P eriprosthetic joint infection (PJI) is thought to be responsible for 15% of the primary THAs undergoing revision [1]. This major complication to THA is expected to increase [1, 18]. Infected THA causes a severe burden on patients, with substantial detrimental effects on quality of life, the health care system, and society, with annual costs estimated in the billions of dollars in the United States alone [8]. The incidence of deep PJI after THA varies, but the pooled incidence has been reported to be 0.9% and 1.1% in two systematic reviews [9, 18]. The incidence of PJI is much higher after revision THA (7%–12%) [17]. An increase in followup time results in a reported increase in prevalence: from 0.2% to 1.1% between discharge and 5 years postsurgery [18]; and from 1.6% to 2.2% between 2 and 10 years postsurgery [11]. Different clinical and laboratory criteria are used to diagnose PJI, with various sensitivity and specificity [5]. Some studies use clinical criteria alone [10], while others use both clinical and laboratory criteria [17]. Diagnosis of PJI can be particularly difficult for low-grade infections that may present with nonspecific clinical signs and normal inflammatory markers. Prosthesis failure within 2 years of implantation has been shown to be highly predictive of infection even when the diagnosis is not obvious [15]. Recently, sonication fluid cultures were shown to be most accurate and sensitive in identifying the microorganism responsible of PJI [6]. This method was found particularly useful in detecting late infections [16].