Fracture blisters are most frequently discovered on a second ED visit or upon orthopedics follow up after a splint or cast is removed. They are understandably but mistakenly often thought to result from friction or pressure from splints or casts. Referring to these as “cast blisters” would be misnomers.
Research by Giordano et al suggests that fracture blisters are cleavage injuries caused by the shearing forces on the soft tissue from the initial trauma itself.1 They are rare complications, associated with 2.9% of all fractures that require hospitalization.2 They seem to be much more common in areas where there is a small amount of soft tissue between bone and skin – ankle, wrist, elbow, and foot.3
Fracture blisters can form as early as 6 hours after injury, and the majority form 24-48 hours after injury.