The present invention is excellent in cutting against the bone cement, it is to provide a guide pin re-polishing is easy. and 2 a plurality of grooves extending along the central axis S is located in the A tip 1a, between the grooves 2, 2 each other are adjacent to each other among the plurality of grooves 2 a surface portion 3 which is located, provided with, in a perpendicular cross section to the central axis S, any plurality of grooves 2 are convex to the central axis S side, a guide pin 1. In the cross section, 2 a plurality of grooves are both a convex curved to the central axis S side.FIELD 1
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