The Joint-Specific BACH classification: A predictor of outcome in prosthetic joint infection

Periprosthetic Joint Infection: What's New?

Total joint arthroplasty (TJA) ranks among the most commonly performed orthopedic surgeries, with its annual incidence on the rise globally. Periprosthetic joint infection (PJI) remains a leading cause of arthroplasty failure. This review aims to summarize recent literature updates on the epidemiology, diagnosis, and management of PJI.

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.

Management of periprosthetic joint infection of the shoulder: A narrative review

Evidence for management of shoulder periprosthetic joint infection (PJI) has traditionally originated from the hip and knee literature. The differing microbiome, anatomy and implants used in the shoulder mean this evidence is not always directly transferrable. The 2018 Philadelphia International Consensus Meeting for the first-time produced evidence-based guidelines and diagnostic criteria relating specifically to PJI of the shoulder. These guidelines and criteria recognize the pathogenicity of lower virulence organisms in the shoulder which often means clinical presentation is less obvious than other joints. The role of Cutibacterium acnes in shoulder PJI is the subject of increasing basic science and clinical research and advances in microbiological research may help to understand the pathology behind shoulder infections. There is new evidence that outcomes after revision shoulder arthroplasty are dependent on the virulence of the causative organism. An individualised approach to treatment considering host factors, organism, soft tissues and bone stock is recommended. Debate continues in the literature regarding the indications of one- or two-stage revision and the latest evidence is discussed and synthesized in this review article. We advocate careful multidisciplinary team decision making for cases of shoulder PJI and recognize a limited role for debridement and implant retention in acute shoulder PJI (<6 weeks). There appears to be a role for one-stage revision in lower risk cases with low virulence organisms but caution against its' universal adoption. In higher risk or complex cases, there remains a clear role for two-stage revision arthroplasty, and we detail the specifics of this protocol and procedure from our tertiary shoulder and elbow unit.

Local Antimicrobial Therapy with Combined Aminoglycoside and Vancomycin Compared to Aminoglycoside Monotherapy in the Surgical Management of Osteomyelitis and Fracture-Related Infection

We investigated the effect of combination aminoglycoside and vancomycin local antibiotic treatment compared to aminoglycoside alone in the surgical management of bone infection. Data including patient demographics, type of surgery, microbiological characteristics, BACH score, duration of antibiotic treatment and clinical outcomes were collected. Failure of therapy was a composite of recurrence of infection, continued or new antimicrobial therapy, or reoperation with suspected or confirmed infection at one year after index surgery. A total of 266 patients met the inclusion criteria. 252 patients reached the final follow-up and were included in the final analysis. 113 patients had treatment with aminoglycoside alone and 139 patients had combination aminoglycoside and vancomycin. There was no difference in the failure rate between groups; 10/113 (8.8%) in the aminoglycoside alone and 12/139 (8.6%) in the combination group, p = 0.934. Multivariate analysis showed that there was no added benefit of combination therapy (OR 1.54: 95% CI 0.59-4.04, p = 0.38). BACH score and low BMI were associated with increased risk of failure (BACH OR 3.49: 95% CI 1.13-10.76, p = 0.03; Low BMI OR 0.91: 95% CI 0.84-0.99, p = 0.037). The form of the carrier material (pellets or injectable paste) had no effect on failure rate (p = 0.163). The presence of aminoglycoside resistance had no effect on failure rate (OR 0.39: 95% CI 0.05-3.01, p = 0.37). Clinical outcome was not improved by the addition of vancomycin to aminoglycoside alone as local therapy for the management of bone infection.

The PJI-TNM classification for periprosthetic joint infections

Aims

This study aimed to evaluate the clinical application of the PJI-TNM classification for periprosthetic joint infection (PJI) by determining intraobserver and interobserver reliability. To facilitate its use in clinical practice, an educational app was subsequently developed and evaluated.

Methods

A total of ten orthopaedic surgeons classified 20 cases of PJI based on the PJI-TNM classification. Subsequently, the classification was re-evaluated using the PJI-TNM app. Classification accuracy was calculated separately for each subcategory (reinfection, tissue and implant condition, non-human cells, and morbidity of the patient). Fleiss' kappa and Cohen's kappa were calculated for interobserver and intraobserver reliability, respectively.

Results

Overall, interobserver and intraobserver agreements were substantial across the 20 classified cases. Analyses for the variable 'reinfection' revealed an almost perfect interobserver and intraobserver agreement with a classification accuracy of 94.8%. The category 'tissue and implant conditions' showed moderate interobserver and substantial intraobserver reliability, while the classification accuracy was 70.8%. For 'non-human cells,' accuracy was 81.0% and interobserver agreement was moderate with an almost perfect intraobserver reliability. The classification accuracy of the variable 'morbidity of the patient' reached 73.5% with a moderate interobserver agreement, whereas the intraobserver agreement was substantial. The application of the app yielded comparable results across all subgroups.

Conclusion

The PJI-TNM classification system captures the heterogeneity of PJI and can be applied with substantial inter- and intraobserver reliability. The PJI-TNM educational app aims to facilitate application in clinical practice. A major limitation was the correct assessment of the implant situation. To eliminate this, a re-evaluation according to intraoperative findings is strongly recommended.

Proceedings of the United Kingdom Periprosthetic Joint Infection Meeting 2022: Combined and Arthroplasty Sessions

Considerable variation in practice exists in the prevention, diagnosis, and treatment of periprosthetic joint infection (PJI), which is a devastating complication for patients and surgeons. The consensus principle has been increasingly embraced by the orthopaedic community to help guide practice, especially where high-level evidence remains unavailable. The third United Kingdom Periprosthetic Joint Infection (UK PJI) Meeting was held in Glasgow on April 1, 2022, with more than 180 delegates in attendance, representing orthopaedics, microbiology, infectious diseases, plastic surgery, anesthetics, and allied health professions, including pharmacy and arthroplasty nurses. The meeting comprised a combined session for all delegates, and separate breakout sessions for arthroplasty and fracture-related infection. Consensus questions for each session were prepared in advance by the UK PJI working group, based upon topics that were proposed at previous UK PJI Meetings, and delegates participated in an anonymized electronic voting process. We present the findings of the combined and arthroplasty sessions of the meeting in this article, and each consensus topic is discussed in relation to the contemporary literature.

Mortality, patient-reported outcome measures, and the health economic burden of prosthetic joint infection

Prosthetic joint infection (PJI) is one of the most devastating complications for a patient following arthroplasty. This scoping review aims to evaluate the burden of PJI on individual patients and the healthcare system regarding the mortality rate, patient-reported quality of life, and healthcare resource utilisation. Patients with PJI have up to a five-fold higher mortality rate than those who have undergone an uninfected primary arthroplasty. There is an increased use of ambulatory aids and reduced joint function scores in patients with PJI. Global quality of life is poorer, specifically measured by the EQ-5D. Direct hospitalisation costs are two- to five-fold higher, attributed to surgery and prostheses, antibiotics, and a prolonged inpatient stay. There is an immense clinical and health economic burden secondary to PJI worldwide. This is expected to rise exponentially due to the increasing number of primary procedures and an ageing population with comorbidities Improving preventative and treatment strategies is imperative for patients and the healthcare system.

The Impact of Antimicrobial Therapy Duration in the Treatment of Prosthetic Joint Infections Depending on Surgical Strategies: A Systematic Review and Meta-analysis

The aim of this systematic review was to address the question if short antibiotic treatment (SAT; at least 4 but <12 weeks) versus long antibiotic treatment (LAT) affects outcomes in prosthetic joint infections (PJIs). Database research (Medline, Embase, Web of Science, Scopus, Cochrane) retrieved 3740 articles, of which 10 studies were included in the analysis. Compared to LAT, 11% lower odds of treatment failure in the SAT group were found, although the difference was not statistically significant (pooled odds ratio, 0.89 [95% confidence interval, .53-1.50]). No difference in treatment failure was found between SAT and LAT once stratified by type of surgery, studies conducted in the United States versus Europe, study design, and follow-up. There is still no conclusive evidence that antibiotic treatment of PJIs for 12 weeks or longer is associated with better outcomes, irrespective of the type of surgical procedure. Most recent, high-quality studies tend to favor longer antibiotic courses, making them preferable in most situations.

Microbial Persistence, Replacement and Local Antimicrobial Therapy in Recurrent Bone and Joint Infection

We report microbiological results from a cohort of recurrent bone and joint infection to define the contributions of microbial persistence or replacement. We also investigated for any association between local antibiotic treatment and emerging antimicrobial resistance. Microbiological cultures and antibiotic treatments were reviewed for 125 individuals with recurrent infection (prosthetic joint infection, fracture-related infection, and osteomyelitis) at two UK centres between 2007 and 2021. At re-operation, 48/125 (38.4%) individuals had an organism from the same bacterial species as at their initial operation for infection. In 49/125 (39.2%), only new species were isolated in culture. In 28/125 (22.4%), re-operative cultures were negative. The most commonly persistent species were Staphylococcus aureus (46.3%), coagulase-negative Staphylococci (50.0%), and Pseudomonas aeruginosa (50.0%). Gentamicin non-susceptible organisms were common, identified at index procedure in 51/125 (40.8%) and at re-operation in 40/125 (32%). Gentamicin non-susceptibility at re-operation was not associated with previous local aminoglycoside treatment (21/71 (29.8%) vs. 19/54 (35.2%); p = 0.6). Emergence of new aminoglycoside resistance at recurrence was uncommon and did not differ significantly between those with and without local aminoglycoside treatment (3/71 (4.2%) vs. 4/54 (7.4%); p = 0.7). Culture-based diagnostics identified microbial persistence and replacement at similar rates in patients who re-presented with infection. Treatment for orthopaedic infection with local antibiotics was not associated with the emergence of specific antimicrobial resistance.

Pre-Referral Microbiology in Long Bone Infection: What Can It Tell Us?

Background: It remains unclear how accurately patients’ previous microbiology correlates with that ascertained from deep sampling in long bone infection. This study assessed the quality of microbiology referral information and compared it to the gold standard of intra-operative deep tissue sampling. Methods: All patients referred to a single specialist centre within the UK between January 2019 and March 2020 who received surgery for long bone infection were eligible for inclusion. Data on microbiological testing that was performed prior to referral was collected prospectively at the time of clinic appointment and prior to surgery. Pre-referral microbiology was compared to microbiology from deep tissue samples taken during surgery. Results: 141 patients met the diagnostic criteria for long bone infection and were included for analysis. Of these, 72 patients had microbiological information available at referral from 88 samples, obtained from either sinus swab (n = 40), previous surgical sampling (n = 25), biopsy (n = 19) or blood cultures (n = 4). In 65.9% of samples, pre-referral microbiology was deemed to be a non-match when compared to intra-operative samples. Factors that increased risk of a non-match included presence of a sinus (odd’s ratio (OR) 11.3 [95% CI 2.84−56.6], p = 0.001), increased duration of time from sampling (OR 2.29, [95% CI 1.23−5.90], p = 0.030) and results from prior surgical sampling (OR 23.0 [95% CI 2.80−525.6], p = 0.011). Furthermore, previous surgical debridement gave an increased risk of multi-, extensively or pan-resistant isolates cultured from intra-operative sampling (OR 3.6 [95% CI 1.5−8.7], p < 0.01). Conclusions: We have demonstrated that presence of a sinus, a long time from the sample being taken and results from prior surgical sampling are more likely to give inaccurate representation of current microbiology. Importantly, in cases with previous debridement surgery, there was an increased risk of multi drug resistant isolates which should be planned for in future treatments.