Methodological Considerations in Combined Pudendal Nerve Block and Wrist-Ankle Acupuncture for Postoperative Analgesia After Perianal Abscess Surgery [Letter]

Dear editor

We read with interest the randomized controlled trial by Zhang et al¹ evaluating ultrasound-guided pudendal nerve block (PNB) combined with wrist-ankle acupuncture for postoperative analgesia after perianal abscess surgery The authors should be commended for investigating a clinically relevant strategy to improve pain control after anorectal surgery. Their results suggest that the combined approach was associated with lower postoperative pain scores, longer analgesic duration, reduced rescue analgesia, and better sleep quality than either intervention alone. Several methodological issues, however, merit further consideration.

First, the main outcomes were largely subjective, including pain scores, sleep quality, and patient satisfaction, yet the manuscript does not clearly describe blinding of participants, care providers, or outcome assessors. In addition, no sham control was used for the acupuncture component. This is relevant because studies of pain interventions, particularly those involving acupuncture, are susceptible to expectation and observer-related bias.^2,3 Although participant blinding may be difficult in this setting, blinded outcome assessment and the use of an appropriate sham procedure would have strengthened internal validity.

Second, there appears to be an inconsistency in the reported study timeline. The abstract states that enrollment occurred between January 2023 and June 2024, whereas the Methods section indicates that the trial was conducted between January and December 2024. The reported registration number also raises the question of whether registration preceded patient enrollment, although the manuscript does not explicitly clarify this point. Because prospective registration and consistency between protocol and final reporting are important safeguards in randomized trials, clarification would be helpful.^4,5

Third, the timing of the two interventions complicates interpretation of the early analgesic findings. PNB was performed at the end of surgery, whereas wrist-ankle acupuncture was initiated 6 hours postoperatively. Accordingly, the 6-hour pain assessment may primarily reflect the effect of the nerve block rather than a true combined effect. A design with more closely aligned intervention timing, or a prespecified analysis separating early and later postoperative periods, would better clarify whether the benefit was additive or sequential.

Overall, this study provides encouraging preliminary evidence for combining PNB with wrist-ankle acupuncture after perianal abscess surgery. Further clarification regarding blinding, study chronology, and intervention timing would strengthen confidence in the findings and improve interpretation of the reported treatment effect.