What is an Air Cast?
An Air Cast (also known as Aircast ankle brace or Air-Stirrup ankle brace) is a prefabricated, removable orthopedic device that uses air-filled cushions to provide compression and semi-rigid support for injured ankles and lower extremities. 1
Structure and Design
The Air Cast is constructed with:
- Air-filled bladders that conform to the contours of the ankle and lower leg
- Semi-rigid plastic shells on the medial and lateral sides
- Adjustable straps for customized compression
- Removable design allowing the patient to take it on and off for bathing or skin examination
The device extends from below the knee to the foot, providing stabilization while allowing some controlled movement.
How It Functions as an Immobilization Device
The Air Cast works through several mechanisms:
Compression and Support: The air-filled cushions provide circumferential compression that reduces swelling and edema while the semi-rigid shells limit excessive inversion and eversion movements 2.
Controlled Motion: Unlike rigid casts, the Air Cast allows controlled dorsiflexion and plantarflexion while restricting potentially harmful lateral movements. This "functional support" approach permits protected weight-bearing and early mobilization 3, 4.
Pressure Distribution: The air bladders distribute pressure evenly across the ankle joint, reducing localized stress on injured structures.
Clinical Applications
The Air Cast is primarily used for:
- Acute lateral ankle sprains (Grade I and II)
- Stable lateral malleolar fractures
- Avulsion fractures of the fifth metatarsal base
- Post-surgical ankle stabilization procedures
Clinical Evidence
For ankle sprains, the Air Cast demonstrates superior functional outcomes compared to elastic bandages. At 10 days and one month post-injury, patients using an Air Cast showed significantly higher Karlsson ankle function scores (mean 50 vs 35 at 10 days, p=0.028) 4.
For stable fractures, the Air Cast provides comparable outcomes to traditional walking casts with the added benefit of removability. Studies show no significant differences in long-term healing or stability 5, 6.
Restriction of movement: The Air Cast significantly restricts inversion and eversion movements more effectively than elastic bandages, which is crucial for preventing re-injury, while maintaining adequate range of motion for functional activities 2.
Important Clinical Considerations
Adherence is critical: The main limitation of the Air Cast is that it's removable, which can lead to non-compliance. Patients must be counseled to wear the device at all times during weight-bearing activities, as premature removal can delay healing or cause re-injury 7.
Not appropriate for all injuries: The Air Cast should not be used as the sole treatment for:
- Unstable fractures requiring rigid immobilization
- Active Charcot neuro-osteoarthropathy (requires knee-high non-removable devices) 7
- Severe Grade III ankle sprains with complete ligament rupture
Skin monitoring: Because the device is removable, patients should inspect their skin daily for pressure areas, blisters, or breakdown, particularly if they have peripheral neuropathy.
Duration of use: Typical treatment duration ranges from 4-6 weeks for ankle sprains, with gradual weaning as symptoms improve and functional rehabilitation progresses 3.