Official Definitions: Cast vs Splint
A cast is a circumferential immobilizer made of plaster or fiberglass that completely encircles the limb, while a splint is a non-circumferential immobilizer that provides support on only one or more sides of the limb and is held in place by elastic bandages or wraps. 1, 2
Key Structural Differences
Cast Characteristics
- Circumferential design that completely surrounds the injured area, providing rigid 360-degree immobilization 1, 2
- Typically constructed from plaster of Paris or fiberglass materials that harden to create a solid, non-removable structure 3
- Total contact casts represent a specialized form: custom-made, well-molded, minimally padded, knee-high non-removable devices maintaining total contact with the entire plantar surface and lower leg 3
- Cannot be removed by the patient without cutting or specialized tools 3
Splint Characteristics
- Non-circumferential design that provides support without completely encircling the limb 1, 2
- Allows accommodation for tissue swelling due to open design 1, 2
- Removable by the patient, making them accessible for wound inspection, bathing, and examination 3
- Held in place by elastic bandages, wraps, or straps rather than being self-supporting 2
Clinical Implications and Usage
When Casts Are Preferred
- Definitive fracture management requiring superior immobilization for complex or unstable injuries 1
- Situations where patient compliance with immobilization is critical and non-removability is advantageous 3
- Treatment of active Charcot neuro-osteoarthropathy where continuous immobilization prevents progressive deformity 3
When Splints Are Preferred
- Acute injury management where significant swelling is anticipated, as splints accommodate tissue expansion without causing compartment syndrome 1, 2
- Initial stabilization of reduced, displaced, or unstable fractures before definitive orthopedic intervention 1
- Minimally displaced fractures where rigid circumferential immobilization is unnecessary 3
- Situations requiring frequent wound inspection or skin examination 3
Important Clinical Caveats
Advantages and Disadvantages
Cast advantages:
- Superior immobilization compared to splints 1
- Better control of fracture alignment and prevention of displacement 1
- Eliminates patient non-compliance with immobilization 3
Cast disadvantages:
- Less forgiving during acute inflammatory phase when swelling occurs 2
- Higher complication rates including compartment syndrome, pressure sores, and thermal injuries 2
- More technically difficult to apply 2
- Cannot be easily removed for examination 1
Splint advantages:
- Faster and easier to apply than casts 2
- Accommodate natural swelling during acute inflammatory phase 1, 2
- Easily removed for injury site inspection 2
- Preferred by patients for comfort 4
Splint disadvantages:
- Risk of patient non-compliance with wearing schedule 3
- Increased motion at injury site compared to casts 2
- May lead to delayed healing if not worn consistently 3
Common Pitfalls to Avoid
- Excessive immobilization duration with either device can lead to chronic pain, joint stiffness, muscle atrophy, or complex regional pain syndrome 1
- Using removable devices when continuous immobilization is medically necessary (such as in active Charcot neuro-osteoarthropathy) risks progressive deformity 3
- Applying circumferential casts during the acute inflammatory phase without adequate monitoring risks compartment syndrome 2
Hybrid Approaches
- Non-removable walkers represent a middle ground: prefabricated removable boots rendered non-removable by wrapping with fiberglass or cast material circumferentially, also called "instant total contact cast" 3
- This approach combines the ease of application of prefabricated devices with the compliance benefits of non-removable immobilization 3