It is worth noting, however, that one detailed audit found no difference in overall outcome between ulcers covered with superficial slough and those that were clean.19 This might suggest that it is unnecessary (for the purposes of audit) to specify the appearance of the wound surface, and that superficial colonisation is of little relevance in terms of healing.
In the case of (ii) and (iii), thought should be given to including the option of specifying infection as either ‘definite’ or ‘possible’, and to changing the categorisation when further information is available.
On the other hand an infection may be graded in terms of severity, and in line with the guidelines published by the International Working Group on the Diabetic Foot.29 This approach has been proposed as part of the attempt to reach international consensus on classification (Table 7.5).10 Once again, the need for precise definition results in the whole appearing rather complex.
Moreover, it should be noted that classification guidelines that are based on severity will not necessarily distinguish between infection of deep soft tissue and of bone, and this is a significant limitation.
Systemic symptoms and signs probably occur less frequently in patients with osteomyelitis than in those with soft tissue infection, and yet the presence of osteomyelitis has major implications for limb salvage.
Table 7.5 Categorisation of infection according to severity, rather than tissues affected
Grade 1 No symptoms or signs of infection Grade 2 Infection involving skin and subcutaneous tissue only, with at least two of the following (having excluded other possible causes): Local swelling or induration Erythema >0.5 and <2.0 cm around the ulcer Local tenderness and pain Local warmth Purulent discharge Grade 3 Erythema >2.0 cm around the ulcer plus One or more of the items listed in grade 1, or Infection involving tissues deeper than skin and subcutaneous tissue Grade 4 Any infection associated with systemic signs , i.e. two or more of Temperature >38 or <36◦ C Heart rate >90 beats/min Respiratory rate >20 breaths/min PaCO2 <32 mm Hg White cell count >12 000 or <4000/mm3 >10% immature neutrophils
Adapted from Schaper.10
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Wound bed appearance It is debatable whether it is necessary to include the appearance of the wound bed in any classification.
However, this appearance is a crucial part of clinical assessment, and plays an important part in determining local management.
The state of the wound bed may also correlate with outcome, although this has not yet been conclusively proved.
It has been suggested that the appearance of the wound bed can be described under four separate headings: percent visible granulation tissue, percent covered by fibrin and debris, percent covered by hard eschar and the presence or otherwise of exudate.30 Consideration of such features may well form a part of the selection of lesions for both clinical description and selection of ulcers/lesions for prospective research.
Cross-sectional area Cross-sectional area may be determined with reasonable precision either by tracing the cir- cumference of the ulcer or, in a more rough and ready way, by taking the two maximum widths of the wound at an angle of 90◦ to each other, and multiplying them as if the ulcer were rectan- gular in shape. It is, however, very easy to obtain more precise measures using digital imaging with appropriate software, such as ‘Mouseyes’.31
Depth Judging the depth of the wound can be very difficult, as many clinicians have only an ap- proximate understanding of the divisions between the various soft tissue layers.
It can thus be difficult to decide when an ulcer is confined to ‘skin and subcutaneous tissue only’ and when it becomes ‘deep , but without involving bone and joint capsule’.
Moreover, deep structures such as joint capsule and periosteum may be very close to the skin in some parts (as the medial aspect of the first metatarso-phalangeal joint) and relatively distant from it in others (the plantar aspect of the heel).
In practice, all three of the recently published classifications use the same criteria to grade depth.8,10,19 Two of them also include the option for lesions of zero depth , in which the epithelium is intact.
Such lesions might include blisters, cellulitis with no obvious portal of entry and the acute Charcot foot.
There is no precise means of measuring (as opposed to describing) depth.
Even if there were, it would be debatable whether a measure of depth in millimetres was necessarily meaningful, given the variation in thickness of different tissue layers at different sites on the foot.
FRAMEWORK FOR THE IDEAL SYSTEM It is apparent that very similar measures are used when a classification is for the purpose of clinical care, research and audit, even though they may be used in different ways.
For the purposes of clinical care, the aim is to ensure that any ulcer or lesion is described with clarity and simplicity , such that its status is immediately apparent to any clinician who has not seen it.
The system should also convey to the clinician an impression of severity and of the urgency required for intervention.
Site and side should be specified in order to eliminate confusion when multiple lesions are present.
When a system is intended for research, the overriding concern is the need for precision, with clear definition of the clinical measures used.
However, the greatest difficulty
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102 THE DESCRIPTION AND CLASSIFICATION OF DIABETIC FOOT LESIONS
is encountered when choosing a classification system for the purpose of audit. The ideal system needs to be both simple and precise: simple enough to be remembered and applied on a routine basis in busy clinical practice, and yet precise enough to generate data that are meaningful.
PUBLISHED CLASSIFICATIONS
Previous published classifications have been well reviewed.9 The Meggitt, Wagner system32,33 suffers from lack of specificity. Meggitt, Wagner grades 1, 2 and 3 are essentially measures of increasing ulcer depth (with or without infection), while 4 and 5 refer to localised and extensive gangrene, respectively. Although the Meggitt, Wagner classification has been used for almost 30 years, it is insufficiently precise for modern purposes.
University of Texas The University of Texas (UT) system for ulcer classification8 is also primarily based on depth and, as a result, has been shown to correlate well with the Wagner system.34 However, the inclusion of an additional option of scoring an ulcer by the presence of ischaemia or infection greatly enhances its usefulness (Table 7.6).
Different grades of ulcers (from superficial and non-infected in a foot with good blood supply, to deep and infected in an ischaemic foot) have a close correlation with later amputation , which is, perhaps, not surprising.
Being based on simple clinical criteria, the UT system is eminently easy to use in clinical practice, and is being increasingly adopted as a means of describing ulcers and for defining best management.
However, the UT classification suffers from one main limitation: the omission of any reference to cross-sectional area, when it is known that there is a clear association between cross-sectional area and outcome at baseline.14,19,35 Another factor that limits the application of the UT classification for the purposes of either research or systematic audit is the omission of any reference to neuropathy.9 Neuropathy is undoubtedly a major causative factor in the majority of cases , although it is more true to say that it is not so much neuropathy as a single entity that contributes, as the various features of peripheral nerve damage: motor, sensory and vasomotor.
The reason for its exclusion is that
Table 7.6 The University of Texas (UT) classification of ulcers
0 1 2 3
Deep but not involving Involving Skin intact Superficial bone or joint bone or joint
A Not infected, not ischaemic
B Infected but not ischaemic
C Ischaemic but not infected
D Both infected and ischaemic
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the presence of neuropathy (either in isolation or in association with ischaemia) does not really dictate treatment , since offloading is part of the management of all ulcers, irrespective of aetiology. Despite this, the classical neuropathic or mal perforans ulcer is a discrete and well- recognised clinical entity, and it would therefore be odd to exclude it either from any system attempting comprehensive audit of clinical practice, or from a research classification. It follows that the omission of reference to neuropathy and cross-sectional area from the UT system means that its application is effectively limited to the description of ulcers in the process of clinical care.