The purpose of this study is to determine the efficacy of retrieving tissue samples via an x-ray guided needle that is inserted into the infected tissue in the shoulder. The procedure using the guided needle is called a synovial biopsy versus an open tissue biopsy, which is done at the time of surgery. By doing the synovial biopsy prior to a revision surgery, the investigators hope to avoid more invasive intervention if it is not needed. Some patients may appear to have an infection but once the biopsy is taken and the results are read, there may not be an infection and therefore no need for a revision surgery.