Colles Fracture

Introduction

Introduction to Colles Fracture

A Colles fracture is an extra‑articular fracture of the distal radius with dorsal angulation and dorsal displacement of the distal fragment, often accompanied by an ulnar styloid fracture. It is the most common fracture of the distal forearm, typically occurring in osteoporotic postmenopausal women after a fall on an outstretched hand with the wrist in extension. The anatomical distortion involves the radiocarpal joint surface, the distal radioulnar joint, and the surrounding soft tissues, giving rise to the classic ‘dinner fork’ deformity. Despite being extra‑articular, the close proximity to the carpal tunnel, extensor tendons, and the median nerve makes this injury clinically significant.

Understanding the applied anatomy of the distal radius, its articular relationships, and the adjacent neurovascular structures is essential for proper diagnosis, management, and prevention of complications such as malunion, carpal tunnel syndrome, and tendon rupture.

Study

1. Anatomy of the Distal Radius and Surrounding Structures

The distal radius forms the major proximal articular surface of the radiocarpal (wrist) joint. It articulates with the scaphoid (laterally) and the lunate (medially), while the triquetrum articulates with the triangular fibrocartilage complex (TFCC) on the ulnar side. The distal radius has three important angulations: palmar tilt (approximately 11–12° of volar inclination), radial inclination (approximately 22°), and radial height (approximately 11 mm). These anatomical parameters are critical for normal wrist function and are altered in a Colles fracture.

The distal radius metaphysis is a region of trabecular bone that is susceptible to fracture, especially in osteoporotic individuals. The pronator quadratus lies anteriorly, inserting on the distal radius and providing a muscular cover. The brachioradialis tendon inserts on the radial styloid and can exert a deforming force on the distal fragment. The extensor pollicis longus (EPL) tendon passes around Lister’s tubercle on the dorsal radius and is at risk of attrition rupture following a fracture.

The carpal tunnel is located just palmar to the distal radius and contains the median nerve and the long flexor tendons. Swelling or displacement of the fracture fragment into the carpal tunnel can cause acute carpal tunnel syndrome.

2. Mechanism of Injury

The classic mechanism is a fall on an outstretched hand (FOOSH) with the forearm pronated and the wrist in dorsiflexion. The impact transmits axial load through the carpus to the dorsal metaphysis of the radius, causing the fracture to propagate dorsally. The degree of comminution and displacement depends on the energy of the fall and bone quality. In younger patients, higher‑energy trauma is required.

3. Pathoanatomy and Deformity

The fracture line is extra‑articular and typically transverse or oblique, located 2–3 cm proximal to the radiocarpal joint. The distal fragment displaces dorsally and radially, and tilts dorsally (loss of palmar tilt). This results in the characteristic ‘dinner fork’ or ‘bayonet’ deformity when viewed from the side. The radial styloid is elevated, reducing radial inclination, and the radius shortens relative to the ulna (positive ulnar variance). An associated avulsion fracture of the ulnar styloid is present in up to 60% of cases due to TFCC avulsion.

4. Clinical Assessment

The patient presents with pain, swelling, and obvious deformity of the wrist. The ‘dinner fork’ deformity is visible on the lateral aspect. Palpation reveals tenderness over the distal radius. A thorough neurovascular examination is mandatory, specifically assessing median nerve function (sensation in the thumb, index, middle, and radial half of ring finger, and thenar muscle strength). The ulnar and radial pulses, capillary refill, and skin integrity are assessed.

5. Radiographic Evaluation

Standard radiographs include posteroanterior (PA) and lateral views of the wrist. Key measurements include: (1) Palmar tilt on the lateral view (normally 11–12° volar); in a Colles fracture, this is lost or reversed (dorsal angulation). (2) Radial inclination on the PA view (normally 22°); this is reduced. (3) Radial height (normally 11 mm); this is shortened. (4) Ulnar variance; typically becomes positive due to radial shortening. These measurements guide reduction and fixation.

6. Management Principles

The goal of treatment is to restore the normal anatomical relationships of the distal radius to prevent pain, stiffness, and loss of function. Displaced fractures require closed reduction under haematoma block or sedation, using traction, flexion, and ulnar deviation. The reduced position is maintained by a below‑elbow cast or a Colles cast (wrist in slight flexion and ulnar deviation). Indications for surgical fixation (percutaneous pinning, external fixation, or volar locking plate) include unstable fracture patterns, comminution, and unacceptable reduction parameters (palmar tilt < 0°, radial inclination < 10°, radial shortening > 3 mm, articular step > 2 mm).

7. Complications Based on Anatomy

Acute carpal tunnel syndrome can occur from haematoma or fracture fragment compression of the median nerve in the carpal tunnel. Extensor pollicis longus (EPL) rupture is a late complication caused by attrition of the tendon against the roughened dorsal fracture surface at Lister’s tubercle. Malunion with residual dorsal angulation leads to loss of wrist flexion and ulnar deviation, and altered carpal mechanics. Complex regional pain syndrome (CRPS) and finger stiffness are common. Ulnar styloid non‑union can cause persistent ulnar‑sided wrist pain if the TFCC remains unstable.

Summary

Summary of Colles Fracture

A Colles fracture is a dorsally angulated, extra‑articular distal radius fracture, typically from a fall on an outstretched hand. The fracture distorts normal radial inclination, palmar tilt, and radial height, producing a dinner fork deformity. The median nerve, extensor pollicis longus tendon, and the distal radioulnar joint are at risk. Treatment aims to restore anatomical alignment by closed or open means. Knowledge of the regional anatomy is essential for preventing and managing complications.