Ganglion Impar Blocks for Coccydynia: A Case Series Prerequisite for Efficacy Trial

Pain Medicine

Volume 16, Issue 7, page 1245, 2015

Bogduk N.

The University of Newcastle, Callaghan, New South Wales, Australia

In this issue, Gunduz et al. [1] report their experience with blocks of the ganglion impar for coccydynia. Critics might ask why this article was published, arguing that it was not a randomized, placebo-controlled trial. In response, a variety of reasons justify its publication.

In the first instance, the literature on blocks of the ganglion impar is limited to case reports. Gunduz et al. [1] provide the first, substantial case series. That series is of sufficient size to provide estimates of the success rates of this intervention, with reasonable confidence intervals. Such information is an essential prerequisite for any controlled trial. There is no point undertaking a controlled of a treatment that does not work, or has a low success rate. Therefore, the likely success rate needs to be known. Moreover, the magnitude of the success rate is critical for power calculations necessary for determining sample size. In that regard, Gunduz et al. [1] show a substantial success rate that could readily be tested with a relatively small sample.

Another virtue of the article is how the authors dealt with a troublesome chestnut that plagues studies of injection therapies. Some patients had one treatment; some had two; and others had three. This can cause confusion for readers when it is not clear if the outcomes claimed are those achieved by one, two, or multiple treatments. In the study of Gunduz et al., [1] it was easier to deal with this problem with a graphic than with words. The graphic shows that all patients had a first treatment; and from those data rates can be calculated for technical failure, clinical failure, and clinical success. Second and third treatments were used only subsequently, in an effort to reinstate relief that had waned. Therefore, from the data, success rates for repeat treatment can be calculated, as well representative durations of relief from first and subsequent treatments.

In deference to critics, readers should be mindful that the report of Gunduz et al. [1] is no more than a well-presented biographical account of experience; it does not constitute evidence of efficacy or effectiveness. Efficacy requires a placebo-controlled trial that establishes the attributable effect of the treatment. Effectiveness requires field experience of an otherwise proven treatment. For blocks of the ganglion impar, too many questions remain unanswered for the treatment to be released wholesale into practice. We do not know if the apparent benefit is due to the steroid used, the local anesthetic used, or merely that the patients underwent an impressive, technologic treatment in a convincing manner. Nor do we know if blocks of the ganglion impar restore function, and eliminate the need for other health care. Once these questions are answered, blocks of the ganglion impar can be appraised for release into the retail market.


1 Gunduz OH, Sencan S, Kenis-Coskun O. Pain relief due to transsacrococcygeal ganglion impar block in chronic coccygodynia: a pilot study. Pain Med 2015;16(7)

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