Staging pressure ulcers and defining evolving pressure ulcers is an arduous journey for the wound care profession, wound care leaders, and the international organizations advancing our field on behalf of the patients we serve. The purpose of this editorial is to focus on the deep tissue injury (DTI) model as it relates to current definitions and the staging of this nebulous entity. I would also like to suggest a new term for DTI.

Recently, the wound care literature has heightened our awareness of the "purple heel" and its hypothesized relationship to DTI. Among the many industry leaders characterizing this phenomenon are the National Pressure Ulcer Advisory Panel, the Wound, Ostomy and Continence Nurses Society, and the European Pressure Ulcer Panel (EPUAP). The EPUAP has essentially defined DTI as a Stage IV pressure ulcer (PrU). It is my understanding that DTI is classified as such for simplicity and because the EPUAP's consensus is that a DTI is analogous to a Stage IV PrU. Moreover, the components of injury in DTI (muscle fascia subcutaneous tissues and skin) are indeed similar to a Stage IV PrU and, therefore, similar to the DTI conception.

In my observation, it seems that the EPUAP is following an age-old axiom: the more words we use to describe a condition, the less we know about it. For example, Stage I and DTI require more words to describe their characteristics compared with Stage IV, which is universally understood as significant and down to the bone. If one doubts that the concept of DTI is complicated, just try to define it to a patient, a colleague, or a payer. I hope we can all agree that we need clarity, simplicity, and objectivity in our taxonomy of discourse about the staging of chronic wounds.

Honing the Concept

I envision at least 2 ways to hone a concept. First, we can keep the original term and come up with a more carefully formulated definition. On the other hand, we could coin a new terminology that captures the essence of the concept. Here, I suggest a new term for DTI: "myosubcutaneous infarct." This term is well chosen if its intension matches its extension, and the intension is as "succinct" as possible. Intension refers to the complete set of meanings or properties that are implied by a concept, whereas extension refers to the set of all actual things the word describes.

In this respect, DTI has too wide an intension because any deep tissue lesion, such as myocardial infarction, brain infarction, bowel infarction, lung cancer, or pancreatitis, is an injury to the deep tissues and can be included in the intension of DTI. However, we want the extension of DTI to cover only those pressure-related lesions.

The Phraseology

In coining a medical term designating a disease, squeezing all the information known about the disease into a couple of words would be ideal, but is obviously impossible. Therefore, the goal is to convey in a few words the key information about the disease or condition. Oftentimes, names that reveal the etiology of the illness are favored because etiology is at the top of the causality chain. Names of many infectious diseases fall into this category. Modern medicine, however, is still unaware of the causes of an astounding number of diseases, precluding the etiology-based naming in these cases.

In many cases, the disease entity is named after its most prominent phenomenologic feature. Some terms, such as myocardial infarction and glomerulonephritis, exhibit the pathology; other terms, such as high blood pressure, display the most striking abnormal physiology. Yet other terminology only describes the condition's outward appearance, such as "purple heel," which is the DTI of the heel. In contrast, some terms do not give any clue to the nature of the underlying problem. This is evident in diseases that are named after people, such as Hashimoto's disease or Lou Gehrig's disease. These poorly coined terminologies-"poorly" in terms of the amount of information content-are deeply ingrained and resistant to change.

I believe the broad consensus is that DTIs primarily involve muscle and subcutaneous tissue with intact skin as in the purple heel, and that the predominant pathology is infarction caused by either prolonged, unrelieved pressure or ischemia/reperfusion assault due to pressure loading and unloading. I propose the term "myosubcutaneous infarct" (or possibly myohypodermal infarct as myosubcutaneous infarct may not be able to prevent full-blown Stage 4 PrUs from being included in this category) to show the extent of injury-muscle and subcutaneous tissue-and the most conspicuous pathology-infarction. This terminology omits the predominant etiologic factor of "pressure," but this is partly compensated by the fact that this term is also meant to be a particular stage of a more comprehensive entity. The term pressure ulcer already shows the cause of the problem and that staging is generally performed with a view to delineate the extent of the disease or PrUs.

Our current taxonomy of discourse regarding pressure-related DTI and staging is an opportunity to apply the wisdom of a medieval philosopher, William of Occam, who is attributed to the principle of Occam's razor: "One should not increase, beyond what is necessary, the number of entities required to explain anything." This maxim helps us to "shave off" those concepts, variables, or constructs that are not really needed to explain the phenomenon. By doing that, developing a model will become much easier. It will also reduce the chance of introducing inconsistencies, ambiguities, and redundancies. In my opinion, this maxim also holds true in coining medical terminology. I hope that thoughts about new terminology can help our taxonomy of discourse or, more simply put, enhance our communication.

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