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A study was published in a 2006 issue of the Journal of Athletic Training that I found interesting back then and wanted to revisit again now. The study, entitled Cortisol Concentrations in Human Skeletal Muscle Tissue After Phonophoresis with 10% Hydrocortisone Gel, was of interest to me because I have performed many a phono treatment over my career and wanted to see “if this stuff really worked”. (Kind of backwards isn’t it but continual learning, that’s the point of all this right.)

Phonophoresis is a treatment that is commonly prescribed by physicians to treat musculoskeletal injuries and the goal of this study was to help determine if the technique really was able to deliver the hydrocortisone to the skeletal muscle tissue that was being targeted with the treatment.

The samples consisted of 6 individuals in the sham group and 6 in the phonophoresis group. Each leg of each subject was utilized for this study. One leg was chosen for treatment and the other was chosen as the control for each subject.

The study involved 12 indivduals who were split into the treatment and sham group. Treatments utilized 10% hyrdrocorisone for the medication and the region being treated was the vastus lateralis. The treatment protocol utilized ultrasound delivered at 1.0 MHz x 1.0 W/cm2 and at 7 minutes utilizing a continuous treatment setting.

After some prep work was done following the single treatment, a needle biopsy was performed in which a sample was extracted from the vastus lateralis muscle. The muscle biopsy was then examined for cortisol concentrations.

Now, the authors acknowledge that phonophoresis has been effective in the driving low-molecular-weight compounds through the dermal layer.  After that however, it is uncertain if the medication is able to make it to the targeted tissues. Hence, this study.

The results as reported by the authors showed no significant difference in cortisol concentration between the control limb and the treatment limb, in either the sham or phonophoresis samples. No significant differences were noted between the sham and phonophoresis groups. So the final conclusion resulting from this study was that 10% hydrocortisone based phonophoresis treatment (delivered at the said parameters) did not raise the concentration of cortisol in human skeletal muscle tissue following treatment.

As we try to base our treatment decisions upon sound evidence, I thought that this study would help give us some additional insight into this common treatment.

Here are some of my observations as well as some additional commentary and discussion added by the authors:

  1. First off, the subjects were better men and women than me. Offering to have some muscle extracted for the sake of science is quite admirable. As you read the study, you’ll think the same thing.
  2. The authors admit that the sample size is small and I would agree. I would have loved to see a much larger sample but going back to the first point, getting many more to commit to what these subjects did may have been a minor miracle in and of itself.
  3. Probably one of the more interesting points the authors brought up centered around treatment length and intensity. At first blush, my thought was that the intensity was probably too low and the treatment length could have been longer. (Treatment lengths for ultrasound will generally vary from 5-20 minutes). The authors did report however that studies with swine showed an increase in cortisol levels with prolonged treatment (17+ minutes) and with lower intensities. I found this very interesting. Treatments at .1 and .3 W/cm2 were more effective in the swine. I may have surmised that higher intensity coupled with longer treatment times would be more effective but previous studies indicate otherwise. How this translates to human studies remains to be seen but the authors do note that utilizing multiple treatment settings for the delivery of phonophoresis should be further investigated. I agree.
  4. Another point the authors brought up was regarding injured vs. uninjured tissue. All of the subjects in this study were of apparent good health. The authors noted that healthy tissue may be more resistant to pharmaceutical delivery. Some studies have also shown injured cells to be more amenable to pharmaceutical delivery. This is a very valid point and very well could have some merit.
  5. Another point the authors discuss revolves around thermal vs. non-thermal delivery. The authors site a reference that notes that non-thermal delivery played a significant role in transdermal drug delivery. This is a valid consideration as well. Does the thermal aspect of the treatment alter or hinder the delivery of the medication versus the mechanical delivery settings? Is a pulsed setting more appropriate in this type of treatment?
  6. The authors also discuss the delivery of the medication indirectly through the blood (once the drug is delivered subdermally, the medication is delivered to the muscle through its blood supply) as opposed to directly through delivery of the medication to the  muscle tissue itself. They discuss this possibility as unlikely but do address it for discussion purposes.

Overall, the study was very interesting and I commend the authors for venturing into this study. It is important to have research validate our methodology. There are a lot of variables that this study was unable to account for but I do think that we did discover some important findings as a result.

So what are some takeaways.
Well aside from the point regarding injured vs. non-injured tissue, the study stongly shows that trying to deliver phonophoresis using 10% hydrocortisone cream to deep muscle tissue at the settings demonstrated is largely ineffective. One would argue that using similar parameters as illustrated and expecting different results is not good practice.

Secondly, the medication is not cheap. I wouldn’t necessarily consider “wasting” this medication utilizing application settings that are ineffective as good practice either.

Does this study particular study discount the use of phonophoresis? At this point, I’d say no but it definitely helps us to start thinking more about what we are trying to accomplish with this treatment and what methods we may go about  in order to accomplish our goals. We really need to consider the area we are treating and the parameters that we are using. What are our goals for the treatment as well? This study should help us to be more specific with our treatment goals.

I think that the authors clearly point to the fact that more research needs to be done and I agree. The trick is to take what we learned through this study and apply it to our daily practice.

What are your thoughts? Do you have any additional observations? Do you know of additional studies that refute or validate these findings. Feel free to share your comments.

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