Clinically Asymptomatic Patients Show a High Bacterial Colonization Rate of Osteosynthetic Implants Around the Knee but Not the Hip

Patients with osteosynthetic implants around the hip and knee show higher infection rates after joint arthroplasty. Our aim was to evaluate the bacterial colonization of any osteosynthetic implants around the hip and knee in patients without clinical signs of infection.

Consecutive patients with osteosynthetic implant removal because of related soft tissue irritations or before elective total joint arthroplasty of the hip and knee were prospectively included. Patients with signs of infection were excluded. Based on sonication fluid cultures, implants were classified according to microbial growth as negative (no growth), contaminated (nonsignificant growth), or colonized (significant growth).

Sonication cultures were positive in 54 of 203 implants (27%), including 8 of 34 (24%) after orthopedic and 46 of 169 (27%) after traumatological surgery. Of 203 sonication cultures, 22 (11%) grew significant bacterial counts. Most common microorganisms were coagulase-negative staphylococci (46%). Implants around the knee showed a significantly higher rate of positive sonication cultures compared with those around the hip (14% vs 2%, P = .017).

We detected high bacterial implant colonization rates regardless of the initial type of surgery. Predominant pathogens were staphylococci, the most common causative agents of periprosthetic joint infections. Positive sonication results do not necessarily lead to postoperative surgical complications and thus do not equal infection. It remains unclear if patients with evidence of bacterial implant colonization show a higher risk of periprosthetic joint infection after adjacent subsequent total joint arthroplasty. Nevertheless, surgeons should be aware of a significantly higher colonization rate of implants around the knee and take this into consideration when total knee arthroplasty is scheduled in patients with osteosynthetic devices.