While external fixation will not replace internal fixation in the surgical toolbox, it does offer a number of specific advantages. Using external fixation has become routine for initial reduction and stabilization of comminuted long bone fractures, and is often used in conjunction with a few judiciously placed lag screws. In the presence of compromised soft tissue, external fixation becomes essential.
Unlike internal fixation, which becomes a fixed, static construct once you apply it, external fixation can be quite dynamic in certain forms. It is common during postoperative periods to adjust the fixators in order to improve skeletal alignment or apply compressive or distractive forces across joint fusions. In addition, one can gradually adjust Ilizarov frames to correct chronic angular and torsional deformities via bone callus distraction and ligamentotaxis. Severe deformities, such as untreated adult clubfoot, are often not acutely correctable because of neurovascular adaptation. However, one can achieve correction of these deformities through the Ilizarov method.
Since many external fixation constructs are, by design, extremely rigid and stable, it’s possible for patients to have partial to full weightbearing status while they use the devices. It is not uncommon for an individual being treated for a segmental bone loss of the tibia with external fixation to be walking on his affected limb during lengthening. Furthermore, while managing fusions and comminuted fractures, once consolidation of the bone fragments has begun, one can gradually decrease the rigidity of the construct in order to allow the underlying bone to bear increasing loads (dynamization). Obviously, this would be impossible with internal fixation.
Perhaps the most exciting application of external fixation is in the treatment of both acute and chronic Charcot neuroarthropathy. It has been shown that patients with this disorder have reduced bone mineral densities in the bones of their feet. As a result of this osteopenia, rigid internal fixation becomes a rather poor option in any reconstructive procedure. However, by using thin wires in a multi-planar array, one can apply rigid fixation to the foot and leg without significant risk of loosening of the implants.
Other advantages of using external fixation include the following:
• it provides neutralization or fixed distraction in limb length discrepancies;
• it is ideal for treating infected joints in which arthrodesis is desirable or non-unions; and
• it facilitates direct visualization of local wound status, flaps or skin grafts.
Weighing The Potential Disadvantages
However, one should also be aware that there are some distinct disadvantages to external fixation. Since there are multiple sites where you would apply both thin wires and thicker bone pins percutaneously, there is always the risk of pin tract infection. This risk approaches 100 percent when frames must remain in place for more than six weeks. When treating significant long bone deformities, keep in mind that it is not uncommon for fixators to remain on a limb for more than six months.
Given the exposed hardware, the patient must play an active role in caring for his or her fixator, in terms of avoiding pin tract infections, not putting the frame at risk and notifying you if problems develop. External fixators, particularly circular frames, should be avoided when treating noncompliant patients.
Indeed, patient acceptance of an external fixator for extended periods of time may wane during the period of treatment. Ensuring adequate preoperative education on the length of treatment as well as proper care of the device will help prevent the development of “cage rage.” However, there are certain patients who are not comfortable with the concept and would not be suitable candidates for external fixation.
When using external fixation, another potential problem one may encounter is inadvertent neurovascular injuries. This may occur by a poorly placed wire or bone pin or occur during a lengthening procedure in which the rate of distraction exceeds the rate of growth of nerves in the area. One can avoid most of these complications by simply being cognizant of the location of the major neurovascular bundles, and by monitoring for sensory loss several times daily during lengthening procedures.