Causes / typical injury mechanism: Colles fracture describes an extra-articular distal radius fracture that occurs around 2-3 cm proximal to the radiocarpal joint and is associated with an ulnar styloid fracture. These fractures typically result from a low-energy fall onto an outstretched hand (FOOSH). Falling onto an extended wrist with the forearm in pronation can result in a dorsally displaced, extra-articular distal radius fracture fragment.

Classic history and presentation: Patients with a Colles fracture typically present with recent history of a FOOSH. There is tenderness localized to the distal radius and over the ulnar styloid. Swelling may or may not be present depending on the timing of the injury. A visible deformity may be present in more severe cases. A classic appearance of Colles fracture is known as the "dinner-fork" or "bayonet" appearance, with dorsal displacement of the distal fragment.

Prevalence: Distal radius fractures are one of the most common orthopedic injuries. They account for up to 20% of fractures in the skeletally mature adult population. Up to 9% of individuals are impacted by distal radius fractures by age 90.

• Age – Prevalence of Colles fractures increases with age.
• Sex / gender – Women are more commonly affected than men. The lifetime risk of distal radius fracture is reported to be 15% in women by age 50, whereas the risk for men is around 4%.

Risk factors:

• Older age
• Female sex
• Decreased bone mineral density
• History of recurrent falls
• History of a previous fracture after age 50

Pathophysiology: Colles fracture typically occurs from a FOOSH. An extended wrist and pronated forearm at the time of impact results in a dorsal displacement of an extra-articular distal fragment. Depending on the severity of the displacement, neurovascular structures may be injured.

Grade / classification system: There are many classification systems that are used to stratify distal radius fractures including the Frykman, AO, Melone, and Fernandez classifications. Most classifications focus on extra- versus intra-articular involvement, degree of displacement, presence / absence of ulnar styloid fracture, and/or distal radioulnar joint (DRUJ) involvement.