09 - mech of injury & classification

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Mechanism of injury & Classification

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Mechanism of injury

Most commonly, injuries occur after a simple fall from standing

height. Rarely do clinicians take any more detailed history. Yet much

information can be gained from asking patients to describe their fall.[46]

It is natural to pronate the forearm as you fall forwards, and supinate it

as you fall backwards. Impact on the pronated forearm is likely to be on the

radial side of the wrist, whilst that on the supinated forearm is likely to be on

the ulnar side of the wrist. This information stimulates thought as to which

other associated structures could be injured during the fall. A fall forwardswill focus the examination on the radial structures in the wrist; a fall

backwards will draw attention to the ulnar structures.[46]

Almost all distal radius fractures (apart from dorsal rim avulsion

fractures) can be produced by hyperextension of the wrist.[47] Bending forces

tend to occur in low-energy falls and typically produce dorsal displacement.

Shearing forces disrupt the ligamentous connections of the wrist andproduce unstable fracture-dislocations, whilst axial loading, high-energy

injuries compress the articular surface and cause fragments of joint surface

to be impacted.[46]

Important work, published by Rikli and Regazzoni[15], on load transfer

across the wrist described the existence of three separate structural

columns within the wrist.This 3 column concept highlights not only howthe intact wrist functions, but also provides clear mechanical guidance on

how best to reconstruct fractures in this area. The radius has both a radial

and intermediate column, and the ulna represents the third column (Fig.

12).[15]The understanding of this concept allows the surgeon to think about


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rebuilding the fragmented wrist in a logical and natural manner and also

emphasizes the importance of distal ulnar injuries. Indeed, this concept has

also been pivotal in the design of anatomic implants for both the distal radius

and ulna.[48]

The intermediate column is the major load-bearing column of the

wrist, confirmed by the dense subchondral bone seen in X-rays of the intact

radius. This also explains its involvement in dye-punch articular

depression injuries. In addition to being a central structural column, the

intermediate column also provides the radial component of the distal

radioulnar joint (DRUJ) with the sigmoid notch. The bone quality in this

distal ulnar corner of the radius is universally good (as a result of its

function) and, by virtue of its involvement in both flexion/extension and

forearm rotation movements, forms the key area when planning surgical

fracture reconstruction. Consequently, surgical reconstruction of the

fractured distal radius will concentrate on restoring the integrity and shape of

the intermediate column (together with the orientation of the two associated

joint surfaces) before restoring the buttressing function of the radial column,

and the pivotal function of the distal ulna.[46]


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(Fig. 12)The three column concept of Rickli & Regazzoni.[15]

Classification

Various classification systems have been proposed to describe the

injury and help formulate a treatment plan. Broadly they tend to be

anatomical classifications that group fracture patterns, biomechanical that

describe the mechanism of injury and fracture stability or a combination of

both.[46]

The eponymous descriptions associated with distal radius fractures

have traditionally been good indicators of the type of injury and treatment.

Colles fracture: It is an extra-articular distal radius fracture with dorsal

comminution, dorsal angulation, dorsal displacement, and radial

shortening.[49]


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(Fig. 13): Colles' fracture, Diagrammatic representation of displacement, Top, Characteristic dorsal

angulation and impaction with shortening (lateral view). Below, loss of radial angulation, Radial shortening

with impaction and radial displacement (postero-anterior view) [50]

Smiths fracture: It is a fracture of the distal radius with volar

displacement.[51]

(Fig. 14): Smith's fracture. Modified Thomas classification. Palmar angulated fracture. Type 1, extra-

articular transverse, Type 2,extra-articular oblique with palmar carpal displacement and Type 3,intra-

articular palmar displacement of the carpus entering the radiocarpal joint. Type 3, is equivalent to a palmar

Barton fracture-dislocation[50]


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Bartons fracture:It is is a displaced, unstablearticular fracture-subluxation

of the distal radius with displacementof the carpus along with the articular

fracture fragment.These may be either dorsal or volar.[52]

(Fig. 15): Palmar Barton's fracture, palmar displacement of the carpus with intra-articular component

(identical to Smith type 3). Dorsal Barton's fracture, dorsal displacement of the carpus, presenting as

complex fracture of the distal radius or as fracture-disloaction of the wrist. [50]

Chauffeurs fracture: It is a fracture of the radial styloid. It may beassociated with displacement of the carpus and may be the only bony

component of perilunate injury.[53]

Die-punch fracture: It is an intra-articular fracture with depression of the

dorsal aspect of the lunate fossa.[54]

FRYKMAN'S CLASSIFICATION:

In 1967, Frykman published a classification system that was important

in being the first to recognize the involvement (and relevance) of injuries to

the distal ulna.[55]


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Type I:

Is an extra-articular radial fracture.

Type II: Is an extra-articular radial fracture with an ulnar styloid

fracture.Type III: Is an intra-arlicular fracture of the radiocarpal joint.

Type IV:

Is an intra-articular fracture of the radiocarpal joint with an

ulnar styloid fracture.

Type V: Is an intra-articular fracture of the radioulnar joint.

Type VI: Is an intra-articular fracture of the radioulnar joint with

fracture of the ulnar styloid.

Type VII:

Is an intra-articular fracture involving both radio-carpal and

radioulnar joints.

Type VIII:

Is an intra-articular fracture involving both radiocarpal and

radioulnar joints with an ulnar styloid fracture.

(Fig. 16): Frykman classification. Six types of intra-articular fractures: 3/4, radiocarpal joint alone+/- ulnar

styloid; 5/6, radioulnar joint alone +/- ulnar styloid; and 7/8, both radiocarpal and radioulnar joints. [50]


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MELONE'S CLASSIFICATION OF INTRA-ARTICULAR

FRACTURES:

The Melone system (1993) identified the importance of fragmentation

patterns and articular involvement. This classification was developed from

the observation that components of articular fractures consistently fall into

four basic parts despite frequent comminution; they are:[56]

1. The radial shaft.

2. The radial styloid.

3. The dorsal medial fragment.

4. The palmar medial fragment.

Type I: Undisplaced or displaced but stable after closed reduction

Type II:

The medial complex is displaced as a unite with

comminution and instability which may affect dorsal

fragment (Die-punch fragment) or less often the palmar

fragment (volar Barton's fracture)

Type III:

It equals to type II with displacement of a spike fragment

which may injure the median nerve or flexor tendons

Type IV: Fractures demonstrate wide separation or rotation of the

dorsal or palmar medial fragments with profound disruption

of the distal radial articulations, usually associated with

severe damage to adjacent soft tissues.


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(Fig. 17): Melon classification. A, classification of articular fractures on the basis of consistent patterns

results from the characteristic die punch mechanism of injury. Four articular fractures: 1, Radial shaft; 2,

Radial styloid; 3, Lunate fossa, dorsal medial ; and 4, Lunate fossa , palmar medial. [50]

UNIVERSAL CLASSIFICATION:

A fracture may be defined as either extra-articular or intra-articular.[57]

Type I: Extra-articular non displaced

Type II:

Extra-articular displaced

Type III: Intra-articular non-displaced

Type IV:

Intra-articular displaced

Further, displaced articular or nonarticular fractures may be:

a) Reducible, Stable.

b)

Reducible, Unstable.

c)

Complex, Irreducible.

Indicators of instability are:

i.

Shortening of greater than 5 mm.

ii. Dorsal angulation greater than 20.

iii. Marked dorsal comminution.

iv.

Displacement in a plaster of Paris cast.


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(Fig. 18): Universal classification. Type I, Nonarticular (extra-articular), undisplaced, and stable. Type II,

Nonarticular (extra-articular), displaced, and unstable. Type III, Intra-articular, undisplaced, and

stable.Type IV, Intra-articular and displaced.A, Reducible and stable after the reduction.B, Reducible but

unstable.C, Irreducible and unstable. D, Complex (comminuted, unstable, and irreducible) (not shown) [50]

MODIFIED "MAYO CLINIC" CLASSIFICATION:

For more clear distinguishing of different articular fractures that

individually can be involved with DRFs, this classification has been

proposed as a second sub-classification in which the scaphoid, lunate, and

sigmoid notch of the distal radius are considered as separate articulations.[58]

This classification has four types:-

Type I:

Fractures are intra-articular but un-displaced.

Type II: Fractures are displaced and involve the radio-scaphoid joint.

Type III: Fractures are displaced and involve the radio-lunate joint.

Type IV: Fractures are displaced and involve both the radio-scapho-lunate

joints and the sigmoid fossa of the distal radius.


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(Fig. 19): Modified Mayos classification of DRFs. Intra-articular fractures involve one or more

articular fossae of the distal radius. Type I, Intra-articular but undisplaced involving the radio-lunate

joint. Type II, Radioscaphoid (RS) fossa fracture, displaced. Type III, Radiolunate fossa fracture with

die punch fracture (thin arrows) components. Direction of fracture displacement (thick arrows). Type

IV, Radio-scapho-lunate fossa involvement with extension into the distal radioulnar joint. The fracture

surface involvement extends into all three joints with articular step-off and displacement. D, dorsal; L,

lunate; S, scaphoid; V, volar.[50]


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A.O. CLASSIFICATION:

This classification is proposed by Mller et al., (1988). They

differentiated between simple and multi-fragmentary fractures and between

extra and intra-articular fractures with further recognition of different

degrees of articular surface involvement.[59]

Group A: Extra-articular fractures:-

Al: Extra-articular fracture, of ulna, radius intact.

1. Styloid process

2. Metaphyseal simple

3. Metaphyseal multi-fragmentary

A2 Extra-articular fracture, of radius, simple and impacted

1. Without any tilt

2. With dorsal tilt (Pouteau-Colles')

3. With volar tilt (Goyrand-Smith)

A3 Extra-articular fracture, of radius, multi-fragmentary

1. Impacted with axial shortening

2. With a wedge

3. Complex


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Group B: Partial articular fractures:-

B1: Partial articular fracture of radius, sagittal

1. Lateral simple

2. Lateral multi-fragmentary

3. Medial

B2 Partial articular fracture of radius, dorsal rim

1. Simple

2. With lateral sagittal fracture

3. With dorsal dislocation of the carpus

B3 Partial articular fracture of radius, volar rim

1. Simple, with a small fragment

2. Simple, with a large fragment

3. Multi-fragmentary

Group C: Complete articular fractures:-

C1: Complete articular fracture, of radius, articular simple metaphyseal

simple

1. Posteromedial articular fragment

2. Sagittal articular fracture line

3. Frontal articular fracture line


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C2: Complete articular fracture, of radius, articular simple, metaphyseal

multi-fragmentary

1. Sagittal articular fracture line

2. Frontal articular fracture line

3. Extending into diaphysis

C3: Complete articular fracture, of radius, multi-fragmentary

1. Metaphyseal simple

2. Metaphyseal multi-fragmentary

3. Extending into diaphysis

(Fig. 20) AO Classification of DRFs.[60]

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