The clinical presentation of prosthetic joint infection.

Prosthetic joint infection (PJI) complicates ∼1% of arthroplasties but accounts for considerable morbidity. Both the timing and features of PJI can vary widely. Patients may present with early (≤3 months post-operatively), delayed (3-24 months) or late disease (>24 months). They may be acutely unwell with systemic signs of sepsis or describe only a chronically painful joint with or without sinus formation. Diagnostic criteria as proposed by the Infectious Diseases Society of America and the Musculoskeletal Infection Society highlight the importance of joint sampling to obtain histological and robust microbiological evidence. Staphylococcus aureus and coagulase-negative staphylococci account for >50% of infections. Early infections are likely to have been acquired intra- or peri-operatively, whereas late infection is usually haematogenous in origin. Acute joint inflammation suggests the presence of intra-articular free-living bacteria, whereas chronic infections are associated with the formation of biofilm at the bone-cement or bone-prosthesis interface. The most significant risk factors predisposing to PJI are previous operation on the index joint, previous arthroplasty at a different site, American Society of Anesthesiologists' grade 2, 3 or 4, body mass index >25, malignancy and procedure duration <2 or >4 h.