In medicine, a fixator is a device which provides support and stability to a particular part of the body when it is in motion. Fixators can be either internal or external. Internal fixation uses screws and other small devices to support healing bones. An external fixator is a device which is used to provide stability and support for fractured bones. They are used in cases where a cast will not provide sufficient support while the bone is healing.
This term is also used in anatomy, where a similar principle applies. Many muscles in the body can act as fixators, preventing unnecessary movement of muscles when other parts of the body are moving. When someone performs a bicep curl, for example, the bicep muscle is the prime mover which regulates the action, while the back, abdominal, shoulder, and wrist muscles act as fixators, supporting the body during the movement.
Most simple fractures can be healed with the use of a cast, which immobilizes the fractured bone and provides the support it needs to heal correctly. Internal or external bone fixation is used as a treatment for complicated fractures which cannot heal through the use of a cast. These devices are fitted during a surgical procedure that sets the fractured bones in place before applying an external or internal fixator.
Internal bone fixation is performed via a procedure called open reduction internal fixation. For this procedure, metal screws, plates, or rods are used to hold fractured bones in place so that they can heal correctly. Severe fractures may require the use of an intermedullary rod, a long thin metal rod which is inserted into a long bone such as a tibia or femur. The rod helps promote healing by sharing the weight-bearing load of the bone as it heals.
External bone fixation tends to be used as a temporary fracture treatment, or may be used in cases where internal fixation is not possible. To fit an external fixator device, holes are first drilled into undamaged bone surrounding the location of the fracture. Metal pins are inserted into the holes, and the external fixation device is then fitted onto the pins and adjusted to provide the necessary support for the fractured bone. Most of the fixation device is located outside the body, with only the metal pins coming into contact with the bone.
Placement of both types of fixator is carried out by an orthopedic surgeon, with the patient under general anesthetic. Internal fixators, particularly intermedullary rods, are often left in place permanently, to provide support to a bone which may have been weakened by a fracture. External fixators are removed once a bone has finished healing; depending on the severity of the fracture this will take at least six weeks, and may take as long as several months.