Prosthetic Joint Infectious Arthritis

Infections are more common in prosthetic joints than in native joints. They are frequently caused by perioperative inoculations of bacteria into the joint or by postoperative bacteremia resulting from skin infection, pneumonia, ra, invasive instrumentation, urinary tract infection, possibly falls, or rarely dental procedures.

Joint infections develop within 1 year of surgery in two-thirds of cases (1). During the first few months after surgery, Staphylococcus aureus is the cause of infection in approximately 50% of cases; less common causes are mixed flora, gram-negative organisms, and anaerobes (2). Cutibacterium acnes is especially common in infected prosthetic shoulder joints and may require prolonged culture (up to 2 weeks) to detect (3). Candida species can infect prosthetic joints, but Candida infection is rare (4).

Patient-related and surgical risk factors may increase the risk of a prosthetic joint infection.

Patient-specific risk factors include (1).

• Immunosuppression (eg, from prednisone, TNF inhibitors, other biologics)

• Rheumatoid arthritis

• Diabetes mellitus

• Malignancy

• Chronic kidney disease

• Obesity

Surgery-specific risk factors include prior arthroplasty, prior surgical site infection, duration of surgery, post operative complications (eg hematoma or wound dehiscence), and concomitant S. aureus bacteremia (2).

Symptoms and signs of prosthetic joint infection are dependent on time from surgery and can be further classified as early, delayed onset, and late onset (1), (2).

Early/acute infection occurs within 3 months of surgery. The onset is sudden, and the joint appears swollen, painful, and erythematous. Systemic symptoms such as fevers and chills are usually present. These infections are typically acquired during the surgical procedure.

Delayed onset infection occurs between 3 to 12 months after surgery. There may be persistent wound drainage (eg, sinus tract) and the joint appears warm, swollen, and painful. The infection is likely acquired during arthroplasty or in the early postoperative period.

Late onset infection occurs more than 12 months after the initial surgery. There is an acute onset of joint pain, tenderness, and erythema in a previously well-functioning joint. The infection is likely acquired by hematogenous seeding from another infection site.

• Clinical, microbiologic, pathologic, and imaging criteria

The diagnosis of infection in a prosthetic joint often requires a combination of clinical, microbiologic, pathologic, and imaging criteria. There is no standardized approach to diagnosing a prosthetic joint infection, and multiple criteria have been proposed (1, 2, 3, 4).

Definitive diagnosis of a prosthetic joint infection can be made when 2 cultures from the joint are positive for the same organism. A communication between a sinus tract and the prosthesis may also be diagnostic (2).

The serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and D-dimer may all be elevated in prosthetic joint infections. Synovial fluid should be sampled for cell count and culture. In early infection, the synovial fluid white blood count (WBC) is typically > 10,000 cells/mcL (10 × 10⁹/L) (5).

In delayed-onset or late-onset infection, the synovial fluid WBC count is typically > 3000 cells/microL. The synovial fluid should also be analyzed for cell count differential.

In acute infection, the percentage of polymorphonuclear neutrophils (PMNs) is typically > 90% and in delayed-onset and late-onset infections, the percentage of PMNs is typically > 80%. A positive synovial fluid alpha-defensin test may be a marker of infection as well (6).

Radiographs may show periosteal reaction or loosening of the prosthesis or periosteal reaction but are not diagnostic. Technetium-99m bone scanning and indium-labeled white blood cell scanning are more sensitive than radiographs but lack specificity in the immediate postoperative period. Periprosthetic tissue collected at the time of surgery may be sent for culture and histologic analysis (4).

• Arthrotomy with debridement

• Prosthesis replacement

• Long-term systemic antibiotic therapy

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 replacement, or placement of an antibiotic-impregnated spacer and then delayed (2 to 4 months) implantation of a new prosthesis using antibiotic-impregnated cement (1).

Long-term systemic antibiotic therapy is used in either case (1); empiric therapy is initiated after intraoperative culture is done and usually combines coverage for methicillin-resistant gram-positive organisms (eg, vancomycin 1 g IV every 12 hours) and aerobic gram-negative organisms (eg, piperacillin/tazobactam 3.375 g IV every 6 hours or ceftazidime 2 g IV every 8 hours) and is revised based on results of culture and sensitivity testing.

If the prosthetic joint infection is caused by S. aureus, antibiotic therapy includes a 6-week course of pathogen-specific therapy in combination with rifampin 300 mg to 450 mg orally twice a day for biofilm penetration. After the initial treatment course of 6 weeks, therapy is continued with rifampin plus a companion oral antibiotic (ideally levofloxacin or ciprofloxacin if susceptible) for 3 months in hip infections and 6 months in knee infections (1).

The overall rate of infection-free success at 5 years depends on the surgical approach, but can be close to 80% after combined medical and surgical treatment (2), (3).

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), prophylactic antibiotics are not routinely recommended before dental work (1). See Appropriate Use Criteria from the American Academy of Orthopaedic Surgeons (AAOS) for the prevention of orthopedic implant infection in patients undergoing dental procedures. However, prophylactic antibiotics may be recommended for patients undergoing urologic procedures associated with a high risk of bacteremia (eg, lithotripsy).

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 (2).

• Suspect prosthetic joint infectious arthritis in patients with a warm, erythematous, tender joint, or persistent unexplained joint pain, with the highest risk being within a year of surgery.

• Perform joint aspiration and send for culture and synovial fluid analysis;radiographs and routine laboratory studies are seldom helpful.

• Treat with both arthrotomy and debridement and targeted long-term systemic antibiotics.

• Add rifampin to antistaphylococcal antibiotics to increase biofilm penetration.