1 Principles topenlarge
Ulnar diaphyseal fractures require a long arm cast to control forearm rotation and therefore decrease the risk of displacement.
Correct molding of the cast helps to prevent redisplacement of the fracture.
If a complete cast is applied in the acute phase after injury, it is safer to split the cast down to skin over its full length.
Reduction and casting of displaced fractures is performed with conscious sedation or general anesthesia in children.
The environment should be one in which the child and the parents/carers are comfortable.
Important considerations include:
- A child-sensitive approach
- A child-friendly clinical area
- Careful explanation of the procedure, in language that is understood by the child and the parents/carers
- Availability of all equipment and material
A provider familiar with pediatric sedation and airway management should take responsibility for the safety of the anesthetic.
Periosteum as a factor in fracture stability
Children’s periosteum is thick, tough tissue and is often intact on the concave (compression) side of a fracture.
This confers extra stability with three-point molding as the concave periosteum acts as a tension band.
2 Preparation for cast application topenlarge
- Examination couch
- Tubular bandage (40-80 mm wide, depending on the size of the child)
- 2-4 rolls of padding (40-150 mm wide, depending on the size of the child)
- 2-8 plaster of Paris (POP) or synthetic fiberglass bandages (40-150 mm wide, depending on the size of the child)
- Malleable (thermoplastic, leather, or lead) strip
- Bucket with cold water
- Protective aprons for the team members and the child
- Appropriate equipment to cut, split, or remove the cast
- Finger traps and a pole to suspend them
- C-arm if available
This procedure is normally performed with the patient in a supine position.
Convenient OR setup for single surgeon work is illustrated here.
Holding the arm using finger traps as illustrated allows easy manipulation, reduction, imaging, and mobilization for a surgeon working without an assistant.
To avoid damage to the skin of the fingers ensure that the pressure is evenly distributed, and that prolonged or excessive force is avoided.
3 Closed reduction of ulnar fracture topenlarge
Direction of radial head dislocation and ulnar deformity
Before performing a reduction determine the direction of the dislocation of the radial head and also the direction of the apex of the ulnar deformity. Usually the angulation of the ulnar fracture points in the same direction as the dislocation of the radial head.
From most to least frequent the radial head dislocation can be:
In young children, in a stable transverse fracture pattern, a closed reduction of the ulna may be sufficient to maintain the reduction of the radial head.
Reduction maneuvers for complete fractures
Place the thumb on the radial head and the fingers at the epicondyles and grasp the distal ulna to provide longitudinal traction. Simultaneously reduce the ulnar angulation and the radial head dislocation.
Direct thumb pressure on the apex of the ulnar deformity may help.
Closed reduction of greenstick fracture
Reduction of a greenstick fracture follows the reduction principles for complete fractures.
It is straightforward to correct the angular deformity and a crack is heard when the reduction is completed. Intact periosteum on the concave side confers stability to the ulna and therefore of the radial head.
Closed reduction of bowing
Apply prolonged and direct force for several minutes to reverse the bowing.
It is not helpful to briefly reduce the bony deformity as it will revert to the original deformity due to the elasticity of the bone.
Depending on the size of the child and the direction of the deformity, apply three-point bending with a thumb or a firm folded towel as a fulcrum.
After reduction of the ulnar deformity the radial head often reduces spontaneously.
Pitfall: Late redisplacement of the radius may occur due to the elastic recoil of the ulna.
Confirmation of proximal radioulnar joint reduction
A line drawn through the center of the proximal radial metaphysis should be centered on the capitellum in any view throughout the whole range of movement.
If the radial head appears improperly reduced on any view, then operative treatment of the ulna may be required (eg ESIN, external fixation or plate).
Acceptable closed reduction of the ulnar fracture
The ulna needs to be fully out to length and anatomically reduced or overcorrected by 5-10° to maintain reduction of the radial head.
4 Cast application topenlarge
Flex the elbow to 90-100° prior to application of the tubular bandage and padding, to avoid compression at the antecubital fossa.
Place the forearm in supination for most anterior Monteggia lesions as this is the most stable position to maintain the radial head reduction.
Preparation for splitting the cast
A temporary malleable (thermoplastic, leather or lead) strip can be placed beneath the tubular bandage, prior to plaster application, to protect the skin when plaster splitting is required.
The location of the strip should be planned to avoid areas of molding.
Application of tubular bandage
Apply a tubular bandage directly onto the skin and malleable strip, from the axillary crease to just distal to the MCP joints allowing sufficient bandage for protection of the cast edges.
Cut a hole for the thumb.
Application of padding
Apply a single layer of padding from the MCP joints of the fingers and thumb to the axillary crease.
Overlap each layer by 1/2.
Apply extra padding over pressure areas, including the olecranon.
Take care not to constrict the antecubital fossa.
The tubular bandage and padding should be applied without creases.
Consistent firm but not tight wrapping should result in a neat stable layer of padding that does not constrict the arm.
Application of plaster
Immerse the POP/fiberglass bandage for 5-10 seconds and then remove excess water by gentle squeezing.
Apply a first layer of circumferential POP/fiberglass.
The plaster extends distally exposing the metacarpal heads and palmar flexor crease and proximally to just distal to the axillary crease.
Trim excess plaster to accommodate the thumb and fingers.
Apply a slab the width of the forearm over the ulnar aspect and the posterior humerus.
Completion of plaster cast
Fold the proximal and distal ends of the tubular bandage over the cast and cover the cast with an additional single layer of POP/fiberglass bandage.
Ensure that the edges of the cast are well-padded and smooth, to avoid abrasion during the period of plaster immobilization.
Molding the cast
For an undisplaced fracture the cast should be molded to an oval cross-section to match the shape of the forearm.
To prevent displacement, mold the cast to provide a three-point fixation against the anticipated direction of displacement.
The assistant should support the limb until the cast is hardened.
5 Final assessment topenlarge
X-ray confirmation of reduction
Take an x-ray in both AP and lateral views.
The relationship between the radial head and the capitellum is demonstrated with the beam centered over the elbow flexed to 90°-100°, orientating the beam at 45° to the axis of the forearm.
X-ray evaluation of the cast
An x-ray of a well applied forearm cast will show:
- A cast index of 0.7 or less (width on lateral view/width on AP view; CI = A/B)
- Correctly applied three-point molding
- Dense material where the mold has been applied, but no bumps or wrinkles
The ability to fully extend the fingers passively, or actively, without discomfort indicates absence of muscle compartment ischemia.
Flexion of MCP joints
Care should be taken to ensure that the plaster cast does not restrict flexion of the MCP joints.
The arm is supported in an arm sling around the shoulder.
6 Cast splitting topenlarge
When required, the plaster should be split along the entire length.
Once the cast is hardened, mark it, then split using an oscillating saw, a hand saw, or a sharp plaster knife (1).
Take great care to avoid injury to the underlying skin.
Widen the split with a cast spreader. Then divide the underlying padding with scissors (2) and remove the protective strip to expose the skin.
Apply a crêpe bandage to protect the split cast.
When the swelling has subsided (after 5-7 days), complete the cast with a single POP bandage.