Early infections (occurring within 4 weeks of a joint replacement) are usually due to Staph aureus, streptococci or enterococci.
[4] Whereas late infections (occurring 3 months or later after the joint replacement) are usually due to coagulase negative staphylococcus or cutibacterium.
[4] The highest risk of PJI is in the immediate post-operative period, when direct inoculation of bacteria into the joint space may occur during surgery.
[4] Dental procedures may cause a transient bacteremia which can lead to inoculation of the artificial joint and PJI, with strep viridans being the most common causative organism.
[3] Risk factors for PJI include diabetes, immunosuppression, smoking, obesity, chronic kidney disease, the presence of a soft tissue infection, or an infection in another part of the body or increased fat tissue around the replaced joint.
[2] Prolonged operative times, in which the joint is left open to the external environment, determined as greater than 90 minutes in a single study, also increases the risk for PJIs.
[2][4] Functional imaging tests such as white blood cell Scintigraphy or PET scan may help to identify hypermetabolic areas consistent with infection and aid with the diagnosis.
[4] Magnetic resonance imaging is specific to soft tissue infections, with metal artifact reduction sequence (MARS) MRIs having great utility to aid in the diagnosis of PJIs.
[2] Antibiotic loaded polymethylmethacrylate (PMMA) which are placed in the joint are helpful, however these non-resorbable beads may themselves be colonized by bacteria with an associated biofilm, therefore bio-absorbable local antibiotic carriers (calcium sulfate beads, resorbable gentamicin sponges) are preferred.
A strategy of surgical debridement to decrease the bacterial load prior to starting systemic antibiotics is sometimes employed.
[4] Intravenous ampicillin-sulbactam or amoxicillin with clavulanic acid with vancomycin added in cases of MRSA is a commonly employed empiric antibiotic treatment strategy.
[4] If surgery fails or the PJI persists despite optimal antibiotic therapy, resection arthroplasty of the hip with a pseudarthrosis (Femoral head ostectomy) is sometimes done.
[2][1] Screening for and eradication of MRSA carriage and chlorhexidine wipes or soap and water skin cleansing prior to surgery may possibly decrease the risk of PJIs.
However specific circumstances placing patients at higher risk, as determined by the dentist or other physicians, may warrant antibiotic prophylaxis.
This increase is believed to be due to the much greater number of hip and knee arthroplasties being performed presently.