Thumb Base Fractures

High Yield Overview

THUMB BASE FRACTURES

Bennett's vs Rolando | CMC Joint Involvement | Deforming Forces | Articular Reduction

2nd MCMost fractured metacarpal (after 5th)

less than 2mmAcceptable articular step-off

65%Bennett's (most common intra-articular)

APLPrimary deforming force on shaft

Critical Must-Knows

Bennett's: 2-part intra-articular fracture-subluxation with small volar-ulnar fragment held by anterior oblique ligament (AOL/Beak ligament)
Deforming forces: APL pulls shaft proximally and radially, adductor pollicis pulls head into adduction → shaft subluxates dorsally
Rolando: 3+ part comminuted intra-articular (Y or T pattern) - worse prognosis than Bennett's
Robert's view (hyperpronated thumb AP) is the key view to assess volar fragment size and step-off
Threshold for surgery: greater than 1-2mm articular step-off or CMC subluxation that cannot be maintained

Examiner's Pearls

"
Know the Green/O'Brien classification: Type I (Bennett's), Type II (Rolando), Type IIIA (transverse extra-articular), Type IIIB (oblique extra-articular)
"
Bennett's reduction manoeuvre: Traction + Extension + Pronation + Abduction (TEPA) - reverse the deformity
"
Rolando 'bag of bones' comminution → external fixation with ligamentotaxis, not ORIF
"
X-ray OA does NOT always correlate with symptoms (Livesley 26-year follow-up)

Exam Warning

You must know the deforming forces in a Bennett's fracture. The small volar-ulnar fragment stays in place (anchor). The main metacarpal shaft fragment is pulled proximally, dorsally, and radially. Know which tendon pulls where: APL pulls shaft proximally/radially; Adductor Pollicis pulls head into adduction (supination). Deep volar oblique ligament holds the volar fragment.

At a Glance

Thumb base fractures include Bennett's (2-part intra-articular), Rolando (3-part or comminuted intra-articular), and extra-articular patterns. Bennett's fracture is characterised by a small volar-ulnar fragment held by the anterior oblique ligament while the shaft displaces proximally, dorsally, and radially due to APL and adductor pollicis pull. Treatment aims to restore articular congruity (under 1-2mm step-off) to prevent CMC arthritis: CRPP is standard for Bennett's (traction + extension + pronation + abduction reduction), while Rolando fractures require ORIF for large fragments or external fixation for comminuted "bag of bones" injuries. Extra-articular fractures are generally stable and managed with casting.

Mnemonic

PADBennett's Deforming Forces

Proximal

APL pulls shaft proximally and radially

Abducted

Base moves into radial (abducted) position

Dorsal

Shaft subluxates dorsally from joint

Memory Hook:The shaft moves on a PAD - away from the anchored volar fragment

Mnemonic

TEPABennett's Reduction Manoeuvre

Traction

Longitudinal traction on the thumb

Extension

Extend the MCP joint

Pronation

Pronate the thumb

Abduction

Radial pressure on base (abduct)

Memory Hook:TEPA reverses the deformity - Think 'TEPA the thumb back into place'

Mnemonic

BREThumb Base Fracture Types

Bennett's

2-part intra-articular with volar-ulnar fragment

Rolando

3+ part comminuted Y or T intra-articular

Extra-articular

Winterstein - transverse or oblique, stable

Memory Hook:BRE - like 'break' - the 3 ways to break the thumb base

Overview

Thumb Base Fracture Overview

Definition:

Fractures involving the base of the first metacarpal
May be extra-articular or intra-articular (CMC joint)
Bennett's and Rolando patterns are intra-articular subtypes

Fracture Pattern Overview

Pattern	Description	Articular Involvement
Bennett's	2-part fracture-dislocation with volar-ulnar fragment	Intra-articular
Rolando	Comminuted Y or T pattern (3+ fragments)	Intra-articular
Winterstein	Extra-articular transverse or oblique fracture	Extra-articular

Anatomy

Deforming Forces

Bennett's Fracture (Two-part intra-articular):

Volar-Ulnar Fragment:
- Remains in place.
- Anchored by the Anterior Oblique Ligament (Beak ligament).
Metacarpal Shaft (Main Fragment):
- Abductor Pollicis Longus (APL): Pulls base Proximally and Radially.
- Adductor Pollicis: Pulls head towards palm (Adduction) -> pivots base Dorsally.

Resultant Deformity:

Subluxation of the CMC joint.
Shaft migrates dorsally and radially.

At a Glance

Mnemonic

PADBennett's Deforming Forces

Proximal

APL pulls shaft proximally and radially

Abducted

Base moves into radial (abducted) position

Dorsal

Shaft subluxates dorsally from joint

Memory Hook:The shaft moves on a PAD - away from the anchored volar fragment

Mnemonic

TEPABennett's Reduction Manoeuvre

Traction

Longitudinal traction on the thumb

Extension

Extend the MCP joint

Pronation

Pronate the thumb

Abduction

Radial pressure on base (abduct)

Memory Hook:TEPA reverses the deformity - Think 'TEPA the thumb back into place'

Mnemonic

BREThumb Base Fracture Types

Bennett's

2-part intra-articular with volar-ulnar fragment

Rolando

3+ part comminuted Y or T intra-articular

Extra-articular

Winterstein - transverse or oblique, stable

Memory Hook:BRE - like 'break' - the 3 ways to break the thumb base

Classification

Overview

Thumb Base Fracture Overview

Definition:

Fractures involving the base of the first metacarpal
May be extra-articular or intra-articular (CMC joint)
Bennett's and Rolando patterns are intra-articular subtypes

Fracture Pattern Overview

Pattern	Description	Articular Involvement
Bennett's	2-part fracture-dislocation with volar-ulnar fragment	Intra-articular
Rolando	Comminuted Y or T pattern (3+ fragments)	Intra-articular
Winterstein	Extra-articular transverse or oblique fracture	Extra-articular

Anatomy

CMC Joint Anatomy

First CMC Joint (Trapeziometacarpal):

Biconcave saddle joint with 2 degrees of freedom
Allows flexion/extension, abduction/adduction, and circumduction
Critical for opposition and pinch function

Key Stabilising Structures:

Anterior oblique ligament (AOL/Beak ligament) - primary stabiliser
Posterior oblique ligament
Dorsoradial ligament
Intermetacarpal ligament (to 2nd MC)

CMC Joint Ligaments

Ligament	Location	Function
Anterior Oblique (AOL)	Volar-ulnar trapezium to MC base	Primary restraint to subluxation
Dorsoradial	Dorsal trapezium to MC base	Resists palmar translation
Intermetacarpal	1st to 2nd MC base	Limits radial deviation

Clinical Assessment

History and Examination

Mechanism:

Axial load on flexed thumb (punch, fall on thumb)
Direct blow to thumb base
High-energy (MVA) or low-energy (sports)

History Points:

Hand dominance and occupation
Time since injury
Previous thumb injuries
Smoking status (affects healing)

Examination:

Swelling and tenderness at thumb base/thenar eminence
Deformity - shortened, adducted thumb
Assess neurovascular status (radial sensory nerve)
Check IP and MCP joint motion
Assess other injuries (scaphoid, distal radius)

Clinical Signs by Pattern

Pattern	Key Findings	Deformity
Bennett's	CMC swelling, tenderness, instability	Adducted, shortened thumb
Rolando	More swelling, crepitus	Similar but more severe
Extra-articular	Shaft tenderness, apex dorsal	Less CMC involvement

Investigations

Imaging Assessment

Plain Radiographs:

AP of thumb (Robert's view - true AP with hyperpronation)
Lateral of thumb
PA and lateral of hand
Assess articular involvement, displacement, comminution

Robert's View (Key View):

Hand maximally pronated (thumb facing down)
Gives true AP of 1st CMC joint
Best view to assess Bennett's volar fragment

Imaging Indications

Modality	When to Use	Key Information
X-ray (3 views)	All cases	Fracture pattern, displacement
Robert's view	Suspected intra-articular	Volar fragment size, step-off
CT scan	Rolando/comminuted patterns	Fragment size, surgical planning

Types of Thumb Base Fractures

Bennett's Fracture:

Intra-articular.
2 parts.
Oblique fracture line separating volar-ulnar beak.
Unstable due to tendon pull.

Rolando Fracture:

Intra-articular.
3 parts (or comminuted).
"Y" or "T" shaped pattern.
Worse prognosis than Bennett's.

Extra-Articular:

Transverse or Oblique.
Does not involve joint surface.
Generally easier to treat (cast).

Management

Bennett's Fracture

Principles:

Intra-articular step-off must be under 1-2mm.
Joint stability must be restored.

Treatment Options:

Closed Reduction Percutaneous Pinning (CRPP):
- Most common.
- Reduction manoeuvre: Traction + Extension + Pronation + Abduction (Reverse the deformity).
- Pin 1st MC to Trapezium or 1st MC to 2nd MC.
ORIF:
- If reduction fails or fracture fragment large.
- Wagner approach (L-shaped incision).
- Lag screws or small plate.

Rolando Fracture

Principles:

Much harder to reconstruct.
Goal is to mould articular surface.

Treatment Options:

ORIF:
- If fragments large enough (over 3mm).
- T-plate or locking plate.
External Fixation +/ K-wires:
- If severe comminution ("Bag of Bones").
- Distraction (ligamentotaxis) restores length and alignment.
- Allows early motion? No, fixator holds it.
Conservative:
- If highly comminuted in low demand.
- Early ROM to mould congruity.

Original Description of Bennett's Fracture

Bennett EH • Dublin J Med Sci (1882)

Key Findings:

First description of 'fracture of the metacarpal bone of the thumb'
Noted the oblique fracture pattern entering the joint
Described the characteristic displacement
Recognized it was distinct from extra-articular fractures

Clinical Implication: Historical context: Bennett recognized the instability pattern over 140 years ago.

Operative vs Non-operative Bennett's

Livesley PJ, et al. • JBJS Br (1990)

Key Findings:

Long term follow up (26 years)
Residual step-off correlated with arthritic changes on X-ray
HOWEVER, X-ray arthritis did not correlate strongly with symptoms
Good functional results can be achieved even with distinct radiographic OA

Clinical Implication: Aim for anatomic reduction to prevent OA, but reassure patients that radiographic OA doesn't always equal pain.

Percutaneous Pinning of Bennett's Fractures

Kjaer-Petersen K, et al. • Acta Orthop Scand (1986)

Key Findings:

Series of 41 Bennett's fractures treated with CRPP
Anatomic reduction achieved in 90% of cases
Mean follow-up 4.5 years with good/excellent outcomes in 85%
Step-off greater than 2mm associated with worse outcomes

Clinical Implication: CRPP is effective first-line treatment for Bennett's fractures when anatomic reduction is achievable.

Rolando Fracture Outcomes

Langhoff O, et al. • J Hand Surg Br (1991)

Key Findings:

Review of 22 Rolando fractures with mean 7-year follow-up
30% developed radiographic CMC arthritis
Comminuted patterns had significantly worse outcomes
External fixation effective for severely comminuted 'bag of bones' patterns

Clinical Implication: Counsel patients with Rolando fractures about higher risk of post-traumatic arthritis despite optimal treatment.

Articular Step-off Threshold

Cannon SR, et al. • J Bone Joint Surg Br (1986)

Key Findings:

Compared CRPP vs ORIF for Bennett's fractures
Similar outcomes if articular reduction achieved
Step-off greater than 2mm threshold for considering surgery
Method of fixation less important than quality of reduction

Clinical Implication: Focus on achieving anatomic reduction regardless of technique - CRPP is reasonable first-line if reduction adequate.

Management Algorithm

Surgical Technique

CRPP Technique (Bennett's)

Setup:

Supine, arm on hand table
Regional or general anaesthesia
Image intensifier (mini C-arm preferred)
Tourniquet optional

Reduction:

Longitudinal traction on thumb
Extend MCP joint
Pronate thumb
Abduct thumb (radial pressure on base)
Direct dorsal pressure on MC base

Fixation:

1.6mm K-wires (2 wires usually)
1st MC to trapezium (trans-articular)
OR 1st MC to 2nd MC base
Check reduction on fluoro (AP, lateral, Robert's)

Closure:

Protect wire ends, bend and cut short
Thumb spica splint/cast

CRPP vs ORIF Decision

Factor	CRPP	ORIF
Reduction quality	Adequate closed reduction	Irreducible or inadequate
Fragment size	Any size (pins bypass)	Large enough for screws
Stability	Maintained with pins	Needs absolute stability

Complications

Potential Complications

Early Complications:

Pin site infection (superficial or deep)
Radial sensory nerve injury (numbness)
Loss of reduction/fixation failure
Wound complications

Late Complications:

Post-traumatic CMC arthritis (most significant)
Malunion with dorsal prominence
Stiffness (CMC, MCP)
Chronic instability
Complex regional pain syndrome (rare)

Complications and Prevention

Complication	Risk Factor	Prevention/Treatment
Post-traumatic arthritis	Articular step-off greater than 2mm	Anatomic reduction
RSN injury	Pin placement, surgical incision	Careful technique, protect nerve
Malunion	Inadequate reduction	Intraoperative fluoro check
Stiffness	Prolonged immobilisation	Early ROM after 4-6 weeks

Postoperative Care

Rehabilitation Protocol

Immobilisation Phase (0-6 weeks):

Thumb spica cast or splint
Elevate hand to reduce swelling
Active finger ROM to prevent stiffness
Check X-ray at 2 and 6 weeks

K-Wire Removal (4-6 weeks):

Office procedure under local anaesthesia
After radiographic evidence of healing
Transition to removable splint

Mobilisation Phase (6-12 weeks):

Wean from splint over 2-4 weeks
Active and passive ROM exercises
Hand therapy referral
Avoid heavy loading initially

Postoperative Timeline

Time	Activity	Goal
0-6 weeks	Thumb spica cast, finger ROM	Fracture healing
6 weeks	K-wire removal, X-ray check	Union confirmed
6-12 weeks	Active ROM, hand therapy	Restore motion
12+ weeks	Progressive strengthening	Return to function

Outcomes

Functional Outcomes

Bennett's Fracture:

Good to excellent results in 85-90% with adequate reduction
Articular step-off correlates with radiographic OA
Radiographic OA does not always correlate with symptoms

Rolando Fracture:

Worse outcomes than Bennett's
Higher rate of post-traumatic arthritis
Comminuted patterns have poorest prognosis

Extra-Articular:

Generally excellent outcomes
Tolerates 20-30 degrees malunion without functional deficit

Outcome by Pattern

Pattern	Good/Excellent Outcome	OA Rate
Extra-articular	Greater than 95%	Less than 5%
Bennett's (reduced)	85-90%	10-20% (often asymptomatic)
Rolando	60-75%	30-50%

Evidence Base

Key Studies

Historical:

Bennett (1882): First description of 2-part fracture-dislocation
Rolando (1910): Described comminuted variant

Clinical Outcomes:

Livesley (1990): 26-year follow-up, radiographic OA does not equal symptoms
Kjaer-Petersen (1986): Series confirming importance of anatomic reduction

Evidence Summary

Study	Key Finding	Clinical Impact
Livesley 1990	X-ray OA does not correlate with symptoms	Reassure patients with OA changes
Cannon 1986	CRPP vs ORIF similar outcomes if reduced	CRPP is reasonable first-line
Rolando 1910	Comminuted pattern has worse prognosis	Set patient expectations

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Bennett's Fracture

EXAMINER

"A 25-year-old boxer presents with pain at the base of his right thumb. X-ray shows a 2-part intra-articular fracture with a small volar-ulnar fragment. The shaft is subluxed dorsally. How do you manage this?"

EXCEPTIONAL ANSWER

This is a **Bennett's Fracture**. **Pathology:** - Unstable intra-articular fracture-subluxation. - Deforming force: **APL** pulls shaft proximally and radially, **Adductor** pulls head into adduction. Volar beak held by anterior oblique ligament. **Management Plan:** 1. **Attempt Closed Reduction:** - Traction, Extension, Pronation, Abduction (pressure on dorsal base). - Check Fluoroscopy. 2. **If Reducible (under 1mm step, congruent):** - **Percutaneous Pinning (CRPP):** - Two 1.6mm K-wires. - Metacarpal to Trapezium usually. - Thumb Spica cast 4-6 weeks. 3. **If Irreducible (over 2mm step):** - **Open Reduction (ORIF):** - Radiopalmar approach (Wagner). - Avoid Radial Sensory Nerve. - Fix with 2.0mm lag screws or mini-plate. **Rationale:** - In a young manual worker/boxer, restoring articular congruity is paramount to prevent early CMC arthritis.

KEY POINTS TO SCORE

Deforming force is primarily the APL

Volar fragment is the 'anchor'

Reduction requires Extension + Pronation + Abduction

Threshold for surgery is low (under 1-2mm step)

COMMON TRAPS

✗Misting it for an extra-articular fracture

✗Thinking a cast alone will hold it (it's unstable)

✗Injuring RSN during pinning

LIKELY FOLLOW-UPS

"How does a Rolando fracture differ?"

"What is the reverse Bennett's fracture?"

"What ligament holds the volar fragment?"

VIVA SCENARIOChallenging

Scenario 2: Rolando Fracture - Surgical Decision Making

EXAMINER

"A 35-year-old carpenter presents with a thumb base injury. X-rays show a comminuted intra-articular fracture of the first metacarpal base with a Y-shaped pattern - there are volar, dorsal, and shaft fragments visible. CT confirms three main fragments with the volar and dorsal pieces each approximately 5mm in size. He is concerned about returning to carpentry work which requires strong pinch grip. What are your treatment options and what would you recommend?"

EXCEPTIONAL ANSWER

This is a Rolando fracture, which is a more complex injury than Bennett's fracture due to the comminution. The key decision is whether the fracture is amenable to ORIF versus requiring external fixation. From the description, there are three main fragments (Y-pattern) with the volar and dorsal pieces both around 5mm - this suggests they may be large enough for stable internal fixation. My management options are ORIF with plate fixation, external fixation with ligamentotaxis, or conservative management with early motion. Given he is a carpenter requiring strong pinch grip and the fragments appear large enough for fixation on CT, I would recommend ORIF. My surgical approach would be a Wagner incision (L-shaped radiopalmar approach) protecting the radial sensory nerve branches. I would reduce the volar fragment first and provisionally fix it with a K-wire, then reduce the dorsal fragment and fix both to the shaft with either lag screws or a small T-plate or locking plate. The goal is anatomic reduction of the articular surface with less than 1mm step-off if possible. If the CT showed severe comminution with fragments smaller than 3mm that are not reliably fixable, I would instead recommend external fixation spanning from the radius to the thumb metacarpal shaft using ligamentotaxis to restore length and roughly mould the articular surface. I would counsel him that Rolando fractures have worse outcomes than Bennett's fractures due to the articular cartilage damage from the injury itself, and there is a significant risk of post-traumatic CMC arthritis even with perfect reduction. His return to carpentry should be expected around 3-4 months post-fixation with progressive strengthening.

KEY POINTS TO SCORE

Rolando = comminuted intra-articular (Y or T pattern), worse prognosis than Bennett's

ORIF appropriate if fragments over 3-5mm and reducible

External fixation for severe comminution (bag of bones)

Goal: Anatomic articular reduction less than 1-2mm step

High risk of post-traumatic CMC arthritis even with good reduction

COMMON TRAPS

✗Attempting ORIF on fragments too small to fix (leads to further comminution)

✗Using Bennett's fixation techniques (K-wires alone insufficient for Rolando)

✗Not warning about worse prognosis compared to Bennett's

✗Overpromising complete recovery in manual laborer

LIKELY FOLLOW-UPS

"How would you apply external fixation for a severely comminuted Rolando?"

"What is ligamentotaxis and why does it help with comminuted fractures?"

"If ORIF fails to achieve reduction, what would you do intraoperatively?"

VIVA SCENARIOCritical

Scenario 3: Post-Traumatic CMC Arthritis After Bennett's

EXAMINER

"A 42-year-old presents with chronic thumb base pain 5 years after a Bennett's fracture that was treated with closed reduction and casting. He was told at the time surgery was not needed. X-rays show well-healed fracture with 3mm articular step-off at the CMC joint and moderate osteoarthritis with joint space narrowing and osteophytes. He has pain with pinch and gripping affecting his work as a mechanic. What would you discuss regarding management?"

EXCEPTIONAL ANSWER

This patient has post-traumatic CMC arthritis from inadequate reduction of his Bennett's fracture. The 3mm articular step-off was above the acceptable threshold of 1-2mm and has predictably led to arthritis. Unfortunately, the damage is done and we cannot reverse the arthritis. My management would follow a stepwise approach from conservative to surgical. Initially, I would try conservative measures: activity modification, NSAIDs, thumb spica splint for flare-ups, and potentially corticosteroid injection into the CMC joint which can provide temporary relief. If conservative measures fail and he has severe pain affecting his work, I would discuss surgical options. The main salvage procedures for CMC arthritis are trapeziectomy with or without ligament reconstruction and tendon interposition (LRTI), CMC arthrodesis, or total joint arthroplasty. For a 42-year-old mechanic requiring power grip, I would recommend CMC arthrodesis. Fusion provides excellent pain relief and maintains thumb length and strength, which is critical for his heavy manual work. The fusion position would be 40 degrees palmar abduction, 20 degrees radial abduction with the thumb metacarpal in line with the radius. I would fix it with plate and screws or crossed screws. The disadvantage is loss of CMC motion, but the MCP and IP joints compensate well for most activities. Trapeziectomy is an alternative but results in some loss of strength and pinch power which may be problematic for a mechanic. I would also discuss that his initial treatment 5 years ago was not optimal - Bennett's fractures are inherently unstable and rarely do well with casting alone, and the 3mm step-off should have triggered surgical intervention. However, explaining this serves to set realistic expectations rather than to assign blame. The arthritis is established and surgery is salvage, not curative.

KEY POINTS TO SCORE

Articular step-off over 1-2mm leads to post-traumatic CMC arthritis

Conservative: Splint, NSAIDs, injection for temporary relief

Salvage surgery: CMC fusion (best for heavy manual work) vs trapeziectomy

CMC fusion: 40° palmar abduction, 20° radial abduction, excellent pain relief

Set realistic expectations - salvage surgery, not restoration to normal

COMMON TRAPS

✗Attempting corrective osteotomy (arthritis already established)

✗Recommending trapeziectomy for heavy manual worker (loss of strength)

✗Not explaining initial treatment was suboptimal

✗Overpromising return to heavy work after trapeziectomy

LIKELY FOLLOW-UPS

"What is the technique for CMC fusion and what is the optimal position?"

"What are the advantages and disadvantages of trapeziectomy vs fusion?"

"Could you offer him a CMC joint replacement instead?"

MCQ Practice Points

Exam Pearl

Q: What is a Bennett fracture and what deforming forces cause subluxation?

A: Bennett fracture is an intra-articular fracture-dislocation at the thumb CMC joint with a volar-ulnar fragment remaining attached to the anterior oblique ligament (AOL) while the metacarpal shaft displaces radially, proximally, and supinates. Deforming forces: Abductor pollicis longus (APL) pulls the metacarpal base proximally and radially; Adductor pollicis adducts the thumb; Thumb extensors hyperextend the MCP. The key is the AOL keeps the volar fragment reduced while the metacarpal shaft subluxates away from it.

Exam Pearl

Q: What is the difference between a Bennett fracture and a Rolando fracture?

A: Bennett fracture: Two-part intra-articular fracture-dislocation with single volar-ulnar fragment. Rolando fracture: Comminuted intra-articular fracture with T or Y pattern (minimum three fragments - volar, dorsal, and metacarpal shaft). Rolando pattern is less common but has worse prognosis due to comminution and articular damage. Treatment: Bennett's - closed reduction and K-wire fixation or single screw if fragment adequate; Rolando's - may need plate fixation or external fixation with ligamentotaxis for severe comminution.

Exam Pearl

Q: What are the indications for surgical fixation of thumb metacarpal base fractures?

A: Surgical indications: 1) Articular step-off greater than 1-2mm after closed reduction; 2) Subluxation of CMC joint that cannot be maintained; 3) Bennett fracture with greater than 3mm displacement; 4) Rolando fracture with reducible fragments; 5) Unstable extra-articular fractures. Goals are anatomic articular reduction and stable CMC joint. Options include closed reduction and percutaneous K-wires, ORIF with screws (for Bennett's with adequate fragment), or plate fixation (for Rolando's or comminuted patterns).

Exam Pearl

Q: How do you differentiate an extra-articular thumb metacarpal base fracture from a Bennett fracture clinically and radiographically?

A: Extra-articular fracture (Winterstein): Fracture line does not involve the CMC joint surface. The CMC joint remains congruent. Deformity is apex dorsal angulation at fracture site. Bennett fracture: Fracture line enters the CMC joint. Intra-articular fragment visible on Roberts view (true AP of thumb with hand hyperpronated). CMC joint shows subluxation with widening. On lateral, Bennett's shows joint incongruity. Extra-articular fractures tolerate more angulation (20-30 degrees) than intra-articular fractures.

Exam Pearl

Q: What is the significance of the anterior oblique ligament (AOL) in Bennett fractures?

A: The anterior oblique ligament (AOL) is the primary stabilizer of the thumb CMC joint against subluxation. In Bennett fractures, the volar-ulnar fragment remains attached to the AOL, keeping it reduced to the trapezium while the metacarpal shaft subluxates. This creates the classic fracture-subluxation pattern. Surgical reduction must restore the metacarpal shaft to the volar fragment (and thus to the trapezium). The AOL also limits radial translation and supination - damage leads to chronic instability. Post-traumatic arthritis results from articular incongruity and instability.

Australian Context

Australian Healthcare Considerations

Medicare (MBS) Item Numbers:

47726: Closed reduction and K-wire fixation of metacarpal fracture
47729: Open reduction and internal fixation of metacarpal fracture
Hand surgery items may require appropriate credentials

Setting:

CRPP can be performed as day surgery
ORIF typically day surgery or overnight
Public hospital emergency lists for acute cases
Private rooms for elective revisions

Australian Healthcare Pathway

Setting	Typical Use	Considerations
ED/Fracture Clinic	Initial assessment, splinting	X-rays, referral to hand surgery
Day Surgery	CRPP Bennett's	Most cases manageable as day case
Private Rooms	ORIF, complex cases	Faster access, patient choice