Patient-related risk factors for periprosthetic joint infection and postoperative mortality following total hip arthroplasty in Medicare patients.

BACKGROUND: The patient-related risk factors for periprosthetic joint infection and postoperative mortality in elderly patients undergoing total hip arthroplasty are poorly understood. The purpose of this study was to identify the specific patient comorbidities that are associated with an increased risk of periprosthetic joint infection and of ninety-day postoperative mortality in U.S. Medicare patients undergoing total hip arthroplasty.
METHODS: The Medicare 5% sample claims database was used to calculate the relative risk of periprosthetic joint infection and of ninety-day postoperative mortality as a function of preexisting comorbidities in 40,919 patients who underwent primary total hip arthroplasty between 1998 and 2007. The impact of twenty-nine comorbid conditions on periprosthetic joint infection and on postoperative mortality was examined with use of Cox regression, controlling for age, sex, census region, public assistance, and all other baseline comorbidities. The adjusted hazard ratios for all comorbid conditions were evaluated, and the Wald chi-square statistic was used to rank the degree of association of each condition with periprosthetic joint infection and with postoperative mortality. The Bonferroni-Holm method was used to adjust for the multiple comparisons resulting from the number of comorbid conditions analyzed.
RESULTS: Comorbid conditions associated with an increased adjusted risk of periprosthetic joint infection (in decreasing order of significance, p < 0.05 for all comparisons) were rheumatologic disease (hazard ratio [HR] = 1.71), obesity (HR = 1.73), coagulopathy (HR = 1.58), and preoperative anemia (HR = 1.36). Comorbid conditions associated with an increased adjusted risk of ninety-day postoperative mortality (in decreasing order of significance, p < 0.05 for all comparisons) were congestive heart failure (HR = 2.11), metastatic cancer (HR = 3.14), psychosis (HR = 1.85), renal disease (HR = 1.98), dementia (HR = 2.04), hemiplegia or paraplegia (HR = 2.62), cerebrovascular disease (HR = 1.40), and chronic pulmonary disease (HR = 1.32).
CONCLUSIONS: We identified specific patient comorbidities that were independently associated with an increased risk of periprosthetic joint infection and of ninety-day postoperative mortality in Medicare patients who had undergone total hip arthroplasty. This information is important when counseling elderly patients regarding the risks of periprosthetic joint infection and mortality following total hip arthroplasty, as well as for risk adjustment of publicly reported total hip arthroplasty outcomes.