Certainly, macrovascular disease is more common in the diabetic population.
It has been reported that patients with peripheral arterial disease (PAD) and diabetes experience worse lower extremity function than those with PAD alone.46 Commensurately, PAD is twice as common in persons with diabetes as in persons without diabetes47 and is also a major risk factor for lower extremity amputation especially in patients with diabetes.46 The American Diabetes Association (ADA) consensus statement, the most comprehensive document on this issue, recommends that the initial assessment of PAD in patients with diabetes begins with a thorough medical history and physical examination.46 A thorough walking history is especially important, as it will help elicit classic claudication symptoms and variations thereof; furthermore, patients should be asked specifically about these types of symptoms, as they are often not volunteered by people with diabetes.46 Vascular assessment should include palpation of all lower extremity pulses, including femoral, popliteal, posterior tibial and dorsalis pedis pulses.
In addition, clinical evidence of dependent rubor, pallor on elevation, absence of hair growth, dystrophic toenails and cool, dry, fissured skin should also be noted, as they may be concomitant signs of vascular insufficiency.46 Ankle, brachial pressure index (ABPI) is an easily reproducible and reasonably accurate method of diagnosing vascular insufficiency in the lower limbs but, as described in Chapter 20, cannot be used to exclude PAD, as it may be falsely elevated in those with vascular calcification.46 Peripheral circulation may also be assessed by transcutaneous oxygen tension measurement, a non-invasive measurement of limb perfusion.48 Patients with occlusive disease have significantly reduced transcutaneous oxygen tension, and this has been used to determine the possibility of ulcer healing and optimal amputation healing.
As discussed above, identification of ischaemia is of utmost importance when evaluating a wound.
Ischaemic wounds were found to have a longer duration of healing, compared with neuropathic wounds without deformities.49 If pulses are not palpable, or if a wound is sluggish to heal even in the face of appropriate offloading and local wound care, non-invasive vascu- lar studies are warranted, followed by a prompt vascular surgery consultation and possible intervention to improve perfusion and thereby effect healing.
Is the Wound Infected?
The definition of wound infection is not an easy one.
Although cultures, laboratory values and subjective symptoms are often helpful, the diagnosis of an infection’s genesis and resolution has and continues to be a clinical one.
While criteria for infection may be something less than clear-cut, there is little question that presence of infection is a prime cause of lower extremity morbidity and frequently eventuates into wet gangrene and subsequent amputation.
Therefore, in an effort to facilitate communication and effect consistent results, the foot care team should agree on the criteria for this very important risk factor.
Depth of the Wound
When examining the wound, it is important to determine depth of the ulceration as well as the involvement of underlying structures. There is a possible contribution of depth to ulcer-healing times.49 We have known for some time that wounds that penetrate to bone
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ASSESSMENT FOR AMPUTATION RISK 435
are frequently osteomyelitic.50 Additionally, we have observed that morbid outcomes are intimately associated with progressive wound depth.
Depth of the wound and involvement of underlying structures may best be appreciated through the use of a sterile blunt metallic probe.
The instrument is gently inserted into the wound and the dimensions of the wound may be explored.
Additionally, bony involvement is typically readily appreciable through this method.
A flowchart for screening and treatment of the diabetic foot is depicted in Figure 40.1.
This algorithm is adapted from the University of Texas diabetic foot risk classification and the International Working Group on the Diabetic Foot risk classification systems.
It is designed to comprehensively assess for risk of diabetic foot ulceration and amputation.
The clinician begins by asking questions assessing for the risk of amputation (ischaemia, infection and ulceration).
Subsequently, the clinician may ask questions related to ulcer risk (neuropathy, deformity, history of previous ulcer or amputation).
While the specific classification system utilised is not overtly important, what is critical is to ask the key questions (some described above) and subsequently utilise consistent operational definitions during every workup.
This, more than anything else, will drive consistency of care and ultimately a reduction in lower extremity complications in persons with diabetes.
0 1 2 3 UT wound classification Debridement
Pre- or Superficial wound, Wound post-ulcerative not involving Wound penetrating A penetrating to lesion completely tendon, capsule to bone or joint tendon epithelialised or bone Dressings/ advanced modalities
Antibiotics and drainage/ X-ray , bone B Infection debridement, as complications required Pressure relief
Referral to vascular Vascular C Ischaemia surgeon for possible assessment intervention
Antibiotics Infection and and drainage/ Possible hospital D ischaemia debridement, as admission required
(a)
Figure 40.1 Sample algorithms for assessing (a) diabetic foot wounds and (b) generalised foot risk Copyright C 2000, DG Armstrong. Modified for print by Andrew Findlow
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436 ALGORITHMS FOR ASSESSING RISKS FOR ULCERATIONS AND AMPUTATIONS
Foot category 6 Diabetic foot risk classification system flowchart YES Critical ischaemia Critical ischaemia
NO
Foot category 5 Infected wound YES Diabetic foot infection
NO
Foot category 4B Acute Charcot YES Acute Charcot arthropathy arthropathy
NO
Foot category 4A Non-infected, non-ischaemic YES Non-infected, non-ischaemic wound wound
NO
Foot category 3 History of ulcer; LOPS, deformity, history YES amputation; or of pathology Charcot RTC q 1-2 mos
NO
Foot category 2 Deformity or Loss of protective YES limited joint YES sensation (LOPS) LOPS with deformity mobility RTC q 2-3 mos
NO NO
Foot category 0 Foot category 1
Protective sensation intact Loss of protective sensation Yearly visit RTC q 3-4 mos
(b)