Essential Insights On Surgical Management Of Diabetic Foot Ulcers

Diabetic foot ulcers can lead to an array of complications including osteomyelitis and soft tissue infection. Surveying the research and relying on clinical experience, these authors provide a guide to surgically managing diabetic foot ulcers to reduce the risk of re-ulceration and complications.

Diabetic foot ulcers (DFU) occur in at least 15 percent of all people with diabetes mellitus and are the reason for approximately 20 percent of all hospitalizations of patients with diabetes.¹ The most common causes of DFUs are diabetic peripheral neuropathy, existing foot deformity such as Charcot neuroarthropathy or partial foot amputation(s), biomechanical abnormalities, and/or peripheral vascular disease (PVD).

Proper identification of the etiological factors leading to DFUs is important in determining the best course of treatment and possibly to reduce the risk of re-ulceration. Diabetic foot ulcers can be associated with a spectrum of complications including soft tissue infection, osteomyelitis and Charcot neuroarthropathy.

Since inadequate blood supply is a common predecessor of foot gangrene and subsequent infection, patients with diabetes and clinically evident PVD should have an appropriate vascular workup to determine whether revascularization procedures are necessary to promote healing of the DFU. Worldwide, diabetic foot infections are the most common skeletal and soft tissue infections in patients with diabetes mellitus.¹ We often encounter an impaired immune response in patients with diabetes along with common medical comorbidities such as coronary artery disease and end-stage renal disease. As a result, diabetic foot infections can worsen and further increase the risk of limb loss.

While acute DFUs proceed through the normal sequence of events consisting of the inflammatory, proliferative and remodeling phases, chronic wounds often take different pathways in wound repair, which can lead to non-healing and further complications. The treatment of chronic DFUs includes converting the cellular environment to that of an acute wound with subsequent soft tissue closure. Aggressive surgical wound debridement can accomplish this task with the removal of any necrotic or fibrotic tissue as these are heavily contaminated tissues that carry diseased cells and bacteria. Furthermore, the presence of devitalized tissues can limit the effects of systemic antibiotic delivery.  

Conventional surgical debridement using scalpels and other sharp instrumentation can facilitate the rapid removal of devitalized tissues. More recently, hydrosurgical debridement has provided an alternate technique, utilizing systems that pump high-pressure sterile normal saline in combination with handheld cutting and aspirating tools. This technique facilitates the precise cutting of tissues while also removing debris from the wound. In a prospective randomized controlled trial, Caputo and colleagues compared hydrosurgical debridement against conventional surgical debridement for lower extremity ulcerations.² The authors found that the hydrosurgical technique provided quicker wound debridement times without compromising overall wound healing rates.

In the last 30 years, negative pressure wound therapy (NPWT) has become one of the most widely used modalities in the treatment of DFUs.³ The technique delivers subatmospheric pressure through open-cell foam placed into the wound, ultimately expediting granulation tissue formation and decreasing bacterial counts to promote wound healing. While there is controversy surrounding the quality of evidence available on the efficacy of NPWT for chronic DFUs, future clinical trials may provide better data for its use. Surgeons should keep in mind that this modality serves as an adjunctive therapy and is not currently meant to replace the fundamental principles of surgical debridement, infection control and wound management. Following surgical debridement, one can use NPWT to prepare the wound bed for final closure with biologic dressings, skin grafts and/or plastic surgical techniques depending on the wound characteristics.

Studies have reported several biologic dressings as successful in facilitating healing for diabetic foot ulcers.^4,5 Following appropriate debridement and treatment of any soft tissue and bone infection, one can place acellular dermal regenerative tissue matrices directly onto granular wounds. Clinicians can use these biologic dressings to decrease wound healing times, address wounds of varying depths and use the dressings in combination with NPWT.⁶  

Skin grafting is a relatively simple, reliable and effective technique for the closure of DFUs in patients without significant comorbidities.⁷ Wounds at certain locations of the foot or ankle may be more amenable to local skin flaps for definitive wound closure while intrinsic muscle, local random and/or pedicle flaps provide other options for extensive wounds of the diabetic foot.  

Managing Diabetic Foot Ulcers In The Presence Of Soft Tissue Infection

Soft tissue infections are a common complication of DFUs since their location often favors the entry of pathogenic bacteria. Diabetic foot ulcers that go untreated can lead to soft tissue infection involving any level such as skin, fascia and/or muscle prior to bone involvement. One can use oral or intravenous antibiotics to treat diabetic foot ulcers with only local skin infection such as cellulitis.

One must consider the chronicity of the wound prior to the infection as surgical debridement may be required to convert the wound to a clean, acute wound. However, ulcers with underlying abscess and infection of fascia and muscle, or infection that resulted in tissue necrosis require aggressive surgical debridement combined with antibiotic therapy. Adequate surgical debridement requires rapid decompression of the infection using incisions that extend from the original DFU and into any adjacent compartments that may be involved.⁸

Necrotizing fasciitis is a less common severe infection involving the subcutaneous tissues and fascia that spreads rapidly and is associated with a high mortality, especially in the diabetic population. One must address cases of necrotizing fasciitis immediately with surgical debridement of all infected and necrotic tissues. In severe cases, multiple surgical debridements may be required to resolve the infection and prepare the surgical wound(s) for subsequent closure. Appropriate selection of antibiotic therapy without overuse is imperative as there have been increasing reports of multi-drug resistant organisms involved with diabetic foot infections.⁹

When Osteomyelitis Arises In The Diabetic Foot

Osteomyelitis in the diabetic foot most frequently occurs through the contiguous spread of infection from soft tissue into bone. The underlying bone at the ulceration site is exposed to bacteria that invade vascular channels, subsequently increasing the intraosseous pressure that impedes blood flow and finally leads to ischemic bone necrosis.

Resect all grossly infected, necrotic soft tissue and bone. Be sure to preserve viable healthy tissues, keeping in mind the potential function of the remaining structures. The duration of culture-guided systemic antibiotic therapy, either oral or parenteral, depends on whether histologic inspection of intraoperative bone biopsies reveals clean margins.⁹ Perform appropriate soft tissue cultures, bone cultures and bone biopsies to further guide the selection and duration of antibiotic therapy. In certain cases in which the patient cannot undergo a surgical debridement or amputation, perform limited percutaneous biopsies under fluoroscopic guidance.  

Surgeons can amputate digit(s) and resect partial rays for cases of osteomyelitis confined to these areas. For osteomyelitis involving joint complexes, one can attempt isolated resection of the involved joints and stabilization of the surrounding areas, especially adjacent joints. When determining the level of amputation, also consider the potential to maintain ambulatory status and accommodate shoe gear.

Address dead spaces with antibiotic-impregnated beads and/or spacers. Surgeons can manipulate antibiotic-impregnated cement to form beads or blocks that they can place into wound defects and provide local antibiotic delivery without increasing systemic toxicity.¹⁰ In addition, this surgical technique can give structural stability to the surrounding tissues in preparation for more definitive procedures such as bone grafting and arthrodesis.

Addressing DFUs In Patients With Charcot Neuroarthropathy

Skin ulcerations provide a direct pathway for infections and are often present in the diabetic Charcot foot and ankle as consequences of neuropathy and deformity. Patients with chronic Charcot neuroarthropathy of the foot and/or ankle most commonly present in the clinical setting. These patients often do not notice a deformity until an ulcer occurs or deformity impedes their ability to ambulate or wear regular shoe gear.

The midfoot, particularly the tarsometatarsal joint complex or Lisfranc joint, is one of the most frequent locations for joint collapse and disorganization. However, the hindfoot and ankle are becoming increasingly prevalent locations for Charcot. Excessive pressure at these areas in the diabetic insensate foot and in the absence of proper offloading can lead to extensive neuropathic ulcerations. Charcot neuroarthropathy with ulceration can drastically increase amputation risk.¹¹ Surgical management of DFUs in the setting of Charcot calls for approaches not only to close the wound but also to address the underlying deformity. This may include corrective procedures including but not limited to ostectomy, osteotomy and arthrodesis. Circular external fixation may be an option for complicated cases requiring extensive osseous and soft tissue reconstruction as these devices can provide overall stability, access to wounds for frequent care and effective offloading.  

It is important for surgeons to be aware that osteomyelitis can precede the development of Charcot with operative treatment for osteomyelitis itself being known as a trigger for the onset of neuropathic osteoarthropathy.¹² Physicians can often mistake acute Charcot neuroarthropathy, which clinically manifests as a warm, edematous and often erythematous foot and/or ankle, for infection.

A high index of suspicion is necessary to diagnose this stage of Charcot accurately and provide adequate immobilization. This can help prevent further periarticular subluxation and/or dislocations that often lead to severe deformities and bony prominences in the later stages of Charcot neuroarthropathy. Staging of procedures is a useful approach with Charcot foot and ankle osteomyelitis to eradicate infection, leaving healthy, viable soft tissue and bone that can maintain definitive long-term correction.^13,14

When Partial Amputations Can Help Preserve Limb Function
Toe, partial ray (metatarsal and toe) and midfoot amputations are common procedures for the management of infected and/or non-healing DFUs. A well-balanced foot amputation can remove the infected portion of the foot and produce a functional and plantigrade foot that is less prone to future skin breakdown. As techniques for revascularization constantly improve, surgeons are now able to preserve limb function with amputations at the foot level.

Durable soft tissue coverage, biomechanical alterations and muscular balance of the remainder of the foot should be considerations when performing pedal amputations for diabetic foot infections and/or osteomyelitis. Diabetic foot amputations require adequate arterial sufficiency to ensure healing. For this reason, it is paramount to evaluate the vascularity of the limb and coordinate treatment with the vascular team to determine the best level of amputation if peripheral arterial disease is present. Also consider the muscular balance of the foot since an unstable, partially amputated foot can lead to further re-ulceration and/or Charcot neuroarthropathy requiring revision of the amputation or more proximal amputation, which in certain cases may result in major limb loss.

In Conclusion

As DFUs affect a large proportion of the diabetic population, several potential complications place these patients at high risk for major limb loss. Fortunately with ongoing research, treatment protocols and strategies continue to evolve and lead to additional surgical approaches in addressing isolated DFU and those with soft tissue infections, osteomyelitis and Charcot neuroarthropathy.

Dr. Ramanujam is an Assistant Professor in the Division of Podiatric Medicine and Surgery within the Department of Orthopaedic Surgery at the University of Texas Health Science Center in San Antonio, Texas.

Dr. Stapleton is an Associate in Foot and Ankle Surgery at VSAS Orthopaedics in Allentown, Pa. He is the Chief of Podiatric Surgery at Lehigh Valley Hospital in Allentown, Pa. Dr. Stapleton is a Clinical Assistant Professor of Surgery at Penn State College of Medicine in Hershey, Pa. He is also a Fellow of the American College of Foot and Ankle Surgeons.  

Dr. Zgonis is a Professor and the Director of Externship and Reconstructive Foot and Ankle Fellowship Programs in the Division of Podiatric Medicine and Surgery within the Department of Orthopaedic Surgery at the University of Texas Health Science Center in San Antonio, Texas. Dr. Zgonis is also a Fellow of the American College of Foot and Ankle Surgeons.  

References

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