Assessing The Use Of Ex-Fix For Offloading In Diabetic Limb Salvage

Author(s): 
Dong Kim, DPM, Jeffrey McAlister, DPM, and Paul J. Kim, DPM

   Researchers have shown that total contact casting is effective at offloading and ultimately healing neuropathic diabetic ulcers.13 Although options such as a removable CAM walker and polyurethane foam have eliminated some of the disadvantages of casting, they are not favorable in the management of flap reconstructed extremities.14,15 Casts do not give easy access to the flap for observation and monitoring of vascular status.5 If wound care is indicated, frequent cast changes are time consuming and uncomfortable to the patient.16 The only option to access the flap and perform vascular examinations is to create a window in the cast. However, this method is time consuming, dangerous and aesthetically displeasing.

   External fixation addresses many of the postoperative concerns following flap reconstruction. External fixation allows for strict immobilization of joints, specifically the ankle joint.17 Excessive ankle dorsiflexion and plantarflexion not only transmit shear forces to complex flaps but also increase intracompartmental pressures in the limb, which can promote venous congestion.16 Immobilization of the joints also prevents flap contractures that may be detrimental not only to flap survival but to general function of the limb.18

   Another advantage of external fixation is that it allows easy access to observe the flaps and donor sites. Frequent monitoring can identify potential complications such as dysvascularity and hematomas. For example, muscle flaps may drain heavily in the postoperative period and frequent dressing changes are required to prevent maceration and infection.16 It is also easier to perform Doppler checks of flaps through an external fixator than a cast, which initially an intensive care nurse must do every hour.

   External fixation allows offloading not only to the flaps but also other pressure areas such as the heel. Concomitantly, the external fixator allows elevation of the extremity, which is important for flap survival. One can achieve elevation via the construct alone or by hanging the external fixator by a rope tied to a crossbar over a bed.19 In regard to types of external fixation, available options for foot and ankle surgeons include ring fixation with wires, a monolateral frame or a hybrid frame. The foot and ankle surgeon and plastic surgery team should routinely meet preoperatively and decide on the type of device to use based on the anatomic location of the wound and need for offloading the flap. This will assist the pre-surgical planning team and greatly cut down on operative time and complications.

   External fixation is not without its drawbacks. Common complications with external fixation include pin tract infections, hardware failure and muscular atrophy. One can usually treat these complications with local wound care and oral antibiotics, replacement of hardware, and physical therapy.4 External fixation is also a poor choice for patients with psychiatric illnesses, non-adherence or impending mortality.16 Morbid obesity, incapacitation of the contralateral limb and spasticity are relative contraindications as well.16 There is a component of coordination among various surgical and medical teams when applying external fixators during the stages of limb reconstruction and wound coverage. The podiatric surgeon may manage the debridements, wound care and external fixation while the plastic surgeon harvests and inlays the flap.4

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