Do Cultures Obtained During Primary THA Predict the Likelihood of Revision?

Abstract

BackgroundThere can be unexpectedly positive culture results during elective hip arthroplasty, but the degree to which these are associated with an increased risk of subsequent premature revision is not known.Question/purposeAre unexpectedly positive culture results obtained during elective THA associated with an increased likelihood of revision within 5 years of the procedure?MethodsBetween March 2007 and March 2011, the hip unit at our institution performed elective primary THA in 829 patients. We systematically collected three samples in 52% (428 of 829) of the interventions. Of those, 26 patients were excluded because of sampling errors; 94% (402 of 428) had samples that were collected systematically and were eligible for the study. We only considered one hip randomly in bilateral procedures (4% [15 of 428]); patients presenting with acute (< 3 months) periprosthetic joint infection undergoing open debridement (4% [16 of 402]) and patients who died before 5 years of follow-up (2% [seven of 402]) were excluded from the study, leaving 91% (364 of 402) eligible for analysis in this retrospective study of a previous prospective trial. No patient included in the final analysis was lost to follow-up within 5 years from the index surgery. The patient group consisted of 52% (188 of 364) women, with a mean ± SD age of 64.8 ± 13.9 years.ResultsPositives culture results were associated with a higher risk of revision within 5 years of the index surgery. The proportion of revision surgery was higher in the group with positive culture results than in those with negative results (10% [eight of 77] versus 2% [seven of 290]; p = 0.01). The difference was mainly attributable to a higher proportion of aseptic loosening in those with positive culture results than in those with negative results (8% [six of 74] versus 1% [four of 290]; p = 0.01). After a multivariable analysis, the only independent variable associated with 5-year revision surgery was the presence of positive results during THA (odds ratio 4.9 [95% confidence interval 1.72 to 13.99]).ConclusionOur findings suggest that bacterial contamination during THA is associated with an increased likelihood of early revision. This higher risk of revision is mainly because of presumed aseptic loosening; thus, efforts should focus on the need to rule out infection. These results not only open new questions that should be answered in new prospective and well-designed studies, but also may help to better select patients to obtain a more favorable outcome after THA.Level of EvidenceLevel III, therapeutic study.

CORR Insights®: Do Cultures Obtained During Primary THA Predict the Likelihood of Revision?

“…With regard to patient selection, Vargas-Reverón et al [9] noted there were no differences between patients in the culture-negative group and those in the culture-positive group regarding age, gender, laterality, American Society of Anesthesiologists class, surgical duration, BMI, or underlying diagnosis. But what about other factors known to be related to the risk of infection?…”

“…The authors [9] used a mulitvariable analysis to find that routine positive culture results were the only independent factor associated with an increased likelihood of aspetic loosening among the above-noted factors, but if the authors had also controlled for these other known modifiable and nonmodifiable risk factors for infection, could they have idenitfied a confounding variable that is associated with both a routine positive culture result and increased likelihood of revision? Could it be that a culture-positive synovial fluid is the mechanism by which certain patient risk factors manifest?…”

“…The article by Vargas-Reverón et al [9] adds some clinical evidence to support this notion. Their study reported the 5-year survivorship of elective primary THA in patients with positive routine culture results at the time of surgery compared with those with negative results.…”

“…Patient factors including obesity, drug use, smoking, diabetes, perioperative glycemic control, renal disease and dialysis, systemic immunosuppression, malnourishment, and metabolic syndrome also present risks [7]. The current study [9] identifies a risk of infection from the native joint itself. If a researcher were to investigate it, they might find that patients with these host-related risk factors are more likely to have routine positive culture results.…”

“…With the preponderance of evidence suggesting that the common paradigm of loosening is an incomplete guide for clinical practice, some experts have even abandoned the term "aseptic loosening" in favor of the term "undiagnosed septic loosening" [10], and future studies ought to develop reliable and broadly accessible techniques for differentiating mechanical loosening from septic impostors. With regard to patient selection, Vargas-Reverón et al [9] noted there were no differences between patients in the culture-negative group and those in the culture-positive group regarding age, gender, laterality, American Society of Anesthesiologists class, surgical duration, BMI, or underlying diagnosis. But what about other factors known to be related to the risk of infection?…”