My orthopedic surgeon used a steinmann pin to help put in a hip spacer and was unable to get it out. how important is it that it comes out when he goes in to take out the spacer and put in the prosthesis?

Hip spacers are temporary prosthetic devices usually used while treating infections of prior hip replacements that were removed. This is a highly technical area of orthopedic specialization, and you are drilling down to detail specific to your case only. Presumably, that pin WILL come out, and a healthtap orthopedist might give a better answer, but YOUR orthopedist is the one who knows.