Extracorporeal shock wave therapy (ESWT) is increasingly being used in the treatment of a number of soft tissue complaints. Although there has been some evidence to suggest ESWT is useful in the treatment of tendonitis where there are calcium deposits in the tendon, there is a lack of evidence which evaluates the usefulness of ESWT in other musculoskeletal conditions.
Speed et al are a group of researchers based at the University
of Cambridge, UK, and the aim of this study was to establish if
ESWT was effective in the treatment of tennis elbow. The authors
used a double blind placebo controlled trial, which means that the
subjects were split into two groups, with one group receiving ESWT
treatment and the other group receiving 'sham' treatment. None of
the subjects knew which group they were in. The trial of treatment
lasted for 3 months, with the patients' pain scores evaluated objectively
using a valid method (the visual analogue scale).
Extracorporeal shock waves are single pressure pulses of microsecond duration that can be focused upon a specific site using ultrasound guidance. In the past 30 years they have been used as a highly effective treatment of kidney disorders. Recently ESWT has been used in the treatment of a number of musculoskeletal conditions, including tennis elbow, at doses of 10-20% of those used for kidney conditions. The precise mechanism of this treatment is not known, but several theories suggest that shock waves may stimulate tissue healing and reduce both calcification and pain.
Speed et al found that both groups showed significant improvement
after two months of treatment, both actual and sham. There were
no significant differences between the two groups with respect to
pain scores reported. The authors concluded that there was a significant
placebo effect with ESWT, although there was no benefit in having
actual treatment when compared to sham treatment. The study is rigorously
constructed and well presented, and the only criticism can be the
small sample of patients used. Speed et al used 75 patients, when
a sample of over 400 would be necessary to extrapolate the statistical
findings.The authors accept that a natural recovery may have taken
place, since the average time of symptoms of the subjects was around
15 months, and both groups improved. A future study may look at
patients who had more acute symptoms of tennis elbow and see if
ESWT has an affect on the patients' pain scores.