Abstract
Background: A patient who developed a surgical site infection (SSI) after hip arthroplasty was likely to having an extended length of stay and incurring additional costs in terms of bed-days, diagnostic and therapeutic interventions, etc. It would be important to identify any patient-, surgical- and hospital-related factors that could be modified before surgery to control and decrease the risk of post-operative infection. Aim: To identify the risk factors for SSI after primary hip arthroplasty, as well as to estimate the hospital cost of SSI in Norway. Method: Risk factor analysis was a register based retrospective cohort study at the national level in Norway including patients undergoing hip arthroplasty between September 2012 and December 2014. Binary logistic regression models were constructed for assessing relationships between the outcome variable (SSI) and a series of explanatory variables. For cost analysis, a bottom-up approach was adopted. Health care resources utilized for SSI treatment and the quantities of these resources were derived from an expert survey. Unit costs for the resources were obtained from various sources, including Diagnosis Related Groups (DRG) price list, the Norwegian Medicines Agency database, etc. Total cost of SSI was then calculated by multiplying the quantities of resource use (q) by the unit costs (p) of the resources. Result: During the study period, 17,762 total hip arthroplasty operations and 7,334 hemiarthroplasty procedures were registered in the NOIS. The incidence of SSI after THA was 2.2% (390 of 17,762) and that after HA was 3.6% (264 of 7,334). According to the multivariate regression model, the risk factors for SSI after THA were age, male sex, ASA score ≥ 3, surgery lasting more than 120 minutes, elective surgery, cement-less fixation and post-operative hospital stay. Perioperative antibiotic prophylaxis and specialty hospital were associated with lower risk of SSI. For HA, the risk factors were fewer, including male sex, cement-less fixation and post-operative hospital stay. The average cost of a SSI after primary hip arthroplasty for hospital was NOK 198,121. The main cost drivers were readmission stay (56%), followed by reoperation (28%) and additional LOS (11%). Conclusion: Of all the risk factors detected in this study, cemented prosthesis and perioperative antibiotic prophylaxis are the modifiable ones and therefore recommended to orthopedic surgeon and infection control personnel for controlling and reducing SSIs following THA. Surgical site infection following primary hip arthroplasty causes significant economic burden for Norwegian hospitals, mainly due to substantial increase in hospital stay and the resource demanding nature of its revision procedures. The high cost of SSI implies that substantial cost savings can be achieved by reducing the number of SSIs, and in turn, highlights the importance of detecting modifiable risk factors for SSI.