To the Editor:

The randomized controlled trial reported by Ly-Pen et al is an important addition to the evidence-based treatment of carpal tunnel syndrome (1). Two points arise from their study. First is the question, how clinically significant is the modest primary end point of a 20% improvement in nocturnal paraesthesia from baseline? Knowing how many patients had complete abolition of symptoms would be a more meaningful outcome. Using this more rigorous outcome, observational and trial data have shown that surgery provides complete relief in >80% of patients at 1 year, whereas ∼70–90% of patients treated conservatively with steroid injections will relapse at the end of 1–2 years, according to the findings of previous prospective studies and randomized controlled trials (2–8). Second, the authors reported additional injections were required in more than 80% of injected wrists and that the percentage of wrists that had reached the 20% improvement criteria dropped from 94.0% to 69.9% in the steroid group by 12 months (1). Indeed, surgery was superior to steroid injection in terms of 70% improvement in functional impairment by the end of the study.

Extrapolating from this observed decline in responders in the injection group and the improvement in the surgical group, there may be a significant difference in favor of surgical release that would be evident by 18 months (Figure 1). These trends toward better outcomes in the surgical group suggest that with longer followup and using freedom from symptoms as the primary outcome, surgical decompression for carpal tunnel syndrome may provide superior symptom relief as compared with steroid injections in the long term.

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Figure 1. Percentage of wrists reaching 70% improvement on visual analog scale by 18 months of followup, among patients with carpal tunnel syndrome in the surgery group versus the steroid injection group.

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Andrew C. F. Hui FRCP*, Shiu-Man Wong MRCP*, * The Chinese University of Hong Kong, New Territories, Hong Kong, China