Reporting surgical site infections following total hip and knee arthroplasty: impact of limiting surveillance to the operative hospital.

BACKGROUND: Public reporting of surgical site infections (SSIs) by hospitals is largely limited to infections detected during surgical hospitalizations or readmissions to the same facility. SSI rates may be underestimated if patients with SSIs are readmitted to other hospitals. We assessed the impact of readmissions to other facilities on hospitals' SSI rates following primary total hip arthroplasty (THA) or total knee arthroplasty (TKA).
METHODS: This was a retrospective cohort study of all patients who underwent primary THA or TKA at California hospitals between 1 January 2006 and 31 December 2009. SSIs were identified using ICD-9-CM diagnosis codes predictive of SSI assigned at any California hospital within 365 days of surgery using a statewide repository of hospital data that allowed tracking of patients between facilities. We used statewide data to estimate the fraction of each hospital's THA and TKA SSIs identified at the operative hospital versus other hospitals.
RESULTS: A total of 91 121 THA and 121 640 TKA procedures were identified. Based on diagnosis codes, SSIs developed following 2214 (2.3%) THAs and 2465 (2.0%) TKAs. Seventeen percent of SSIs would have been missed by operative hospital surveillance alone. The proportion of hospitals' SSIs detected at nonoperative hospitals ranged from 0% to 100%. Including SSIs detected at nonoperative hospitals resulted in better relative ranking for 61% of THA hospitals and 61% of TKA hospitals.
CONCLUSIONS: Limiting SSI surveillance to the operative hospital caused varying degrees of SSI underestimation and substantially impacted hospitals' relative rankings, suggesting that alternative methods for comprehensive postdischarge surveillance are needed for accurate benchmarking.