A kohen who has a broken leg and needs crutches to support himself can he do birkas kohanim. I remember seeing that if someone is dash biro (seen in town) for 30 days or more then its not considered a distraction . However, I have also,seen that nowadays since kohanim cover their hands and face With a talis there is no issue of distraction . The difference in this case is that the broken leg is not covered by the talis,so would one need to wait 30 days or not?
There is a 35-page Teshuva by a Rabbi Dr. Benjamin Lau(*) - in Hebrew - sub-titled Synagogue Inclusion: Can the Priestly Blessing be Recited in a Wheelchair? that can be read here.
He concludes that since 21st-century society has accepted people with disabilities, as normal fully functional citizens, hence:
- They are no longer considered as inappropriate to be seen in public. So they may participate in Nesias Kapayim as there's no explicit verse prohibiting them from doing so. (As opposed to the Temple Service that has an explicit verse that a broken Cohen cannot participate.)
- They are no longer a distraction - and there wouldn't be a need to wait 30 days.
- If they cannot stand they may sit. The prohibition for sitting is only for those who can stand.
From what I understand, his arguments would hold for a kohen who has a broken leg and needs crutches to support himself, as well as one who cannot stand and would have to sit in a wheelchair.
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(*) I have no idea who this is.