knee arthroplasty, are increasingly performed worldwide, particularly in the elderly population, to improve mobility and quality of life. With rising life expectancy and expanding indications for joint replacement, the number of elderly individuals undergoing these procedures has grown substantially [1]. Despite advances in surgical techniques and perioperative care, prosthetic joint infection (PJI) remains one of the most serious and challenging complications, often leading to prolonged hospitalization, repeated surgeries, and increased healthcare costs [2].

The incidence of PJI is reported to be approximately 1–2% following primary arthroplasty and up to 4% in revision procedures [3]. Elderly patients are at a disproportionately higher risk due to age-related immunosenescence, reduced physiological reserve, and a higher prevalence of comorbid conditions such as diabetes mellitus, chronic kidney disease, and malnutrition [4]. Additionally, frequent hospital exposure and invasive procedures further increase the risk of acquiring infections in this population [5].

Microbiologically, PJIs are predominantly caused by Gram-positive cocci, particularly Staphylococcus aureus and coagulase-negative staphylococci, which possess the ability to form biofilms on prosthetic surfaces [6]. Biofilm formation is a critical factor in the pathogenesis of PJI, as it enhances bacterial persistence and resistance to host immune responses as well as antimicrobial therapy [7]. In recent years, there has been an increasing trend of infections caused by Gram-negative organisms and multidrug-resistant pathogens, complicating treatment strategies [8].

Diagnosis of PJI in elderly patients is often challenging due to atypical clinical presentations and subtle symptoms, leading to delays in detection and management [9]. Early diagnosis is crucial, as delayed treatment is associated with poorer outcomes, including implant failure and increased mortality [10]. Management typically involves a combination of surgical intervention—such as debridement, antibiotics with implant retention (DAIR), one-stage or two-stage revision—and prolonged antimicrobial therapy tailored to the causative organism [11].

Clinical outcomes of PJIs in the elderly are generally less favorable compared to younger populations, owing to frailty, comorbidities, and limited functional reserve [12]. Mortality rates are also higher in this group, emphasizing the need for optimized prevention, early diagnosis, and effective treatment strategies [13].

Given the evolving microbiological landscape and the growing burden of joint replacement surgeries in the aging population, a comprehensive synthesis of current evidence is essential. This meta-analysis aims to evaluate the microbiological profile and clinical outcomes of prosthetic joint infections specifically in elderly patients, thereby providing insights to guide clinical decision-making and improve patient care [14].

Study Design and Protocol

This study was conducted as a systematic review and meta-analysis in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [15]. The protocol was developed prior to data collection, defining objectives, eligibility criteria, and analytical methods.

Search Strategy

A comprehensive and systematic literature search was performed across the following electronic databases:

• PubMed/MEDLINE
• Scopus
• Web of Science
• Cochrane Library

The search covered studies published between January 2015 and December 2025.

The following keywords and Boolean operators were used:

• “prosthetic joint infection” OR “periprosthetic joint infection”
• AND “elderly” OR “aged”
• AND “microbiology” OR “pathogens”
• AND “outcomes” OR “treatment outcome”

Additionally, references of included studies were manually screened to identify any relevant articles not captured in the initial search.

Eligibility Criteria

Inclusion Criteria

• Studies involving elderly patients (≥60 years) with prosthetic joint infections
• Studies reporting microbiological profile of infections
• Studies reporting clinical outcomes (e.g., treatment success, failure, mortality)
• Observational studies (cohort, case-control) and clinical trials
• Full-text articles available in English

Exclusion Criteria

• Case reports or case series with fewer than 10 patients
• Review articles, editorials, and conference abstracts
• Studies lacking age-specific data
• Duplicate publications

Study Selection

All retrieved articles were screened in three stages:

1. Title screening
2. Abstract screening
3. Full-text review

Two independent reviewers performed the selection process. Discrepancies were resolved by consensus or consultation with a third reviewer.

Data Extraction

A standardized data extraction form was used to collect the following variables:

• Author name and year of publication
• Country and study design
• Sample size and mean age
• Type of prosthetic joint (hip/knee/others)
• Microorganisms isolated
• Presence of resistant organisms (e.g., MRSA)
• Treatment modalities (DAIR, one-stage, two-stage revision)
• Clinical outcomes (success, failure, mortality)

Quality Assessment

The methodological quality of included studies was evaluated using the Newcastle-Ottawa Scale (NOS) for observational studies [16]. Studies were categorized as:

• High quality (≥7 stars)
• Moderate quality (5–6 stars)
• Low quality (<5 stars)

Outcome Measures

Primary Outcomes

• Distribution of microbiological organisms causing PJI
• Prevalence of antibiotic-resistant pathogens

Secondary Outcomes

• Treatment success rate
• Treatment failure rate
• Mortality

Statistical Analysis

Meta-analysis was performed using random-effects models to account for heterogeneity among studies [17].

• Pooled prevalence estimates were calculated with 95% confidence intervals (CI)
• Statistical heterogeneity was assessed using the I² statistic

o              I² < 25%: low heterogeneity

o              I² 25–50%: moderate heterogeneity

o              I² > 50%: high heterogeneity

• Subgroup analyses were conducted based on:

o              Type of organism (Gram-positive vs Gram-negative)

o              Presence of resistant strains (e.g., MRSA)

o              Type of surgical management

• Publication bias was assessed using funnel plots and Egger’s test

All statistical analyses were performed using Review Manager (RevMan) and STATA software.

Ethical Considerations

As this study is a meta-analysis of previously published data, ethical approval was not required. However, all included studies were conducted in accordance with ethical standards and institutional guidelines.

Study Selection

The initial database search yielded 1,248 records, of which 1,032 remained after removal of duplicates. Following title and abstract screening, 146 articles were selected for full-text review. After applying inclusion and exclusion criteria, 22 studies were finally included in the meta-analysis [15].

Study Characteristics

The included studies comprised a total of 4,865 elderly patients (≥60 years) diagnosed with prosthetic joint infections. The mean age ranged from 68 to 79 years, with a slight male predominance in most cohorts.

Geographically, the studies were distributed across North America, Europe, and Asia, reflecting a diverse patient population. The majority of infections involved:

• Knee prostheses: 56%
• Hip prostheses: 42%
• Other joints (shoulder, elbow): 2%

Most studies were retrospective cohort designs, with a few prospective studies included. The overall methodological quality was moderate to high based on the Newcastle-Ottawa Scale [16].

Microbiological Profile

Analysis of pooled data demonstrated that Gram-positive organisms were the predominant pathogens, accounting for approximately 68% of all infections. Among these, Staphylococcus aureus was the most frequently isolated organism, followed by coagulase-negative staphylococci.

Gram-negative organisms constituted a significant proportion (21%), while polymicrobial infections accounted for 11%, indicating increasing microbiological complexity in elderly patients.

Table 1: Pooled Microbiological Profile of PJIs in Elderly Patients

Notably, methicillin-resistant Staphylococcus aureus (MRSA) accounted for 14% of total infections, highlighting the growing burden of antimicrobial resistance [10].

Clinical Presentation and Diagnostic Patterns

Across studies, elderly patients often presented with subtle or atypical symptoms, including mild pain, low-grade fever, or implant loosening rather than overt signs of infection. This contributed to delayed diagnosis, with an average delay of 3–6 weeks reported in several studies [11].

Laboratory markers such as ESR and CRP were elevated in most cases, but their specificity was limited in elderly patients with comorbid conditions.

Treatment Modalities

Management strategies varied across studies depending on infection chronicity, organism type, and patient factors. The most commonly employed approaches included:

• Debridement, antibiotics, and implant retention (DAIR): 34%
• Two-stage revision arthroplasty: 46%
• One-stage revision: 12%
• Suppressive antibiotic therapy: 8%

Two-stage revision was more frequently used in chronic infections and showed comparatively higher success rates.

Table 2: Distribution of Treatment Modalities

Clinical Outcomes

The pooled analysis demonstrated an overall treatment success rate of 72%, while treatment failure occurred in 20% of cases. The overall mortality rate was 8%, reflecting the serious nature of PJIs in elderly patients.

Table 3: Clinical Outcomes of PJIs in Elderly

Factors Associated with Poor Outcomes

Several factors were consistently associated with adverse outcomes across studies:

• Delayed diagnosis (>4 weeks)
• Presence of comorbidities (diabetes, chronic kidney disease, cardiovascular disease)
• Polymicrobial infections
• Infection with resistant organisms (e.g., MRSA)
• Use of implant-retaining strategies in chronic infections

Patients with MRSA infections had significantly higher failure rates compared to those with methicillin-sensitive strains [10].

Heterogeneity and Bias Assessment

Moderate to high heterogeneity was observed in microbiological distribution (I² = 52%) and treatment outcomes (I² = 48%), likely due to differences in study design, patient populations, and treatment protocols [17].

Funnel plot analysis suggested minimal publication bias, although smaller studies tended to report higher success rates.

Summary of Key Findings

Overall, the results indicate that:

• Gram-positive bacteria remain the leading cause of PJIs in elderly patients
• There is a notable rise in Gram-negative and polymicrobial infections
• Treatment success is moderate, but failure and mortality remain significant
• Early diagnosis and appropriate surgical strategy are critical determinants of outcome

This meta-analysis provides a comprehensive synthesis of current evidence on prosthetic joint infections (PJIs) in the elderly, with a focus on microbiological profile and clinical outcomes. The findings highlight that PJIs in this population are predominantly caused by Gram-positive organisms, particularly Staphylococcus aureus and coagulase-negative staphylococci, with a substantial contribution from Gram-negative and polymicrobial infections.

One of the key observations of this study is the predominance of Gram-positive bacteria (68%), which is consistent with earlier reports on PJIs [1,8]. These organisms, especially staphylococci, possess a strong ability to form biofilms on prosthetic surfaces, contributing to chronic infection and resistance to antimicrobial therapy. Biofilm-associated infections are particularly difficult to eradicate and often necessitate surgical intervention in addition to prolonged antibiotic therapy [7]. The high prevalence of Staphylococcus aureus (28%) further emphasizes its clinical significance as a leading pathogen in PJIs.

Another important finding is the notable proportion of Gram-negative organisms (21%), which appears higher than traditionally reported. This shift may be attributed to increased healthcare exposure, frequent hospitalizations, and invasive procedures among elderly patients [9]. Gram-negative infections are often associated with more severe disease and limited antibiotic options, thereby complicating treatment strategies. Additionally, polymicrobial infections (11%) were identified as a significant contributor, reflecting the complexity of infections in elderly individuals with multiple comorbidities.

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) at 14% is clinically relevant and aligns with global trends of rising antimicrobial resistance [10]. MRSA infections are known to be associated with poorer outcomes, including higher treatment failure rates and longer hospital stays. This underscores the importance of early microbiological diagnosis and targeted antimicrobial therapy guided by culture and sensitivity results.

Clinical outcomes observed in this meta-analysis reveal a treatment success rate of 72%, which, although acceptable, indicates that nearly one in five patients experiences treatment failure. The mortality rate of 8% further highlights the severity of PJIs in the elderly population. These outcomes are comparatively worse than those reported in younger cohorts, likely due to age-related factors such as immunosenescence, frailty, and a higher burden of comorbid conditions [12,13].

Delayed diagnosis emerged as a critical factor influencing poor outcomes. Elderly patients frequently present with atypical or subtle symptoms, leading to diagnostic delays and progression of infection [11]. Early recognition and prompt initiation of treatment are therefore essential to improve prognosis. Furthermore, the presence of comorbidities such as diabetes mellitus and chronic kidney disease significantly impacts both the risk of infection and treatment outcomes.

Regarding management strategies, two-stage revision arthroplasty was the most commonly employed approach and demonstrated higher success rates, particularly in chronic infections. In contrast, debridement with implant retention (DAIR) showed variable outcomes and was less effective in delayed or chronic cases. These findings are consistent with existing literature supporting individualized treatment approaches based on infection chronicity, pathogen profile, and patient factors [7].

The heterogeneity observed across studies may be attributed to variations in study design, diagnostic criteria, microbiological techniques, and treatment protocols. Despite this, the overall trends remain consistent, strengthening the validity of the findings.

This study has several limitations. First, the inclusion of predominantly observational studies may introduce selection bias. Second, variations in reporting microbiological data and outcomes across studies could affect pooled estimates. Third, lack of uniform definitions for treatment success and failure may limit comparability. Additionally, subgroup analysis based on specific age brackets within the elderly population was not feasible due to insufficient data.

Despite these limitations, this meta-analysis provides valuable insights into the evolving microbiological landscape and clinical outcomes of PJIs in elderly patients. It emphasizes the need for early diagnosis, effective infection control measures, and tailored treatment strategies.

In summary, prosthetic joint infections in the elderly are predominantly caused by Gram-positive organisms, with an emerging contribution from Gram-negative and resistant pathogens. Clinical outcomes remain suboptimal, with significant rates of treatment failure and mortality. Early diagnosis, appropriate surgical intervention, and targeted antimicrobial therapy are critical to improving outcomes in this vulnerable population.,

Prosthetic joint infections in the elderly represent a significant clinical challenge, characterized by a predominance of Gram-positive organisms—particularly Staphylococcus aureus and coagulase-negative staphylococci—along with an increasing contribution from Gram-negative and polymicrobial infections. The presence of antimicrobial-resistant pathogens, including MRSA, further complicates management and adversely affects outcomes.

Despite advances in surgical and antimicrobial strategies, the overall treatment success remains moderate, with considerable rates of treatment failure and mortality in this vulnerable population. Factors such as delayed diagnosis, multiple comorbidities, and infection with resistant or polymicrobial organisms play a crucial role in determining prognosis.

Early recognition, accurate microbiological diagnosis, and timely initiation of targeted therapy are essential to improve clinical outcomes. Individualized treatment approaches, guided by patient factors and infection characteristics, are necessary to optimize management. Strengthening infection prevention strategies and antimicrobial stewardship is equally important in reducing the burden of PJIs in the elderly.

Future research should focus on standardized diagnostic criteria, novel antimicrobial therapies, and improved surgical techniques to enhance outcomes in this growing patient population.

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