Infection of an orthopaedic implant: epidemiology and diagnosis

Infection of an orthopaedic implant is a source of considerable morbidity. Infection rates for primary total hip arthroplasties have been reported to be 1-2%. Major risk factors for deep infection are rheumatoid arthritis and diabetes mellitus. Other potential risk factors have also been described. From the majority of the patients with an infected hip arthroplasty, Gram-p ositive microorganisms can be isolated. Coagulase-negative staphylococci an d Staphylococcus aureus are isolated in > 50 % of cases, in almost equal nu mbers. Gramnegative bacilli are usually secondary invaders of open, drainin g wounds in patients with deep sepsis of a hip arthroplasty. Anaerobic micr oorganisms are isolated in 10 % of such patients. To facilitate the managem ent of the patients with an infected hip arthroplasty several classificatio n systems have been described, but none of these is universally accepted. I t can be difficult to make the correct diagnosis of infected joint arthropl asty with reasonable certainty: a diagnosis can be reached with an acceptab le degree of certainty only by combining various investigations. In most ca ses, an infection can be diagnosed or excluded on the basis of a carefully obtained clinical history and the measurement of the sedimentation rate and /or the C-reactive protein level. Other preoperative investigations, such a s radiography, arthrography, radionuclide imaging, aspiration of the joint and peroperative investigations, such as frozen sections, Gram stains and c ultures, may provide additional evidence. Peroperative cultures provide the most accurate diagnostic information. (C) 2000 Lippincott Williams & Wilki ns.