# A Retrospective Cohort Study of Early Prosthetic Joint Infections at a US Academic Medical Center (2014-2023)

## TL;DR

This study examines early prosthetic joint infections after hip and knee surgeries, identifying risk factors like revision surgery, male sex, and obesity.

## Contribution

The study provides updated insights into risk factors and microbiology of early prosthetic joint infections at a U.S. academic hospital from 2014 to 2023.

## Key findings

- Early prosthetic joint infections occurred in 0.90% of 13,197 surgeries.
- Hip arthroplasties had a 1.55 times higher risk of early PJI compared to knee arthroplasties.
- Gram-positive bacteria caused 74.8% of infections, with Gram-negative infections linked to longer surgeries.

## Abstract

Background

Prosthetic joint infections (PJIs) are rare but serious complications of hip and knee arthroplasties, associated with high morbidity and substantial healthcare costs. PJIs that occur within the first three months of surgery are considered “early” PJIs. We investigated the incidence, risk factors, and microbiology associated with early PJIs among patients undergoing hip or knee arthroplasties at Stanford Hospital.

Methods

A retrospective cohort study was conducted using data from the Centers for Disease Control’s (CDC) National Healthcare Safety Network (NHSN) for Stanford Hospital from 2014 to 2023. The study included adults who underwent hip or knee arthroplasties and developed early PJI. Potential PJI risk factors, including surgery type, age, sex, American Society of Anesthesiologists (ASA) score, diabetes status, body mass index (BMI), and the duration of surgery, were selected for analysis. Generalized estimating equations (GEE) were used to calculate adjusted odds ratios (aORs) for the development of early PJIs.

Results

Out of 13,197 surgeries, 119 cases of early PJIs were identified, with a cumulative incidence of 0.90%. Significant risk factors for early PJI included revision surgery (aOR: 2.44), male sex (aOR: 2.18), obesity (BMI of ≥30 kg/m²) (aOR: 1.57), ASA score of >2 (aOR: 1.66), and prolonged duration of surgery (aOR: 1.05 per 10-minute increment). Notably, hip arthroplasties were associated with a higher risk of early PJI compared to knee arthroplasties (aOR: 1.55). The most common causative pathogens were Gram-positive bacteria, making up 74.8% of cases. PJIs caused by Gram-negative organisms were associated with significantly longer index surgery durations compared to those caused by Gram-positive organisms (201 versus 153 minutes, p = 0.03).

Discussion

The findings align with existing literature that identifies revision surgery, male sex, obesity, ASA score, and surgical duration as risk factors for early PJIs. The higher incidence of PJIs in hip arthroplasties compared to knee arthroplasties may be influenced by underlying patient characteristics or surgical complexities. The microbiological profile revealed a predominance of Gram-positive organisms, and prolonged surgical time was associated with Gram-negative infections.

Conclusion

In this study, we report a relatively low incidence rate of early PJIs following hip and knee arthroplasties at our institution and identify key risk factors of PJIs, including revision surgery, male sex, obesity, ASA score, and surgical duration. Understanding these factors can aid in risk stratification and inform preoperative optimization strategies to reduce the incidence of PJIs in this patient population.