Trapezium Fractures

Trapezium fractures are fractures of the trapezium, the carpal bone on the radial side of the distal row. They account for 3-5% of all carpal fractures, and the trapezium is the second most commonly fractured bone of the distal row, after the hamate. The patients are young to middle-aged adults, with a male predominance.

Two patterns. Two injuries share the name, and treatment depends on which one is in front of you.

• Ridge fractures are the more common: an extra-articular avulsion of the volar trapezial ridge at the FCR attachment, usually treated conservatively
• Body fractures are less common but more significant: they run through the body into the articular surface of the thumb CMC joint, need anatomic reduction and carry a higher complication rate

Why the joint matters. The trapezium articulates with the thumb metacarpal at the CMC joint, the most mobile and most important joint of the thumb, which allows opposition, flexion, extension and abduction. Injury here costs grip and pinch strength, and a body fracture deserves the same respect as a Bennett's fracture.

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Shape and joints. The bulk of the bone is the body, which carries the articular surfaces. Distally it forms a saddle joint with the first metacarpal that allows multiplanar thumb motion; medially it articulates with the trapezoid and proximally with the scaphoid.

The volar ridge. A prominent projection on the palmar surface. It forms the radial border of the groove through which the flexor carpi radialis (FCR) passes, and it gives attachment to the transverse carpal ligament and the FCR sheath.

Blood supply. Multiple small vessels enter through the non-articular dorsal and volar surfaces, with no single dominant vessel and adequate anastomoses. The trapezium has good healing potential and a lower AVN risk than the scaphoid or lunate. The tip of the volar ridge is the exception (see the Palmer classification below).

Load. The CMC is a biaxial saddle joint that allows opposition and circumduction. Forces from the thumb concentrate on the trapezium, with high stress during pinch and grip, and the joint is predisposed to arthritic change.

Anatomical classification. Location and articular involvement guide treatment.

Walker classification. A practical scheme that separates the extra-articular injuries, with a good prognosis, from the articular ones, which are more complex.

• Type A, ridge - volar avulsion (most common) or dorsal avulsion (rare), extra-articular; conservative for most
• Type B, body - B1 vertical split with the CMC involved, B2 horizontal split, B3 comminuted; ORIF for displaced fractures, fusion for comminuted
• Type C, associated injuries - a trapezium fracture with a first metacarpal base fracture, a Bennett's or Rolando's variant, or another complex pattern; address every component

Mechanism helps predict the pattern. Ridge fractures are low-energy avulsions: FCR traction during forceful wrist flexion, with the pull of the transverse carpal ligament, produces an extra-articular fracture. Body fractures come from an axial load through the thumb metacarpal, similar to the Bennett's mechanism, which splits the trapezium into the joint.

Direct and combined injuries. A direct blow to the base of the thumb gives a variable, high-energy pattern that may be comminuted. Combined mechanisms, with several force vectors, produce complex patterns, often with associated injuries, and carry the worst prognosis.

History. The mechanism points towards the pattern:

• A fall on the outstretched hand with the thumb abducted
• A direct blow to the thenar eminence
• An axial load from a punch or a fall onto the thumb
• Forceful wrist flexion, avulsing the ridge

Establish the exact mechanism and thumb position, the energy of injury, the immediate symptoms, hand dominance and occupation, and any prior thumb or wrist pathology.

Inspection and palpation. Look for swelling over the thenar eminence and bruising at the thumb base, comparing with the other hand. Tenderness directly over the trapezium at the thenar eminence, or at the volar wrist crease over the ridge, localises the injury; palpate along the FCR for tenosynovitis. The anatomic snuffbox may be tender too, which overlaps with the scaphoid.

Movement and stability. Pain limits CMC motion, and opposition is particularly affected. Stress the CMC joint for stability once analgesia is adequate, comparing with the opposite side.

Neurovascular status. Usually preserved, but the thenar branch of the median nerve may be at risk. Document a baseline.

Special tests.

• Grind test - axial load with rotation at the CMC; pain suggests CMC pathology, and it may be positive with both fracture and arthritis
• FCR provocation - resisted wrist flexion; pain suggests FCR involvement, which matters in ridge fractures
• Pinch strength - markedly reduced with trapezium injury; compare with the other side and record it as the baseline for recovery

Differential diagnosis. Radial-sided wrist and thumb-base pain after trauma has several mimics. The trapezium sits at the crossroads of the scaphoid, the thumb metacarpal base, the scaphotrapeziotrapezoid (STT) joint and the FCR tunnel, so each must be actively excluded, and the examination helps separate a ridge fracture from a body fracture.

Radiographs. Start with the standard views:

• PA - may show a body fracture
• Lateral - displacement
• Oblique - an additional perspective

They are available and quick, and their primary role is the body fracture.

On the films, look for a ridge fragment on the carpal tunnel view, a body fracture line on the PA or oblique, CMC joint congruity, and an associated thumb metacarpal injury.

The carpal tunnel view. Standard PA and lateral views may miss a ridge fracture, and without the carpal tunnel (Gaynor-Hart) view it is easily missed. The wrist is hyperextended and the beam angled at 25 degrees, which shows the volar ridge clearly. It needs a specific technique and must be requested specifically whenever a ridge fracture is suspected.

The Betts view. Hyperpronation isolates the trapezium from the overlapping bones. It is good for assessing a body fracture and complements the carpal tunnel view.

CT. Essential for ORIF. It plans surgery for a body fracture by showing the fracture orientation (vertical or horizontal), the articular step-off or gap, fragment size and displacement, comminution and associated injuries, and it detects occult fractures.

MRI. Rarely needed acutely. It assesses the soft tissues and detects occult fractures, showing bone marrow oedema, FCR tenosynovitis and ligament integrity.

Algorithm

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Ridge fractures. Extra-articular, with a generally excellent prognosis in a thumb spica splint or cast for 4-6 weeks, the thumb in a functional position. A removable splint may be used if the patient is compliant, and mobilisation begins once the ridge is non-tender (protocol under Postoperative Care).

Symptomatic ridge non-union. Occurs in a minority, with persistent thenar pain, FCR tenosynovitis symptoms, pain on wrist flexion and extension, and tenderness over the volar ridge. Treatment is stepwise:

1. A trial of splinting and anti-inflammatories
2. A steroid injection, which may give temporary relief
3. Fragment excision if symptoms persist

Undisplaced body fractures. Cast when the fracture is undisplaced (step-off under 2mm), the patient is low-demand, or surgery is medically contraindicated. A thumb spica cast for 6-8 weeks, with serial radiographs to catch displacement, and mobilisation once healed.

Displaced body fractures. The indications for surgery:

• Articular step-off over 2mm
• CMC joint subluxation
• A displaced vertical or horizontal body fracture
• Failed conservative treatment

The goals are anatomic CMC articular reduction, stable fixation, early mobilisation when possible, and prevention of post-traumatic CMC arthritis.

Which approach. The dorsal approach, between EPB and EPL, is the common one: it gives good visualisation of the CMC joint and access for screws or K-wires. A volar approach through the thenar muscles is used for volar fragments and protects the radial artery.

Ridge fractures. The problems come from the FCR and from failure to unite.

• FCR tenosynovitis - common with symptomatic non-union, as the fragment irritates the tendon; early treatment prevents it, and excision with debridement treats it
• FCR rupture - rare, from chronic irritation by the fragment, usually in untreated symptomatic cases; fragment excision, with tendon repair if possible
• Symptomatic non-union - conventionally quoted at 10-20% of ridge fractures, though no series exists to measure it (see the caveat under the Palmer classification); non-union may be asymptomatic, and excision is for the symptomatic

Body fractures. The problems come from the joint surface.

• Malunion - CMC articular incongruity that leads to early arthritis; anatomic reduction prevents it, and it may need osteotomy or fusion
• Post-traumatic CMC arthritis - the most significant long-term complication, related to residual step-off, with progressive thumb-base pain; treated by CMC arthroplasty or fusion
• Non-union - uncommon with proper treatment; adequate immobilisation or fixation prevents it, and it may require bone grafting, with internal fixation considered
• Stiffness - the CMC joint may stiffen; early mobilisation when stable prevents it, and hand therapy and patience treat it

Surgical complications.

• Radial sensory nerve injury - a risk of the dorsal approach, prevented by careful identification; it usually recovers, and may need neurolysis
• Hardware problems - joint penetration or prominent hardware, treated by removal when healed
• Infection - rare, managed on standard principles

Ridge fractures in a cast. A thumb spica splint or cast for weeks 0-4, with finger motion encouraged and ice and elevation for swelling, and a clinical review at 2 weeks. At 4-6 weeks assess tenderness and mobility; if the ridge is non-tender, begin mobilisation and wean the splint. From 6 weeks, progressive motion and strengthening, return to activities as tolerated, and a watch for late FCR symptoms.

Undisplaced body fractures in a cast. A thumb spica cast for weeks 0-6, with radiographs at weeks 2 and 4 and finger exercises throughout. At 6-8 weeks, if healed, move to a splint and begin gentle thumb motion and progressive activity.

After ORIF of a body fracture. Rehabilitation is longer than for a ridge fracture because the CMC joint is involved.

After ridge excision. A light splint for comfort, suture removal at 10-14 days, and motion from 1-2 weeks. Progressive activity and strengthening follow from 2 weeks, with full activities by 4-6 weeks; patients are usually fully recovered by 6 weeks and back to work and sport.

Follow-up.

Ridge fractures. Over 90% heal with casting, and function is excellent in most. Symptomatic non-union is conventionally quoted at 10-20%, but this is an estimate rather than a measured rate: the literature on this injury is case reports, and Palmer's classification itself rests on three patients. After fragment excision over 95% are satisfied with their pain relief, patients return to their previous activities, and FCR problems resolve.

Body fractures in a cast. Outcomes are good when the fracture is truly undisplaced, but there is a risk of secondary displacement, so close monitoring is essential.

Body fractures after ORIF. The articular reduction determines the outcome. A step-off under 1mm gives good outcomes and one over 2mm a higher arthritis rate, and range of motion recovers to 80-90% of the other side. Anatomic reduction lowers the arthritis rate; malreduction leads to progressive CMC osteoarthritis that may require later CMC arthroplasty.

Prognostic factors.

Return to activity.

Global Epidemiology

Trapezium fractures are uncommon, comprising roughly 3-5% of carpal fractures, and non-scaphoid carpal fractures as a whole are rare. In the population-based Australian Geelong/Barwon cohort, the incidence of non-scaphoid carpal fractures was 15.9 per 100,000 person-years in males and 4.5 per 100,000 person-years in females, with a male predominance, a peak in young adulthood (20-29 years), and most fractures resulting from a fall (Holloway et al., Arch Osteoporos 2015, PMID 25910867). Contemporary hand-surgery reviews emphasise that these injuries are frequently associated with other carpal or metacarpal injuries and are easily missed on standard radiographs (Suh, Ek, Wolfe, J Hand Surg Am 2014, PMID 24679911).

Guideline & Society Positions

No fracture-specific society guideline (AAOS, NICE, BOA/BSSH, AO, EFORT) is dedicated to the trapezium given its rarity; practice is driven by general carpal-fracture principles and hand-surgery consensus. The table below summarises the converging guidance and its evidence basis.

Registry Evidence

No national fracture registry tracks trapezium fractures specifically. Indirect registry-adjacent signals come from arthroplasty literature: trapezium fracture is a recognised complication of certain CMC implants (for example, implant subsidence into the trapezium), reinforcing that the bone is mechanically loaded and that articular integrity matters. The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) does not separately report trapezium fracture but documents thumb-base arthroplasty activity, the downstream burden that post-traumatic CMC arthritis can contribute to.

Practice Variation

• Imaging access: dedicated carpal tunnel (Gaynor-Hart) views and early CT are routine in well-resourced systems but variably available elsewhere, driving differences in detection of ridge and occult body fractures.
• Fixation choice: headless compression screws are preferred where fragment size permits; K-wires remain widely used for small fragments or in lower-resource settings.
• Rehabilitation: structured hand-therapy pathways (well established in high-income settings such as Australia, the UK, and North America) shorten time to return of function; access varies internationally.
• Imaging request practices: dedicated carpal tunnel (Gaynor-Hart) views must be specifically requested; targeted education of emergency and primary-care clinicians reduces missed ridge fractures.

Understanding these key concepts will help with exam success.

The evidence supports distinct management approaches for ridge and body fractures, anchored by a contemporary reference review, the classic body-fracture series, anatomic and clinical data linking the volar ridge to the FCR, and population-based epidemiology from the Geelong/Barwon cohort.