Cardinal Rule: NO degree of rotation is acceptable - fingers must converge to scaphoid tubercle

Remember 10-10-30-50:

  • 2nd (Index): 10° acceptable
  • 3rd (Middle): 10° acceptable
  • 4th (Ring): 30° acceptable
  • 5th (Little): 50° acceptable

Why? 4th/5th CMC joints have 20-30° flexion-extension arc to compensate

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

RayCMC MobilityAngulation Tolerance
2nd (Index)Rigid10-15°
3rd (Middle)Rigid10-15°
4th (Ring)Mobile30-40°
5th (Little)Mobile50-70°

Exam Viva Point

Deforming Forces:

  • Interossei flex MCP, extend IPJs
  • In fractures: Distal fragment flexes (apex dorsal angulation)
  • Head drops into palm (loss of knuckle prominence)

Effect of Shortening:

  • Greater than 4-5mm shortening = extensor lag
  • Loss of tension on extensor apparatus
  • MCP cannot fully extend

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

PatternDeformity RiskFixation Preference
TransverseApex dorsal angulationPlate or IM screws
Oblique (greater than 2x diameter)Shortening, rotationLag screws
SpiralRotation, shorteningLag screws or plate
ComminutedShortening, instabilityPlate +/- bone graft

Exam Viva Point

Special Patterns:

  • Boxer's fracture: 5th MC neck with apex dorsal angulation
  • Reverse Bennett: 5th MC base intra-articular (baby Bennett)
  • Hamate hook fracture: Associated with 4th/5th MC base injuries

Open Fracture Classification:

  • Always assess for fight bite (tooth penetration)
  • Gustilo-Anderson applies to open metacarpal fractures
  • Fight bite = contaminated wound requiring washout

Examination

Inspection:

  • Swelling (dorsal hand)
  • Loss of knuckle prominence (depressed head)
  • Rotational Alignment:
    1. Ask patient to make a fist
    2. Fingertips should all point to Scaphoid Tubercle
    3. Look for scissoring/overlap
    4. 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

📊 Management Algorithm
metacarpal fractures management algorithm
Click to expand
Management algorithm for metacarpal fracturesCredit: OrthoVellum

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)
Boxer's fracture - 5th metacarpal neck fracture on X-ray
Click to expand
Oblique hand X-ray demonstrating a classic boxer's fracture - a 5th metacarpal neck fracture (circled). This is the most common metacarpal fracture pattern, typically occurring from striking with a closed fist. Note the apex dorsal angulation at the fracture site. Up to 50 degrees of angulation is acceptable for 5th metacarpal neck fractures due to compensatory CMC joint mobility.Credit: PMC - CC BY 4.0

Special Views

ViewIndicationWhat It Shows
BrewertonMCP collateral ligament injuryCollateral ligament avulsions
SkylineMetacarpal head assessmentArticular surface fractures
CT scanComplex base fracturesCMC joint involvement

Exam Viva Point

Rotation Assessment:

  • Cannot assess rotation on X-ray
  • MUST assess clinically (finger cascade, scissoring)
  • Check nail plate alignment
  • Compare to contralateral hand

CT Indications:

  • Complex CMC joint fractures
  • Intra-articular head fractures
  • Preoperative planning for ORIF

Management Algorithm

Treatment Algorithm

Conservative Indications:

  • Stable fractures with acceptable angulation
  • No rotational deformity
  • Closed injury (no fight bite)

Conservative Techniques:

  • Buddy taping: Simple, allows early motion
  • Ulnar gutter splint: 4th/5th metacarpal
  • Radial gutter splint: 2nd/3rd metacarpal
  • Duration: 3-4 weeks

Surgical Indications:

  • ANY rotational deformity (cardinal rule)
  • Unacceptable angulation for the ray
  • Shortening greater than 5mm
  • Open fractures
  • Multiple metacarpal fractures
  • Intra-articular displacement

Treatment by Pattern

PatternFirst-LineSurgical Option
Boxer's (acceptable)Buddy tape or ulnar gutterRarely needed
Shaft with rotationSurgery indicatedK-wires or plate
Head fractureOften surgeryLag screws or plate
Base (CMC)Assess stabilityK-wires or ORIF

Exam Viva Point

Jahss Manoeuvre:

  • Reduction technique for neck fractures
  • Flex MCP and PIP to 90 degrees
  • Apply dorsal pressure on proximal phalanx
  • This pushes metacarpal head dorsally

Fixation Options:

  • K-wires: Transverse (to adjacent MC) or retrograde IM
  • Lag screws: For long oblique/spiral (greater than 2x diameter)
  • Plates: Transverse, comminuted, need absolute stability
  • IM screws: Newer option for neck/shaft

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:

  1. K-wire Fixation:

    • Retrograde (intramedullary) or Transverse (pinning to adjacent bone)
    • Minimally invasive, wire removal later
  2. ORIF (Plate/Screws):

    • For shaft fractures, unstable patterns
    • Anatomical reduction
    • Risk: Tendon adhesions, prominent hardware
  3. Intramedullary Screw:

    • Newer technique for neck/shaft
    • Headless compression screw

Poolman et al. Cochrane Review

Poolman RW, et al. • Cochrane Database Syst Rev (2005)
Key Findings:
  • 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
Clinical Implication: Most Boxer's fractures can be treated simply with potential for early mobilisation.

Rotational Malunion Impact

Low CK, et al. • J Hand Surg Br (1995)
Key Findings:
  • 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
Clinical Implication: Any rotational deformity requires correction - this is the cardinal rule of metacarpal fractures.

Fight Bite Infections

Patzakis MJ, et al. • J Bone Joint Surg Am (1987)
Key Findings:
  • Eikenella corrodens primary pathogen in human bites
  • Polymicrobial infection common
  • High rate of septic arthritis if treatment delayed
  • Amoxicillin-clavulanate provides appropriate coverage
Clinical Implication: Fight bites are surgical emergencies requiring formal washout - never primarily close these wounds.

Intramedullary Screw Fixation

Borbas P, et al. • Hand (NY) (2017)
Key Findings:
  • Headless compression screw for MC neck fractures
  • Minimally invasive, no hardware removal needed
  • Comparable outcomes to K-wires with fewer complications
  • Allows early mobilisation
Clinical Implication: Intramedullary screw is a valid modern alternative to K-wires for metacarpal fractures requiring fixation.

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

ComplicationCauseTreatment
Rotational malunionMissed rotation, inadequate reductionDerotation osteotomy
Extensor lagShortening greater than 5mmAccept or lengthening osteotomy
StiffnessProlonged immobilisationHand therapy, tenolysis
Septic arthritisFight biteUrgent washout, IV antibiotics

Exam Viva Point

Rotational Malunion:

  • Every 5° rotation at MC = 1.5cm fingertip overlap
  • Derotation osteotomy at MC shaft
  • Through dorsal approach
  • Fix with plate

Hardware Complications:

  • Plates: Tendon adhesions, prominence
  • K-wires: Pin site infection, migration
  • May require hardware removal

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

TreatmentImmobilisationReturn to Work
Buddy tapingImmediate ROM1-2 weeks light duties
Splinting3-4 weeks4-6 weeks
K-wires4-6 weeks to removal6-8 weeks
ORIF plate1-2 weeks splint8-12 weeks manual

Exam Viva Point

Early Motion Rationale:

  • Stable fixation allows early ROM
  • Reduces stiffness and adhesions
  • Better functional outcomes

Sport Return:

  • Contact sport: 8-12 weeks
  • Boxing: 12-16 weeks minimum
  • May need protective splinting initially

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

PatternUnion RateMain 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 fracture90-95%MCP arthritis

Exam Viva Point

Poolman Cochrane Review (2005):

  • Conservative treatment for Boxer's is effective
  • No difference between splinting and buddy taping
  • Surgery has higher complication rate without clear benefit

Key Outcome Factors:

  • Rotation correction is paramount
  • Early motion improves outcomes
  • Patient occupation and demands matter

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

StudyKey FindingClinical Impact
Poolman 2005Conservative = surgical for Boxer'sAvoid unnecessary surgery
Ali 2005K-wire biomechanics effectiveK-wires are reasonable fixation
Kollitz 2014Review of treatment optionsAlgorithm-based approach

Exam Viva Point

Level of Evidence:

  • Cochrane review: Level I for conservative vs surgical
  • Most surgical studies: Level IV (case series)
  • Rotation malunion outcomes: Level V (expert opinion)

Consensus Points:

  • Rotation requires correction (universal agreement)
  • Angulation thresholds vary by ray (widely accepted)
  • Early motion improves outcomes (good evidence)

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Boxer's Fracture

EXAMINER

"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?"

EXCEPTIONAL ANSWER
This is a classic **Boxer's Fracture**. **Classification:** 5th Metacarpal Neck fracture. **Decision Making:** - Angulation is 40°. Limit for 5th ray is often cited as 40-70°. - CMC joint of little finger is mobile (20-30°), allowing compensation. - No rotation (Critical finding). - Assuming no open wound ("fight bite"). **Management Plan:** - **Conservative Treatment** is appropriate. - **Why?** Functional outcomes are excellent despite radiographic deformity. Surgery introduces risks (stiffness, infection, hardware). - **Technique:** Ulnar gutter splint or just buddy strapping (to ring finger) to allow early motion. - Evidence (Poolman et al.) supports functional treatment. **Follow-up:** - Check X-ray at 1 week (ensure no further slip). - Mobilise out of splint at 3-4 weeks. - Warn about: Loss of knuckle prominence (cosmetic), bump in palm. **When I would operate:** - If angulation greater than 70° (severe pseudoclawing risk). - If ANY rotation developed. - If open fracture.
KEY POINTS TO SCORE
5th ray tolerates significant angulation (mobile CMC)
Rotation is the main indication for surgery
Loss of knuckle is expected cosmetic outcome
Always assume punched a 'tooth' (check for wounds)
COMMON TRAPS
✗Operating purely for X-ray appearance
✗Missing a fight bite
✗Missing malrotation (scissoring)
LIKELY FOLLOW-UPS
"How does the management differ for the 2nd metacarpal?"
"What is the Jahss manoeuvre?"
"What is the maximum acceptable shortening?"
VIVA SCENARIOChallenging

Scenario 2: Third Metacarpal Shaft Fracture with Rotation

EXAMINER

"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?"

EXCEPTIONAL ANSWER
This scenario illustrates the cardinal rule of metacarpal fractures: any degree of rotational deformity is unacceptable and requires surgical correction. Although the angulation of 15 degrees is within acceptable limits for the third metacarpal (rigid CMC joint allows up to 15 degrees), the rotational malalignment causing scissoring is not tolerable and will significantly impair hand function, causing weak grip and inability to fully flex the fingers without overlap. My management would be surgical fixation. I would first explain to the patient that while some fractures can be treated with splinting, the rotation in his finger means the bones are twisted and will not heal in a functional position without surgery. At surgery, I would use an open approach to the third metacarpal shaft - typically a dorsal longitudinal incision between the second and third metacarpals, reflecting the extensor tendons radially or ulnarly. I would reduce the fracture correcting both the angulation and the rotation - this is where the surgery becomes technically demanding because you must ensure the nail plane is correct and the finger points to the scaphoid tubercle when checking alignment intraoperatively. For fixation of this short oblique fracture, I would use either a dorsal plate (2.0 or 2.3mm) with at least 3 screws each side of the fracture, or if the obliquity is favorable, I could use lag screws alone (2 or 3) perpendicular to the fracture line. Post-operatively, I would use a short period of splinting (1-2 weeks) for comfort, then start early protected motion to prevent tendon adhesions which are a significant risk with dorsal plating. I would warn him about risks including stiffness (most common), prominent hardware potentially requiring later removal, infection, and incomplete correction of rotation.
KEY POINTS TO SCORE
ANY rotational deformity requires surgical correction (cardinal rule)
Clinical assessment (finger cascade, scissoring) more important than X-ray
Third metacarpal rigid CMC allows only 10-15° angulation
ORIF with plate or lag screws, must correct rotation intraoperatively
Stiffness from tendon adhesions is main complication of dorsal plating
COMMON TRAPS
✗Accepting rotational deformity because angulation is acceptable
✗Attempting closed reduction and K-wires (will not maintain rotation correction)
✗Not checking rotational alignment intraoperatively
✗Prolonged immobilization causing stiffness
LIKELY FOLLOW-UPS
"How do you assess rotational alignment intraoperatively?"
"What is the biomechanical advantage of lag screws in oblique fractures?"
"How much fingertip overlap results from 5 degrees of rotation?"
VIVA SCENARIOCritical

Scenario 3: Fight Bite with Septic Arthritis

EXAMINER

"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?"

EXCEPTIONAL ANSWER
This is a fight bite with septic arthritis of the MCP joint until proven otherwise. The story of 'cutting on glass' is a classic cover story - any laceration over an MCP joint in a young person presenting from a bar should be assumed to be from punching someone in the teeth. The mechanism is that when the fist impacts the teeth, the tooth penetrates the extensor tendon and MCP joint capsule while the MCP is flexed. When the finger extends, the tract closes, sealing bacteria (particularly Eikenella corrodens and oral anaerobes) deep in the joint. The 3-day delay and current presentation with fever, purulent drainage, and joint signs indicate established septic arthritis which is a surgical emergency. My immediate management would be IV antibiotics - I would use amoxicillin-clavulanate (Augmentin) which covers Eikenella, Streptococcus, Staphylococcus, and anaerobes. I would take him urgently to theatre for formal open washout of the MCP joint. Under general or regional anesthesia, I would extend the laceration longitudinally, inspect the extensor tendon (often lacerated or frayed), open the MCP joint capsule widely, and perform copious irrigation with several liters of saline. I would inspect the metacarpal head for cartilage damage and debride any devitalized tissue. Critically, I would leave the wound open - primary closure of a fight bite is contraindicated as it creates an abscess. I would dress it with wet-to-dry dressings and plan for delayed primary closure or healing by secondary intention. Post-operatively, he needs IV antibiotics for 48-72 hours minimum, then transition to oral Augmentin for a total of 2 weeks. I would also send wound swabs and joint fluid for culture, though these are often negative. If there is significant tendon damage, he may need delayed tendon repair or reconstruction. I would counsel him honestly that he likely punched someone, this is serious, and if not properly treated he could lose function of his finger or develop chronic osteomyelitis requiring further surgery.
KEY POINTS TO SCORE
Laceration over MCP = fight bite until proven otherwise
Eikenella corrodens and oral flora cause rapidly progressive infection
Septic arthritis requires urgent surgical washout, not just antibiotics
NEVER primarily close a fight bite wound
Amoxicillin-clavulanate (Augmentin) is antibiotic of choice
COMMON TRAPS
✗Accepting 'cut on glass' story and treating as simple laceration
✗Treating with oral antibiotics alone without washout
✗Primary closure of the wound (creates abscess)
✗Not inspecting extensor tendon and joint capsule
LIKELY FOLLOW-UPS
"What organisms are typically involved in fight bites?"
"Why is Eikenella corrodens particularly concerning?"
"What would you do if the patient refuses to admit punching someone?"

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

PresentationSettingManagement
Boxer's (stable)ED/Fracture clinicBuddy tape, early review
Rotational deformityTheatre (day case)K-wires or ORIF
Fight biteTheatre (urgent)Washout + IV antibiotics

Exam Viva Point

Antibiotics for Fight Bite:

  • First-line: Amoxicillin-clavulanate (Augmentin) 875/125mg BD
  • Alternative: Doxycycline + metronidazole
  • Covers Eikenella corrodens

WorkCover Considerations:

  • Common workplace injury (manual workers)
  • Document mechanism clearly
  • Return to work assessment important

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

  1. Ali A, et al. Biomechanical stability of intramedullary K-wire fixation of metacarpal neck fractures. J Hand Surg Br. 2005.
  2. Kollitz KM, et al. Metacarpal fractures: treatment and complications. Hand (NY). 2014.
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Reading Time88 min
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