Forearm as a functional unit
The radius, ulna, proximal radioulnar joint, distal radioulnar joint and interosseous membrane act together. Malalignment of one component can impair pronation-supination even when the fracture itself unites.
Assessment
- open injury
- compartment syndrome
- radial, median/AIN and ulnar nerve function
- pulses
- elbow and DRUJ stability
Obtain AP and lateral radiographs of the entire forearm including wrist and elbow.
Adult diaphyseal both-bone fractures
Most displaced adult diaphyseal fractures require anatomical restoration of:
- length
- rotation
- radial bow
- relationship of radius to ulna
Compression plating is used for simple patterns; bridge principles are used for comminuted fractures.
Galeazzi injury
A radial shaft fracture, classically in the distal third, is associated with DRUJ disruption.
After fixing the radius:
- assess DRUJ reduction and stability through rotation
- if reduced and stable, protect according to stability
- if reduced but unstable, temporary stabilisation may be required
- if irreducible, explore for interposed tissue or tendon
A Galeazzi injury consists of a radial-shaft fracture with disruption or instability of the distal radioulnar joint.
Clues to DRUJ injury include:
- widening of the DRUJ
- ulnar styloid fracture
- radial shortening
- dorsal or volar displacement of the ulna
- instability after radial fixation
In adults, accurate restoration of the radius is central. The DRUJ is then assessed for stability through forearm rotation.
Monteggia injury
An ulnar fracture or plastic deformity is associated with radial-head dislocation.
In adults, restoration of ulnar length and alignment often restores the radial head. Persistent dislocation requires reassessment of ulnar reduction and possible exploration.
A Monteggia injury combines an ulnar fracture or plastic deformity with radial-head dislocation.
The radial-head position must be checked on every view. A line drawn along the radial neck/shaft should intersect the capitellum in all projections.
The key treatment principle in acute injuries is often restoration of ulnar length and alignment. Correcting the ulna may reduce the radial head; persistent dislocation suggests malreduction, interposed tissue or another obstacle.
In children, plastic deformation of the ulna can be subtle and the radial-head dislocation easily missed.
Complications
- compartment syndrome
- nerve injury
- malunion with loss of forearm rotation
- radioulnar synostosis
- nonunion
- DRUJ or radiocapitellar instability
General principles
Forearm fractures are not simply fractures of two long bones. The radius and ulna function as a unit with the proximal and distal radioulnar joints, interosseous membrane and rotational relationship between the bones.
Restoring:
- length
- alignment
- radial bow
- rotation
- DRUJ/PRUJ congruity
is essential for useful pronation and supination.
Interosseous membrane
The interosseous membrane contributes to load transfer and longitudinal forearm stability. Its importance is especially evident in Essex-Lopresti injury, where radial-head injury is combined with interosseous membrane disruption and DRUJ instability.
Failure to recognise longitudinal instability can lead to proximal migration of the radius and chronic wrist/elbow symptoms.
Fixation principles
Adult diaphyseal forearm fractures usually require accurate reduction and stable fixation because small errors in length or rotation significantly impair function.
Avoid:
- cross-union between radius and ulna
- excessive stripping
- malrotation
- failure to assess both radioulnar joints
FRCS synthesis
Whenever shown a forearm fracture, look beyond the fracture line. Ask: where is the radial head, where is the DRUJ, and has radial bow/length been restored?