Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Distal Radius Fractures: Types, Biomechanics, and Management

Colles Fracture

Definition: An extra-articular distal radius fracture with dorsal displacement of the distal fragment.
Mechanism: Low-energy fall onto an outstretched hand (FOOSH).
Demographics: Most common in patients older than 50 years.
Deformity: Classic dinner fork deformity caused by dorsal tilt and displacement.
TFCC Injury: Associated Triangular Fibrocartilage Complex (TFCC) tears occur in roughly 50% of extra-articular fractures.
Cast Failure Predictors:
- Dorsal comminution exceeding 33% to 50% of the dorsal cortex precludes stable cast treatment.
- More dorsal comminution correlates directly with secondary displacement in a cast.
- Extension of the fracture line into the distal radioulnar joint (DRUJ) carries the worst prognosis.

Definition: A predominantly extra-articular distal radius fracture with volar (palmar) displacement.
Mechanism: Fall onto a flexed wrist.
Deformity: Classic garden spade deformity.
Treatment: Open reduction and internal fixation (ORIF) via a volar approach using a buttress or locking plate.

Type	Fracture Pattern	Key Anatomical Features
Type 1	Extra-articular transverse	Most common subtype; classic reverse Colles
Type 2	Intra-articular oblique	Fracture line enters the dorsal articular surface
Type 3	Intra-articular oblique	Crosses into radiocarpal joint; identical to a Volar Barton fracture

Definition: A depressed, intra-articular fracture of the lunate fossa of the distal radius.
Mechanism: Pure axial load transmitted directly through the lunate bone.
Clinical Red Flag: High incidence of occult carpal bone dissociation.
Assessment: Requires careful evaluation of articular step-off and depression.

Definition: An intra-articular fracture-subluxation or fracture-dislocation of the radiocarpal joint.
Mechanism: Fall onto an extended, pronated wrist with significant shear force.
Pathoanatomy: Strong radiocarpal ligaments remain intact. They avulse the articular rim, causing the carpus to dislocate along with the bone fragment.

Parameter	Volar Barton (Most Common)	Dorsal Barton
Displacement	Volar rim avulsion with palmar carpal dislocation	Dorsal rim avulsion with dorsal carpal dislocation
Classification Overlap	Equivalent to Smith Type 3	Often grouped with intra-articular dorsal shear injuries
Fragment Size	Variable, typically substantial	Often smaller than volar fragments
Surgical Approach	Volar (Henry) approach with volar buttress plate	Dorsal approach with dorsal buttress plate

Definition: An isolated intra-articular fracture of the radial styloid process.
Mechanism: Direct compression or shear of the scaphoid bone against the radial styloid.
Associated Pathology: High risk of concomitant scapholunate dissociation.
Imaging Requirement: Always obtain a supinated wrist view to assess the scapholunate interval.
Scapholunate Instability & DISI Deformity:
- Normal scapholunate angle: 47 degrees (normal range: 30 to 60 degrees).
- Angle greater than 60 degrees indicates abnormal dorsal intercalated segment instability (DISI).
- The scaphoid flexes volarly while the lunate extends dorsally.
- AP radiograph shows widening of the scapholunate space (Terry Thomas sign).
Treatment: Anatomic reduction with compression lag screws across the radial styloid, followed by scapholunate ligament assessment and stabilization if unstable.

Check for articular surface involvement (dorsal vs. volar rim).
Assess the lunate fossa for depressed die-punch components.
Evaluate the distal radioulnar joint (DRUJ) for articular step-off or widening.
Determine carpal translation and the direction of subluxation or dislocation.
Inspect carpal intervals on AP and lateral views to rule out scapholunate or lunotriquetral dissociation.