To The Editor:
Dr. Ogden and colleagues recently reported the results of a trial of
shock-wave treatment for chronic plantar fasciitis in "Electrohydraulic
High-Energy Shock-Wave Treatment for Chronic Plantar Fasciitis"
(2004;86:2216-28). We seek clarification about whether this is a reanalysis of
a previously published trial1, and, if so, why the sample sizes are
substantially different. While the results appear similar, the authors now
claim a significant difference in the mean score for the subjective
self-assessment of pain at twelve weeks favoring the active treatment group (p
= 0.014). While this cannot be verified from the data presented, as no
measures of variance are provided, independent t test comparison of mean
scores for subjective self-assessment of pain at twelve weeks on the basis of
data published in the original trial report submitted to the U.S. Food and
Drug Administration demonstrated no significant difference between groups
(mean scores [and standard deviation], 3.48 ± 3.11 and 4.18 ±
3.04 for 115 and 114 patients in the active and placebo-treatment groups,
respectively; mean difference = 0.7 [95% confidence interval, -0.1 to 1.5; p =
0.08])2.
We would also like to respond to the criticisms of our trial3
expressed by Ogden et al. in their paper. While the median duration of
symptoms of the participants in our trial (six to seven months) was shorter
than that in the trial by Ogden et al., we also found no benefit of shock-wave
treatment over a placebo when we restricted our analysis to those participants
who had had symptoms for longer than six months. A trivial dose of shock wave
was given to the placebo group (6 mJ/mm2), and it is highly
unlikely that this resulted in any clinical benefit. This belief is supported
by previous observations that high-energy shock-wave treatment is required to
effect any local histological changes. Rompe et al. found no sonographic or
histological changes in the Achilles tendon of a rabbit model given a total
dose of 80 mJ/mm2 and only transient swelling of the tendon with a
minor inflammatory reaction when 280 mJ/mm2 was
administered4. The mean total dose of shock wave that the active
group received in our trial was 1401.7 mJ/mm2, which is higher than
the 1300-mJ/mm2 total dose delivered to patients in the active
group of previous trials of single-dose high-energy extracorporeal shock-wave
therapy1,5. As we also reported, our results were consistent
irrespective of the total dose of shock-wave therapy received (n = 68 for
=1000 mJ/mm2; n = 13 for <1000
mJ/mm2)3.
All patients in our trial were included on the basis of strict criteria,
and standardized assessments were performed at each time-point. The first
author of the study (R.B.) is a rheumatologist experienced in the management
of plantar fasciitis, and many patients were referred into the study by
orthopaedists. An additional strength of our trial was the requirement for
confirmation of the clinical diagnosis according to well-described ultrasound
criteria for plantar fasciitis. These explicit criteria provide additional
assurance about the uniformity of the study population and increase the
generalizability of the results.