Editorial: Physiologic, Behavioral Factors Affect Wound Healing
John H. Bowker, MD
The healing of foot wounds in persons with such concomitant diseases as diabetes mellitus continues to be a major challenge to the treating team. Development of our approach to the problem was stimulated by two major factors. The first was, and continues to be, the daily necessity of managing a large number of open foot amputations, debridement wounds (wounds produced by the excision of infected and necrotic tissue), and ulcers in persons with diabetes. The second is the ongoing need to critically evaluate reports in the literature purporting to show the benefits of a particular wound care treatment, substance, or system. On subjecting these studies to critical analysis, it becomes apparent that only one or two factors known to affect wound healing were controlled for or even considered.
This approach consists of obtaining the answers to two groups of key questions regarding factors affecting the healing of open partial foot amputations, debridement wounds, and ulcers, and then formulating an individualized wound healing program based on the answers and the treatment options available. The first group of questions addresses physiologic factors, while the second addresses behavioral factors affecting wound healing, specifically in persons with diabetes, with or without dysvascularity.
Physiologic Factors
Is tissue oxygen perfusion adequate? A comparative clinical evaluation must include the search for pedal pulses, temperature of the feet relative to each other and to the more proximal leg, and the color of the feet with an emphasis on noting dependent rubor followed by blanching on elevation. Good hair growth will generally indicate adequate perfusion in most chronic situations. When pedal pulses cannot be palpated, a pocket Doppler device is sometimes useful. Determination of an ankle-brachial index, however, may be difficult in the presence of severe medial calcification of the smaller vessels. When major vessels are occluded, pulse volume recordings can be quite useful to determine the adequacy of collateral circulation. Determining transcutaneous oxygen levels is especially helpful if flow appears to be marginal when measured by other methods. In this case, if the TcPO2 levels are low, the test should be combined with an oxygen challenge to see if 100% oxygen will significantly elevate the TcPO2 levels, justifying postoperative hyperbaric oxygen treatments. If the oxygen challenge indicates that healing is unlikely, the patient should be referred for possible vascular recanalization or reconstruction. Poor tissue oxygen perfusion secondary to anemia associated with diabetic nephropathy may be amenable to treatment.
Is nutritional status normal? Many of our patients with difficulty in wound healing will exhibit a low serum albumin level (< 3 to 3.5 ml/dl). This may be related to malnutrition based on an unbalanced diet or actual starvation. In either case, oral hyperalimentation may be corrective. On the other hand, if protein loss is secondary to severe diabetic nephropathy, consultation with a nephrologist is essential.
Is protective sensation present? Although patients will often concede that their foot sensation has decreased, in many it occurs so gradually that they are unaware of it. Some patients may walk into your office on a foot with an unprotected open wound or fracture. Use of a 10 gram (5%) Semmes-Weinstein filament can be used to determine the presence of protective sensation, as can a 128 cps tuning fork applied just proximal to the nail of the great toe.
Is there evidence of persistent bacterial infection versus mere colonization? Bacterial colonization of open wounds is to be expected. Persistent cellulitis or osteomyelitis, however, can be suspected if the wound is erythematous, warm, and producing purulent exudate. Merely swabbing the surface of the wound is rarely productive. If wounds are not healing as expected, deep cultures should be repeated to detect changes in the type and antibiotic resistance of the causative bacteria.
Is the blood glucose level well controlled? It has been firmly established that chronic hyperglycemia leads to glycation of tissues and also interferes with the mobility of leukocytes that are attempting to destroy bacteria. Obtaining a baseline glycohemoglobin (HbA1c) level can be helpful in guiding patients toward better control of their average blood glucose levels.
Is locomotor function impaired? Hopefully, the patient with a foot lesion is told to avoid direct weight-bearing on the wound to prevent further damage and to allow progressive healing. Patients are also frequently and mistakenly told to hop on the "unaffected foot" using crutches or a walker. Careful examination of the "normal" lower limb will often show that its proprioception is severely impaired and that its superficial sensation may be absent to the level of the knee. Motor dysfunction, in the form of foot drop, may also be present. In addition, truncal obesity will result in severe imbalance, especially when on one leg. It is therefore unrealistic to expect the patient to comply with this request, and they rarely do.
Behavioral Factors
The next series of questions addresses behavioral factors affecting wound healing. While caregivers often assume that these particular factors are the exclusive province of the patient, the uncomfortable fact is that they apply equally to the caregiver and the patient.
Have appropriate weight-relief devices been fitted? The implications for the caregiver are that devices that will remove or substantially reduce forces on the foot wound must first be judiciously considered and then realistically recommended. Before embarking on the care of a wound using any of these devices, it must be ascertained that deep infection is not present. All wounds must be probed to ascertain that they do not penetrate to bone. If bone is contacted, surgical intervention is generally required.
For many decades now, various versions of healing casts have been successfully used for treating plantar wounds if their volume does not dictate frequent dressing changes. These have been so successful that they may be considered the "gold standard." More recently, various ankle foot orthoses, such as custom bivalved neuropathic walkers or prefabricated walkers, have been developed for the same purpose with good results. Weight-relief shoes can also be used for the management of plantar wounds provided that the shoe design (forefoot relief vs. midfoot relief vs. rearfoot relief) is carefully matched to the location and size of the wound.
The corollary to the last question also needs to be asked: Are they (weight-relief devices) being used appropriately by the patient? It is axiomatic that any nonweight-bearing option can be abused or overridden by the noncompliant patient. Although casts cannot be removed without detection, many patients subvert healing by attempting to carry on all of their usual activities, resulting in additional leg and foot ulcerations, which may lead to amputation. Orthoses and weight-relief shoes, of course, can easily be removed or misused. The advantage shared by healing casts or orthoses and weight-relief shoes is that weight-bearing forces on the plantar surface of the foot are redistributed more evenly over the entire plantar surface of the foot. This helps to protect the wound from further trauma while allowing minimal weight-bearing ambulation for activities of daily living. The additional advantage of the orthoses and weight-relief shoes is that they are easily removed for dressing changes and tend to be more cost-effective than casts-when properly used.
Weight-relief shoes are commercially available in two types, those that relieve weight in the forefoot and those that relieve weight in the rearfoot. Since more than 90% of plantar ulcers in diabetics occur in the forefoot, the forefoot-relief shoes are most commonly required. Weight-relief of heel wounds can be effectively achieved with a shoe, such as the one available through ipos, that has been designed to allow little or no weight-bearing on the heel. It is widely open in the posterior aspect to allow access for dressing changes. Relief of pressure on midfoot wounds can be achieved with various types of bridging shoes, which transfer weight from the midfoot to the forefoot and rearfoot. As with all methods of treatment, there are limitations to the use of these shoes. There will be pressure on the wound if the shoes are the wrong size or improperly fitted; thus they may require some modification by the pedorthist or orthotist involved. They do require good patient compliance in that they must be consistently worn for all weight-bearing activities, including trips to the bathroom during the night. They are designed, as are casts, for minimal weight-bearing only. In the case of the forefoot-relief shoes, the patient must be assiduous in avoiding rollover onto the forefoot wound at the end of stance phase. The most important thing to stress in the use of any of these devices is that their use does not substitute for attention to the other requirements of wound healing on the part of the patient or the physician.
Have vasoconstrictors been prohibited? Is the patient abstaining from nicotine and caffeine? Evidence continues to accumulate that use of these substances may impair healing in many different body tissues.
Is strict control of blood glucose levels a primary goal of the physician? Is the patient adhering to the program? The unequivocal results of the Diabetes Control and Complications Trial have proved a boon to the conscientious physician and patient and a bane to the uninformed.
Is the blood glucose control program based on a comprehensive and comprehensible program regularly evaluated by glycohemoglobin levels? If the patient is kept uninformed and uneducated in regard to this basic requirement, one cannot expect compliance. It is important that education be individually adapted to the patient's ability to understand.
In addition, reasons for poor patient compliance often include significant elements of denial, depression, and displaced locus of control. In fact, compliance appears to be more related to these factors than to intelligence. With education and proper psychologic intervention, compliance can often be improved. In contrast, compliance can be extremely difficult to obtain from patients with personality disorders and frank psychoses.
Team Approach
There is no one medical professional who can deal with all of the needs presented by patients with diabetes. It is essential that an interdisciplinary and interactive team be organized, however informally. The most important member of that team, of course, is the patient. The traditional paternalistic patient/system interaction must be abandoned for a more holistic approach that sees the diabetic as a person, not merely a collection of organ systems to be manipulated.
References are available upon request by fax at 415/905-2235.
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