Thumb Base Fractures

High-yield overview

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

1st MCBase fracture = ~25% of metacarpal #

under 2mmAcceptable articular step-off

Bennett'sMost common intra-articular pattern

APLPrimary deforming force on shaft

Critical Must-Knows

Bennett's: 2-part intra-articular fracture-subluxation with small volar-ulnar fragment held by the deep anterior oblique (beak) ligament
Deforming forces: APL pulls shaft proximally and radially, adductor pollicis pulls the head into adduction, so the shaft subluxates dorsally and supinates
Rolando: 3-or-more-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

Clinical 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 favours distraction external fixation (ligamentotaxis) over ORIF
"
Radiographic CMC OA does NOT always correlate with symptoms (Cannon 1986, Livesley 1990)

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 the shaft proximally and radially; adductor pollicis pulls the head into adduction (supination). The deep anterior oblique (beak) 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 deep anterior oblique (beak) ligament while the shaft displaces proximally, dorsally, and radially under APL and adductor pollicis pull. Treatment aims to restore articular congruity (under 1-2mm step-off) to limit CMC arthritis: CRPP is standard for Bennett's (traction + extension + pronation + abduction reduction), while Rolando fractures require ORIF for large fragments or distraction external fixation for comminuted "bag of bones" injuries. Extra-articular fractures are generally stable and managed with casting.

Mnemonic

PADBennett's Deforming Forces

P	Proximal APL pulls shaft proximally and radially
A	Abducted Base moves into radial (abducted) position
D	Dorsal Shaft subluxates dorsally from joint

P	Proximal APL pulls shaft proximally and radially
A	Abducted Base moves into radial (abducted) position
D	Dorsal Shaft subluxates dorsally from joint

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

Mnemonic

TEPABennett's Reduction Manoeuvre

T	Traction Longitudinal traction on the thumb
E	Extension Extend the MCP joint
P	Pronation Pronate the thumb
A	Abduction Radial pressure on base (abduct)

T	Traction Longitudinal traction on the thumb	P	Pronation Pronate the thumb
E	Extension Extend the MCP joint	A	Abduction Radial pressure on base (abduct)

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

Mnemonic

BREThumb Base Fracture Types

B	Bennett's 2-part intra-articular with volar-ulnar fragment
R	Rolando 3+ part comminuted Y or T intra-articular
E	Extra-articular Winterstein - transverse or oblique, stable

B	Bennett's 2-part intra-articular with volar-ulnar fragment
R	Rolando 3+ part comminuted Y or T intra-articular
E	Extra-articular Winterstein - transverse or oblique, stable

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 (1st CMC joint)
Bennett's and Rolando patterns are the 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 (with screw-home rotation)
Critical for opposition and pinch function

Key Stabilising Structures:

Deep anterior oblique ligament (dAOL / beak ligament) - intra-articular pivot, attaches to volar-ulnar beak
Superficial anterior oblique ligament (sAOL)
Dorsoradial ligament (DRL) - increasingly recognised as a key dorsal restraint
Posterior oblique ligament
Intermetacarpal ligament (1st to 2nd MC)

CMC Joint Ligaments

Ligament	Location	Function
Deep anterior oblique (beak)	Volar-ulnar beak of MC base to trapezium	Pivot for pronation, restrains subluxation
Dorsoradial (DRL)	Dorsal trapezium to MC base	Major restraint to dorsal subluxation
Intermetacarpal	1st to 2nd MC base	Limits radial deviation / tension band

Deforming Forces in Bennett's (summary):

Volar-ulnar (beak) fragment stays reduced, anchored by the deep anterior oblique ligament
APL pulls the shaft proximally and radially
Adductor pollicis pulls the head into adduction, pivoting the base dorsally and into supination
Net result: dorsoradial subluxation of the 1st CMC joint

Classification

Green & O'Brien Classification (first metacarpal base)

Green & O'Brien Classification

Type	Pattern	Stability
Type I	Bennett's - 2-part intra-articular fracture-subluxation	Unstable
Type II	Rolando - comminuted intra-articular (Y / T)	Unstable
Type IIIA	Extra-articular transverse	Usually stable
Type IIIB	Extra-articular oblique	Can be unstable
Type IV	Paediatric epiphyseal (Salter-Harris) base injury	Variable

Key points:

Types I and II are intra-articular and threaten the CMC joint surface
Type III (extra-articular) tolerates more angulation because remodelling and CMC mobility compensate

Clinical Assessment

History and Examination

Mechanism:

Axial load on a flexed thumb (punch, fall onto thumb)
Direct blow to the thumb base
High-energy (motor vehicle) or low-energy (sport, fall)

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
Look for associated 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 onto the plate)
Gives a true AP of the 1st CMC joint
Best view to assess the Bennett's volar fragment and step-off

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

Differential Diagnosis

A swollen, painful thumb base after trauma is not always a Bennett's fracture. The differentials below are the ones examiners expect you to actively exclude.

Differential Diagnosis of the Painful Thumb Base

Diagnosis	Distinguishing Feature	Key Test / Clue
Bennett's fracture	2-part intra-articular base #, dorsoradial subluxation	Robert's view shows volar-ulnar fragment
Rolando fracture	Comminuted Y/T intra-articular base #	CT shows 3+ fragments
Extra-articular base #	Joint surface intact, apex-dorsal angulation	Congruent CMC on Robert's view
1st CMC dislocation (no #)	Pure ligamentous dislocation, no bony fragment	Reduces but re-subluxes; beak ligament tear
UCL injury (skier's/gamekeeper's)	Pain at MCP not CMC; valgus laxity	Stress MCP in extension and 30 deg flexion
Scaphoid fracture	Anatomical snuffbox tenderness	Scaphoid views; MRI if occult
1st CMC osteoarthritis	Older patient, insidious pain, grind test positive	X-ray osteophytes; no acute trauma

Management

Surgical Technique

CRPP Technique (Bennett's)

Setup:

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

Reduction:

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

Fixation:

1.4-1.6mm K-wires (usually 2 wires)
1st MC to trapezium (trans-articular) OR 1st MC to 2nd MC base
Confirm reduction on fluoroscopy (AP, lateral, Robert's)

Closure:

Protect wire ends, bend and cut short (or bury)
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 fragment)	Large enough for a screw
Stability	Maintained with pins	Needs absolute stability

Complications

Potential Complications

Early Complications:

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

Late Complications:

Post-traumatic CMC arthritis (most significant)
Malunion with dorsal prominence and varus base angulation
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 fluoroscopy 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 the 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 a removable splint

Mobilisation Phase (6-12 weeks):

Wean from the 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 roughly 85-90% with adequate reduction
Residual step-off correlates with radiographic OA (Kjaer-Petersen 1990)
Radiographic OA does not always correlate with symptoms (Cannon 1986)
Conservative management of displaced patterns gives poor long-term joints (Livesley 1990)

Rolando Fracture:

Worse outcomes than Bennett's
Higher rate of post-traumatic arthritis
Comminuted patterns have the poorest prognosis, though modern ligamentotaxis series report grip/pinch around 90% of the contralateral side (Houshian 2013, Marsland 2012)

Extra-Articular:

Generally excellent outcomes
Tolerates 20-30 degrees malunion without a 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%

Controversies & Areas of Uncertainty

Does anatomic reduction prevent symptomatic arthritis? Kjaer-Petersen (1990) found residual displacement correlated with radiographic arthritis, yet Cannon (1986) found no reliable correlation between reduction accuracy and symptoms at a mean of 9.6 years. Cartilage injury at the moment of impact may matter as much as the residual step-off.
CRPP vs ORIF for Bennett's. There is no randomised evidence. Most surgeons reserve ORIF for large, irreducible fragments and use CRPP first-line; the quality of articular reduction matters more than the implant chosen.
Acceptable articular step-off. The widely quoted "1-2mm" threshold is derived from small retrospective series, not high-level evidence; some authors accept up to 1mm only, others tolerate 2mm.
Trans-articular vs extra-articular pinning. Pinning the 1st MC to the trapezium crosses the joint; pinning to the 2nd MC base spares it. Both are used; no clear superiority.
Rolando: ex-fix vs ORIF. Distraction external fixation (ligamentotaxis) gives reproducibly good function for comminuted patterns (Houshian 2013, Marsland 2012), challenging the older default of attempting plate ORIF on small fragments.
Beak ligament dogma. Anatomic work (Bettinger 1999; Ladd/Hagert group) shows the dorsoradial ligament is also a major restraint, so the classic teaching that the AOL is the sole stabiliser is an oversimplification.

Evidence Base

The evidence base for thumb base fractures is predominantly Level IV (case series and retrospective reviews); there are no randomised trials comparing CRPP with ORIF. The cards below summarise the landmark anatomical, long-term outcome, and reconstructive studies.

Original Description of Bennett's Fracture

Bennett EH • Dublin J Med Sci (1882)

Key Findings:

First description of a 'fracture of the metacarpal bone of the thumb'
Described the oblique fracture line entering the CMC joint
Recognised the characteristic subluxation of the shaft
Distinguished it from extra-articular base fractures

Clinical Implication: Historical context: Bennett described this intra-articular fracture-subluxation over 140 years ago, and it still carries his name.

Anatomy of the Trapeziometacarpal Stabilising Ligaments

Bettinger PC, Linscheid RL, Berger RA, Cooney WP, An KN • J Hand Surg Am (1999)

Key Findings:

Cadaveric study identifying 16 ligaments stabilising the trapezium and TMC joint
The deep anterior oblique (beak) ligament acts as a pivot for the metacarpal during palmar abduction and pronation
The dorsoradial and deep anterior oblique ligaments play a substantial role in TMC stability
Trapezio-2nd/3rd metacarpal ligaments act as tension bands resisting cantilever bending

Clinical Implication: Reframes the classic Bennett's teaching: the beak ligament anchors the volar fragment, but the dorsoradial ligament is also a key restraint to dorsal subluxation.

Verify on PubMed (PMID 10447171)

Quality of Reduction and Outcome in Bennett's Fracture

Kjaer-Petersen K, Langhoff O, Andersen K • J Hand Surg Br (1990)

Key Findings:

41 Bennett's fractures treated by closed reduction, percutaneous K-wire, or open reduction
Median 7.3-year follow-up of reviewed patients
15 of 18 with excellent reduction were symptom-free vs only 6 of 13 with residual displacement
Radiographic arthritis in 3 of 14 anatomically reduced vs 7 of 10 with residual displacement

Clinical Implication: Residual articular displacement predicts both symptoms and radiographic arthritis - reinforces the goal of anatomic reduction.

Verify on PubMed (PMID 2307882)

Long-term Outcome of Conservatively Treated Bennett's

Cannon SR, Dowd GS, Williams DH, Scott JM • J Hand Surg Br (1986)

Key Findings:

25 Bennett's fractures reviewed at mean 9.6 years (5-16 years); 22 treated conservatively
Only 2 patients had significant symptoms despite frequent loss of TMC motion
Symptoms could NOT be reliably correlated with the accuracy of reduction
Little evidence that imperfect reduction led to symptomatic arthritis long-term

Clinical Implication: Radiographic OA and a small residual step-off do not always equal pain - useful for counselling, while still aiming for anatomic reduction.

Verify on PubMed (PMID 3794490)

26-year Follow-up of Conservatively Managed Bennett's

Livesley PJ • J Hand Surg Br (1990)

Key Findings:

17 conservatively treated Bennett's fracture-dislocations reviewed at a mean of 26 years
All had decreased range of movement and grip strength; 12 had a characteristic deformity
Radiographs showed persistent CMC subluxation and marked degenerative change
Authors recommend that this injury should NOT be managed conservatively

Clinical Implication: Long-term data underpinning the modern preference for reduction and fixation of displaced Bennett's fractures rather than casting alone.

Verify on PubMed (PMID 2230493)

Distraction External Fixation for Rolando Fractures

Houshian S, Jing SS • Hand Surg (2013)

Key Findings:

16 comminuted Rolando fractures treated by capsuloligamentotaxis with a Pennig mini external fixator
Supplementary K-wires used to maintain reduction; mean follow-up 20 months
Excellent union in all cases; all but 2 patients pain-free at final review
Mean grip 96% and pinch 93% of the unaffected thumb

Clinical Implication: Supports ligamentotaxis-based external fixation as an effective, joint-sparing option for significantly comminuted Rolando fractures.

Verify on PubMed (PMID 23413855)

Spanning External Fixation for the Rolando Fracture

Marsland D, Sanghrajka AP, Goldie B • Ann R Coll Surg Engl (2012)

Key Findings:

8 Rolando fractures treated with a static two-pin trapeziometacarpal-spanning external fixator (ligamentotaxis)
Mean time to frame removal 28 days
Mean QuickDASH 7.95 at mean 2.7-year follow-up; all returned to previous activity
Three superficial pin-site infections, no significant joint incongruity or malunion at 4 months

Clinical Implication: A simple static spanning external fixator reliably restores function in comminuted Rolando fractures, with pin-site infection the main risk.

Verify on PubMed (PMID 22391382)

Exam Viva Scenarios

Use these scenarios to practise clinical reasoning and management decisions

CLINICAL SCENARIOStandard

Scenario 1: Bennett's Fracture

CLINICAL PROMPT

"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?"

PRACTICAL APPROACH

This is a **Bennett's Fracture**. **Pathology:** - Unstable intra-articular fracture-subluxation. - Deforming forces: **APL** pulls the shaft proximally and radially, **adductor pollicis** pulls the head into adduction. The volar beak fragment is held by the deep anterior oblique ligament. **Management Plan:** 1. **Attempt Closed Reduction:** - Traction, Extension, Pronation, Abduction (with pressure on the dorsal base). - Check on fluoroscopy. 2. **If Reducible (under 1mm step, congruent):** - **Percutaneous Pinning (CRPP):** - Two 1.4-1.6mm K-wires. - Metacarpal to trapezium (or to the 2nd MC base). - Thumb spica cast 4-6 weeks. 3. **If Irreducible or large fragment:** - **Open Reduction (ORIF):** - Radiopalmar (Wagner) approach. - Protect the radial sensory nerve. - Fix with a 2.0mm lag screw or mini-plate. **Rationale:** - In a young manual worker / boxer, restoring articular congruity is paramount to limit early CMC arthritis.

KEY CLINICAL POINTS

The main deforming force on the shaft is the APL

The volar-ulnar fragment is the anchor (held by the beak ligament)

Reduction requires Extension + Pronation + Abduction

Threshold for surgery is low (greater than 1-2mm step or unstable)

COMMON PITFALLS

Mistaking it for an extra-articular fracture

Assuming a cast alone will hold it (it is unstable)

Injuring the radial sensory nerve during pinning

FURTHER QUESTIONS

"How does a Rolando fracture differ?"

"What is a reverse Bennett's fracture?"

"Which ligament holds the volar fragment reduced?"

CLINICAL SCENARIOChallenging

Scenario 2: Rolando Fracture - Surgical Decision Making

CLINICAL PROMPT

"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?"

PRACTICAL APPROACH

This is a Rolando fracture, which is more complex than a Bennett's fracture because of the comminution. The key decision is whether the fracture is amenable to ORIF or whether it is better treated by distraction external fixation. From the description there are three main fragments (Y-pattern) with the volar and dorsal pieces both around 5mm, which suggests they may be large enough for stable internal fixation. My options are ORIF with plate or screw fixation, external fixation with ligamentotaxis, or conservative management with early motion. Given he is a carpenter requiring strong pinch and the fragments appear fixable on CT, I would favour ORIF. My approach would be a Wagner radiopalmar incision protecting the radial sensory nerve branches. I would reduce the volar fragment first and provisionally hold it with a K-wire, then reduce the dorsal fragment and fix both to the shaft with lag screws or a small T-plate or locking plate, aiming for an articular step-off under 1mm. If at surgery, or on CT, the fragments were smaller than about 3mm and not reliably fixable, I would instead use a distraction external fixator spanning from the trapezium or radius to the thumb metacarpal, using ligamentotaxis to restore length and mould the articular surface - modern series report grip and pinch around 90% of the normal side with this technique. I would counsel him that Rolando fractures have worse outcomes than Bennett's because of the articular cartilage damage at the time of injury, with a real risk of post-traumatic CMC arthritis even after perfect reduction. Return to carpentry should be expected around 3-4 months with progressive strengthening.

KEY CLINICAL POINTS

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

ORIF is appropriate if fragments are over 3-5mm and reducible

Distraction external fixation (ligamentotaxis) for severe comminution

Goal: anatomic articular reduction, step-off under 1-2mm

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

COMMON PITFALLS

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

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

Not warning about the worse prognosis compared with Bennett's

Overpromising complete recovery in a manual labourer

FURTHER QUESTIONS

"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 intraoperatively, what would you do?"

CLINICAL SCENARIOCritical

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

CLINICAL PROMPT

"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 a 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?"

PRACTICAL APPROACH

This patient has post-traumatic CMC arthritis from an inadequately reduced Bennett's fracture. The 3mm step-off was above the accepted 1-2mm threshold and has predictably led to arthritis. The damage is established and the arthritis cannot be reversed, so management is a stepwise progression from conservative to surgical. I would start with conservative measures: activity modification, NSAIDs, a thumb spica splint for flares, and a corticosteroid injection into the CMC joint for temporary relief. If these fail and pain continues to affect his work, I would discuss salvage surgery. The main options are trapeziectomy with or without ligament reconstruction and tendon interposition (LRTI), CMC arthrodesis, or arthroplasty. For a 42-year-old mechanic needing power grip, I would recommend CMC arthrodesis, which gives reliable pain relief and preserves thumb length and strength for heavy work. A typical fusion position is around 40 degrees palmar abduction and 20 degrees radial abduction with the metacarpal aligned with the radius, fixed with a plate or crossed screws. The trade-off is loss of CMC motion, though the MCP and IP joints usually compensate. Trapeziectomy is an alternative but sacrifices some pinch power, which may not suit a mechanic. I would explain that the original casting was suboptimal because a displaced Bennett's is inherently unstable and the 3mm step-off should have prompted fixation - framed to set realistic expectations rather than to assign blame. Surgery here is salvage, not restoration to normal.

KEY CLINICAL POINTS

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

Conservative first: splint, NSAIDs, injection for temporary relief

Salvage surgery: CMC fusion (best for heavy manual work) vs trapeziectomy +/- LRTI

CMC fusion approx 40 deg palmar abduction, 20 deg radial abduction; reliable pain relief

Set realistic expectations - salvage surgery, not restoration to normal

COMMON PITFALLS

Attempting corrective osteotomy when arthritis is already established

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

Not acknowledging that the initial treatment was suboptimal

Overpromising a return to heavy work after trapeziectomy

FURTHER QUESTIONS

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

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

"Could you offer this patient a CMC joint replacement instead?"

MCQ Practice Points

Clinical Pearl

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

A: A Bennett fracture is an intra-articular fracture-subluxation at the thumb CMC joint with a volar-ulnar fragment held reduced by the deep anterior oblique (beak) ligament 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; the thumb extensors hyperextend the MCP. The beak ligament keeps the volar fragment reduced while the shaft subluxates away from it.

Clinical Pearl

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

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

Clinical 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) CMC subluxation that cannot be maintained; 3) any displaced Bennett fracture (inherently unstable); 4) Rolando fracture with reducible fragments; 5) unstable extra-articular fractures. The goals are anatomic articular reduction and a stable CMC joint. Options include closed reduction and percutaneous K-wires, ORIF with a lag screw (Bennett's with an adequate fragment), or plate / external fixation (Rolando or comminuted patterns).

Clinical Pearl

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

A: An extra-articular fracture (Winterstein): the fracture line does not involve the CMC joint surface, the joint remains congruent, and deformity is apex-dorsal angulation at the fracture site. A Bennett fracture: the fracture line enters the CMC joint, an intra-articular fragment is visible on the Robert's view (true AP of the thumb with the hand hyperpronated), and the CMC joint shows subluxation with widening. Extra-articular fractures tolerate more angulation (20-30 degrees) than intra-articular fractures because CMC mobility compensates.

Clinical Pearl

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

A: The deep anterior oblique (beak) ligament runs from the volar-ulnar beak of the metacarpal base to the trapezium and is a key stabiliser of the thumb CMC joint. In a Bennett fracture the volar-ulnar fragment remains attached to the beak ligament, keeping it reduced to the trapezium while the metacarpal shaft subluxates - producing the classic fracture-subluxation. Surgical reduction must bring the shaft back to the volar fragment (and thus to the trapezium). Anatomic studies (Bettinger 1999) show the dorsoradial ligament is also a substantial restraint, so the beak ligament is not the only stabiliser.

Guidelines, Registries & Global Practice

Global Epidemiology

Thumb metacarpal base fractures account for roughly a quarter of all metacarpal fractures and around 1-2% of all fractures.
Bennett's is the most common intra-articular thumb base fracture; Rolando is considerably less common.
Typical demographic: young to middle-aged men, dominant hand, from axial loading of a flexed thumb (punch, fall, sport).

Side-by-Side Guideline / Reference Comparison

How Major Bodies Frame Thumb Base Fractures

Body	Emphasis	Practical Recommendation
AO Foundation / AO Surgery Reference	Pattern-based decision making	Anatomic articular reduction; CRPP for Bennett's, ex-fix or ORIF for Rolando
BOA / BSSH (UK)	Hand trauma pathways, timely hand-surgery review	Reduce and stabilise unstable intra-articular base fractures; restore congruity
AAOS / ASSH (US)	Restore articular surface and CMC stability	Surgery for step-off greater than 1-2mm or maintained subluxation
EFORT / European consensus	Function over radiographic perfection	Aim for congruity but counsel that radiographic OA may be asymptomatic

Registry note: Unlike arthroplasty, isolated thumb base fractures are not tracked by national joint registries (NJR, AJRR, AOANJRR, SHAR). Evidence therefore rests on case series and small comparative studies rather than registry data - reflected in the predominantly Level IV evidence base.