Casting is a commonly used technique for external coaptation or fixation in veterinary medicine and surgery. Casts are primarily used to provide rigid support of an injured limb and are typically molded around a fractured distal extremity to provide relatively motionless stability for bone fragments during the healing process. Healing occurs by secondary bony union and callus formation. As long as the joints above and below the fracture are included within the cast, bending and rotational forces are counteracted and adequate rigid stability is usually achieved. Compressive and distractive forces are not neutralized in most cases. Therefore, indications for casting include minimally displaced, closed, simple fractures of the radius, ulna, tibia, fibula, metacarpus, metatarsus, and phalanges.
Casting can be used successfully when a fracture depends on its intact paired bone to provide support (eg, fractured radius and intact ulna, isolated metacarpal/metatarsal fracture). Fracture ends should have at least 50% anatomic reduction in 2 orthogonal radiographic planes. Casting can also be used as adjunct support with internal fixation when necessary. Situations in which casts are not indicated include comminuted and significantly displaced fractures in which casting cannot neutralize forces present, fractures above the elbow or stifle, and distal radius/ulna fractures in toy or small-breed dogs.