Presentations of foot injury in diabetes

This Practice Nurse Clinical Update explores common foot problems seen in diabetes, and how managing fissures, calluses, puncture wounds and burns can prevent ulceration.

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Introduction

AS THE proportion of general practice patients diagnosed with diabetes increases, it is important to be alert to the complications of diabetes, their detection and management.

Currently, 3.6% of the adult population has diabetes.1 Prevalence is higher among older patients, indigenous Australians, those born overseas and those from lower socioeconomic backgrounds.

The inclusion of diabetic foot assessment in the annual cycle of care has the potential to improve the early detection of foot problems, reducing the incidence of foot ulcers and amputations.

This article follows an Update on the prevention of foot ulcers in people with diabetes which appeared in the April 2009 issue of Medical Observer Practice Nurse.

It described foot assessment, foot care education and outlined appropriate footwear.

The current article addresses some common foot problems that can lead to foot ulceration in diabetes which may present during routine foot assessment or at other times.

The treatment of such conditions is a key strategy in the management of the diabetic foot as described by the International Diabetes Federation’s International Working Group on the Diabetic Foot (IWGDF).

That strategy includes the following measures2:
1. Regular inspection and examination of the at-risk foot
2. Identification of the at-risk foot
3. Education for patients, family and healthcare providers
4. Appropriate footwear
5. Treatment of non-ulcerative foot pathology.

Presentation

The significance of prompt identification and treatment of foot problems is best appreciated by understanding why foot ulcers occur. In most cases, the patient has lost protective sensation in their feet as a result of peripheral neuropathy and suffered a minor foot problem or injury that went unnoticed (and untreated).

Even when detected by the patient, an absence of pain may convince them the injury is not serious. It is therefore typical for patients with sensory loss to present late. Unfortunately, this is associated with worse outcomes, as chronic wounds are slower to heal and more likely to have deep infection.

It is worth reiterating that people with diabetes who have loss of sensation must be encouraged to examine their feet daily. and seek help from their healthcare professional for any foot problem, even if it is painless.

Figure 1: An ulcerated heel fissure. 

Types of foot problems

1. HEEL FISSURES

Anhidrosis (dry skin) of the feet can be a manifestation of peripheral neuropathy in people with diabetes. The autonomic nerve dysfunction reduces sweating, which together with the effect of non-enzymatic glycosylation of skin renders the feet dry, hard and predisposed to fissures.3,4

Fissures most commonly present on the heels where the skin is often callused from pressure (see Figure 1).

Preventing heel fissures

Strategies to prevent heel fissures include:
 • Daily application of moisturising creams or “heel balms” that contain urea, which increases the moisture uptake of the skin.
 • Wearing shoes that enclose the heels, which helps support the heel fat pad.

Bleeding heel fissures

A fissure extending to the dermis (bleeding) must be treated as a wound. Any callus associated with the fissure will need to be debrided and the wound cleaned with normal saline.

The wound should be covered with a soft, non-adherent, permeable dressing, such as a foam dressing, which should be changed every 1-3 days until the wound is healed.

Wound closure dressings (such as Steri-Strips) may be useful for fissures with a clean, granulating base. Footwear with a supportive heel counter is usually better than open-heeled footwear, although the potential for trauma from the shoes must also be considered.

Instruct the patient on how to rest with their heel over a pillow or use a pressure-relieving device such as those used to prevent heel pressure ulcers during bedrest. Warn patients that walking will delay healing and advise them to avoid any unnecessary weight-bearing.

A podiatrist may assist with supportive strapping of the heel or specialised footwear prescription. Monitor closely to ensure the wound is healing and to identify potential infections early.

2. CALLUS

An area of localised callus (hyperkeratosis), in the at-risk diabetic foot, should be considered a preulcerous lesion requiring debridement by a podiatrist.9 Callus results from chronic pressure on the area and is itself a pathology. Once debrided, it is important to identify the cause of the callus.

Footwear

When the toes are affected, the patient’s footwear is usually to blame. Observe the patient in their footwear to detect any obvious cause of pressure, and ensure the patient stops wearing the shoes if this is the case.

Without sensation to warn them, patients will often claim the causative footwear is “comfortable” despite obvious signs to the contrary.

For calluses on the sole of the foot, a change of footwear and insoles to those that cushion and accommodate the foot are often needed long term.

While the aim is to prevent or delay the formation of callus, many of these patients will still require continuing preventive podiatry care.

Necrosis and ulceration

Debridement of callus is effective in reducing pressure, but if left untreated callus can very often lead to necrosis and ulceration beneath the callus.10

Ulceration of callus is sometimes heralded by a dark discolouration caused by bleeding. This type of callus requires urgent sharp debridement by a podiatrist, which may reveal a wound (see Figures 2 and 3).

Ulcer management

Any wound should be cleaned with saline and dressed using a soft, nonadherent foam dressing. It is necessary to assess and treat any infection and reduce pressure on the area as this is critical for healing.

Podiatrists with expertise in diabetic foot disease should be involved in the management of patients with this type of foot ulcer. Ideally, refer the patient to a specialist diabetic foot/high-risk foot clinic.

Initially, advise patients to restrict their walking and to wear a well-cushioned shoe that does not put pressure on the affected area. A podiatrist or diabetic foot/high-risk foot clinic will be able to provide more effective pressure offloading.

3. PUNCTURE WOUNDS

Patients with reduced sensation are vulnerable to injury from penetration of sharp objects such as nails and glass. These injuries force bacteria deep into the foot and may involve foreign bodies which are difficult to detect and remove (see Figure 4).

Managing puncture wounds

Small foreign objects should be removed if this can be done without further injury. Irrigate the wound with normal saline, or if the wound is very contaminated, consider a topical antimicrobial such as povidone iodine, followed by saline.

Cover the wound with a soft and non-adherent dressing and examine the foot carefully for any sign of infection, particularly over the first 48 hours.

A tetanus booster may also be needed. If a foreign body is suspected, an x-ray or ultrasound can often detect its location.

Deep, penetrating wounds can deteriorate rapidly with infections tracking through the foot compartments. If the wound is deep or infected, contact a specialist diabetic foot/high-risk foot clinic with a consulting surgeon, or send the patient to the emergency department.

4. BURNS

Burns are often the result of placing the feet in a hot foot bath, resting the feet on or near hot surfaces such as metal outdoor furniture during summer or sitting with the feet too close to a heater (see Figure 5).

The risk of infection is very high and the extent of tissue necrosis may only be evident 48 hours after the initial injury.

Managing burns The management of burns is the same whether the patient has diabetes or not; however, healing is more likely to be delayed because of the impaired immunological function and peripheral arterial disease associated with diabetes.

Burns should be reviewed and a topical antimicrobial agent such as silver sulfadiazine applied under a non-adherent secondary dressing.

Systemic antibiotics may need to be considered and the affected area should be protected from further trauma such as from footwear. A soft accommodative “healing sandal” or post-operative shoe is usually needed.

Refer the patient to a specialist diabetic foot/high-risk foot clinic if accessible to the patient. Patients with extensive burns (more than 10% of the body surface) should be referred to the nearest specialised burns unit.

Conclusion

Nurses in general practice involved in the care of patients with diabetes need to identify those patients whose feet are at particular risk and encourage them to check their feet daily and report changes.

Owing to the serious consequences of delayed treatment and infection in the diabetic foot, all foot problems need prompt management and treatment.

To avoid serious adverse outcomes, patients with foot ulceration or infection should be referred to a specialist diabetic foot/highrisk foot clinic when one is available.

Tip: Useful patient information on foot care
• Diabetes Australia diabetesaustralia.com.au
• Australian Podiatry Association podiatry.asn.au 

Tip: When not to debride
Inadequate blood supply for healing is a contraindication for debridement. If pedal pulses cannot be palpated or ischaemia is otherwise suspected, refer the patient to a vascular specialist for assessment and opinion. 

Tip: Antibiotics
Foot infections in diabetes warrant prompt treatment with systemic antibiotics. More severe infections with greater than 2 cm of cellulitis, in particular those that progress rapidly, may need referral for intravenous antibiotics, and patients exhibiting systemic symptoms need hospital admission. Even when patients with diabetes have severe infections or osteomyelitis they can present afebrile with no raised white cell count or raised erythrocyte sedimentation rate.8 

Tip: Debriding calluses
Have a podiatrist debride calluses. Patients with loss of protective sensation must be warned against the use of home remedies for calluses (such as abrasive tools or pumice) as self-treatment can easily lead to injury. 

Tip: Hidden infection
The signs of infection may be masked by the effects of ischaemia and/or neuropathy in patients with diabetes. However, these patients are likely to develop cellulitis and can deteriorate rapidly.5,6 For this reason it is critical to monitor wounds closely for signs of infection.7 

Figure 4: Severe puncture wound caused by a metal screw. The patient required admission for intravenous antibiotics.

Figure 5: A diabetic foot injury from a heater. 

This Update is by Vanessa Nube, Dip Appl Sci (Pod), Msc (Med) and senior podiatrist at the Diabetes Centre High Risk Foot Clinic, Royal Prince Alfred Hospital, Sydney.