Methodological Challenges in Predicting Periprosthetic Joint Infection Treatment Outcomes: A Narrative Review

External Validation of the Joint-Specific Bone Involvement, Antimicrobial Options, Coverage of the Soft Tissues, and Host Status (JS-BACH) Classification for Predicting Outcome in Periprosthetic Joint Infections: A Cohort of 653 Patients

BACKGROUND

Periprosthetic joint infection (PJI) is a devastating complication in hip and knee joint arthroplasty. The "Joint-Specific Bone Involvement, Antimicrobial Options, Coverage of the Soft Tissues, and Host Status (JS-BACH)" classification system was developed in 2021 to stratify the complexity of PJI, and more importantly, to act as a tool to guide referrals to specialist centers. The "JS-BACH" classification has not been validated in an external cohort. This study aimed to do so using a large prospective cohort from Australia and New Zealand.

METHODS

We applied the JS-BACH classification to the Prosthetic Joint Infection in Australia and New Zealand Observational (PIANO) cohort. This prospective study of newly diagnosed PJI collected 2-year outcome data from 653 participants enrolled in 27 hospitals. The definition of PJI treatment failure at 24 months was any of the following: death, clinical or microbiological signs of infection, destination prosthesis removed, or ongoing antibiotic use. Individual cases were classified as per JS-BACH into "1: uncomplicated" (n = 268), "2: complex" (n = 330), and "3: limited options" (n = 55). This cohort was similar to the original JS-BACH population in terms of baseline characteristics. However, there was a difference in complexity, with more debridement, antibiotics, and implant retention procedures, fewer revision procedures, and a higher proportion of uncomplicated patients in the PIANO cohort.

RESULTS

The risk of treatment failure correlated strongly with the JS-BACH category, with odds ratios (95% confidence interval) for category 2 versus 1 of 1.75 (1.24 to 2.47) and for category 3 versus 1 of 7.12 (3.42 to 16.02).

CONCLUSIONS

Despite the PIANO study population being less complicated than the original derivation cohort, the JS-BACH classification showed a clear association with treatment failure in this large external cohort.

Acute Haematogenous Revision Total Knee Arthroplasty Infection by Streptococcus canis Treated by Debridement, Antibiotics, and Implant Retention: A Case Report

Prosthetic joint infections (PJIs) are one of the most feared complications by orthopaedic surgeons. Haematogenous PJI represents an important part of PJI cases. Streptococcus canis is an extremely rare cause of haematogenous PJI and its medical and surgical treatment and prognosis are not well established. We present a 79-year-old female patient who had a revision total knee arthroplasty (rTKA) surgery three years before. She was admitted to the hospital referring to three days of knee pain, restricted range of motion, and fever. Blood tests demonstrated leukocyte and C-reactive protein elevation. Joint fluid aspiration showed elevated white blood cell count with a high neutrophil differential and its conventional culture was positive for Streptococcus canis. She did not have pets but she took care of her daughter's dog. An acute haematogenous infection of the rTKA was diagnosed and treated with debridement, antibiotics (eight weeks of IV ceftriaxone), and implant retention (DAIR). After one year, the patient remains clinically asymptomatic without changes on X-rays and with normal serum levels of inflammatory blood markers. Streptococcus canis has to be kept in mind as a possible cause of haematogenous TKA infection in patients who have contact with domestic pets and patients should be asked for this contact. We recommend DAIR as a viable treatment option for this type of infection, which may show excellent results.

Validation of a Classification System for Optimal Application of Debridement, Antibiotics, and Implant Retention in Prosthetic Joint Infections following Total Knee Arthroplasty: A Retrospective Review

INTRODUCTION

Periprosthetic joint infection (PJI) remains a serious complication after total knee arthroplasty (TKA). While debridement, antibiotics, and implant retention (DAIR) are considered for acute PJI, success rates vary. This study aims to assess a new scoring system's accuracy in predicting DAIR success.

METHODS

119 TKA patients (2008-2019) diagnosed with PJI who underwent DAIR were included for analysis. Data were collected on demographics, laboratory values, and clinical outcomes. This was used for validation of the novel classification system consisting of PJI acuteness, microorganism classification, and host health for DAIR indication. Statistical analysis was carried out using SPSS programming.

RESULTS

Mean follow-up was 2.5 years with an average age of 65.5 ± 9.1 years, BMI of 31.9 ± 6.2 kg/m2, and CCI of 3.04 ± 1.8. Successful infection eradication occurred in 75.6% of patients. The classification system demonstrated 61.1% sensitivity, 72.4% specificity, and 87.3% positive predictive value (PPV) when the DAIR cutoff was a score less than 6. For a cutoff of less than 8, sensitivity was 100%, specificity was 37.9%, and PPV was 83.3%.

CONCLUSIONS

To date, no consensus exists on a classification system predicting DAIR success. This novel scoring system, with high PPV, shows promise. Further refinement is essential for enhanced predictive accuracy.