Abstract

1. Introduction

Surgical site infections (SSIs) account for over $3 billion in healthcare costs per year, with more than 150,000 new cases occurring annually in the US.¹ A large portion of these costs are attributed to longer hospitalizations, readmissions, and additional surgeries required for the treatment of infected patients.² The risk of developing surgical site infections (SSIs) varies tremendously, with orthopedic trauma demonstrating higher rates of SSI than many other surgical specialties.^3,4 However, since orthopedic trauma surgeons are currently reimbursed through a fee-for-service model, there has been little incentive to investigate the costs of treating SSIs among trauma patients. With the recent shift of our healthcare system toward a value-based system of reimbursement, treatment for patients who develop SSIs will potentially go uncompensated. In order to develop appropriate cost-cutting measures⁵ and optimize care for high-risk patients, we will require the ability to measure the costs of SSI treatment,⁶ identify the major factors driving these costs and investigate potential risk factors for infection.^7,8

Although several studies have investigated the cost of treating SSIs in orthopedics,^2,9–17 most of these studies included only a small number of orthopedic trauma patients. Therefore, research related to SSIs for patients who sustain fractures and other trauma-related injuries remains limited. The few studies that have analyzed the cost of treating the wound or SSIs following orthopedic trauma only have focused on a specific type of injury and were conducted in other countries.^18,19 Currently, no study has provided a comprehensive analysis of the costs of treating SSIs among a large number of orthopedic trauma patients in the US.

Therefore, the aim of this study was to identify and categorize the costs of care related to SSIs among orthopedic trauma patients. By conducting a matched case/control analysis in which orthopedic trauma patients were matched with patients who did not develop an infection at a single-level I trauma center, we were able to (1) identify increases in costs for infected patients, (2) analyze the major drivers of these costs, and (3) analyze risk factors for SSIs in orthopedic trauma.

2. Methods

3. Results

A total of 78 patients (4.3%) with SSIs and isolated orthopedic trauma injuries were matched to controls. 96% of matched pairs were within 10 years of age and 87% had their initial surgery within 2 years of each other.

Table 1 compares demographics for our case and control groups. In terms of fracture type, both groups had 41 patients with closed fractures and 37 patients with open fractures. The majority of patients in both groups had an ASA class of 2. Both groups had 19 acetabulum/hip fractures, 5 upper extremity fractures and 54 lower extremity fractures (Table 1).

4. Discussion

Our study demonstrates that SSIs nearly doubled the costs for treating isolated orthopedic trauma injuries. The actual costs of treating SSIs are most likely higher than our estimates as some infected patients may have required additional hospitalization and surgery beyond the initial readmission. When divided over the 5-year period of our study, the cost of treating SSIs ended up averaging almost $2 million per year. The major driver of these costs was the technical charges instead of the professional fees, which included pharmaceuticals, room and board, radiographs, laboratory procedures, and surgical equipment. In fact, pharmaceutical costs, which account for the cost of antibiotics, were nearly doubled for patients with SSIs ($15,801 for the case group compared to $7091 for the control group). Calderone et al. reported similar findings in patients who developed wound infections following lumbar fusion for spinal surgery. They concluded that technical charges may be the largest driver of costs in treating infections for orthopedic injuries.¹⁴

A few other studies have measured the cost of infection following orthopedic surgery in the US.^12,13,17 In a recent study of 59 infected patients, Whitehouse et al.¹³ found that SSIs in orthopedics increase costs by 300% and prolong hospital stay by more than 2 weeks. Although these costs are higher than those reported in our study, only a small portion of their participants had fractures. Therefore, our results may indicate that the costs for treating an SSI may be less following trauma than other types of orthopedic procedures. Furthermore, our study only looked at the initial readmission for infections and therefore may have not included the costs of treatment for further readmissions required to treat the infection.

Only a few other studies have investigated the costs of treating infections among orthopedic trauma patients that sustained fractures of the hip or lower extremity. A study on patients with proximal femoral fractures in the U.K. found that LOS and costs following deep wound infection were about three times higher than they were for controls (80 days vs. 28 days).¹⁸ Edwards et al.¹⁹ also found that wound infections tripled overall costs and quadrupled LOS to 77 days for hip fracture patients in the U.K. The differences in our findings demonstrate how national healthcare reimbursement systems can strongly influence LOS and costs. As the US moves toward a value-based system of reimbursement, hospitals will face even more pressure to minimize LOS for surgical patients to prevent financial losses due to uncompensated care for SSIs.

A major driver of costs for infected patients in our study was increased LOS. When combining the LOS for both the index surgery and initial readmission, we found that patients with SSIs were hospitalized on average 4 days longer than uninfected patients and incurred almost two times the costs for room and board. Other studies have found similar results; for example, Lissovoy et al. conducted a nationwide study of seven different surgical procedures and found that SSIs increased mean LOS by 9.7 days for orthopedic surgery,¹² which was comparable to the number of days cited in other studies.²¹ However, patients undergoing orthopedic trauma surgeries, including ORIF or hip arthroplasty, only composed a small component of these patients. The economic burden of SSIs most probably varies dramatically for patients with trauma injuries compared to those that have laminectomies, tumor resections, and other orthopedic procedures. Additionally, based on previous research and our own findings, this overall increased duration of hospitalization is most likely due to the need for additional surgery among patients who present with SSIs.²¹

Similar to other case vs. control studies, the majority of comorbidities analyzed were not found to be significant risk factors for infection, including smoking and diabetes.^19,21,22 Nevertheless, there was a considerably higher rate of diabetes in the infected group, 12% vs. 4%, but this was not significant (p = 0.07). Postoperative stay was also not found to be associated with SSIs, which has been demonstrated by previous studies. For example, Manian et al.²² reported that a long postoperative hospital stay was not a significant risk factor for MRSA SSI and instead discharge to a long-term care facility and postoperative antibiotic treatment for more than 1 day increased the risk of MRSA SSI. On the contrary, other orthopedic studies have determined a correlation between length of hospital stay and SSIs¹⁷; however, other factors, such as age over 75, metastatic disease and congestive heart failure, have also been linked to increased LOS.²¹

Our findings from the risk factor analysis lead to several implications. For instance, changing hospital protocol to prevent SSIs in patients with longer than average LOS may not decrease infection rates. A study by Rowell et al. found that quality improvement programs, such as proper antibiotic administration, glycemic control, and no closure of contaminated wounds, reduced SSI. Interestingly, decreasing the LOS was not considered a valuable method to decrease the risk of infection.⁷

Our study is limited due to several factors. Because we used a retrospective design, we could only collect information about the patients of our institution that was available within the electronic medical records. Therefore, we were unable to control for differences in body mass index, as this parameter was missing from the medical record for the majority of our patients. With this in consideration, it is important to note that a near significant difference in the rate of diabetes between patients who developed an infection and those who did not (p = 0.07) may have biased the risk factors for SSI. Also, we only analyzed the initial readmission following the primary admission for surgical fixation. However, it is possible that patients who developed SSIs may have had more than one readmission. Therefore, our costs probably underestimate the true costs for treating infection. However, even prospective studies on this topic have limited the follow-up period for identifying readmissions from 30 days to 1 year. We were also limited by the number of factors that could be controlled due to the case/control design of the study; therefore, based on previous similar studies, we controlled the factors that would have the highest impact on cost. However, a variety of other factors, such as mechanism of injury, could have also played a role in increasing the costs of treating infection. When analysing the impact of LOS on the risk of SSI, there were several factors that could not be controlled for, including the time of the day of surgery (morning or evening), the time of the year of the surgery (weekend/holiday), as well as the difference in time to discharge for lower and upper extremity fractures, that would have biased the results. It was also difficult to find control patients matched to cases within a specific age and date of surgery or by the exact procedure performed. Finally, like many past studies, we used hospital charges to estimate costs for treating SSIs.^14,15,23,24 However, hospital charges are usually overestimates of the actual costs to the hospital for the services provided during treatment. We attempted to offset this limitation by using a matched case–control method so that the difference in charge to cost ratio was partially accounted for.²⁴

This study is the first to provide a comprehensive analysis of the major costs and risk factors for SSIs across orthopedic trauma patients. In the current reimbursement model, hospitals and physicians are compensated for additional treatment required for infections. In a future global payment model, however, orthopedic trauma surgeons will be challenged to cover the costs of treating SSIs. Based on the findings presented, physicians must implement methods such as quality improvement programs to decrease the rate of SSIs. A prospective study that measures the actual costs of materials and services that hospitals incur when treating infected patients and focuses on specific anatomic regions would be able to better demonstrate the potential financial implications of SSIs in a changing healthcare landscape.

IRB approval

This study has approval from the Vanderbilt IRB.

Conflicts of interest

William Obremskey has been previously consulted for biometrics; provided expert testimony in legal matters, and received a grant from the Department of Defense. For the remaining authors, no conflicts of interest were declared.

References