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Revised AO/OTA classification (Jan 2018)

Introduction

A revision of the AO/OTA Fracture and Dislocation Classification was published in the January 2018 issue of the Journal of Orthopaedic Trauma (Compendium and support material). This module is organized according to the 2007 version. Please read through its revised classification (below) before returning to the AO Surgery Reference.

2R3A1 Radius, extraarticular, radial styloid avulsion fracture

2R3A1 Radial styloid avulsion fracture

2R3A2 Radius, extraarticular, simple fracture

2R3A2.1 Transverse, no displacement/tilt (may be shortened)

2R3A2.2 Dorsal displacement/tilt (Colles)

2R3A2.3 Volar displacement/tilt (Smith’s)

2R3A3 Radius, extraarticular, wedge or multifragmentary fracture

2R3A3.1 Intact wedge fracture

2R3A3.2 Fragmentary wedge fracture

2R3A3.3 Multifragmentary fracture

2U3A1 Ulna, extraarticular, styloid process fracture

2U3A1.1 Tip of styloid fracture

2U3A1.2 Base of styloid fracture

2U3A2 Ulna, extraarticular, simple fracture

2U3A2.1 Spiral fracture

2U3A2.2 Oblique fracture (≥30°)

2U3A2.3 Transverse fracture (<30°)

2U3A3 Ulna, extraarticular, multifragmentary fracture

2U3A3 Ulna, extraarticular, multifragmentary fracture

2R3B1 Radius, partial articular, sagittal fracture

2R3B1.1 Involving scaphoid fossa

2R3B1.3 Involving lunate fossa

2R3B2 Radius, partial articular, dorsal rim (Barton’s) fracture

2R3B2.1 Simple fracture

2R3B2.2 Fragmentary fracture

2R3B2.3 With dorsal dislocation

2R3B3 Radius, partial articular, volar rim (reverse Barton’s, Goyrand-Smith’s II) fracture

2R3B3.1 Simple fracture

2R3B3.3 Fragmentary fracture

2R3C1 Radius, complete, simple articular and metaphyseal fracture

2R3C1.1* Dorsomedial articular fracture

*Qualifications:
t - DRUJ stable
u - DRUJ unstable

2R3C1.2* Sagittal articular fracture

*Qualifications:
t - DRUJ stable
u - DRUJ unstable

2R3C1.3* Frontal/coronal articular fracture

*Qualifications:
t - DRUJ stable
u - DRUJ unstable

2R3C2 Radius, complete, simple articular, metaphyseal multifragmentary fracture

2R3C2.1* Sagittal articular fracture

*Qualifications:
t - DRUJ stable
u - DRUJ unstable

2R3C2.2* Frontal/coronal fracture

*Qualifications:
t - DRUJ stable
u - DRUJ unstable

2R3C2.3* Extending into the diaphysis

*Qualifications:
t - DRUJ stable
u - DRUJ unstable

2R3C3 Radius, complete, multifragmentary articular, simple or multifragmentary metaphyseal fracture

2R3C3.1* Simple metaphyseal fracture

*Qualifications:
t - DRUJ stable
u - DRUJ unstable

2R3C3.2* Metaphyseal multifragmentary fracture

*Qualifications:
t - DRUJ stable
u - DRUJ unstable

2R3C3.3* Extending into the diaphysis

*Qualifications:
t - DRUJ stable
u - DRUJ unstable

Executive Editor: Steve Krikler

Authors: Renato Fricker, Jesse Jupiter, Matej Kastelec

Distal forearm 23-C2 External fixation

Joint-spanning external fixation (temporary or definitive)

1. Note on illustrations

Throughout this treatment option illustrations of generic fracture patterns are shown, as four different types:

A) Unreduced fracture
B) Reduced fracture
C) Fracture reduced and fixed provisionally
D) Fracture fixed definitively

2. Principles of joint-spanning external fixation

Joint-spanning external fixation of the wrist may be used as a temporary or definitive treatment in simple or complex distal forearm fractures.

The external fixator may be used on its own or to supplement K-wire fixation. Specifics of K-wire fixation are given in separate treatment options for each appropriate fracture type.

Details of external fixation are described in the basic technique for application of modular external fixator.

Specific considerations for the wrist are given below.

In joint-spanning external fixation of the wrist, the 4 mm (small) external fixator system is commonly used and may be combined with the 8 mm (medium) system. They are applied as described in the basic technique for the 11 mm (large) system.

There are several other external fixation systems available.

3. Pin insertion (wrist)

Complications with pin insertion

The following three potential complications are of concern when inserting threaded pins for external fixation:

  • Injury to extensor tendons
  • Injury to the superficial branch of the radial nerve
  • Metacarpal fracture

The following precautions minimize the risk of these complications:

  • Knowledge of the anatomy and specific landmarks for pin insertion
  • Larger surgical incisions (1 cm over the second metacarpal, longer incision over the radius), instead of stab incisions
  • Blunt dissection to the bone
  • Predrilling prior to insertion of the pins 
Landmarks for pin insertion into the second metacarpal

The distal pin should be inserted proximal to the transition of the metacarpal head into the shaft.

The more proximal pin is inserted distal to transition of the shaft into the metacarpal base.


The pins should obtain a good hold in both cortices.

Pitfall: Eccentric pin positioning
An eccentric position of a pin may weaken the metacarpal, leading to fracture.

The extensor tendon hood must not be transfixed with the distal metacarpal screw.

In order to avoid this complication, the index metacarpophalangeal (MCP) joint should be passively flexed 90° so that the extensor hood moves slightly distally and the tendons are pulled in an ulnar direction.

In the frontal plane, the pins should be inserted at an angle of 30°-40° in relation to the sagittal plane to avoid transfixing the extensor tendon/hood.

Landmarks for pin insertion in the radial shaft

The proximal two pins should be inserted proximal to the muscle bellies of abductor pollicis longus (APL) and extensor pollicis brevis (EPB), and should not penetrate them.

These muscles are usually easy to identify. Proximal to these muscles, the radial shaft can be palpated through the skin between the bellies of the extensor digitorum communis (EDC) and extensor carpi radialis longus/brevis (ECRL/ ECRB) over a distance of 3-4 cm. This is the preferred area for proximal pin insertion in the radial shaft.

The pins are inserted perpendicular to the transverse section of the radius.

4. Frame construction / reduction and fixation (wrist)

Reduction and fixation

Longitudinal traction is applied on the thumb and index finger or the distal partial frame to reduce the fracture. Additional maneuvers may be necessary depending on the specific fracture pattern. Pressure from the dorsal side of the carpus may be helpful to restore volar tilt of the distal radius joint surface.

Additional K-wires

In multifragmentary fractures, additional K-wires may be inserted percutaneously, if the external fixator is used as a definitive treatment.

For details of K-wire insertion see the corresponding treatment option for the specific fracture type.

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