Management of heel pain syndrome with acetic acid iontophoresis

Letter to the Editor

To the Editor:

I am writing to you regarding an article published in the May 1999 issue of the Journal titled “Management of Heel Pain Syndrome with Acetic Acid Iontophoresis” by Christopher J. Japour, Richa Vohra, Praveen K. Vohra, Loretta Garfunkel, and Nena Chin.

I was excited at the prospect of having another treatment modality for recalcitrant heel pain but was disappointed with this article. Not having any control experiment is a significant deficiency of the study. How do we know that the acetic acid did anything at all? Were there any trials with different concentrations? Saline? Cortisone? Was the study double-blind? Did the patients and experimenter know if they were getting a therapeutic trial or a control trial? What is the placebo effect of a tingling modality attached to a patient?

The second issue is the follow-up period. The abstract mentions a 27-month average, but the body of the article itself does not explain. I do not see anything in the results section about the follow-up period or the 0.64 pain score at follow-up. Was there any other treatment during those 27 months? Orthoses? I also think it would be useful to know what previous conservative therapy was administered to the 35 patients.

While it appears that this form of treatment has merit, I do not think it can be said that this particular study demonstrates this. The conclusion is not supported by the facts as presented in this article.

Author’s Response

To the Editor:

I would like to thank Dr. Plotkin for reading our article and expressing his concerns, which are addressed below.

Iontophoresis, with iontophoretic substances, is a long-standing and well-established modality for the conservative treatment of pain; the literature on the topic is abundant. For this reason, we decided not to “reinvent the wheel” and prove that iontophoresis works. The literature already supports that contention.

Specifically, Dr. Joseph Kahn [1,2] initially reported on acetic acid iontophoresis as an effective treatment for heel pain in several patients. Our goal was to expand on his work. The first sentence in our abstract states: “This study was undertaken to determine the effectiveness of acetic acid iontophoresis in the treatment of heel pain.” Clearly, our goal was not to compare the effectiveness of various iontophoretic substances or different concentrations of a substance in the relief of heel pain. Nor was the purpose of the article to compare acetic acid iontophoresis with individual conservative-care modalities. Rather, we wanted to examine a population of individuals whose pain had been recalcitrant to prior conservative care, as stated in the second paragraph of the methods section.

I will attempt to answer Dr. Plotkin’s specific questions below:

Q: “How do we know that the acetic acid did anything at all?”

A: Please refer to references 1 and 2 in the article.

Q: “Were there any trials with different concentrations? Saline? Cortisone?”

A: Please refer to references 1 through 5 in the article.

Q: Was the study double-blind?

A: No, the study was not double-blind.

Q: “Did the patients and experimenter know if they were getting a therapeutic trial or a control trial?”

A: All patients and the “experimenter,” who is a certified occupational therapist and also board certified by the American College of Pain Management, were aware that acetic acid was being used with iontophoresis.

Q: “What is the placebo effect of a tingling modality attached to a patient”?

A: The effect of a tingling modality attached to a patient was not tested.

Q: “The second issue is the follow-up period. The abstract mentions a 27-month average, but the body of the article itself does not explain. I do not see anything in the results section about the follow-up time or the 0.64 pain score at follow-up.”

A: The patient follow-up period averaged 27 months. As stated in the fourth paragraph of the methods section, pain was measured using a numeric pain-intensity scale ranging from 0 to 10. The pain score of 0.64 represents 0.64/10. It is correct that the results section does not mention the average follow-up time of 27 months and the 0.64 pain score at follow-up. Rather, emphasis was placed on the finding that 2.8 weeks of treatment with acetic acid iontophoresis was needed to alleviate first-step pain, compared with 7.8 weeks reported in other studies of various conservative treatment modalities (see Table 2 on page 255).

Q: “Was there any other treatment during those 27 months? Orthoses?”

A: There was no other treatment during the 27 months. Two patients had custom-made orthoses but did not consistently wear them.

Q: “I also think it would be useful to know what previous conservative therapy was administered to the 35 patients.”

A: Previous conservative care administered to the 35 patients was the same as the treatment modalities listed in Table 2 on page 255.

I enjoy our profession tremendously, and when I see a treatment modality that can alleviate pain, I wish to share it with other professionals. Acetic acid iontophoresis works.