The following patient information sheet is meant to help patients and family better understand a specific pediatric orthopaedic condition. It is not meant to be comprehensive, and only reflects one viewpoint. This page does not replace a medical evaluation by a pediatric orthopaedic surgeon, and your own surgeon may have a different approach to your condition.
What is an external fixator?
An external fixator is a metal device that allows precise control of a bone. The fixator is composed or one or more metal bars and rings, which in turn connect to a child via metal pins and wires. By gradually manipulating the fixator on the outside, we can carefully control the position of the bones and joints on the inside. The fixator is moved just a little bit at a time every day until the desired position is obtained. It is then held in place until the bone heals.
Why is an external fixator sometimes necessary?
Most orthopaedic surgeries are performed with internal or implanted devices. The bone is corrected at the time of surgery, and the only thing visible from the outside is the new shape of the leg and a surgical incision. Here are three common reasons for using an external fixator:
1. The bone is too short: In general, devices implanted into the leg cannot increase the length of bone, although some lengthening rods can also achieve this. The rods, however, do carry some risk of mechanical failure, and cannot always correct the other deformities seen with a short bone.
2. The bone has too much deformity: Sometimes a bone is so deformed that it becomes technically challenging to straighten it all at once. If this is the case, then gradual correction with an external fixator is desirable.
3. The soft tissues cannot allow for correction all at once: When a bone is straightened, there can be a large amount of stretch on nerves, blood vessels, tendons, and even skin. In some cases there is concern that fixing the bone in one surgery will cause too much of a stretch and potentially damage the soft tissues. In these cases, gradually moving the bone one day at a time is safer.
What is involved in caring for an external fixator?
An external fixator can be daunting. It is not unusual to have some fear regarding touching and using the device. In order to allow patients to familiarize themselves with the fixator as soon as possible, I prefer to keep the device as uncovered as possible after surgery.
Generally, an external fixator is mounted quite securely to the bone, and can withstand mild contact, any positioning of the body, and oftentimes even weightbearing immediately after surgery. In fact, it is often more comfortable to pick up the leg by grabbing the fixator, rather than holding the leg itself.
Usually the pin sites are covered for about one week, and then the dressings are removed either at home or in clinic. At that point, showering is okay, followed shortly by soaking and even swimming depending on how the tissues have healed. For fixators on the thigh (femur bone) I prefer wrapping with gauze to minimize movement between the skin and the pins. For the lower leg (tibia bone) the fixator can either be left free, or the pin sites wrapped if there is some drainage at the pin sites. Pin sites are generally cleaned with soap and water daily, although in some circumstances I may recommend a short period of cleansing with half strength peroxide (half peroxide and half water).
Pin site infections are common. Signs of pin tract infection include redness at the pin sites, tenderness at the pin sites, and discharge at the pin sites. I will oftentimes prescribe a 10-14 day course of antibiotics for a pin site infection.
When the frame is still being manipulated on a daily basis, it is oftentimes more painful and weightbearing is difficult. It is common to require pain medications, and oftentimes muscle relaxants as well. After the bone has reached its final position, the frame is kept in place until the bone has healed (consolidation phase). During this time, pain should improve, and activity level gradually increases.
Frames on the tibia (lower leg) generally include struts that need to be adjusted daily. Please click here for an instruction sheet on strut changes.
What kinds of problems can I expect with an external fixator?
Complications with external fixation are common and oftentimes unpredictable, given the complexity of the treatment. However, the ultimate goal of surgery is almost always achievable.
Pin site infections are discussed in the section above. Rarely, pin site infections can become severe enough that surgical debridement, exchange of pins, or early removal of the frame is necessary. If the frame is removed early, one must be very cautious in protecting the leg until it has adequately healed.
The osteotomy (site of the bony cut) can heal either too quickly or too slowly. If it heals too quickly, then the bone may need to be re-broken at a different site to allow further correction of the bony deformity. If it heals too slowly, then the frame may need to stay on for a longer duration, and sometimes a bone graft is necessary. This is a surgery where bone is generally taken from the hip and placed in the osteotomy site.
Joint contractures (lack of movement of the hip, knee or ankle) can occur in particularly with large limb lengthening procedures. We prescribe aggressive physical therapy during and after the lengthening to maintain motion. If too much motion is lost then we may need to stop the lengthening early. Sometimes surgical tendon lengthenings are necessary to regain motion.
How long do I need to have an external fixator?
During lengthening procedures, one can expect at least one month for every centimeter of length, with longer durations for slower healing bones (such as in the ankle region or with previous surgery). Generally, about half of this time is spent obtaining the length (lengthening phase), and half of this time is spent to allow for healing (reconsolidation phase).
What happens after the external fixator is removed?
Frame removal is an ambulatory surgery (go home the same day). If any screws were implanted for a tibial lengthening, they are removed at the same time. If possible, I will utilize a cast or brace to protect the bone for the first month after surgery. Physical therapy is suspended for the first month after frame removal. In some instances, I may recommend placement of an internal rod to protect the bone from fracture. If there is no cast, then dressings can be removed at one week and showers started at that point as long as all of the pin sites have scabbed over.