**2. Risk factors for infection**

Patient-related risk factors for infection include previous revision arthroplasty or previous infection associated with a prosthetic joint at the same site, tobacco abuse, obesity, rheumatoid arthritis, a neoplasm, immunosuppression, and diabetes mellitus.

infections are increasingly difficult to treat with the rise in antibiotic-resistant forms.

Staphylococcus Infection Associated with Arthroplasty 461

sufficiently cured joint infection can cause trophic and functional limitations or can even be the starting point of a progressive infection spreading in continuity, lymphogenic or haematogenic. In general, the detection and treatment of acute infectious arthritis is an acute emerging situation, in which a delay may progress to further septic inflammation[23].

The arthroplasty associated infection may distinguishes two major types―septic arthritis and osteomyelitis, which both cause serious morbidity and are often difficult to manage. Septic arthritis is a joint disease typified by bacterial colonisation and rapid articular destruction[6]. Infiltration and growth of bacteria within the synovium results in inflammation with infiltration of leukocytes into the joint fluid [4]. The production of reactive oxygen species and host matrix metalloproteinases (MMPs), lysosomal enzymes and bacterial toxins contribute to the destruction of cartilage. This starts with degradation of host proteoglycans followed by collagen breakdown within hours of infection, and is mediated by polymorphonuclear leukocytes[3-5,24]. The containment of the inflammatory process within the joint results in increasing pressure, which impedes blood and nutrient supply to the joint exacerbating joint damage and facilitating destruction of cartilage and the synovium. Permanent destruction of articular cartilage and subchondral bone can occur

Osteomyelitis describes a range of infections in which bone is colonized with microorganisms, with associated inflammation and bone destruction. Acute osteomyelitic foci are characterized by pus-forming inflammation at the site of microbial colonisation. Damage to bone matrix and compression and destruction of vasculature is also observed as the infection spreads to surrounding soft tissues, which can further exacerbate bone necrosis[7,10].Sections of dead bone, known as sequestra, can form which may then detach to form separate infectious foci which, due to the lack of vasculature, are protected from immune cells and antibiotics[7,10]. Such areas of dead, infected tissues that are inaccessible to antimicrobials or the immune response can lead to chronic persistence of the

The principal routes of these infection involve: (I) haematogenous or lymphogenous seed of the pathogen, (II) contiguous, by contact with a neighboring infected site, (III) or direct, resulting from infiltration of bone, often following inj ury, surgery or implantation of a foreign body, such as joint repalcement[25]. The range of environments experienced by the bacterium differs for each route and hence the virulence factors that are involved in

Another classification of arthroplasty associated infection distinguishes acute, chronic and reactive forms, which differ in their type of joint infection and their triggering bacteria. Infection with virulent organisms (e.g., S. aureus and gram-negative bacilli) inoculated at implantation is typically manifested as acute infection in the first 3 months (or, with hematogenous seeding of the implant, at any time) after surgery, whereas infection with less virulent organisms (e.g., coagulase-negative staphylococci and P. acnes) is more often manifested as chronic infection several months (or years) postoperatively. The most common symptom of infection associated with a prosthetic joint is pain. In acute infection, local signs and symptoms (e.g., severe pain, swelling, erythema, and warmth at the infected

**3. Classification of the arthroplasty associated infection** 

rapidly, within just a few days[24].

pathology may be different for each route of infection.

infection[10].

Surgical risk factors include simultaneous bilateral arthroplasty, a long operative time(>2.5 hours), and allogeneic blood transfusion.

Postoperative risk factors include woundhealing complications (e.g., superficial infection, hematoma, delayed healing, wound necrosis, and dehiscence), atrial fibrillation, myocardial infarction, urinary tract infection, prolonged hospital stay, and *S. aureus* bacteremia[12- 15],[18-21].

Fig. 1. Total Arthroplasties Performed and Prosthetic Infections, According to Procedure. Panel A shows the number of total arthroplasties performed from 1990 through 2006. Data are from the Centers for Disease Control and Prevention. Panel B shows the number of prosthetic joint infections from 1990 through 2004. Data are from Kurtz et al.

An increased rate of infection occurs in the pre-damaged joint and is also associated with particular predispositions of the patients (Table 1) [22-24]. In articular, a joint prosthesis is a high risk predisposition for an infection. Perioperatively the initial bacterial entry into the joints may occur. On the other hand the implanted foreign material causes in addition to the severe joint disease present an additional reduction in local resistance, which facilitates haematogenous infections. The prosthetic materials are also additional binding sites for various bacteria, and act as a starting point for prosthetic infections. Thus, in addition to the local conditions, the bacterial properties and their specific pathogenity have to be considered for understanding the whole mechanism of infection. Basically, a too late or not

Table 1. Predisposing factors

Surgical risk factors include simultaneous bilateral arthroplasty, a long operative time(>2.5

Postoperative risk factors include woundhealing complications (e.g., superficial infection, hematoma, delayed healing, wound necrosis, and dehiscence), atrial fibrillation, myocardial infarction, urinary tract infection, prolonged hospital stay, and *S. aureus* bacteremia[12-

Fig. 1. Total Arthroplasties Performed and Prosthetic Infections, According to Procedure. Panel A shows the number of total arthroplasties performed from 1990 through 2006. Data are from the Centers for Disease Control and Prevention. Panel B shows the number of

An increased rate of infection occurs in the pre-damaged joint and is also associated with particular predispositions of the patients (Table 1) [22-24]. In articular, a joint prosthesis is a high risk predisposition for an infection. Perioperatively the initial bacterial entry into the joints may occur. On the other hand the implanted foreign material causes in addition to the severe joint disease present an additional reduction in local resistance, which facilitates haematogenous infections. The prosthetic materials are also additional binding sites for various bacteria, and act as a starting point for prosthetic infections. Thus, in addition to the local conditions, the bacterial properties and their specific pathogenity have to be considered for understanding the whole mechanism of infection. Basically, a too late or not

prosthetic joint infections from 1990 through 2004. Data are from Kurtz et al.

hours), and allogeneic blood transfusion.

Table 1. Predisposing factors

15],[18-21].

sufficiently cured joint infection can cause trophic and functional limitations or can even be the starting point of a progressive infection spreading in continuity, lymphogenic or haematogenic. In general, the detection and treatment of acute infectious arthritis is an acute emerging situation, in which a delay may progress to further septic inflammation[23].
