Overview
Cast immobilization remains a central part of pediatric fracture treatment. Its success depends on correct fracture selection, adequate padding, purposeful molding and accommodation of swelling. A cast can fail by allowing displacement or by applying damaging pressure; neither problem is prevented simply by adding more material (Tachdjian, Chapter 27).
Assessment and Planning
Establish the fracture pattern and stability before choosing a cast. A minimally displaced complete fracture may resemble a torus injury but be substantially less stable.
Assess and record skin, swelling, circulation and neurologic function before manipulation or immobilization.
Choose the required joint position and length of immobilization for the injury. The acceptable alignment and follow-up schedule are fracture-specific.
Anticipate whether swelling requires an initial splint or a split cast. A painful, rapidly swelling extremity needs reassessment rather than increasingly tight immobilization.
Arrange appropriate analgesia, support and assistance. Applying a carefully molded cast to a moving child is an acquired procedural skill and requires supervision when performed by a trainee.
(Tachdjian, Chapters 27 and 29.)
Materials and Preparation
Element | Purpose and limitations |
|---|---|
Padding | Protect skin and prominences while permitting an effective mold. Excess padding reduces control; too little increases pressure and saw-injury risk. |
Plaster or fiberglass | Choose according to the required mold, durability and expected swelling. The source does not establish one material as best for every injury. |
Splint or split cast | Allows swelling accommodation when a rigid circumferential construct would be inappropriate. |
Assistant support | Maintains the reduction and final joint position while materials are applied and set. |
(Tachdjian, Chapter 27.)
Application Technique
Position and Pad
Place the entire limb in the intended final position before applying the padding and rigid material.
Support the fracture and maintain the selected reduction throughout application.
Pad all regions adequately and add protection over bony prominences. Balance skin protection with the close fit needed to control the fracture.
Avoid changing joint position after the padding and plaster have been applied: movement can create an internal crease and focal pressure.
(Tachdjian, Chapter 27.)
Apply and Mold
Apply material so that it conforms to the limb without excess accumulation on the concave side of a bent joint.
Fan material over the convex side or use a suitable splint configuration to accommodate the different inner and outer lengths.
Create a deliberate three-point mold appropriate to the fracture, rather than a cylindrical shell that does not resist the deforming force.
Maintain the mold and joint position while the material sets. A bulky, inadequately molded cast can allow even a previously undisplaced fracture to angulate.
Account for the possibility of distal migration. Immobilization in equinus or extension may require particularly careful molding around appropriate contours; otherwise the edge may impinge on the heel or other vulnerable tissue.
(Tachdjian, Chapter 27.)
Accommodate Swelling
Reassess the expected swelling and select a splint or appropriately split construct when indicated.
Do not assume that a reassuring initial examination guarantees safety as swelling increases.
For elbow injuries, avoid immobilization in excessive flexion merely to maintain reduction. A fracture that cannot be held safely may require fixation rather than a more constrictive position.
When splitting or removing a cast, consider the thickness of padding and the additional saw-injury risk in a sedated or uncooperative child.
(Tachdjian, Chapters 27 and 29.)
Final Checks
Confirm the intended alignment with the imaging appropriate to the injury.
Document perfusion and neurologic findings after the cast or splint is applied.
Inspect the edges and exposed skin for focal impingement and assess the possibility of migration or pressure at prominences.
Ensure that the cast supports the fracture with an effective mold and permits the intended swelling accommodation.
Give the family a clear plan for review and reassessment if pain or swelling worsens.
(Tachdjian, Chapters 27 and 29.)
Aftercare and Surveillance
Explain the required elevation for the particular injury. For a swollen elbow or forearm, Chapter 29 stresses that a sling alone may leave the extremity dependent; elevation should put the hand above the elbow and elbow above the heart during the early swelling period. Provide explicit instructions to return for increasing pain, a tightening cast or concerning changes in the limb.
The follow-up schedule and need for repeat radiographs depend on the fracture's stability and the risk of displacement. The source demonstrates how poorly controlled minimally displaced fractures may collapse after casting. As swelling subsides, a loose cast may lose its ability to maintain reduction (Tachdjian, Chapters 27 and 29).
Complications and Pitfalls
Pressure injury: insufficient padding, creases, excessive material on the concavity or a migrating cast can damage skin.
Loss of reduction: too much padding, poor three-point molding or an unstable fracture treated in an unsuitable construct.
Compartment syndrome: increasing analgesic requirements, anxiety or escalating pain require urgent examination; a palpable pulse does not rule it out.
Saw injury: thin padding and inability to report discomfort increase risk during splitting or removal.
False reassurance from remodeling: pediatric remodeling is not equally effective for every plane, age or anatomic region; fracture-specific alignment requirements still apply.
(Tachdjian, Chapters 27 and 29.)
References
Herring JA, ed. Tachdjian's Pediatric Orthopaedics: From the Texas Scottish Rite Hospital for Children. 6th ed. Elsevier; 2022. Chapter 27, General Principles of Managing Orthopaedic Injuries, casts and application principles, pp. 1152–1153.
Herring JA, ed. Tachdjian's Pediatric Orthopaedics. 6th ed. Elsevier; 2022. Chapter 29, Upper Extremity Injuries, neurovascular monitoring, elevation and cast precautions in elbow fractures, pp. 1195–1209.