Emerging Insights On Ex-Fix Offloading For Diabetic Foot Ulcers

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Author(s): 
William P. Grant, DPM, FACFAS, Lisa M. Grant, and Bryan R. Barbato, BS

   A different situation exists if there is a wound on the weightbearing surface. In this case, one can construct an offloading external fixator to completely remove all pressure from the plantar foot. The surgeon can accommodate this by simply adding an additional ring below the foot plate after applying post-op dressings.

   Be aware though that adding this offloading ring has consequences, both positive and negative.

   In terms of benefits, the offloading frame absolutely removes all weight from the wound, permitting an environment that is conducive to wound healing 24 hours per day. This eliminates surface tension on the plantar foot.

   Surgeons can incorporate split thickness skin grafts, local flaps or free flaps without any interference due to unremitting pressure from a cast or accidental partial weightbearing. Using external fixation for offloading also allows one to examine the wound daily. Podiatrists can manage draining wounds and deal with post-op complications in real time. Surgeons can also perform reconstruction or limb salvage simultaneously, including an arthrodesis osteotomy or partial amputation.

   Conversely, offloading external fixation has a variety of limitations specific to its nature. First, application of an external fixator requires a surgeon confident of having the skills necessary to apply and maintain an external fixator. The procedure to apply a frame typically requires approximately 30 to 60 minutes of OR time. All of the skinny wires must be tensioned for the frame to function. Aftercare requires cleansing of the pin sites and application of an antibacterial dressing at the pin-skin interface. Pin sites can become irritated or infected, or the pins may fail. These complications would require a prompt return to the operating room for a pin exchange.

   In our experience, the offloading frame typically has a slightly higher complication rate with pin breakage, irritation and pin site infection. This is likely due to the frame now carrying the entire body load and not sharing it with the foot. Typically, we see the most proximal pin above the ankle as the most likely pin to become irritated or break.

Recommended Indications For Using External Fixator Offloading Frames

1. Ulcer greater than grade IIA (University of Texas Wound Classification System)
2. Ulcer occupies a large portion of the plantar foot
3. The ulcer location precludes appropriate offloading
4. The ulcer is infected or ischemic
5. The ulcer is associated with a complex deformity
6. The ulcer requires a flap or graft
7. Non-weightbearing not possible
(e.g. amputation of opposite limb)

What One Preliminary Study Revealed

A preliminary study initiated in our office included 11 consecutive patients with complex diabetic wounds. We utilized offloading external fixation in all of these patients, who additionally had multiple surgical procedures. Seventy-seven percent of the patients had deep wounds, 92 percent of the wounds were infected and 39 percent of the wounds were ischemic.

   Prior to our intervention, the average ulcer duration was 281 days and 100 percent of the wounds were neuropathic. In regard to adjunctive procedures, we utilized 25 acellular matrices, seven skin grafts and four local flaps prior to ex-fix application. We utilized five skin grafts and seven local flaps in combination with ex-fix application. All of the wounds healed and the average number of days to ulcer healing was 59. There was a 15 percent complication rate with two pin site infections. There was no ulcer recurrence.

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