Study of plantar fasciitis treatment is flawed

Editor—Haake et al performed a multi-centre randomised controlled trial of extracorporeal shock wave treatment for plantar fasciitis.¹ They say that their study is definitive and they therefore recommend against any further experimental testing of this treatment, but the study has sufficient methodological flaws to render their conclusions questionable.

Although the study seems to be well designed statistically, they do not highlight that fewer than half of their patients received minimal conservative care that includes stretching exercises and casting or night splinting before their inclusion in the study (data available online in web table B).

Such interventions have been shown to be effective.²,³ Failure of such treatment is an essential aspect of the inclusion criteria for extracorporeal shock wave treatment. Including such patients in this study therefore violates one of the precepts of extracorporeal shock wave treatment—failure of previous standard conservative care. Physical treatment is not a substitute for stretching exercises as it occurs a few times a week, whereas stretching is performed three to four times daily.

The end point assessment makes much of several unvalidated rating scales for heel pain. However, the observation that 56% of the placebo group required further treatment, compared with 56% of the treatment group (P < 0.008, χ² test) is completely at odds with their rating scale results. Obviously, showing equivalence of outcome at the final follow up is uninterpretable because of this treatment bias during the follow up period.