ABSTRACT
Background: This study compared post-total hip arthroplasty (THA) and total knee arthroplasty (TKA) surgical site infection (SSI) rates calculated using two surveillance methodologies to assess their reliability as quality indicators in a community hospital. SSI rates from the National Surgical Quality Improvement Program (NSQIP) were compared with those from an independent Infection Prevention and Control (IPAC) SSI surveillance program based on National Healthcare Safety Network (NHSN) guidance.
Fatima Noman, MD, FCPS (Microbiology), CIC1* and Jeya Nadarajah MD, MSc, FRCPC1 d
1 Infection Prevention and Control department, Oak Valley Health, Ontario, Canada
*Corresponding author
Fatima Noman
Infection Control Professional
Oak Valley Health
12 The Shire Lane
Markham, Ontario, L6B 0N2
Canada
email: fatimanoman06@gmail.com
Article history:
Received 9 February 2026
Received in revised form 14 March 2026
Accepted 13 April 2026
ABSTRACT
Background: This study compared post-total hip arthroplasty (THA) and total knee arthroplasty (TKA) surgical site infection (SSI) rates calculated using two surveillance methodologies to assess their reliability as quality indicators in a community hospital. SSI rates from the National Surgical Quality Improvement Program (NSQIP) were compared with those from an independent Infection Prevention and Control (IPAC) SSI surveillance program based on National Healthcare Safety Network (NHSN) guidance.
Methods: The study period ranged from April 1, 2021, to March 31, 2023. The IPAC program actively reviewed all THA and TKA cases for 90 days post-operatively, while NSQIP followed a subset of patients for 30 days. Both methodologies applied the same NHSN case definitions to identify complex SSI cases, and SSI rates were calculated. All identified cases were reviewed and shared with stakeholders. The IPAC program audited compliance with SSI preventive measures beginning in April 2022.
Results: In the first fiscal year, IPAC surveillance identified six complex SSI cases (THA: 3; TKA: 3), with SSI rates of 0.71 for THA and 0.54 for TKA. NSQIP identified one case (THA: 1; TKA: 0), with SSI rates of 0.87 for THA and 0 for TKA. In the second fiscal year, IPAC identified six additional complex SSI cases (THA: 3; TKA: 3), with SSI rates of 0.58 for THA and 0.36 for TKA, while NSQIP identified no cases. Using IPAC surveillance, SSI rates decreased by 18% for THA and 33% for TKA over the study period.
Of the 12 SSI cases identified by IPAC, five (41.2%) were detected beyond 30 days post-operatively and would not have been captured by NSQIP. Improvements in preventive practices were observed, including normothermia compliance increasing from <20% to 80% and appropriate hair removal education improving from 60% to 93%.
Conclusion: The IPAC SSI surveillance program provided a more accurate and sensitive indicator for detecting changes in SSI rates.
KEYWORDS:
Surgical Site Infections, hip and knee arthroplasty, surveillance, national surgical quality improvement program, national healthcare safety network
INTRODUCTION
Total Hip Arthroplasty (THA) and Total Knee Arthroplasty (TKA) are surgical procedures in which parts of a joint are removed and replaced with a metal, plastic or ceramic device called a prosthesis. Post arthroplasty surgical site infection (SSI), a procedure-related healthcare-associated infection is a severe complication resulting in increased morbidity and mortality, particularly from complex SSI as a result of deep incisional and organ/space infection. At least half of SSIs can be prevented through improved application of evidence-based basic preventive measures (Umscheid et al., 2011).
In order to implement and assess evidence-based infection prevention strategies, regular monitoring of the rate and trend of SSI events is imperative. SSI monitoring requires active, prospective surveillance including concurrent and post-discharge surveillance methods. But the results of the surveillance may vary depending on the surveillance methodologies (Rennert-May et al., 2018), (Ellison et al 2022).
A successful surveillance program includes the use of epidemiologically sound definitions for both numerators and denominators. Meanwhile, the surveillance methods include surveillance period, time frame of SSI elements, and feedback.
The aim of the current study involves a comparison of two post-arthroplasty surgical site infection surveillance methodologies. Surveillance for SSIs that involve Infection Control Professionals (ICPs) and feedback to stakeholders has been shown to be associated with reductions in rates of SSIs (Brandt et al., 2006).
METHODS
The study was conducted at a 309-bed community hospital which is a participant of the National Surgical Quality Improvement Program (NSQIP). This program collects data on pre-operative risk factors, intra-operative variables, and 30-day post-operative outcomes for major surgical procedures. Cases are selected utilizing a systematic sampling process. From the NSQIP data, a report was generated exclusively for SSI events post THA and TKA.
In 2021, the Infection Prevention and Control (IPAC) program initiated a parallel SSI surveillance program for THA and TKA, to identify complex SSI rates (deep incisional and organ/space) in alignment with the CDC-NHSN and Canadian Nosocomial Infection Surveillance Program (CNISP) guidelines.
In addition to tracking SSI rates, the IPAC program audited compliance with SSI prevention practices based on Canadian Patient Safety Institute (CPSI) guidance.
Study period
The study period included two fiscal years (April 1, 2021 to March 31, 2022, and April 1, 2022 to March 31, 2023).
The two surveillance programs (NSQIP and IPAC SSI Surveillance program) for SSI post-hip and knee arthroplasty ran in parallel during this period independently. Cases meeting the CDC-NHSN definitions (Centers for Disease Control and Prevention [CDC], 2025) of
complex SSI events were identified in both methodologies.
National Surgical Quality Improvement Program (NSQIP)
The NSQIP picked a random sample every month from the total
cases who underwent total hip and knee arthroplasties during that month through a systematic sampling process. These sampled cases were followed for 30 days to identify those meeting the definitions of superficial and complex SSI events (Centers for Disease Control and Prevention [CDC], 2025).
The quarterly post-THA and TKA complex SSI rates were calculated using the formula below:
Complex SSI identified during the 30 days post procedure/Number of THA and TKA cases reviewed among the THA and TKA performed during that quarter X 100.
The superficial SSI rates obtained through the NSQIP were not compared as the IPAC SSI surveillance program only reviewed for complex SSIs.
IPAC Surgical Site Infection Surveillance Program
All patients undergoing THA and TKA every month, were reviewed from April 1, 2021, to March 31, 2023. Revision surgeries were excluded.
As per CDC-NHSN recommendation for surgeries with implants, all the cases were followed for 90 days through chart reviews using Electronic Health Record (EHR) platform, including all post-discharge hospital visits, admissions, and investigations to identify complex SSI cases. The quarterly post-THA and TKA complex SSI rates were calculated using the formula below:
Complex SSI identified during the 90 days post procedure/total Number of TKA or THA procedures performed during that quarter X 100.
The post-THA and TKA complex SSI rates collected through the IPAC SSI Surveillance program for the first fiscal year (April 1, 2021 to March 31, 2022) was considered as the baseline for comparison for the subsequent year.
CNISP conducts national surveillance of hospital-acquired infections across multiple hospitals throughout Canada. CNISP data for complex SSI post-THA and TKA collected from 28 acute care hospitals (four small, 16 medium and eight large hospitals) between January 1, 2017, and December 31, 2021, were taken as the external benchmark. (Canadian Nosocomial Infection Surveillance Program [CNISP], 2022).
In addition to SSI rates, the IPAC SSI surveillance program also collected data on the category of SSI and causative microorganisms. Auditing compliance to SSI preventive measures was initiated in October 2021. Charts of 20% of patients undergoing TKA and THA were randomly selected and reviewed for compliance with SSI preventive measures and monthly compliance rates were calculated.
SSI preventive measures reviewed for compliance during the period of October 2021 to August 2022 included:
1. Percentage of patients with Appropriate Antibiotic Prophylaxis.
a) Percentage of patients receiving prophylactic antibiotic infused prior to incision.
b) Percentage of patients with timely prophylactic antibiotic administration.
2. Percentage of patients having anti-septic wash, night before surgery.
3. Percentage of patients with proper operative site preparation.
4. Percentage of patients with normothermia (36ºC-38ºC) within 15 minutes prior to skin closure or on arrival in the post-anaesthetic care unit.
In September 2022, two further preventive measures were added to the compliance review.
5. Percentage of patients with appropriate hair removal.
6. Percentage of patients who received education on appropriate hair removal.
The compliance rates were presented quarterly to the surgical quality committee team, gaps were identified, and improvement strategies applied throughout the course of the study. A surgical quality improvement plan (SQIP) was created through collaboration between the surgical clinical reviewer, the perioperative professional practice leader and the clinical leader of the surgical admission and discharge unit. Change ideas and strategies were developed to improve compliance to identified gaps in SSI preventive measures including patient questionnaires and education of patients and staff.
RESULTS
Surgical Site Infection Cases
IPAC surveillance methodology
In the first fiscal year (April 1, 2021 to March 31, 2022), a total of 977 total hip and knee arthroplasties were performed (THA: 421 TKA: 556). The IPAC SSI Surveillance program, during the 90-day surveillance period, identified six complex SSI with three among THA cases (two deep incisional, and one organ/space) and three among TKA cases (all organ/space) (Table 1).
In the second fiscal year, (April 1, 2022- March 31, 2023) a total of 1,330 total hip and knee arthroplasties were performed (THA: 511 and TKA: 819). The IPAC SSI Surveillance program, during the 90-day surveillance period, identified another six complex SSI with three among THA cases (one deep incisional and two organ/space) and three among TKA cases (all organ/space) (Table 1 and Figure 1).
It should be noted that 41% of complex SSI cases identified through the IPAC SSI Surveillance program occurred after day 30 (between day 31 and day 90) post-surgery.
During the first fiscal year, 50% (3/6) of the complex SSI were identified after 30 days, while in the second fiscal year 33% (2/6) of the complex SSI were identified after 30 days (Table 1 and Figure 1).
National Surgical Quality Improvement Program (NSQIP) Methodology
During the first fiscal year, 22.6% of the total THA and TKA performed were reviewed (THA: 114 out of 421 cases and TKA: 107 out of 556 cases). One complex SSI (deep incisional) was identified among THA cases and zero complex SSI identified among TKA cases in the 30 days post-surgery. The single identified case of SSI by NSQIP, was also identified by the IPAC SSI surveillance methodology (Table 2).
In the second fiscal year, NSQIP reviewed 15.4% of total THA and TKA performed (THA: 102 out of 511 cases and TKA: 103 out of 819 cases) with no identified complex SSI in the 30 days post-surgery (Figure 1 and Table 2).
Surgical site infection rates
IPAC surveillance methodology
During the first fiscal year, the post-THA SSI rate was 0.71% (3/421) and post-TKA was 0.54% (3/556). During second fiscal year, the post-THA SSI rate was 0.58% (3/511) and post-TKA was 0.36% (3/819). A reduction of 18% and 33% in the SSI rates was observed in THA and TKA respectively in the 2nd Fiscal year (Figure1).
National Surgical Quality Improvement Program (NSQIP) Methodology
The post-THA SSI rate during the first fiscal year was 0.87% (1/114) and post-TKA was zero. The SSI rates in the second Fiscal year was zero for both THA and TKA (Figure 1).