Part of arm exhibiting unusual neuralgia, on both ends (4)

I believe the answer is:

ulna

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'part of arm' is the definition.
(bone of the arm)

I cannot understand how the remainder of the clue works.

(Other definitions for ulna that I've seen before include "Radius partner" , "Part of bone-structure" , "One of two bones of the forearm" , "Part of body" , "Thinner and longer of two bones in forearm" .)

I've seen this clue in The Irish Times.

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