I have a needle stuck in my foot for at least 4 years now. last surgeon couldn't get it out. new surgeon says its a tarsal coalition and not needle.

This: doesn't make sense. A needle is easily recognizable on an xray, and there is not even a remote possibility that anyone could confuse it with the xray appearance of tarsal coalition. Perhaps you have both the needle and tarsal coalition, and your doctor thinks the symptoms are due to the coalition, not the needle?

?Foreign body: A good Radiologist and the appropriate X-ray would be able to definitively tell you if there was a metal object in your foot. If metal present, a Foot surgeon would be be ultimately able to remove the object. Best wishes.

Needle: As stated , a needle is readily apparent on an x ray . Reappoint with your new doctor and have him show you the x rays - I do that with all my patients - and any needle would be easily seen .