Distal Radius-Ulna Metaphyseal Fracture
Metaphyseal fractures have a peak incidence during the adolescent growth spurt (girls aged 11-12 years, boys 12-13 years) due to weakening through the metaphysis with rapid growth.
Up to 13% incidence of other arm injuries (hand, forearm, and elbow) occurs on the same side.
These include more proximal forearm fractures, such as Monteggia fracture-dislocations, supracondylar humeral fractures, and hand fractures.
Distal radius metaphyseal fractures can be classified according to:
Displacement (whether undisplaced or displaced)
Bone involvement (radius only, both radius and ulna)
Buckle injury: Compression injury failure of bone resulting in the cortex bulging outwards (unilateral or bilateral). Also known as a torus injury. Although there is a disruption to the cortical bone, the integrity of the bone is minimally compromised, resulting in different patient management from other fractures.
Complete: A fracture that extends through both cortices. Most complete metaphyseal fractures involve both the radius and ulna. The radius is commonly a complete fracture. The ulna may have a complete fracture, greenstick fracture, or a plastic deformity.
The most common mechanism of injury is a fall on an outstretched hand.
Extension of the wrist at the time of injury causes the distal fragment to be displaced dorsally (posteriorly).
Volar (anterior) displacement of the distal fragment is usually the result of a fall on a flexed wrist.
There is usually pain and tenderness directly over the fracture site, and limited range of motion in the wrist and hand.
Deformity depends on the degree of fracture displacement.
Buckle injuries present with no or minimal deformity. Buckle injuries are often misdiagnosed as a wrist sprain. An x-ray of the wrist should be ordered to clarify the diagnosis.
All fractures should be assessed using the Advanced Trauma Life Support (ATLS) principles to ensure associated and potentially significant injuries are identified.
A ‘wrist x-ray’ request will provide AP and lateral views of the distal forearm and wrist.
If the injury is to the mid-forearm or the pain is poorly localized, a ‘forearm x-ray’ should be ordered.
Avoid ordering ‘x-ray arm’ as it is better to have images focused on the region of local tenderness.
If there are any elbow joint symptoms, an ‘elbow x-ray’ should be ordered as some fractures around the elbow can be difficult to detect.
As a rule of thumb, if the deformity is clinically visible, reduction may be indicated.
Acceptable angulations are dependent on the age of the child.
The acceptable angulations for distal radius metaphyseal fractures-
0-5 years: <20 degrees
5-10 years: <15 degrees
10-15 years:<10 degrees
Fractures angulated more than these values usually need to be reduced.
Angulation in the coronal plane (as seen on AP x-ray) is less tolerated as it does not remodel as well as angulation in the sagittal plane (as seen on the lateral x-ray).
Bayonet apposition is acceptable in children up to the age of six as long as angulation alignment parameters are acceptable.
Buckle fractures are treated with below elbow slab immobilization.
Undisplaced complete fracture and displaced fractures after closed reduction are immobilized in an above elbow plaster cast.
Operative treatment is indicated when acceptable reduction cannot be obtained or maintained by closed methods, open fractures, fractures with associated neurovascular compromise, and an associated arm fracture in the same upper limb or opposite limb. Radial fixation should be always done with physeal sparing pins.
The ulnar metaphyseal fracture usually reduces to an acceptable alignment on the reduction of the radial metaphyseal fracture. So treating the radial metaphyseal fracture is of utmost importance.
Emphasis should be placed on the elevation of the limb (elbow above the heart) for the first 48 hours and active finger mobilization.
Back slab and sling should be worn under clothing and not through the sleeve.
Distal metaphyseal fractures of the radius have very good remodelling potential because of the proximity to the growth plate. There is a very low risk of growth arrest.
For complete metaphyseal displaced fractures and fractures involving the radius and ulna, the need for close follow-up should be emphasized due to the risk of loss of reduction.
The main early complication is the loss of reduction.
One in ten (10%) will lose position and will need a re-reduction.
Contributing factors are poor cast technique and residual angulation/displacement after the initial reduction.
Loss of position and the opportunity for re-reduction can only happen with appropriately timed follow-up.
Complete fractures in patients over 10 years of age have a high risk of loss of reduction, thus proper follow-up is important.
Another complication is compartment syndrome due to restriction by the cast.
Malunion can occur if the fracture is malreduced or reduction is lost.
Non-union or physeal injury is rare.