Prosthetic Joint Infectious Arthritis
Infections are more common in prosthetic joints than in natural joints. They are frequently caused by perioperative inoculations of bacteria into the joint or by postoperative bacteremia resulting from skin infection, pneumonia, dental procedures, invasive instrumentation, UTI, or possibly falls.
Joint infections develop within 1 yr of surgery in two thirds of cases. During the first few months after surgery, the causes are Staphylococcus aureus in 50% of cases, mixed flora in 35%, gram-negative organisms in 10%, and anaerobes in 5%. Propionibacterium acnes is especially common in infected prosthetic shoulder joints and may require prolonged culture (up to 2 wk) to detect. Candida spp infect prosthetic joints in < 5% of cases.
There is a history of a fall within 2 wk of symptom onset in about 25% of patients and of prior surgical revisions in about 20%.
Some patients have had a postoperative wound infection that appeared to resolve, satisfactory postoperative recovery for many months, and then development of persistent joint pain at rest and during weight bearing.
Symptoms and signs of prosthetic joint infectious arthritis may include pain, swelling, and limited motion; temperature may be normal.
The diagnosis of infection in a prosthetic joint often requires a combination of clinical, microbiologic, pathologic, and imaging criteria. Communication between a sinus tract and the prosthesis may also be considered diagnostic of infection.
Synovial fluid should be sampled for cell count and culture. X-rays may show loosening of the prosthesis or periosteal reaction but are not diagnostic. Technetium-99m bone scanning and indium-labeled WBC scanning are more sensitive than plain x-rays but lack specificity in the immediate postoperative period. Ultimately, periprosthetic tissue collected at the time of surgery may be sent for culture and histologic analysis.
Treatment of prosthetic joint infection must be prolonged and usually involves arthrotomy for prosthesis removal with meticulous debridement of all cement, abscesses, and devitalized tissues. Debridement is followed by immediate prosthesis revision or placement of an antibiotic-impregnated spacer and then delayed (2 to 4 mo) implantation of a new prosthesis using antibiotic-impregnated cement.
Long-term systemic antibiotic therapy is used in either case; empiric therapy is initiated after intraoperative culture is done and usually combines coverage for methicillin-resistant gram-positive organisms (eg, vancomycin 1 g IV q 12 h) and aerobic gram-negative organisms (eg, piperacillin/tazobactam 3.375 g IV q 6 h or ceftazidime 2 g IV q 8 h) and is revised based on results of culture and sensitivity testing.
Infection develops in 38% of replacement prostheses, whether replaced immediately or after delay.
If patients cannot tolerate surgery, long-term antibiotic therapy alone can be tried. Excision arthroplasty with or without fusion usually is reserved for patients with uncontrolled infection and insufficient bone stock.
In the absence of other indications (eg, valvular heart disease), whether patients with prosthetic joints need prophylactic antibiotics before procedures such as dental work and urologic instrumentation is currently unresolved. See guidelines from the American Academy of Orthopaedic Surgeons (AAOS) and the American Dental Association (ADA) for the prevention of orthopedic implant infection in patients undergoing dental procedures.
At many centers, patients are screened for S. aureus colonization using nasal cultures. Carriers are decolonized with mupirocin ointment before surgery to implant a prosthetic joint.
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