[Infection in Joint Prosthesis. When Should it Be Suspected?]

Joint prosthesis constitute one of the major advances of medicine in the treatment of patients with osteoarticular disease. Infections of prosthetic material, though having a low frequency (1%-3% according to the series and type of prosthesis) constitute one of the larger complications of this surgery and a diagnostic challenge for the physician. The concept of prosthesis infection includes colonization due to germs in periprosthetic material that also leads to clinical manifestations. There are diverse classifications of the prosthetic infections, most of which are based in the form of clinical presentation which largely depends on the germ which is responsible for the infection. In this sense, late forms are generally caused by poorly virulent germs (plasma coagulase negative staphilococcus is the most frequent) and are the most difficult to diagnose. Diagnostic suspicion must be established in relation to the clinical manifestations and a series of accompanying clinical signs. In this sense, in the abscense of baseline inflammatory rheumatism, the persistent elevation of CRP (which normalizes 1-2 weeks after the surgery), or the presence of inflammatory joint fluid (with cell counts over 1700 cells/μL and especially with a predominance of PMN>68%) are signs that strenghten the diagnostic suspicion of bacterial infection. The definitive diagnosis is established by the isolation of the causal germ in culture and, in this sense, the biopsy of periprosthetic material and its study by the pathology department as well as its culture, allow for a trustworthy diagnosis in 80%-90% of cases.