We read with interest the article, “Novel flexible nerve conduits made of water-based biodegradable polyurethane for peripheral nerve regeneration” by Hsu et al.1 In this study, nerve regeneration was evaluated by walking track analysis and histological analyses after 6 weeks. We would like to comment on the time duration for evaluating the walking track analysis and histological analyses in this study, Hsu et al. have not paid attention to the facts that: first for checking the functional recovery and also histological recovery of sciatic nerve at least 8 weeks is necessary. Additionally, although 8 weeks is necessary for checking the functional recovery but in all studies 12 weeks after grafting, nerve regeneration is evaluated. Yang et al. have previously shown an improved outcome of nerve regeneration and functional recovery, 12 weeks after nerve grafting.2 Also Whitlock et al. checked the reconstruction of nerve gaps in rat sciatic nerve model for 12 weeks and even 22 weeks after conduit grafting.3 In another study that use linear ordered collagen scaffold functional evaluation, histological investigation, and morphometric analysis were checked for 12 weeks after surgery.4 As the authors noted, they did not check and follow longterm period of regeneration in this study. Therefore, we think that there is a need for more studies with longer time duration about the conduits made of water-based biodegradable polyurethane for peripheral nerve regeneration. I hope that these comments will be useful in obtaining more reliable results in the future.

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