When you remove culms you remove foliage that helps the plant grow; if you don't remove a large proportion of culms, though, it shouldn't affect new shoot growth. If the culms are old and starting to lose leaves, it won't have any effect. Why do you want to remove culms? and how many culms will remain after you thin it?

They are unsightly. After removal there will be 9 or 10 culms remaining.

You should be fine....