Wound control: debridement and dressings

The TIME framework (tissue debridement, inflammation control, moisture balance, and epithelialization of wound edges) underscores the key elements of wound control . Regular debridement of devitalized and necrotic tissue promotes wound healing by activating repair and reducing the bacterial load. Scalpel or “sharp” debridement is considered as the gold standard, as it triggers the wound healing process by swiftly changing the surface of a chronic wound into an acute wound but provides the added advantage of relieving pressure created by callus ( Fig. 15.2 ). It can be undertaken in the clinic, or if extensive ulceration is present, may also be performed in a surgical theater facility. It is very unusual for patients with DFU to require an anesthetic for sharp debridement. Limitations of the technique include that it can on occasions be painful, requires careful practice and not all practitioners are allowed to perform them.

Before (A) and after (B) sharp debridement. Note the devitalized and hyperkeratotic skin (callus) has been removed.

Other available methods include mechanical, enzymatic, or autolytic debridement techniques. Examples of mechanical debridement include hydrosurgical, using pressurized irrigation, deep cleansing with moistened gauze, brushing with monofilament pads, and the use of ultrasound as a tissue disruptor . In enzymatic debridement, gradual chemical liquefaction of the devitalized tissues is observed after topical application of agent. Water-soluble proteinases such as collagenase and papain are typical examples. The use of larvae-based debridement (maggot debridement) has been popular for many decades , being particularly helpful when there is significant necrotic tissue that is too painful for sharp or mechanical debridement. Autolytic debridement using hydrogels is a very slow process best suited for dry necrotic wounds in care facilities where limited expertise is available to offer other forms of debridement and the individuals themselves are too frail to visit a hospital clinic. The recent consensus statement from the International Working Group on the Diabetic Foot (IWGDF) noted that while there is clear consensus supporting debridement for wound cleansing, the superiority of a single technique over another could not be established . It is therefore important to consider factors such as pain, operator confidence, need for swift control of necrosis, and costs of debridement when considering the optimal approach. However, in the presence of acute severe infection, sharp surgical debridement is the mainstay.

The application of the dressing to a DFU is intended to relieve symptoms, protect the wound and support healing . A wide array of dressings are now available with some modern dressings capable of targeting specific aspects of healing. The wound bed in DFU is notoriously dynamic with a progressive temporal impact from infection, undulations in peri-wound and leg edema, impact of patient mobilization and adherence to the offloading provided. Therefore, it is unlikely that a single dressing type or formulation can support the ulcer over the entirety of its clinical course. Nonadherent dressings such as saline-soaked gauze are simple to use, inexpensive, and for many years, have been used as SC in control arms of dressing trials. Highly exuding wound require dressings that support moisture control such alginate or foam dressings (with additional hydrocolloid or hydrofiber layers) which are absorbent and effective for heavily exuding wounds . Hydrogel-based dressings can moisturize dry, eschar heavy wound and consequently facilitate autolytic debridement but their use in dry gangrene needs to be carefully monitored for signs of progression to wet gangrene at the interface of dead and healthy tissue. Dressings containing iodine and silver are regarded for their antiseptic potential, used typically when local infection is present. All dressings should be changed frequently, and occlusive dressings ideally avoided in infected DFUs. However, presently, there is no evidence to support the use of one dressing type over another as SC in DFU, a fact that has been reiterated in the most recent consensus statements from the IWGDF and the American Podiatric Medical Association/Society for Vascular Medicine . The only exception to this is the recommendation to consider sucrose-octasulfate potassium salt impregnated dressing as an adjunct to SC in difficult-to-heal neuroischemic DFU without infection .

Ischemia and vascular control

It is understood that ischemia complicates 45%–60% of all DFU with prevalence rates becoming evident over the last few decades. It is a clinical spectrum ranging from subtle peripheral arterial disease (PAD) which may have negligible impact on wound healing to more established chronic limb threatening ischemia (CLTI). In itself, CLTI represents a clinical continuum of increasing degrees of ischemia which can delay wound healing and increase risk of amputation . Early characterization of limb perfusion advisable, if possible, on the first visit itself as the outcome will help guide the DFU management options. Neuroischemic DFUs are usually seen on the nonweight-bearing sites of the foot such as the medial and lateral aspects of the feet or the tips of the toes. These regions are often in contact with footwear and experience shear forces during mobilization but may also occur spontaneously . The callus formation surrounding the ulcers is limited, thin, and shiny. This distinguishes neuroischemic DFU from classical neuropathic DFU which typically occur on weight-bearing plantar surfaces overlying bony prominences and often display thick callus overgrowth. The loss of protective sensation also means that individuals with diabetes often do not report intermittent claudication but rather present directly with tissue loss. Thus a common presentation of CLTI in diabetes is a foot with features of critical limb ischemia and areas dry gangrene indicating regions of direct cutaneous infarction ( Fig. 15.3 ). Individuals with diabetes, with or without ulceration, can also develop acute limb ischemia (from emboli, acute trauma, graft thrombosis, or nonatherosclerotic conditions) which has a distinct clinical phenotype and needs immediate support from the vascular surgical specialists. Importantly, individuals undergoing dialysis have higher prevalence of neuroischemia resulting in lower wound healing and greater amputation rates compared to those not receiving dialysis .

The various presentation of diabetic foot ulcers. (A) Classical neuropathic diabetic foot ulceration on the right foot with peri ulcer callus overgrowth over the bony prominence of first MTPJ. Note the forefoot deformities on both feet and preulcerative lesions on the left plantar foot. (B) Lateral neuroischemic diabetic foot ulceration. Noted limited foot deformity and extensive lateral necrosis. (C) Ischemic features in a young individual with longstanding type 1 diabetes. Note the ischemic rubor and areas of early dry gangrene over dorsal second toe. The individual did not report significant rest pain and ignored early symptoms and signs. MTPJ , metatarsophalangeal joint.

The decision to revascularize an individual with DFU and ischemia will depend on multiple factors such as severity of perfusion abnormalities identified, size of ulceration, extent of tissue loss, and infection with restoration of pulsatile in-line flow to the affected region being the primary goal. Those with milder perfusion abnormalities can be observed closely within the MDfS with SC provision and a decision to revascularization made if the DFU deteriorates or when progress is unpredictably slow. Recent advances in interventional radiology alongside ultradistal/pedal bypass surgery within an integrated pathway have facilitated delivery of complex revascularization .

Offloading

The primary aim of adequate offloading is to reduce abnormal pressure over the ulcer and redistribute it to the area surrounding the DFU to promote healing. A wide array of offloading choices is available, with varying degrees of clinical effectiveness to support their use such as the total contact cast (TCC), removable prefabricated cast walkers, custom splints and extra-depth shoes, surgical boots, and half-shoes. In addition, the use of wheelchairs, crutches, and scooters can also be recommended to support with achieving the balance between desired offloading and maintaining quality of life. Among these, the nonremovable TCC is recommended as the first choice for neuropathic forefoot or midfoot plantar ulcerations . However, in those with neuroischemic DFU, TCC is a relative contraindication. If a TCC is not tolerated or contraindicated, options include a removable knee-high or ankle-high boot. Padding the peri-ulcer skin with semicompressed adhesive felt combined with proper fitting footwear may be adequate in small DFUs. Those with chronic or recurrent ulcerations resulting from high-pressure points related to bony deformities should be considered for surgical offloading. Advocating complete nonweight bearing to individuals with DFU is impractical and is not recommended, except in specific situations (e.g., postmajor bony debridement or postorthopedic reconstruction) and even then, for a limited period only. Ensuring adherence to offloading and recommendations on mobilization remains a challenge.

Infection control including osteomyelitis

It is estimated that half of all DFUs become infected during their lifetime. Diabetic foot infection (DFI) can lead to delayed healing, greater odds of hospitalization . The severity of infection can range from mild with features localized around the ulcer, moderate with more locally extensive features including extension to subdermal structures including tendon or bone, and severe infection presenting with systemic inflammatory response alongside limb-threatening features . Imaging with plain radiography and magnetic resosnace imaging (MRI) should be undertaken to asess the extent of the infection and confirm the presence of osteomyelitis. Microbiological specimens are critical to identify the pathogen—tissue sampling is encouraged where such expertise exists; ideally bone specimens are encouraged for the confirmation of ostemyelitis. In those with mild infection, debridement of surrounding callus, slough and necrotic tissue may be sufficient, contributing to reducing the microbial bioburden. The selection of an antibiotic agent will depend on the likely pathogen (or proven by culture) as well as allergies, drug interactions, and the cost. In most European countries gram-positive organisms such as Staphylococcus aureus and Streptococcus spp. are the most commonly encountered pathogens . However, polymicrobial isolates, including a wide array of gram-negative organisms such as Klebsiella spp., Escherichia coli , and Pseudomonas spp. and anaerobes are common in more chronic DFU . In Africa and Asian regions, gram-negative organisms may be presenting pathogen, sometimes declaring multidrug resistance at the onset .

For soft tissue infection ( Fig. 15.4 ), empirical antibiotic therapy should target gram-positive organisms ( as a minimum) , however, DFUs that are chronic or isolating antibiotic-resistant organisms may require bespoke antibiotic treatment plans form the outset. Co-amoxiclav 625 mg thrice daily is our empiric antibiotic of choice for mild infections in individuals without penicillin allergy. The high prevalence of antibiotic-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci (VRE), and carbapenem-resistant organisms is emerging as a major challenge in determining antimicrobial therapy . The recent IWGDF consensus statement has recommended a treatment duration of 1 or 2 weeks for mild soft tissue infection, with longer doses to be considered in the presence of slow healing or PAD . Antibiotic treatment should be combined with other principles of SC including debridement.

Ascending soft infection from a forefoot plantar diabetic foot ulceration. Note the cellulitis tracking into the medial arch which is extending into the dorsum and distal leg.

Infections exhibiting moderate or severe features are considered as potentially limb threatening. These may require hospitalization and possibly surgical debridement. Indications for urgent surgical intervention, among others, include rapidly spreading necrosis, deep abscess with systemic features and gas in the soft tissues on X-ray examination. A consensus on the best choice of antimicrobial agent or combination is lacking but in the presence of severe soft tissue infection (with or without DFO) broad-spectrum intravenous antibiotics such as Co-amoxiclav 1.2 g thrice daily or tazobactam-piperacillin 4.5 g thrice daily along with a glycopeptide such as teicoplanin or vancomycin (in those with suspected or known MRSA infection), are the empirical agents of choice—the glycopeptide is typically discontinued once absence of MRSA is confirmed. Targeted antibiotic regimes are guided by the microbiology results.

Diabetic foot osteomyelitis (DFO) is common, occurring in nearly one in five of moderately infected and one in two of severely infected DFU . Severe DFO (acute or chronic) typically displays active soft tissue infective component, however chronic DFO can exist with only mild extrinsic soft tissue features. Presence of a swollen toe or foot, history of long-standing ulceration or exacerbations of foot infection every time antibiotics are stopped should raise concerns of DFO. Findings include presence of a deep ulcer (or a sinus) which probes to bone. Plain radiography can reveal evidence of cortical destruction or fragmentation ( Fig. 15.5 ) but has poor sensitivity, especially in early DFO and over bony resection areas. In comparison, MRI has a high sensitivity (>90%) and specificity (>90%) for the radiological detection of DFO and can also provide insight to the extent of soft tissue involvement .

Diabetic foot osteomyelitis (A). Note the swollen “sausage”-shaped right hallux. The corresponding X-ray (B) demonstrates destruction of the distal phalanx tip ( yellow arrow ). There is significant soft tissue swelling extending beyond the visible bony changes.

Management of DFO consists of bone debridement along with removal of any sequestrum, targeted antibiotic therapy guided by bone specimen culture and ongoing intensive DFU care. Antibiotic therapy should be offered for 6 weeks but if there is no clinical improvement within 4 weeks, further inquiry into slow progress and antimicrobial confirmation is required . The recently published OVIVA study, while not specifically designed to evaluate response in DFO, has demonstrated the safety and clinical effectiveness of early switch from intravenous to oral antibiotics with no differences in outcomes between the early oral switch group and the group receiving only intravenous therapy for the study duration . There is evidence to support the notion that primary antibiotic therapy only may be adequate, but this is mainly in forefoot predominant, stable (low-grade) osteomyelitis without evidence of necrotizing infection, managed through an MDfS with close podiatric support . There is limited consensus on the optimal mode of antibiotic delivery and recent evidence suggests that short courses of antibiotics may suffice if a high-quality source control has been achieved . Surgical bone debridement should be considered, as part of SC, in DFO with recurrent soft tissue infections, extensive midfoot and hindfoot osteomyelitis or when infection control is not achieved as predicted or there is a strong suspicion of nonviable infected bone .

Diabetic foot attack

Not infrequently, DFUs can present with rapidly spreading infection and ascending cellulitis, tissue necrosis, and systemic inflammatory syndrome. Such a presentation can potentially escalate into a limb threatening scenario without timely intervention and is labeled as a “Diabetic Foot Attack” . Without urgent (at times, immediate) intervention, it carries a significant risk of a major amputation and threat to life. Management of a diabetic foot attack (DFA) frequently involves admission to hospital, initial broad-spectrum empirical antibiotics, medical stabilization, and urgent surgical debridement of all infected tissue followed by culture-guided antibiotic therapy, high-quality wound care and where necessary, revascularization . Soft tissue defects occurring following radical debridement can be managed with negative pressure would therapy (NPWT) and early skin grafting when granulation has reached the surface of the wound. Fig. 15.6 describes a phased approach to the management of a DFA, which is best undertaken in a multidisciplinary setting. Such a protocolized approach has demonstrated high rates of healing and limb salvage .

Management of a diabetic foot attack.