Polymicrobial Infections in Hip Arthroplasty: Lower Treatment Success Rate, Increased Surgery, and Longer Hospitalization.

Background: Polymicrobial hip arthroplasty infections are a subset of periprosthetic joint infection (PJI) with distinct challenges representing 10%-47% of PJI.

Methods: Records were reviewed from all PJIs involving partial or total hip arthroplasty with positive hip cultures between 2005 and 2015 in order to determine baseline characteristics and outcomes including treatment success, surgeries for infection, and days in hospital for infection. Analysis was restricted to patients who had at least 2 years of follow-up after their final surgery or hospitalization for infection. Factors with P-value less than .05 in univariate outcomes analysis were included in multivariable models.

Results: After multivariable analysis, 28 of 95 hip arthroplasty PJIs which were polymicrobial were associated with significantly lower treatment success, more surgery, and longer hospitalizations compared to PJIs which were not polymicrobial. Patients diagnosed with polymicrobial infection later in treatment (4 of 28) had the lowest treatment success rate, underwent the most surgery, and spent the longest time in hospital.

Conclusion: Polymicrobial periprosthetic hip infection is a particularly devastating complication of hip arthroplasty associated with decreased likelihood of treatment success, increased surgery for infection, and greater time in hospital. Patients with late polymicrobial infection had the worst outcomes. This investigation further characterizes the natural history of periprosthetic hip infections with more than one infectious organism. Patients who present with a subsequent polymicrobial infection should be educated that they have a particularly difficult treatment course and treatment success may not be possible.