A Closer Look At Fixation Options For The Charcot Foot

By John Giurini, DPM

What You Should Know About Circular Frames And External Fixation

   Circular frames have gained increased popularity in podiatric surgery due to their ability to bridge the gap between successful internal fixation and amputation. Frames are particularly useful in cases in which internal fixation is contraindicated and the patient is facing a major limb amputation.    As with any new technology, a period of overutilization has been followed by a more rational approach based on clinical experience and published reports. This is the case in podiatric surgery today. While there are few evidence-based reports on the use of external fixation in treating Charcot joint disease, anecdotal reports and personal communications are beginning to shape the indications for circular frames.    The primary utility of external fixation is the ability to insert fixation wires proximal and distal to potentially infected joints or severely destroyed joints. This facilitates stability while the joints consolidate. Surgeons can also apply external fixation devices in the presence of open ulcerations. In fact, the stability they lend to the wound will often expedite wound healing.    External fixation offers key advantages including: the promotion of stability across several joints; the ability to apply them distant from potentially infected bone; and the ability to apply them in the presence of open soft tissue envelope.    Proponents of circular frames indicate that patients can begin early weightbearing. This is especially true with the Ilizarov style frames, which allow surgeons to dissipate weightbearing forces through a set of wires and frames proximally in the lower extremity. This will often counteract the disuse osteopenia that results in these patients from long-term nonweightbearing or immobilization.    In regard to static circular frames (i.e. Ilizarov–style), they provide stability and correction of deformity but little in the way of compression. It is not unusual to add internal fixation along with external fixation to provide the necessary compression. One can make these types of frames dynamic by removing one or two struts later during the course of treatment. This will allow some motion at the fusion site when patients ambulate, thus stimulating bone growth.    One can use dynamic frames such as the Taylor Spatial Frame in the acute phase of Charcot to slowly distract and reduce joint subluxation. After achieving an optimum position of correction, the device can compress the joints and lock the struts until treatment is deemed complete. More commonly, however, surgeons will insert rigid internal fixation and remove the frame once the deformity is reduced.1    The major disadvantages to circular frames have been the risk of pin tract infections, the weight of the frame and patient acceptance of the frame. Pin tract problems, especially infections, result from micromotion at the pin-skin interface and the fact that these frames remain in place for as long as three months. Infection rates have decreased significantly since the introduction of skinny wires over half pins. However, pins can still loosen and one may need to replace these during the course of treatment.    Surgeons should also forewarn the patient that a second surgery will be necessary, whether it is for removing the frame and inserting internal fixation or for removing the frame alone.

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