Due to the high rate of complications in patients with diabetic foot ulcers (DFUs), it is important to continue to evaluate strategies for complex cases involving posterior heel wounds in this high-risk population. Accordingly, these authors discuss the use of external fixation to facilitate offloading, successful wound healing and ultimately limb salvage.
Complications in patients with diabetic foot ulcers (DFUs) are a leading cause of lower extremity amputations.1 Minor wounds can often lead to chronic, non-healing ulcers that are predisposed to infection. Chronic ulcers can subsequently lead to gangrene and/or an amputation. There is a five-year mortality rate of 39 to 68 percent for patients with diabetes and Charcot neuroarthropathy, who have an amputation.2 Limb salvage is essential in this patient population.
For patients with diabetic neuropathy, an important goal is relieving the pressure at the ulcer site. By immobilizing the patient with an offloading device, one can reduce pressure and shear forces, allowing healing to take place.3 The primary methods of offloading include total contact casting (TCC), removable walking boots, healing sandals, surgical shoes and ankle-foot orthoses.
Most consider total contact casting the gold standard for offloading the foot as it reduces pressure at the ulcer site while allowing the patient to remain ambulatory.3 One generally changes these casts every one to two weeks but in patients with edema or other concerns, more frequent cast replacement may be necessary.
Total contact casting significantly reduces pressure at the ulcer site but it also reduces the patient’s activity level, and decreases stride length and cadence. The main disadvantage for patients is that the cast is heavy and hot, and makes bathing, walking and sleeping difficult.3 In our experience, there are also many patients who cannot tolerate total contact casting and others who break the cast in a few days. It is also a possibility that some patients, even after months of wearing a TCC, may still have an open wound.
For these types of patients, the use of external fixation with a kickstand could have multiple benefits. In comparison to internal plates and intramedullary nails, external fixators cause less disruption of the soft tissues, osseous blood supply and periosteum.4 Multiple study authors have reported that in the proper patient population, external fixators make for an excellent adjunct for wound care therapy.5-6
External fixators are a convenient method for offloading and immobilizing patients, particularly nonadherent patients who do not benefit from a total contact cast or removable walking boot. Studies show that patients are adherent with total contact casting only 28 percent of the time, which can lead to poor wound healing.
A circular external fixator is advantageous for biomechanical stability and continuous local wound care in patients with diabetes.5-6 Clemens and colleagues previously noted the successful use of an llizarov apparatus to immobilize and offload the foot and ankle to prevent any interruption of a skin graft.5 In this article, we recommend the use of a circular external fixation device to help facilitate wound healing in complex posterior heel DFUs.
Recognizing The Challenges Inherent To Complex Calcaneal Wounds
The surgical treatment of large posterior plantar soft tissue defects of the heel with underlying calcaneal osteomyelitis presents a significant reconstructive challenge.
This is due to the immobile adjacent soft tissues, limited vascular supply, close proximity to neurovascular and tendinous structures, and significant weightbearing pressure and shear forces during stance and ambulation. As with treatment of any diabetic foot or ankle wound, one should emphasize preoperative optimization of the medical status of the patient. Comorbidities of diabetes, particularly peripheral vascular disease and peripheral neuropathy, have a significant effect on wound healing and warrant evaluation. Vascular assessment of the lower extremities should include evaluation of ankle brachial index, toe brachial index, Doppler waveforms and pulse volume recordings to determine whether there is a need for a vascular surgery consultation to improve perfusion.7
With these concepts in mind, let us take a closer look at two individuals with chronic non-healing DFUs that successfully healed after treatment utilizing an external fixation apparatus.
Case Studies: Addressing Chronic, Limb-Threatening Ulcerations
A 55-year-old male presented with a non-healing heel ulceration and calcaneal osteomyelitis secondary to diabetic neuropathy. The patient had a history of diabetes mellitus, hypertension, hyperlipidemia, peripheral vascular disease and stroke.
After exhausting all conservative measures to avoid a below-knee amputation (BKA), we felt that employing an external fixator to offload the wound could help facilitate healing. We proceeded to surgical treatment, which consisted of a right calcaneal ostectomy, advancement of a skin flap of the right heel for primary closure and application of a multiplanar external fixator.
We debrided the wound down to the level of the plantar muscular compartment with no viable muscle flap available to transfer. After incorporating a wound care matrix product in the deeper wound deficit areas, we placed a bioengineered graft over the ulcer site (see first photo above). We subsequently placed an external fixator on the patient’s limb with an offloading frame (see second photo above). The patient also had negative pressure wound therapy (NPWT) at medium intensity (100 mmHg).
Postoperatively, the patient had NPWT for approximately one month and received weekly local wound care. Once the wound appeared to heal, we removed the frame.
In another case, a 65-year-old male presented with a neuropathic ulceration on the right heel (see fourth photo above). The ulcer measured 4.0 cm by 3.2 cm and consisted of full-thickness granular tissue. His past medical history consisted of type 2 diabetes mellitus, hypertension and spinal stenosis. We exhausted conservative treatment prior to proceeding with the external fixation device.
We performed a calcaneal ostectomy and debrided the osteomyelitic bone and any nonviable tissue. After subsequent application of a biologic graft on the ulcer site, we placed and adjusted an external fixator. Once the ulcer healed, we removed the external fixator and the patient completed an antibiotic regimen prescribed by the infectious disease physician. We then fitted the patient for a zero-gravity boot four to six weeks after wound healing for permanent accommodation.
A Closer Look At The Benefits Of A Hybrid External Fixation Construct
We applied the circular offloading external fixator device by reversing the foot plate. By using it in this manner, it allows access to the wound without the frame being obtrusive. One places the thin wires in a standard fashion beginning at the proximal end of the construct. Surgeons should avoid the area of ulceration, ensuring a distance of about two cm from the rod to the ring to help avoid any pin tract infection.
By using the external fixator as a hybrid construct, both dynamically and statically, we can gradually correct chronic long-standing deformities as well as maintain stability and compression.8 This construct promotes stability by controlling both the proximal and distal ends of the bone, decreasing the distance between the rods and the bone, increasing the number of rods connected and the diameter of the pins.4 One can keep the pin sites clean with gauze applicators and antimicrobial soap. Weekly visits can allow DPMs to assess for any signs of pin drainage, infection or loosening. The external fixator should remain in place for two to three months. After removal of the frame, the patient wears a pneumatic boot for four to six weeks.
Other Considerations With External Fixation
The use of external fixation as a module to offload ulcers is an effective method that can help patients who have difficulty with other offloading modalities. While traditional cast or splint techniques can effectively immobilize the lower extremity, these methods can fail due to improper technique or patient adherence issues. External fixation offers a major advantage by providing suspension of the extremity off of the ground with a stable construct that protects the foot from compressive forces. This technique is especially helpful for complex cases such as Charcot reconstruction. One study of 83 patients with Charcot deformities revealed a 96 percent limb salvage rate after application of an external fixator.9 Circular external fixation devices may also help to discourage weightbearing.
One does need to consider the disadvantages of external fixation, such as high cost and difficult maintenance with increased risk of complications, in determining proper patient selection. When using a combination of internal and external fixation, one study showed a 45 percent pin tract infection rate.10 Complications can include pin tract infections, deep wound infections and non-unions.
For the majority of these patients, the end goal is to save their limb and get a plantigrade, braceable foot. Partial calcanectomy with primary closure or healing by secondary intent continues to be a viable alternative to BKAs. The resultant soft tissue contour defect and gait changes resulting from resection of the Achilles tendon are of significant cosmetic and functional concern. However, the external fixator allows the surgeon to manipulate the foot or ankle to the most appropriate position for repair of the posterior compartments. A circular external fixator also allows for continuous postoperative adjustments. However, to ensure proper healing, it is important to take into account patient selection, family support, surgical experience and ensure an overall multidisciplinary effort to manage the patient’s comorbidities.11
With appropriate patient selection and preoperative planning, external fixation may help to decrease the cost and duration of hospital stays for patients with diabetes and limb-threatening ulcerations. Further prospective and long-term studies are necessary to further assess the efficacy of this treatment. Although this technique may not be applicable for all cases, reconstructive surgeons may consider the use of external fixation with a kickstand for limb preservation.
While amputations are a straightforward and rapid solution to complex wounds that can have the patient return to ambulating in short order, they have risks including decreased life expectancy and increased risk of contralateral limb amputation.12
This treatment approach with an external fixator can give the patient a functional foot and may prevent the need for an amputation. This device also allows access for weekly wound care therapy. In our experience, we have seen promising results with no recurrence of ulcers. We believe this apparatus provides excellent stabilization and can facilitate positive outcomes in diabetic limb preservation.
Dr. Glazer is a Diplomate of the American Board of Foot and Ankle Surgery, a Fellow of the American College of Foot and Ankle Surgeons, and a Fellow of the Academy of Ambulatory Foot and Ankle Surgery. He is in private practice in Mission Viejo, Calif.
Dr. Haider is a second-year resident in the Podiatric Surgery Residency Program at Ascension Providence Hospital in Southfield, Mich.
Dr. Stuto is a fellowship-trained reconstructive foot and ankle surgeon, a Diplomate of the American Board of Foot and Ankle Surgery, and a Fellow of the American College of Foot and Ankle Surgeons. He is in private practice in Brooklyn, N.Y.
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