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THE DETERIORATING DFU: prioritising risk factors to avoid amputation

Abstract

The risk of amputation in a deteriorating diabetic foot ulcer is high. This article identifies the three major risk factors associated with such an infection—tissue loss, ischaemia and infection—and explains how to identify which risk is most prominent, and what to do to reduce the risk of amputation. Examples are included of how this approach has led to successful patient outcomes

Declaration of interest: None

Key words: cost-effectiveness analysis, diabetic foot ulcer, MatriStem, skin substitutes, wound healing

 

 

 

THE DETERIORATING DFU: prioritising risk factors to avoid amputation

When citing this paper use the following: Lew, E.J., Mills, J.L., Armstrong D.G. The deteriorating DFU: prioritising risk factors to avoid amputation.

Journal of Wound Care 2015; 24: Sup2, 31–37


Peripheral arterial disease and diabetes polyneuropathy are the precursors of lower extremity ulceration. They can predispose a limb to further tissue loss and place it at risk of infection. In healed, it is paramount that the tissue is protected in order to reduce the risk of recurrence.4,5 This can be achieved with the use of custom inserts and depth inlay shoes. Often, abnormal biomechanics, such as a tight gastrosoleal muscle complex or clawed/the unfortunate event that this process ensues, the likelihood of amputation can increase. The treatment of diabetic foot ulceration requires close attention to the three factors that place a limb at risk of amputation: tissue loss, ischaemia and infection. These factors are like three intersecting rings that jockey for dominance over a patient’s limb (Fig 1).1 Clinicians must learn how to determine which factor is more dominant. This will help them ascertain which aspects of management should be given priority. Understanding the dynamic between these factors will shed light on what can be done to preserve or salvage a limb. This article provides clinical examples of each of these three rings of dominance. Case examples are also given to illustrate the application of this concept to clinical practice and implementation of the principles of limb salvage.

Tissue loss

Fig 2 shows a precarious plantar-based ulceration in a diabetic patient with polyneuropathy. There is no risk of  ischaemia as non-invasive vascular studies have revealed adequate perfusion and vascular runoff to the distal extremity. Initially, treatment focuses on reducing the chronic, indolent nature of the wound thorough sharp debridement of devitalised tissue,2 offloading3 and the application of simple moisture-retentive dressings. Once such an ulcer is 
healed, it is paramount that the tissue is protected in order to reduce the risk of recurrence.4,5 This can be achieved with the use of custom inserts and depth inlay shoes. Often, abnormal biomechanics, such as a tight gastrosoleal muscle complex or clawed/hammer toe deformities, which contribute to the formation of these types of forefoot ulcerations, can be addressed through surgical intervention.6–9

Ischaemia-dominant lesions

Fig 3 shows a dry gangrenous fourth digit with surrounding ischaemic-appearing tissue. The fifth digit has been amputated because of osteomyelitis and gangrene. The ischaemic area has progressed to encompass the fourth ray. There were no concerns about acute infection. The patient did not have palpable pedal pulses. Treatment of this lesion involved a thorough vascular assessment with a lower extremity pulse and Doppler examination, as well as non-invasive vascular studies including ankle brachial pressure indices, plethysmography, digital pressures and arterial duplex imaging. In more urgent cases, such as acute limb ischaemia, some vascular specialists will opt for more advanced vascular assessments with magnetic resonance angiography. The patient’s overall medical status also needs to be evaluated and, depending on his or her condition, a strategy will be put in place either to monitor the foot or pursue vascular intervention.10,11 If revascularisation is undertaken and successful, the tissue-loss ring may then become the more dominant factor. In these types of gangrenous conditions, limb salvage necessitates transmetatarsal amputation.and gangrene. The ischaemic area has progressed to encompass the fourth ray. There were no concerns about acute infection. The patient did not have palpable pedal pulses. Treatment of this lesion involved a thorough vascular assessment with a lower extremity pulse and Doppler examination, as well as non-invasive vascular studies including ankle brachial pressure indices, plethysmography, digital pressures and arterial duplex imaging. In more urgent cases, such as acute limb ischaemia, some vascular specialists will opt for more advanced vascular assessments with magnetic resonance angiography. The patient’s overall medical status also needs to be evaluated and, depending on his or her condition, a strategy will be put in place either to monitor the foot or pursue vascular intervention.10,11 If revascularisation is undertaken and successful, the tissue-loss ring may then become the more dominant factor. In these types of gangrenous conditions, limb salvage necessitates transmetatarsal amputation.

Infection-dominant lesions

Fig 4 depicts an acutely infected right foot. The patient has palpable pulses and the plantar aspect of the big toe is ulcerated. Thus, there is a component of tissue loss. However, in this case, given the acute signs of infection including increased redness, swelling, pain and purulent drainage, along with an elevated white blood cell count and markers ofInfection-dominant lesions Fig 4 depicts an acutely infected right foot. The patient has palpable pulses and the plantar aspect of the big toe is ulcerated. Thus, there is a component of tissue loss. However, in this case, given the acute signs of infection including increased redness, swelling, pain and purulent drainage, along with an elevated white blood cell count and markers of inflammation, the dominant ring is infection.12 Plain radiography will need to be ordered if there is a strong suspicion of deep bone involvement and to evaluate for soft-tissue emphysema. Treatment involves a combination of surgical and medical interventions.13,14 Once the infection is suppressed or eradicated, the dominant ring would then shift to become tissue loss. Treatment strategies would focus on wound closure and skin coverage. This may beinflammation, the dominant ring is infection.12 Plain radiography will need to be ordered if there is a strong suspicion of deep bone involvement and to evaluate for soft-tissue emphysema. Treatment involves a combination of surgical and medical interventions.13,14 Once the infection is suppressed or eradicated, the dominant ring would then shift to become tissue loss. Treatment strategies would focus on wound closure and skin coverage. This may be accomplished with negative pressure wound therapy (NPWT) and split-thickness skin grafting.15–17

Case studies

Here, real-life clinical scenarios are used to illustrate the three rings or factors that place a limb at risk of amputation.

Case study 1

A 68-year-old male with a past medical history of diabetes mellitus and peripheral neuropathy attended the emergency room complaining of increased pain, redness and swelling in his right foot. He related a 3-day history of worsening symptoms. He also complained of fevers, chills, nausea and vomiting, which he attributed to his history of gastroparesis. Physical examination of the right foot revealed a dorsal-lateral foot ulceration overlying the fifth metatarsal region, with a necrotic-appearing wound bed with surrounding erythema, calor (heat) and oedema extending towards the midfoot. The infection extended directly from an ulcerated callus underlying the fifth plantar metatarsal phalangeal joint. On examination, soft-tissue fluctuance and purulence were noted (Figs 5a and 5b). Plain radiography revealed cortical lysis of the proximal phalanx and fifth metatarsal head. Magnetic resonance imaging revealed findings consistent with septic arthritis of the fifth metatarsal phalangeal joint and associated osteomyelitis of the proximal phalanx and metatarsal head. Non-invasive vascular studies showed no peripheral arterial disease.


Question: What appears to be dominant? Tissue loss, ischaemia or infection?
Answer: This is an infection-dominated foot. There is certainly a component of soft-tissue loss, given the quarter-size lesion. The necrotic appearance is a result of soft-tissue death from the infectious process and not from ischaemia.

Question: How is this condition addressed?
Answer: A combination of surgical and medical interventions is necessary for limb salvage. The patient underwent surgery to drain the infection and to debride and excise the devitalised bone and soft tissue. Deep tissue and bone specimens were collected for culture and histopathological analysis. Broadspectrum antibiotic therapy was initiated. Eventually, the antibiotic therapy was narrowed down and targeted according to the final culture and pathology results. After a thorough debridement, lavage and administration of antibiosis, the infectious process was under suppression. There was also a resultant softtissue deficit from the debridement (Fig 6). The ring of tissue loss now became the more dominant factor. The focus of treatment then shifted towards wound closure and skin coverage. NPWT was initiated, which accelerated granulation tissue formation (Fig 7). Two weeks later, a split-thickness skin graft was applied (Fig 8). This took well (Fig 9) and the patient was given prescriptive inserts and shoes for protection and prevention of ulceration.

Case study 2

A 67-year-old male with a past medical history of peripheral arterial disease, diabetes mellitus and peripheral neuropathy presented with rest pain, a gangrenous fourth digit and a chronic left lateral penetrating midfoot ulceration that appeared to be ischaemic in aetiology (Fig 10). His past surgical history included superficial femoral artery (SFA) angioplasty and a fifth toe resection. Despite intervention and local wound care, his wounds had not improved over 3 months. Non-invasive vascular studies were repeated and revealed an ankle brachial pressure index of 0. The toe pressure was also 0mmHg, with flat waveforms. Duplex ultrasound revealed an occluded SFA artery and stent, along with popliteal and trifurcation occlusion. These findings were consistent with critical limb ischaemia and recurrent arterial occlusive disease. There were no signs of acute infection.

Question: What appears to be dominant? Tissue loss, ischaemia or infection?
Answer: This is an ischaemia-dominant lesion. There is certainly a component of tissue loss given the ulceration and fourth digital gangrene. However, the degree and severity of ischaemia is predominant, which places this limb in the ring of ischaemia, as well as partly in that of tissue loss.

Question: How was this addressed?
Answer: The patient underwent successful vascular re-intervention. The presentation then changed to a primarily tissue-loss dominant ring. One week later, the patient underwent a transmetatarsal amputation toaddress the tissue loss (Fig 11). After successful healing (Fig 12), he was protected with a specially made insert, custom shoe and ankle-foot orthotic brace.

Case study 3

A 40-year-old male with diabetes mellitus and peripheral neuropathy presented with chronic foot ulceration (Fig 13). Hand-held Doppler ultrasound revealed palpable and audible pulses. Wound evaluation, X-ray studies, culture and biopsy detected underlying osteomyelitis of the fifth metatarsal. Question: What appears to be dominant? Tissue loss, ischaemia or infection? Answer: This is a soft-tissue-dominant problem. There are no signs of acute infection. There is also no peripheral arterial disease. However, there is central wound necrosis with direct extension to bone. There is also associated bone erosion and infection. Thus, this limb also falls into the ring of infection. Additionally, the patient has a type of deformity that predisposes him to ulceration on the outside of his foot. Some tendons responsible for eversion of the foot were resected during his previous transmetatarsal amputation, which led to an adductovarus and equinus foot deformity. This is where the foot turns inward towards the midline and points to the ground as the muscles responsible for inversion and plantar flexion overpower the foot (Fig 14).ulceration (Fig 13). Hand-held Doppler ultrasound revealed palpable and audible pulses. Wound evaluation, X-ray studies, culture and biopsy detected underlying osteomyelitis of the fifth metatarsal.

Question: What appears to be dominant? Tissue loss, ischaemia or infection?
Answer: This is a soft-tissue-dominant problem. There are no signs of acute infection. There is also no peripheral arterial disease. However, there is central wound necrosis with direct extension to bone. There is also associated bone erosion and infection. Thus, this limb also falls into the ring of infection. Additionally, the patient has a type of deformity that predisposes him to ulceration on the outside of his foot. Some tendons responsible for eversion of the foot were resected during his previous transmetatarsal amputation, which led to an adductovarus and equinus foot deformity. This is where the foot turns inward towards the midline and points to the ground as the muscles responsible for inversion and plantar flexion overpower the foot (Fig 14).

Question: How do you address the infection and soft-tissue loss? Can anything be done to address the deformity? Answer: Sharp debridement and resection of the osteomyelitis, which involved the fifth metatarsal residuum, were performed. Culture-driven antibiotic therapy was employed. Postoperative wound care comprised NPWT to encourage granulation tissue to fill the soft-tissue deficit (Fig 15). Two weeks later, a split-thickness skin graft was performed to obtain complete wound closure (Figs 16a and 16b). The deformity wasQuestion: How do you address the infection and soft-tissue loss? Can anything be done to address the deformity? Answer: Sharp debridement and resection of the osteomyelitis, which involved the fifth metatarsal residuum, were performed. Culture-driven antibiotic therapy was employed. Postoperative wound care comprised NPWT to encourage granulation tissue to fill the soft-tissue deficit (Fig 15). Two weeks later, a split-thickness skin graft was performed to obtain complete wound closure (Figs 16a and 16b). The deformity was corrected with muscle tendon-balancing procedures including percutaneous tendo Achilles lengthening and total tibialis anterior tendon transfer (Fig 17). Postoperatively, the foot and ankle were protected with a prescriptive insert, modified shoe and brace.corrected with muscle tendon-balancing procedures including percutaneous tendo Achilles lengthening and total tibialis anterior tendon transfer (Fig 17). Postoperatively, the foot and ankle were protected with a prescriptive insert, modified shoe and brace.

 

 

Wound (tissue loss), ischaemia and foot infection (WIfI)

A new and validated classification system has been proposed by the Society for Vascular Surgery (SVS). It focuses on the three factors that place a limb at risk of amputation: tissue loss, including gangrene; ischaemia; and infection (WIfI).18,19 These are all key factors that need to be evaluated when assessing a lower extremity with ulceration. Each component of the WIfI has its own grading scheme, based on objective parameters. Each of the three conditions can be classified as none, mild, moderate or severe. This threatened-limb classification scheme can then be used to stratify the risk of amputation as well as to help determine whether or not a patient would benefit from revascularisation. The scoring system is intended to define the disease burden, and is analogous to the tumour, node, metastasis (TNM) system for cancer staging. One other factor that needs careful evaluation is the abnormal biomechanics that occur in a neuropathicstricken limb. In particular, in the diabetic foot an ‘intrinsic minus’ foot deformity occurs with the onset of motor neuropathy.20,21 Hammer toe deformities and digital contractures form and develop, predisposing the patient to digital ulcerations over prominent bone and joint areas. Equinus contractures resulting from loss of flexibility due to gastrosoleal muscle complex may predispose a neuropathic limb to a host of problems including Charcot neuroarthropathy-related midfoot collapse and increased forefoot pressure and associated lesions.22,23 Coupled with neuropathy, these biomechanical abnormalities predispose these limbs and feet to ulceration. These problematic lesions can be addressed through surgical intervention6–9 or withWound (tissue loss), ischaemia and foot infection (WIfI) A new and validated classification system has been proposed by the Society for Vascular Surgery (SVS). It focuses on the three factors that place a limb at risk of amputation: tissue loss, including gangrene; ischaemia; and infection (WIfI).18,19 These are all key factors that need to be evaluated when assessing a lower extremity with ulceration. Each component of the WIfI has its own grading scheme, based on objective parameters. Each of the three conditions can be classified as none, mild, moderate or severe. This threatened-limb classification scheme can then be used to stratify the risk of amputation as well as to help determine whether or not a patient would benefit from revascularisation. The scoring system is intended to define the disease burden, and is analogous to the tumour, node, metastasis (TNM) system for cancer staging. One other factor that needs careful evaluation is the abnormal biomechanics that occur in a neuropathicstricken limb. In particular, in the diabetic foot an ‘intrinsic minus’ foot deformity occurs with the onset of motor neuropathy.20,21 Hammer toe deformities and digital contractures form and develop, predisposing the patient to digital ulcerations over prominent bone and joint areas. Equinus contractures resulting from loss of flexibility due to gastrosoleal muscle complex may predispose a neuropathic limb to a host of problems including Charcot neuroarthropathy-related midfoot collapse and increased forefoot pressure and associated lesions.22,23 Coupled with neuropathy, these biomechanical abnormalities predispose these limbs and feet to ulceration. These problematic lesions can be addressed through surgical intervention 6–9 or with total contact casting followed by protection in the form of prescriptive inserts and depth inlay shoes.3,24,25

Conclusion

The diagnosis and treatment of diabetic lowerextremity ulcerations can be very challenging. However, by understanding the three factors that place a limb at risk of amputation—tissue loss, ischaemiaConclusion The diagnosis and treatment of diabetic lowerextremity ulcerations can be very challenging. However, by understanding the three factors that place a limb at risk of amputation—tissue loss, ischaemia and infection—evaluation of lower-extremity wounds can become less complicated. By conceptualising the strategy of the three rings, it is possible to learn how to identify which one is most dominant. In turn, this will help determine which aspect to prioritise within a treatment plan. We hope this interactive guide will increase understanding of how to apply the principles of limb salvage. 
 


 

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