Journal Article Review, May 2019

The Effect of Phonophoresis on Carpal Tunnel Syndrome

Boonhong J, Thienkul W: Effectiveness of Phonophoresis Treatment in Carpal Tunnel Syndrome: A Randomized Double-blind, Controlled Trial. PM R. 2019 Apr 21. doi: 10.1002/pmrj.12171. [Epub ahead of print]

Investigators in Thailand recently published the results of a randomized, double-blinded, prospective study investigating the effectiveness of phonophoresis with either steroid (dexamethasone) (PH-D), a non-steroidal (piroxicm [Feldene]) (PH-P), or ultrasound with just gel placebo (US) on mild to moderate carpal tunnel syndrome. Outcome measures included the Boston Carpal Tunnel Questionnaires for both symptoms (BCTQ-S) and function (BCTQ-F) and electrophysiological distal sensory latency (DSL) and distal motor latency (DML).

The investigators divided thirty-three patients (50 hands) who had mild to moderate carpal tunnel syndrome into one of the three treatment groups. All affected hands received 10 ten-minute treatments over four weeks. The outcomes measures were applied before treatment and again at the end of treatment four weeks later.

RESULTS: All three groups showed significant improvements in the BCTQ-S and the BCTQ-F but there was no significant difference between treatment groups. The DSL was trending toward reduction in all three groups but the changes were not statistically significant. The DML decreased in the PH-D and the US groups but the difference was not statistically significant.

CONCLUSION: Ultrasound at the dose, duration, and frequency used reduced symptoms and improved function but phonophoresis with either steroid or non-steroid did not further enhance the results.

COMMENT: I love to see Level I studies: randomized, prospective, double-blinded—all beautiful words. At face value, this study would tend 1) to support the use of ultrasound for the treatment of mild to moderate carpal tunnel syndrome and 2) to refute the premise that phonophoresis with either dexamethasone or piroxicam enhanced the effect. Let’s dissect the second part first.

There is no reason to suspect that phonophoresis would have a local effect, since despite wishful (and faulty) thinking, neither phonophoresis or iontophoresis has EVER been shown to have a local effect on CTS, tennis elbow, deQuervain tendinitis and other common maladies for which it is used. Why? Because if a drug gets through the epidermis, as soon as it is driven into the dermis and subcutaneous tissue, it is picked up in the capillary circulation and swept away. Thinking that the drug is going to bypass the capillaries and go directly into the target tissue is fanciful. Consider the analogy of shooting arrows at a target in a hurricane-force cross wind. There may be a faint effect of the drug on the target tissue as the drug circulates systemically, but the same can be accomplished with oral administration. Furthermore, the results of this study are tainted because 17 of the subjects had bilateral CTS. and both hands were randomized individually into one of the treatment groups. The authors did not breakdown results for the subjects with bilateral CTS. It is entirely conceivable that if one wrist received PH-D and the other received US and that both got better equally from the systemic distribution of the piroxicam.

Now, let’s look at study result #1. Should we use ultrasound without any phonophoresis to treat CTS? Although the study implies that US is effective, there is more to the issue. To truly conclude that US is effective, the study needs two more control groups: one where the US head is rubbed over the carpal canal with the US machine turned off and another group who has no treatment at all but reports to the clinic ten times over four weeks for the same conversation that the test subjects have with the investigators. This would answer the question of whether it is the US, the massage and attention, or merely the awareness of CTS and the expectation/hope that improvement is eminent. For instance, the paper makes no mention whether or not any of the patients were night splinted. I, for one, am going to make sure that my wrists are in neutral tonight before I go to sleep after having thought about this study.

The other problem I have with this study is the economics. The noted improvements required ten visits over four weeks. That is a huge financial and time commitment on the patient’s part. Then the study gives no indication on how long the effect lasted after the end of treatment. If it was permanent or lasted at least a year, then maybe the commitment could be justified, but we just do not know.

After reading this paper, my paradigm for management of CTS is unchanged: brace and activity modification first, then cortisone injection if necessary, then surgical release if symptoms persist or recur. If readers want to repeat this study with two additional control groups and longer follow-up, I would love to review the results.