You would most often hear "he has his foot in a cast." (cast = plaster cast) Of the two examples you have, you might hear "he has his foot in plaster," though it is not something you would hear often, at least in English. "He's had his foot plastered," is technically a correct sentence, but you would almost never hear it.

Your question should read: Is the sentence (to have ones's foot in plaster) correct? FDMaxey's answer is right. Re John's answer, the word is plastered not plastred.

thanks! that's very thoughtful of you. i didn't know you cared about the things i write :)

"to have ones's foot in plaster" and "to have the foot plastred" both are not sentences so the answer is no, it is not correct

it depends on how you use the sentence. but in your question i think it's "to have one's foot plastered".