Fracture blisters are a complication of severe bone trauma, presenting as tense, fluid-filled sacs that develop over the site of a fracture. They are a distinct type of injury resulting from significant underlying orthopedic forces rather than simple rubbing. These blisters form on visibly swollen skin directly above a broken bone. This condition is uncommon, occurring in approximately 3% of fractures that require a hospital stay. Recognizing fracture blisters is important because their presence significantly impacts the timing and planning of subsequent orthopedic treatment.
How Fracture Blisters Form
The primary cause of fracture blister formation is the severe localized soft tissue swelling (edema) that occurs rapidly following a fracture. When a bone breaks, the body initiates a strong inflammatory response, causing blood vessels to become more permeable and leak fluid into the surrounding tissues. This fluid accumulation creates intense internal pressure beneath the skin, especially in areas where the skin adheres tightly to the bone.
This extreme pressure and tension mechanically stresses the layers of the skin. The fluid buildup acts to shear the superficial epidermis away from the deeper dermis. The resulting separation creates a cavity that fills with the leaked fluid, forming the visible blister.
The mechanism of injury often involves significant shearing forces applied to the skin at the moment of trauma. This initial force, combined with the post-traumatic swelling, determines the depth and severity of the skin layer separation. High-energy injuries, such as those from motor vehicle accidents, are more likely to generate the forces necessary to cause this cleavage.
Types and Appearance
Fracture blisters are classified into two main types based on the fluid they contain, which reflects the depth of the underlying skin damage. These blisters usually appear over bony prominences where the skin is thin and tightly bound to the bone:
- Ankle
- Foot
- Elbow
- Wrist
Clear (Serous) Blisters
Clear, or serous, blisters are the less severe type, presenting as tense lesions filled with a clear or yellowish fluid. This type of blister involves a separation within the epidermis itself, meaning the skin’s basal layer remains mostly intact. These blisters typically heal more quickly because remaining epithelial cells aid in re-epithelialization.
Hemorrhagic Blisters
Hemorrhagic, or blood-filled, blisters represent a deeper and more severe injury. These are filled with dark, bloody fluid because the separation has occurred at the dermal-epidermal junction, completely stripping the epidermis from the underlying dermis. The presence of blood indicates significant microvascular damage and a greater risk of wound healing complications if the blister ruptures.
Medical Approach to Treatment
The presence of fracture blisters significantly complicates the management of the underlying orthopedic injury, particularly when surgery is required. The primary concern is the high risk of infection and wound breakdown if a surgical incision is made through or near the compromised blister bed. Therefore, the medical approach involves delaying definitive fracture fixation surgery until the skin has healed.
Surgeons typically wait approximately 7 to 14 days for the blister to re-epithelialize and the surrounding swelling to subside before operating. During this waiting period, conservative care focuses on protecting the blister and controlling swelling. The limb is elevated, and the blisters are usually kept intact and covered with sterile, non-adherent dressings to act as a biological cover against infection.
While some clear blisters may be carefully aspirated (drained) by a physician to relieve tension, the wisdom is to avoid de-roofing or rupturing the blister, especially the hemorrhagic type. If a blister does rupture, the exposed base is treated like a second-degree burn, using specialized dressings to encourage new skin growth. Once the skin is fully healed, the definitive repair of the fracture can proceed with a lower risk of wound complications.