When members of the American Academy of Orthopaedic Surgeons were asked to list the most significant advances in treatment during the 20th century, the development of internal fixation ranked high on the list.
Internal fixation allows shorter hospital stays, enables individuals to return to function earlier and reduces the incidence of nonunion (improper healing) and malunion (healing in improper position).
A broken bone must be carefully fixed in position and supported until it is strong enough to bear weight. Until the last century, physicians relied on casts and splints to support the bone from outside the body (external fixation). But the development of sterile surgery reduced the risk of infection so that doctors could work directly with the bone and could implant materials in the body.
New materials such as stainless steel, cobalt and titanium were not only durable, but also had the strength and the flexibility necessary to support the bone. These materials are also compatible with the body and rarely cause an allergic reaction or implant failure.
The most common types of internal fixation are wires, plates, rods, pins, nails, and screws used inside the body to support the bone directly.
Wires are often used as sutures or threads to "sew" the bones back together.
- Can be used in conjunction with other forms of internal fixation to hold bones together.
- Can be used alone to treat fractures of small bones, such as those found in the hand or foot.
- Pins hold pieces of bone together. They are usually used in pieces of bone that are too small to be fixed with screws.
- These pins are usually removed after a certain amount of time, but may be left in permanently for some fractures.
Plates are like internal splints that hold the fractured ends of bone together.
- Extend along the bone and are screwed in place. If two bones that run parallel to each other both break, such as in the lower leg, plating one bone may provide enough support for the other bone as well.
- May be left in place or removed (in selected cases) after healing is complete.
In some fractures of the long bones, the best way to align the bone ends is by inserting a rod or nail through the hollow center of the bone that normally contains some marrow.
- Held in place by screws until the fracture has healed.
- May be left in the bone after healing is complete.
Bone screws are used for internal fixation more often than any other type of implant. Although the bone screw is a simple device, there are several designs based on how the screw will be used.
- Can be used alone to hold a fracture, as well as with plates, rods, or nails.
- May be designed for a specific type of fracture.
- May be left in place, or removed after the bone heals.
Pins, screws, and rods are also used to construct external fixators, such as frames and rings. Although they are outside the body, the screws and pins go through the skin and muscle to connect to the bone. In this way, they differ from casts and splints, which rely solely on external support. There may be some inflammation or, less commonly, infection associated with the use of external fixators. Normally, these can be managed with wound care and/or oral antibiotics.
Sterile conditions and advances in surgical techniques reduce, but do not remove, the risk of infection when internal fixation is used. The severity of the fracture, its location, and the medical status of the patient must all be considered.
In addition, no technique is foolproof. The fracture may not heal properly, the plate or rod may break or deform, or the patient may have an allergic reaction to the implant. Although some media attention has focused on the possibility that cancer could develop near a long-term implant, there is little evidence documenting an actual cancer risk and much evidence against that possibility. Orthopaedic surgeons are continuing their research to develop improved methods for treating fractures.