Abstract
Aim
Surgical site infections caused by Staphylococcus aureus (S. aureus) are associated with considerable clinical and economic burden. Studies assessing this burden in Germany have been limited to specific institutions, selected patient groups or not specific to S. aureus infections (SAI). This study was undertaken to further understand the burden of SAI following orthopedic surgeries in Germany.
Method
All patients with at least one spine, endoprosthetic hip or knee surgery between 2012 and 2015 captured in the AOK PLUS claims database were included in this analysis. SAI were identified using S. aureus-specific ICD-10 codes following surgery. Exclusion criteria included: younger than 18, SAI in the 90 days preceding index, any surgery in the 180 days preceding index, surgery at the same body location as index in the preceding 365 days, or more than one surgery of interest during index hospitalization.
Cumulative incidence and incidence density were used to assess SAI. Mortality, healthcare resource utilization and costs were compared between SAI and non-SAI group during the 1year follow-up post index surgery. Multivariate analyses were conducted while controlling for sex, age, Charlson Comorbidity Index (CCI), location of surgery, length of index hospitalization, recent fractures, other bacterial infections during index hospitalization and outpatient prescriptions for antibiotics in the year pre-index.
Results
In total, 74,327 patients were included who underwent a knee (21,285), hip (29,429), or spine surgery (23,613). Mean age was 69.6 years, 61.6% were female and the mean CCI was 2.3.
The SAI incidence post-orthopedic surgery was 20.2 cases per 1,000 patient-years within 1 year of index hospitalization; the cumulative incidence was 1.9%. Knee surgeries were associated with lower SAI risk compared to hip surgeries (HR=0.8; p=0.024), whereas spine surgeries did not differ significantly. Compared to non-SAI group, the SAI group had on average 4.4 times the number of hospitalizations (3.1 vs. 0.7) and 7.7 times the number of hospital days (53.5 vs. 6.9), excluding the index hospitalization (p-values<0.001). One year post-orthopedic mortality was 22.38% in the SAI and 5.31% in the non-SAI group (p<0.001). The total medical costs were significantly different between SAI and non-SAI groups (42,834€ vs. 13,781€; p<0.001). Adjusting for confounders, the SAI group had nearly 2 times the all-cause direct healthcare costs (exp(b)=1.9; p<0.001); and 2.5 times the risk of death (OR=2.5; p<0.001) compared to the non-SAI group.
Conclusions
S. aureus infection risk after orthopedic surgeries persists and is associated with significant economic burden and risk of mortality.
