Letters to the Editor

To the Editor:

In their well-written paper, “Negative-Pressure Wound Therapy and Diabetic Foot Amputations: A Retrospective Study of Payer Claims Data,” Drs. Frykberg and Williams conclude that there is as much as a 35% reduction in the rate of amputations in patients using negative-pressure wound therapy as compared with other forms of wound care. [1] Most of us have had success with the use of this modality in the treatment of diabetic ulcerations; but, in terms of lowering amputations, these figures are quite impressive. There are possible problems, however, associated with this retrospective study that might be artificially inflating these figures.

Retrospective studies share an important place in medical research, but there is an inherent problem with them. The researchers are delving into the past and cannot perform the actual experiment. Important information is often not available, and diagnostic and therapeutic tests in the past may not be state of the art in the present. For example, Frykberg and Williams state that they did not know the exact treatment protocols used to treat ulcers in the control group. They made some guesses and assumptions based on billing data.

A second possible problem is that there may be two subtle co-interventions taking place that in themselves might improve the clinical outcome of patients who use negative-pressure devices but not the negative pressure. One co-intervention is that the normal protocol with negative-pressure wound therapy as advised by one major manufacturer of the device is to have a home health-care nurse change the dressings three times a week. In most cases, these nurses are trained in the use of the modality as well as in wound care. The patients also see their prescribing doctors more frequently, and some insurance companies allow for weekly visits. This intensive degree of clinical care in itself could lead to better outcomes and fewer amputations. A second possible co-intervention is that the actual machine, which is generally attached for 22 hours a day, limits ambulation especially if it is attached to the plantar surface of the foot. We all have had experiences with patients whose feet are insensate and excessively ambulate against doctors orders. The apparatus itself, because of its bulky nature and the way it is attached to the foot, may limit ambulation and hence produce a favorable outcome. I have even heard that some doctors will make the attachment more uncomfortable than necessary in order to deter ambulation. Psychologically, patients willing to put up with 22 hours a day of an attached unit may be more motivated and more compliant with all aspects of the treatment protocol.

The third and most significant problem with this study is that the end point in the study is whether or not there was some form of amputation. This may open a Pandora’s box. The criteria for doing an amputation in cases of diabetic ulcers and osseous infections versus prolonged wound care is often based on subjective criteria and will vary from surgeon to surgeon, medical specialty to medical specialty, clinic to clinic, and even from country to country.

There are disputes in the treatment of very deep wounds, and especially in cases of osteomyelitis, as whether to treat them surgically by removing tissue or to treat them medically. There have been debates at major wound-care seminars by leading authorities on this issue. The economics of a particular health-care system can also impact on it. Having been in practice for more than 27 years, I have had frequent professional disputes with surgeons who examined a mutual patient, observed a deep ulceration, and immediately wanted to amputate a toe, forefoot, or in some cases a leg. Their rationale is that by removing part of the extremity, the deep ulceration or bone infection (if present), is quickly brought to an end. In some of these cases they based their surgical treatment plans on less than state-of-the-art diagnostic techniques. There is also an economic incentive to do the surgery. In most of these cases the patients opted to allow me to administer wound care over a prolonged time and eventually they all healed. I am by no means the only podiatrist who has experienced this controversy first hand. Using the negative-pressure wound therapy device may also buy time for the patient, and there is also an economic incentive for doctors to give this therapy a chance. However, this can raise another question. Is the therapy preventing amputations or just delaying the need for amputation? This also is not addressed by this study.

Frykberg and Williams published an important paper. What needs to be done now is to follow-up their retrospective study with a double-blinded prospective study that will adjust for any of the above possible co-interventions. Patients using the negative-pressure wound therapy and the control groups must have the same unit attached to them along with the same dressings and identical degrees of at-home and in-office wound care. The level of training of the administering nurses and doctors needs to be the same in all cases. The frequency of care needs to be the same. The criteria for determining when to consider amputation should be made by the same doctors according to objective criteria. And those doctors cannot know which treatment was used. The doctors involved in the decision making should have no conflict of interest. Lastly, the sizes and depths of the wounds compared, as well as similarities in vascular and neurologic status, should be the same in both groups. Then and only then can we rule out co-interventions and truly determine if the negative pressure therapy itself really does reduce amputations by such a large percentage.