Smith's Fractures

Smith's fracture is a distal radius fracture with volar angulation of the distal fragment (apex dorsal). It was first described by Irish surgeon Robert William Smith in 1847, 33 years after Abraham Colles described the dorsally angulated variant.

Terminology:

• Also known as "reverse Colles fracture"
• The eponym specifically refers to the volar angulation pattern
• Distinguished from volar Barton (which is a rim fracture with subluxation)

Epidemiology:

• Accounts for approximately 5% of all distal radius fractures
• Less common than Colles fractures (approximately 1:10 ratio)
• Bimodal distribution: young adults (high-energy trauma) and elderly (low-energy falls)
• Male predominance in younger patients (sports, motorcycle accidents)
• Equal gender distribution in elderly

Mechanism of injury:

• Fall on outstretched hand with wrist flexed (most common)
• Direct blow to dorsum of hand forcing wrist into flexion
• High-energy: motorcycle accidents, sports injuries
• Low-energy: falls in elderly with osteoporotic bone

Distal radius anatomy relevant to Smith fractures:

The distal radius has several key features:

• Volar tilt: Normal volar tilt is 10-15 degrees (palmar inclination)
• Radial inclination: Normal is 22-23 degrees
• Radial height: Normal is 11-12mm
• Ulnar variance: Usually neutral to slightly negative

Ligamentous attachments:

• Volar radiocarpal ligaments (radioscaphocapitate, long radiolunate, short radiolunate) are strong
• These ligaments remain attached to the distal fragment
• They pull the fragment volarly, creating the characteristic deformity
• This explains why Smith fractures are inherently unstable

Pathomechanics of Smith fracture:

Force transmission:

1. Fall with flexed wrist applies bending moment
2. Volar cortex fails in tension (transverse fracture)
3. Or direct blow creates shear force (oblique fracture)
4. Volar ligaments pull distal fragment volarly
5. Pronator quadratus may contribute to deforming force

Watershed line:

• Critical landmark on volar distal radius
• Marks transition from flat metaphyseal surface to curved articular surface
• Volar plate should NOT extend beyond this line (causes flexor tendon irritation)

History:

• Mechanism (FOOSH with flexed wrist, direct blow, high-energy trauma)
• Hand dominance
• Occupation and functional demands
• Previous wrist injuries
• Medical comorbidities (diabetes, osteoporosis)

Physical examination:

Neurovascular assessment:

• Median nerve: Most at risk due to volar displacement
  • Sensation in thumb, index, middle finger
  • Motor: abductor pollicis brevis (APB)
  • Carpal tunnel symptoms may develop acutely
• Radial artery: Palpate at anatomical snuffbox and wrist
• Capillary refill: Assess all digits

Associated injuries to assess:

• Scapholunate ligament injury
• TFCC injury
• DRUJ instability
• Carpal fractures (especially scaphoid)
• Ulnar styloid fracture

Differential diagnosis:

The volar-prominence deformity and a distal radius injury on plain films can mimic several patterns. The single most discriminating step is the lateral radiograph (direction of angulation) and whether the fracture is articular.

Radiographic assessment:

Standard views:

• PA view: Assess radial inclination, radial height, ulnar variance
• Lateral view: Critical for diagnosis - shows volar angulation
• Oblique view: Additional assessment of articular involvement

Key measurements on lateral view:

Signs of Smith fracture on X-ray:

• Volar angulation of distal fragment (apex dorsal)
• Volar displacement of carpus
• Loss of normal volar tilt (or reversal)
• Possible intra-articular extension (Type II)

CT imaging:

• Indicated for intra-articular fractures (Type II)
• Defines articular step-off and gap
• Helps surgical planning for fragment-specific fixation
• Not routine for simple Type I fractures

MRI:

• Not routine for acute fractures
• Consider if ligamentous injury suspected (persistent pain)
• Assess TFCC, scapholunate ligament

Flexor tendon complications:

Malunion:

• Volar malunion is better tolerated than dorsal (Colles pattern)
• Loss of volar tilt affects wrist mechanics
• Symptomatic malunion may require corrective osteotomy

Median nerve injury:

• Can occur from initial injury (volar displacement)
• Or from surgical approach
• Most are neuropraxic and recover
• Acute carpal tunnel may require release

Rehabilitation principles:

• Early ROM prevents stiffness
• Volar plate allows early mobilization
• Strengthening delayed until fracture healed (6 weeks)
• Hand therapy optimizes outcomes
• Patient education on activity restrictions

Outcomes with modern treatment:

Volar locked plating of Smith fractures produces excellent results in most patients. Functional outcomes are comparable to or better than historical non-operative management.

Prognostic factors:

• Favorable: Young age, isolated injury, anatomic reduction
• Unfavorable: Intra-articular involvement, associated carpal injury, elderly with osteoporosis

Functional outcomes:

• Most patients achieve functional ROM (60 degrees flexion/extension, 30 degrees radial/ulnar deviation)
• Grip strength typically recovers to 80-90% of contralateral
• Return to work: 4-8 weeks (desk work), 8-12 weeks (manual labor)
• Return to sport: 3-4 months

Long-term considerations:

• Post-traumatic arthritis in intra-articular fractures (Type II)
• Hardware removal if symptomatic (15-20% rate)
• Overall prognosis excellent with modern fixation techniques

Global epidemiology:

Distal radius fractures are among the commonest fractures worldwide, with a bimodal age distribution - a peak in children and young adults from higher-energy mechanisms and a larger peak in older (predominantly female, osteoporotic) patients from low-energy falls. Prevalence has risen over four decades in both groups. Smith (volar-displacing) fractures are far less common than the dorsally displacing Colles pattern, but the volar pattern is over-represented among younger, higher-energy injuries (sport, motorcycle, direct dorsal blow), which is why mechanism shapes the demographic. The figures below are PubMed-verifiable population data, not country-specific framing.

Major guidelines, side by side:

There is no Smith-specific international guideline; recommendations come from the broader distal radius literature and society guidance. The unifying message across bodies is that an unstable, displaced, volarly translating distal radius fracture is poorly controlled by cast alone and is a strong indication for fixation, while low-demand elderly extra-articular fractures may be managed conservatively.

Registry and trial evidence:

National joint registries (NJR, AJRR, AOANJRR, SHAR and others) primarily capture arthroplasty rather than fracture fixation, so distal radius implant-survival data come chiefly from trials and large cohorts rather than registries. The key high-level evidence is therefore:

• Arora 2011 RCT - volar plating gives better early function, grip strength and radiographic restoration than casting in patients 65 and older, but equivalent patient-rated outcomes at 12 months with more complications; this is the central plate-versus-cast trial.
• Soong 2011 - defined the watershed-line plate-prominence grading that governs flexor tendon rupture risk and is now a global benchmark for plate position.
• Handoll & Elliott 2015 Cochrane - no rehabilitation regimen is clearly superior; coached home exercise after stable plating performs at least as well as routine supervised physiotherapy.

Global practice variation:

• High-resource settings: volar locking plate fixation is the default for displaced/unstable Smith and volar-shear (Thomas II) fractures, enabling early motion.
• Limited-resource settings: closed reduction with sugar-tong/cast or K-wire fixation remains common where locking plates or image intensifiers are scarce; for a truly unstable volar-shear pattern this carries a higher redisplacement risk, so buttress fixation is prioritised when available.
• Older, low-demand patients: more variation - acceptance of a degree of malunion in exchange for avoiding surgery is reasonable for extra-articular patterns, but volar-shear instability with carpal translation still favours fixation in any setting.

Implant note (vendor-neutral):

Multiple anatomically pre-contoured volar locking plate systems are available worldwide, with fragment-specific options for complex articular patterns. The principle (a fixed-angle buttress proximal to the watershed line) matters far more than the manufacturer.