Wound care practitioners, clinical science investigators, and educators have invested organizational and individual efforts and resources to gain a deeper understanding of the clinical concept of "deep tissue injury" (DTI). This is unquestionably a contemporary clinical concept, which seems to be reasonably understood in the wound care taxonomy. However, I am often struck by the generalized discourse surrounding and describing DTI, as though it were a standalone clinical entity. Or, perhaps it is seen as possibly a discrete pathology sentineling the potential beginning of a pressure ulcer or, even more onerous, the tip of the iceberg of an already destroyed inverted cone of infarction of the subjacent critical physiologic-anatomic structures that make up the "tissues."
In my opinion, the functional anatomy and physiology of these human tissues are too complex for generalizations. A starting point for linking and conceptualizing the "deep tissues" must begin with reviewing the vital structures that constitute the deep anatomic systems and their clinical relationships to the DTI concept. The vital structures contained in the deep tissue include nerves, arteries, veins, lymph (NAVAL) and, of course, the supportive connective tissues, including dense fibrous connective tissue, large muscles, and fine and flat sheets of muscle such as the panniculus carnosus, which exist in certain locations (plantar aspect of foot and the infracalcaneal area) and are extremely sensitive to ischemia and reperfusion injuries. Adjacent tissues also include fascial envelopes, adipose tissue, bone, ligaments, and tendons. Any disruption to the form, function, or flow of the NAVAL puts the tissues at intrinsic risk (pathophysiologically); likewise, the NAVAL are subject to extrinsic forces (pathomechanical) as well, such as immobility, friction, shear, moisture, and pressure.
When considering the "N," the implications that the neurovascular, neuroendocrine, neurosensory, neuromuscular, and central and peripheral nervous systems have on the deep tissues bear significant consideration. For example, diabetes, stroke, multiple sclerosis, and spinal cord injury, all under the N, are both intrinsic and extrinsic factors that influence the health of the deep tissues.
The arterial system, the "A," is vital to the systemic oxygenation and to the regional and local nourishment of the deep tissues. In addition, a myriad of dysvascular conditions put the vitality of the deep tissues at risk, including atherosclerosis and arteriolar disease. Raynaud disease, a vasospastic phenomenon associated with cold intolerance, may also present as ischemia or gangrene with loss of the distal deep tissues in the fingers, heels, and toes. Buerger disease (thromboangiitis obliterans) affects the small and medium arteries, veins, and nerves. Although the etiology is unknown, there is significant agreement that chronic tobacco use is the major precipitating factor. The arteries of the upper and lower members become narrowed or blocked, resulting in ischemic fingers, hands, toes, and feet. Ultimately, this painful condition leads to gangrene and auto and/or surgical amputation with associated nonhealing wounds.
The venous system, the "V," and associated disease of the veins are well-known complications associated with local, regional, and systemic nonhealing wounds. The thromboembolic damage to deep parenchymal tissues resulting from venous thrombosis, in the lung and other organs, is extremely important to consider when evaluating a patient with suspected DTI. Superficial vein inflammation and symptoms of Raynaud disease occur commonly in patients with Buerger disease as well.
Lymphology is the "L" in the acronym. Acute lymphangitis can be associated with an infected wound, abscess, or cellulitis that could mimic a DTI. In this case, a thorough examination of the regional lymph nodes should be performed. Chronic lymphedema is an abnormal collection of protein-rich fluid in the interstitium due to a defect in the lymphatic drainage network.
Lymphedema most commonly affects the extremities, but it can involve the face, genitalia, or trunk. The triad of lymphatic diseases include (1) congenital, lymphedema praecox; (2) lymphedema tarda; and (3) secondary lymphedema-the most common of the triad associated with chronic wounds. The secondary etiologies include malignancy, infection, obesity, trauma, congestive heart failure, and portal hypertension.The etiologic conditions of lymphedema are variable. However, the disease progression is similar in all conditions and extremely difficult to manage.
To be thorough as clinicians, we should conceptualize DTI as part of a clinical decision-making tree that will include a multitude of nosological variables that anatomically and physiologically are potentially cocontributors to the DTI concept.
Richard "Sal" Salcido, MD