The challenge of Propionibacterium acnes and revision shoulder arthroplasty: a review of current diagnostic options

Increased biofilm formation in dual-strain compared to single-strain communities of Cutibacterium acnes

Cutibacterium acnes is a known opportunistic pathogen in orthopedic implant-associated infections (OIAIs). The species of C. acnes comprises distinct phylotypes. Previous studies suggested that C. acnes can cause single- as well as multi-typic infections, i.e. infections caused by multiple strains of different phylotypes. However, it is not known if different C. acnes phylotypes are organized in a complex biofilm community, which could constitute a multicellular strategy to increase biofilm strength and persistency. Here, the interactions of two C. acnes strains belonging to phylotypes IB and II were determined in co-culture experiments. No adverse interactions between the strains were observed in liquid culture or on agar plates; instead, biofilm formation in both microtiter plates and on titanium discs was significantly increased when combining both strains. Fluorescence in situ hybridization showed that both strains co-occurred throughout the biofilm. Transcriptome analyses revealed strain-specific alterations of gene expression in biofilm-embedded cells compared to planktonic growth, in particular affecting genes involved in carbon and amino acid metabolism. Overall, our results provide first insights into the nature of dual-type biofilms of C. acnes, suggesting that strains belonging to different phylotypes can form biofilms together with additive effects. The findings might influence the perception of C. acnes OIAIs in terms of diagnosis and treatment.

Preventing and Treating Infection in Reverse Total Shoulder Arthroplasty

PURPOSE OF REVIEW

Periprosthetic infection after shoulder arthroplasty is relatively uncommon though associated with severe long-term morbidity when encountered. The purpose of the review is to summarize the recent literature regarding the definition, clinical evaluation, prevention, and management of prosthetic joint infection after reverse shoulder arthroplasty.

RECENT FINDINGS

The landmark report generated at the 2018 International Consensus Meeting on Musculoskeletal Infection has provided a framework for diagnosis, prevention, and management of periprosthetic infections after shoulder arthroplasty. Shoulder specific literature with validated interventions to reduce prosthetic joint infection is limited; however existing literature from retrospective studies and from total hip and knee arthroplasty allows us to make relative guidelines. One and two-stage revisions seem to demonstrate similar outcomes; however, no controlled comparative studies exist limiting the ability to make definitive recommendations between the two options. We report on recent literature regarding the current diagnostic, preventative, and treatment options for periprosthetic infection after shoulder arthroplasty. Much of the literature does not distinguish between anatomic and reverse shoulder arthroplasty, and further high-level shoulder specific studies are needed to answer questions generated from this review.

Prosthetic joint infections of the shoulder: A review of the recent literature

Introduction

Shoulder arthroplasty is a common treatment for shoulder arthritis. Prosthetic joint infection of the shoulder (PJIS) is a debilitating complication to the patient and the healthcare system. Incidence of infection is 0.98-5% for primary arthroplasty. The mean hospital cost for two-stage revision was approximately $35,824. The aim of this paper is to review the recent literature and collate the latest evidence to aid diagnosis and treatment of this serious complication.

Methods

A literature review was performed using PubMed and Google Scholar databases. A search strategy was adopted using the keywords: 'infection' AND 'shoulder arthroplasty' OR 'total shoulder arthroplasty'OR 'TSA' OR 'reverse shoulder arthroplasty' OR 'RSA' OR 'rTSA'. This initial search resulted in 349 articles. A PRISMA flowchart process was followed. Duplicates were removed, screening was performed and the resulting full texts were analysed and further excluded, leaving 46 articles suitable for inclusion. A PICO search strategy was also used.

Results and interpretation

Risk factors for PJIS include procedure type, trauma indications and patient factors.The organism commonly isolated is Cutebacterium acnes, which makes diagnosis challenging due to its indolent nature. Investigations include biochemical tests, synovial aspirate, tissue cultures and radiological examinations.Treatment depends on the depth of the infection and the patient requirements. Medical treatment with antibiotics to local debridement, cement spacer and revision arthroplasty have all been described in the literature. A multidisciplinary decision is made on the microbiological evidence and patient factors.

Conclusion

PJIS is a rare but potentially devastating complication of shoulder arthroplasty and diagnosis is often challenging. There has been much research performed recently, providing more evidence on how to optimise management.

Previous rotator cuff repair increases the risk of revision surgery for periprosthetic joint infection after reverse shoulder arthroplasty

BACKGROUND

Previous studies have indicated an increased risk of periprosthetic joint infection (PJI) in patients treated with reverse shoulder arthroplasty (RSA) compared with patients treated with anatomic total shoulder arthroplasty. The reason for this is unclear but may be related to a high prevalence of previous rotator cuff repair in patients who are treated with RSA. The purpose of this study was to determine previous non-arthroplasty surgery as a risk factor for revision owing to PJI after RSA for cuff tear arthropathy, massive irreparable rotator cuff tears, or osteoarthritis.

METHODS

Data were retrieved from the Danish Shoulder Arthroplasty Registry and medical records. We included 2217 patients who underwent RSA for cuff tear arthropathy, massive irreparable rotator cuff tears, or osteoarthritis between 2006 and 2019. PJI was defined as ≥3 of 5 tissue samples positive for the same bacteria or as definite or probable PJI evaluated based on criteria from the International Consensus Meeting. The Kaplan-Meier method was used to illustrate the unadjusted 14-year cumulative rates of revision. A Cox regression model was used to report hazard for revision owing to PJI. Results were adjusted for previous non-arthroplasty surgery, sex, diagnosis, and age.

RESULTS

Revision was performed in 88 shoulders (4.0%), of which 40 (1.8%) underwent revision owing to PJI. There were 272 patients (12.3%) who underwent previous rotator cuff repair, of whom 11 (4.0%) underwent revision owing to PJI. The 14-year cumulative rate of revision owing to PJI was 14.1% for patients with previous rotator cuff repair and 2.7% for patients without previous surgery. The adjusted hazard ratio for revision owing to PJI for patients with previous rotator cuff repair was 2.2 (95% confidence interval, 1.04-4.60) compared with patients without previous surgery.

CONCLUSION

There is an increased risk of revision owing to PJI after RSA for patients with previous rotator cuff repair. We recommend that patients with previous rotator cuff repair be regarded as high-risk patients when considering RSA.

Common bacteria and treatment options for the acute and chronic infection of the total ankle arthroplasty

BACKGROUND

There is little valid data available on managing infected total ankle arthroplasty (TAA).

METHODS

A single-center, retrospective evaluation from 20 patients with PJI (periprosthetic joint infection) of the ankle compared the bacteria isolated by preoperative arthrocentesis and intraoperative cultures to the pathogens of knee PJI. Long-term failure rates of irrigation and debridement (I&D) and polyethylene exchange, revision arthroplasty, and arthrodesis were analyzed.

RESULTS

The most common bacteria were Staphylococcus aureus and Coagulase-negative staphylococci. There was no significant difference when comparing the causing pathogens of PJI of the ankle with the knee. After a follow-up of 50,4 months, the long-term failure rate after I&D and polyethylene exchange was 40%, and of revision was 9%.

CONCLUSIONS

We concluded that the pathogenesis of PJI of the ankle and knee seems to be comparable. Regarding treatment options, we found that standardized techniques for PJIs of the knee have their limitations regarding infected TAA.

The lexicon for periprosthetic bone loss versus osteolysis after cervical disc arthroplasty: a systematic review

BACKGROUND

Periprosthetic bone loss is a common observation following arthroplasty. Recognizing and understanding the nature of bone loss is vital as it determines the subsequent performance of the device and the overall outcome. Despite its significance, the term "bone loss" is often misused to describe inflammatory osteolysis, a complication with vastly different clinical outcomes and treatment plans. Therefore, the goal of this review was to report major findings related to vertebral radiographic bone changes around cervical disc replacements, mitigate discrepancies in clinical reports by introducing uniform terminology to the field, and establish a precedence that can be used to identify the important nuances between these distinct complications.

METHODS

A systematic review of the literature was conducted following PRISMA guidelines, using the keywords "cervical," "disc replacement," "osteolysis," "bone loss," "radiograph," and "complications." A total of 23 articles met the inclusion criteria with the majority being retrospective or case reports.

RESULTS

Fourteen studies reported periprosthetic osteolysis in a total of 46 patients with onset ranging from 15-96 months after the index procedure. Reported causes included: metal hypersensitivity, infection, mechanical failure, and wear debris. Osteolysis was generally progressive and led to reoperation. Nine articles reported non-inflammatory bone loss in 527 patients (52.5%), typically within 3-6 months following implantation. The reported causes included: micromotion, stress shielding, and interrupted blood supply. With one exception, bone loss was reported to be non-progressive and had no effect on clinical outcome measures.

CONCLUSIONS

Non-progressive, early onset bone loss is a common finding after CDA and typically does not affect the reported short-term pain scores or lead to early revision. By contrast, osteolysis was less common, presenting more than a year post-operative and often accompanied by additional complications, leading to revision surgery. A greater understanding of the clinical significance is limited by the lack of long-term studies, inconsistent terminology, and infrequent use of histology and explant analyses. Uniform reporting and adoption of consistent terminology can mitigate some of these limitations. Executing these actionable items is critical to assess device performance and the risk of revision.

LEVEL OF EVIDENCE IV

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Indolent Infection After Lumbar Interbody Fusion: An Under-recognized Cause of Pseudarthrosis, Which Can Be Successfully Treated With Anterior Revision Fusion

Introduction:

Methods:

Results:

Discussion:

Responsiveness of routine diagnostic tests for vertebral osteomyelitis may be influenced by the infecting organism

BACKGROUND CONTEXT

Vertebral osteomyelitis (VO) becomes increasingly more prevalent as people age, and it is a condition seen frequently by referral center spine surgeons. It can take as long as 6 months for a proper diagnosis to be made. Staphylococcus aureus (S. aureus) is the most common isolated organism in up to 80% of the affected population. The clinical presentation of vertebral osteomyelitis is typically non specific (back pain), which can make timely diagnosis challenging. Fever is often absent. Serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), white blood cell count (WBC) and serum polymorphonuclear leukocyte percentage (PMN%) are traditionally used as first-line tests because of their perceived sensitivity to help diagnose vertebral osteomyelitis. It is not known whether these test values are affected by the infecting organism.

PURPOSE

To determine whether individual first-line diagnostics differed based on infecting organism and whether certain organisms are associated with lower lab values. Additionally, this study sought to determine if VO caused by lower virulent (eg, culture-negative and nonpyogenic organisms) could contribute to delays in treatment due to lack of elevated biomarkers.

STUDY DESIGN/SETTING

Single-center retrospective cohort study.

PATIENT SAMPLE

We reviewed clinical data of 133 patients (60% male) diagnosed with VO from 2015-2019 in a US Midwest academic hospital.

OUTCOMES MEASURES

Primary outcome measures included the maximum temperature upon presentation, serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), white blood cell count (WBC), and percentage neutrophils during the hospital admission.

METHODS

Inclusion criteria were adult patients diagnosed with vertebral osteomyelitis who underwent blood culture and/or biopsy prior to treatment. All patients enrolled in the study were diagnosed with VO and confirmed via magnetic resonance imaging (MRI). MRI findings associated with VO included destruction of endplates, increased signal in vertebral bodies, and the surrounding disc on T2-weighted imaging were confirmed. The patients had laboratory work up and clinical follow up regardless of positive culture or negative culture. The mean peak inflammatory marker levels were compared among organisms with student's t test. Demographics, comorbidities, and CCI were collected and multivariable logistic regression models were used. Receiver operating characteristic curve analysis was performed to delineate separate, optimal cut offs for CRP, ESR, WBC, and PMN% for patients with culture positive osteomyelitis RESULTS: Patients' average age was 57.0±13.7 years with a mean BMI of 30.5±9.70 kg/m², and a mean Charleston Comorbidity Index (CCI) of 3.17±2.35. Staphylococcus aureus and antibiotic resistant organisms (MRSA and VRE) demonstrated a higher mean CRP and ESR than culture negative, fungal and TB cases. Staphylococcus aureus, antibiotic resistant organisms, and coagulase negative Staphylococcus demonstrated a higher mean WBC than culture negative as well as fungal and TB cases. Staphylococcus aureus, antibiotic resistant organisms, coagulase negative Staphylococcus, and Streptococcus species had a higher mean peak PMN%, than culture negative as well as fungal and TB case. Temperature did not correlate with a diagnosis of osteomyelitis.

CONCLUSIONS

Serum laboratory markers in the diagnosis of VO appear to be influenced by the infecting organism type. Laboratory values in patients diagnosed with VO with culture negative or non-pyogenic organisms are lower compared to antibiotic resistant and S. aureus organisms. Fever did not correlate with a diagnosis of VO.

Development of a 3D Bioartificial Shoulder Joint Implant Mimetic of Periprosthetic Joint Infection

Post-surgical infections of the shoulder joint involving Cutibacterium acnes are difficult to diagnose and manage. Despite the devastating clinical complications and costly healthcare burden of joint infections, the scarcity of joint infection models was identified as an unmet need by the 2019 International Consensus on Orthopedic Infections. In this study, we have developed a novel 3D shoulder joint implant mimetic (S-JIM) that includes a surgical metal surface and supports a co-culture of C. acnes and patient-derived shoulder capsule fibroblasts. Our findings indicate the S-JIM can generate a near anaerobic interior environment that allows for C. acnes proliferation and elicit fibroblast cell lysis responses that are consistent with clinical reports of tissue necrosis. Using the S-JIM, we provided proof-of-concept for the use of mass spectrometry in real-time detection of C. acnes joint infections during surgery. The S-JIM is the first in vitro cell culture-based biomimetic of periprosthetic joint infection that provides a preclinical method for the rapid and reliable testing of novel anti-PJI interventions.

What is the clinical impact of positive cultures at the time of primary total shoulder arthroplasty?

BACKGROUND

Cultures taken at the time of primary shoulder arthroplasty are commonly positive for Cutibacterium acnes. Despite our limited understanding of the clinical implication of deep tissue inoculation from dermal colonization, significant efforts have been made to decolonize the shoulder prior to surgery. The purpose of this study is to determine differences in clinical outcomes based on culture positivity at the time of primary shoulder arthroplasty.

METHODS

A series of 134 patients who underwent primary anatomic or reverse total shoulder arthroplasty and had intraoperative cultures obtained via a standard protocol were included. In each case, 5 tissue samples were collected and processed in a single laboratory for culture on aerobic and anaerobic media for 13 days. Minimum 2-year functional outcomes scores (American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form [ASES] and Single Assessment Numeric Evaluation [SANE]) and reoperation data were analyzed.

RESULTS

Forty-two (31.3%) patients had positive cultures (30 C acnes and 21 with at least 2 positive cultures) at the time of surgery. There was no statistically significant difference in postoperative functional outcome scores (ASES: 82.5 vs. 81.9; P = .89, SANE: 79.5 vs. 82.1; P = .54) between culture-positive and culture-negative cohorts. There were no cases of infection. Two patients (4.8%; 2/42) with positive cultures required reoperation compared with 4 patients (5.6%; 4/71) without positive cultures.

CONCLUSION

The apparent colonization by nonvirulent organisms in patients undergoing primary shoulder arthroplasty does not appear to have a clinically significant effect on functional outcomes or need for repeat surgery in the short term.

Does the retention of osseointegrated prosthetic implants during the surgical management of chronic infections following reverse total shoulder arthroplasty (RTSA) influence functional outcomes without impacting the efficacy of the infection treatment?

INTRODUCTION

The gold standard (GS) for treating chronic infections following reverse total shoulder arthroplasty (RTSA) is a complete exchange of the prosthesis carried out in one or two stages. This surgical procedure, which may damage the bone stock, can result in poor functional outcomes due to intraoperative complications. The purpose of this study was to compare the GS to a surgical technique that retained osseointegrated implants: the partial one-stage exchange.

HYPOTHESIS

Partial one-stage exchange was effective in treating chronic infections after RTSA (no recurrent infection) and resulted in better functional outcomes than the GS.

MATERIALS AND METHODS

This retrospective single-center study included 18 patients with chronic infection after a primary RTSA. Two treatments were compared in a non-randomized fashion. The first included 11 patients who underwent a partial one-stage exchange with implant retention in case of macroscopic osseointegration. The second included seven patients who were treated with the GS: six patients with a complete one-stage exchange and one patient with a two-stage surgical approach. The absence of recurrent infection and functional outcomes were assessed after a minimum of two years.

RESULTS

There were no statistically significant differences in treatment efficacy between the two strategies: 91% vs. 100%, respectively. The partial one-stage exchange resulted in a significantly improved shoulder function compared to the GS with postoperative Constant scores of 55±14.58 vs. 44±14.45, respectively (p=.03). In the partial one-stage exchange group, there was a significantly improved shoulder function with a preoperative Constant score of 40 [28-55]±9.04 preoperatively vs. 55 [25-75]±14.58 postoperatively (p=.01). The GS treatment did not significantly improve the postoperative function (p=.09).

DISCUSSION

Partial one-stage exchange does not compromise treatment efficacy of chronic infections after RTSA. This technique resulted in better shoulder function than a conventional GS-type management. A study with greater statistical power is required.

LEVEL OF EVIDENCE

III; clinical series, retrospective, single-center.

A Janus-Faced Bacterium: Host-Beneficial and -Detrimental Roles of Cutibacterium acnes

The bacterial species Cutibacterium acnes (formerly known as Propionibacterium acnes) is tightly associated with humans. It is the dominant bacterium in sebaceous regions of the human skin, where it preferentially colonizes the pilosebaceous unit. Multiple strains of C. acnes that belong to phylogenetically distinct types can co-exist. In this review we summarize and discuss the current knowledge of C. acnes regarding bacterial properties and traits that allow host colonization and play major roles in host-bacterium interactions and also regarding the host responses that C. acnes can trigger. These responses can have beneficial or detrimental consequences for the host. In the first part of the review, we highlight and critically review disease associations of C. acnes, in particular acne vulgaris, implant-associated infections and native infections. Here, we also analyse the current evidence for a direct or indirect role of a C. acnes-related dysbiosis in disease development or progression, i.e., reduced C. acnes strain diversity and/or the predominance of a certain phylotype. In the second part of the review, we highlight historical and recent findings demonstrating beneficial aspects of colonization by C. acnes such as colonization resistance, immune system interactions, and oxidant protection, and discuss the molecular mechanisms behind these effects. This new insight led to efforts in skin microbiota manipulation, such as the use of C. acnes strains as probiotic options to treat skin disorders.

Recognizing Cutibacterium acnes as a cause of infectious pericarditis: A case report and review of literature

Cutibacterium acnes is an anaerobic bacterium commonly thought of as a culture contaminant rather than a pathogen. We present a case of Cutibacterium acnes pericarditis in a 22-year-old immunocompetent woman managed with surgical pericardial window and a 4-week course of penicillin G and review related literature on Cutibacterium acnes pericarditis.

Is postoperative glucose variability associated with adverse outcomes following shoulder arthroplasty?

BACKGROUND

Postoperative infection after shoulder arthroplasty is a devastating complication. Multiple patient risk factors have been associated with postoperative infection, including increased body mass index and diabetes. Although the association between preoperative glucose control and infection has been established, little is known about the effect of perioperative glycemic control on outcomes following shoulder arthroplasty. The purpose of this study was to investigate the association between postoperative glycemic variability and short-term complications after total shoulder arthroplasty (TSA) and reverse total shoulder arthroplasty (RTSA).

METHODS

A retrospective study was performed at a large, single-specialty center from January 2015 to December 2018. Patients were included if they underwent primary TSA or RTSA with a minimum of 90 days' follow-up and had a minimum of 1 serum glucose value obtained per day of the hospital stay or had ≥3 measurements obtained during the hospital admission period. The primary outcome variable was postoperative infection per accepted definitions of surgical-site infection or periprosthetic joint infection. Secondary outcome variables included stiffness, periprosthetic fracture, periprosthetic dislocation, and reoperation.

RESULTS

In total, 1074 TSAs or RTSAs (in 1032 patients) met the eligibility criteria. The mean patient age was 69.9 ± 8.4 years, and 40.3% of patients had a preoperative diagnosis of diabetes mellitus. Of the patients, 670 (62%) had a calculable coefficient of variation. A younger patient age (median, 65 years [interquartile range (IQR), 13.5 years] vs. 71 years [IQR, 11.0 years]; P = .02) and a preoperative diagnosis of diabetes mellitus (P = .01) showed statistically significant associations with postoperative infection. The first in-hospital glucose measurement beyond the reference tertile of 70-140 mg/dL showed a statistically significant association with postoperative infection, with a median of 128.0 mg/dL (IQR, 43 mg/dL) vs. 167.5 mg/dL (IQR, 37.0 mg/dL; P = .01), whereas the second and third glucose measurements showed no association with postoperative infection. We found no associations between the coefficient of variation and reoperations or complications including surgical-site infection, periprosthetic joint infection, death, postoperative infection, periprosthetic fracture, or stiffness.

CONCLUSION

We found an association between a preoperative diagnosis of diabetes mellitus and postoperative infection following shoulder arthroplasty. We also found that an elevated first glucose measurement is associated with the development of postoperative infection. In-hospital glycemic control, as well as preoperative glycemic control and optimization, may be beneficial for reducing postoperative infections following shoulder arthroplasty.

The incidence and incubation period of false-positive culture results in shoulder surgery

BACKGROUND

Postoperative shoulder infection is a significant complication requiring timely identification and treatment. Indolent infections such as those involving Cutibacterium acnes (formerly Propionibacterium acnes) provide a diagnostic dilemma as they present differently, without the acute symptoms associated with most postoperative bone and joint infections. Furthermore, Cacnes is thought to be a common contaminant isolated from intraoperative cultures. With no consensus algorithm, long-held cultures play a major role in guiding management decisions in potential postoperative shoulder infection. Our study sought to determine the incidence of positive culture results in both open and arthroscopic procedures in noninfected patients, as well as to clarify whether an increase in the incubation time frame leads to an increased rate of culture growth.

METHODS

One hundred patients were prospectively enrolled into either the open or arthroscopic procedure group. Patients with abnormal inflammatory laboratory findings, a history of shoulder surgery, or corticosteroid injection within 6 months of surgery were excluded from the study. Three cultures were obtained for each patient: superficial tissue culture, tissue culture, and "sterile" control swab. Cultures were held for 28 days and checked at regular intervals. All patients were followed up clinically for 6 months to ensure no signs of postoperative infection occurred.

RESULTS

Ultimately, 95 patients were included in the final analysis. The false-positive rate was 17.0% in those who underwent open shoulder surgery and 10.4% in those who underwent arthroscopic shoulder surgery. The incidence of positive Cacnes culture results was 6.4% in the open group, whereas Cacnes was not isolated in the arthroscopic group. All positive bacterial culture results were reported within 7 days of collection. One culture result was positive for mold at 26 days.

CONCLUSION

A relatively high false-positive culture rate occurred in both open and arthroscopic shoulder surgery. Cacnes was the most commonly identified bacterium in cultures in the open surgery group. Knowledge of one's institutional false-positive culture rate could be important in avoiding potentially inappropriate treatment. Additionally, we found that holding cultures longer than 14 days did not lead to an increased rate of false-positive culture results.

The management of infected shoulder arthroplasty by two-stage revision

BACKGROUND

There remains no gold standard management for deep shoulder periprosthetic joint infection (PJI). This case series aims to present our experience of two-stage revision arthroplasty, including eradication of infection and reoperation rates.

METHODS

We retrospectively reviewed patients undergoing revision arthroplasty for shoulder PJI between 2006 and 2015. Cases were confirmed using Musculoskeletal Infection Society (MSIS) and American Academy of Orthopaedic Surgeons (AAOS) guidelines. TSA removal, debridement and irrigation preceded antibiotic-loaded cement spacer insertion and a minimum of six weeks intravenous antibiotics. Reimplantation was performed as a second stage following a negative aspirate.

RESULTS

Twenty-eight patients underwent a first stage procedure (mean age 69 years; 16 male, 12 female). Propionibacterium acnes, Methicillin-sensitive Staphylococcus aureus, Coagulase-negative Staphylococcus and Staphylococcus epidermidis were the commonest microorganisms cultured. Five cases had mixed growths and six cases provided no growth. Three patients did not proceed to a second stage. Twenty-five patients underwent reimplantation (mean interval 6.7 months), with 80% remaining infection-free (mean follow-up 38.3 months).

DISCUSSION

Managing complex and late presentation shoulder PJI with two-stage revision is associated with high rates of infection eradication (80%). In the absence of a management consensus, our experience supports two-stage revision arthroplasty for eradicating infection in this complex patient group.

Periprosthetic Infection After Reverse Shoulder Arthroplasty: a Review

PURPOSE OF REVIEW

Periprosthetic infection is a relatively rare but potentially devastating complication after shoulder arthroplasty. The purpose of this article is to review the incidence, diagnosis, prevention, and management of periprosthetic infections after reverse shoulder arthroplasty, with a focus on literature published within the last 5 years.

RECENT FINDINGS

The 2018 International Consensus Meeting on Musculoskeletal Infection provides us with a framework for the diagnosis and management of periprosthetic infections after shoulder arthroplasty. Reverse shoulder arthroplasty has a higher reported rate of infection compared with anatomic total shoulder arthroplasty. Our current diagnostic tests do not appear to be as sensitive when compared with the hip and knee literature. Similar success has been reported with single and two-stage revision protocols, although prospective comparative data are lacking. The significance of unexpected positive cultures during revision arthroplasty remains unclear. We report current diagnostic and therapeutic options for periprosthetic infection after reverse shoulder arthroplasty. Much of the current literature does not distinguish between anatomic and reverse shoulder arthroplasty. Further high-level studies are warranted to refine these definitions and guide management.

Preoperative Skin Cultures Predict Periprosthetic Infections in Revised Shoulder Arthroplasties: A Preliminary Report

Current approaches do not provide a practical method for the accurate prediction of a Cutibacterium periprosthetic joint infection (PJI) in failed arthroplasties. Thus, surgeons revising failed arthroplasties must decide whether to exchange the implants and to institute antibiotic treatment without knowing the results of cultures of deep specimens obtained at the revision procedure. This study tests the hypothesis that the results of preoperative culture specimens of the skin surface obtained in the clinic can predict the presence of culture-positive Cutibacterium PJIs.

METHODS

Revision shoulder arthroplasties performed between October 3, 2017, and February 4, 2020, that had both preoperative clinic culture specimens and surgical culture specimens were included in this analysis. Culture results were assigned a value from 0 to 4. The percentage of the total skin bacterial load contributed by Cutibacterium (Cutibacterium percentage) was determined. To reduce concern about contamination, a robust criterion for culture-positive Cutibacterium PJI was applied: ≥2 surgical specimens with a Cutibacterium value of ≥1. The predictive values for a culture-positive Cutibacterium PJI were determined for a clinic skin culture Cutibacterium value of >1 and a clinic skin percentage of Cutibacterium of ≥75%.

RESULTS

Eighteen cases met the inclusion criteria; of these, 7 (6 male patients) met our criterion for a culture-positive Cutibacterium PJI. For all patients, a preoperative clinic skin Cutibacterium value of >1 predicted the presence of a culture-positive Cutibacterium PJI with an accuracy of 89%, and a clinic skin Cutibacterium percentage of ≥75% predicted the presence of a culture-positive Cutibacterium PJI with an accuracy of 94%. For male patients, a preoperative clinic skin Cutibacterium value of >1 predicted the presence of a culture-positive Cutibacterium PJI with an accuracy of 91%, and a clinic skin Cutibacterium percentage of ≥75% predicted the presence of a culture-positive Cutibacterium PJI with an accuracy of 100%.

CONCLUSIONS

A simple culture specimen of the unprepared skin surface obtained in a clinic prior to revision shoulder arthroplasty may provide valuable assistance to surgeons planning a revision arthroplasty.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Detection of Cutibacterium acnes in arthroscopic rotator cuff and bankart repair

BACKGROUND

We evaluated the detection rate for Cutibacterium acnes (C. acnes) in patients who underwent arthroscopic cuff repair and Bankart repair.

METHODS

Arthroscopic cuff repair was performed in 105 patients (R group) and arthroscopic Bankart repair was performed in 29 patients (B group). Skin swabs prior to antisepsis, intraoperative synovial swabs of the glenohumeral joint (immediately after incision and prior to wound closure), suture of suture anchor, and postoperative swabs from the tip of arthroscope were cultured. Evaluation criteria were compared between groups and included the presence or absence of diabetes mellitus, operation time, frequency of preoperative injections, deep infections, and detection rate of C. acnes in multiple regions of the body.

RESULTS

There were 14 patients (12.2%) in the R group and one patient in the B group (3.6%) with diabetes mellitus, and no significant difference was found between the two groups. The frequency of injections to the shoulder was significantly greater in the R group at 3.6 ± 4.2 times compared to the B group at 1.6 ± 2.0 times. There were no deep infections in either groups. The detection rate for C. acnes was significantly greater in the synovial swabs alone (skin swabs for R and B groups, 42.3% and 47.6%, respectively; synovial swabs, 10.4% and 1.8%; suture, 8.7% and 0%; tip of arthroscope, 4.3% and 0%).

CONCLUSIONS

A significantly greater number of C. acnes samples were detected from synovial swabs of cuff tears, suggesting that its presence may be due to preoperative injections to the shoulder.

Efficacy of Home Prophylactic Benzoyl Peroxide and Chlorhexidine in Shoulder Surgery: A Systematic Review and Meta-Analysis

Two predominant prophylactic home skin-disinfection regimens exist in shoulder surgery, benzoyl peroxide and chlorhexidine. Of these 2 regimens, benzoyl peroxide gel is more effective than chlorhexidine in reducing the rate of positive Cutibacterium cultures on the skin surface. At present, there are no studies that assess the impact of these home prophylactic measures on clinical infection rates.

Factors predictive of Cutibacterium periprosthetic shoulder infections: a retrospective study of 342 prosthetic revisions

BACKGROUND

Cutibacterium are the most common cause of periprosthetic shoulder infections, as defined by ≥2 deep cultures. Established Cutibacterium periprosthetic infections cannot be resolved without prosthesis removal. However, the decision for implant removal must be made from an assessment of infection risk before the results of intraoperative cultures are finalized. We hypothesized that the risk for a Cutibacterium infection is associated with characteristics that are available at the time of revision arthroplasty.

METHODS

In a retrospective review of 342 patients having prosthetic revisions between 2006 and 2018 for whom definitive deep culture results were available, we used univariate and multivariate analyses to compare the preoperative and intraoperative characteristics of 101 revisions with Cutibacterium periprosthetic infections to the characteristics of 241 concurrent revisions not meeting the definition of infection.

RESULTS

Patients with definite Cutibacterium periprosthetic infections were younger (59 ± 10 vs. 64 ± 12, P < .001), were more likely to be male (91% vs. 44%, P < .001), were more likely to have had their index procedure performed for primary osteoarthritis (54% vs. 39%, P = .007), were more likely to be taking testosterone supplements (8% vs. 2%, P = .02), had lower American Society of Anesthesiologists scores (1.9 ± 0.7 vs. 2.3 ± 0.7, P < .001), and had lower body mass indices (29 ± 5 vs. 31 ± 7, P = .005). Patients with definite Cutibacterium periprosthetic infections also had significantly higher preoperative loads of Cutibacterium on their unprepared skin surface (1.7 ± 0.9 vs. 0.4 ± 0.8, P < .001) and were more likely to have the surgical finding of synovitis (41% vs. 16%, P < .001).

CONCLUSIONS

The risk of definite Cutibacterium periprosthetic infections is associated with observations that can be made before or at the time of revision arthroplasty.

Delayed periprosthetic collection after cervical disc arthroplasty

Cervical disc arthroplasty is a treatment option for symptomatic cervical disc disease. There is a paucity of literature on long-term safety outcomes, durability, and device-related failure rates. The M6-C artificial cervical disc is a device with titanium alloy endplates and a complex polymeric centerpiece. To date, trials have exhibited acceptable safety profiles.This case series describes the presentation, management, and pathological findings of a delayed prevertebral periprosthetic mass anterior to the M6-C disc. Four patients at 3 different institutions underwent cervical disc replacement with the M6-C disc. Two to seven years postoperatively, they presented with dysphagia secondary to a compressive mass anterior to the disc. Case notes were reviewed to collect data on symptoms, management, and outcomes. The patients were systemically well and presented with progressive dysphagia. They had imaging findings of a mass anterior to the disc. They underwent a decompressive procedure, with 2 patients undergoing device removal and fusion. In 2 cases, a soft-tissue mass was seen intraoperatively, with frank pus. In 3 cases, Propionibacterium acnes was identified and antibiotic treatment given. Histopathology demonstrated mixed inflammatory infiltrates with foreign body-type granulomas. Postoperatively, the dysphagia resolved.The development of delayed dysphagia in a patient with an M6-C disc should prompt investigation to identify a mass lesion. To the authors' knowledge, this is the first report of delayed infection, or suspected delayed-type hypersensitivity reaction, following M6-C disc implantation. It is important for this to be added to the device safety concerns. Further prospective studies are needed to establish the incidence and the long-term safety and failure rates of the M6-C disc.

Incidence of Cutibacterium acnes in arthroscopic Bankart repair for traumatic anterior shoulder instability

Background

We evaluated the detection rate of Cutibacterium acnes (C. acnes) for patients who underwent arthroscopic Bankart repair for traumatic anterior shoulder instability.

Methods

Study subjects included 36 patients who underwent arthroscopic Bankart repair. Skin swabs prior to antisepsis, intraoperative synovial swabs of the glenohumeral joint (immediately after incision and prior to wound closure), and the suture of the suture anchor were cultured. Evaluation criteria included the detection rate of C. acnes in multiple regions of the body.

Results

Using a skin swab culture test, C. acnes was detected in 63 of 108 samples (58.3%). The bacterium was detected in 2 of 36 samples (5.5%) and 4 of 36 (11.1%) in the synovial swab culture of the glenohumeral joint immediately after surgical incision and immediately before wound closure, respectively. In the suture culture of the suture used in the arthroscopic Bankart repair, C. acnes was detected in 1 of 36 samples (2.8%).

Conclusions

C. acnes was detected in patients undergoing surgeries for shoulder instability. The relationship between C. acnes and the pathological condition of shoulder instability remains unknown.

Incidence and predictors of positive intraoperative cultures in primary shoulder arthroplasty following prior ipsilateral shoulder surgery

Background

To our knowledge, the rate of positive intraoperative cultures in patients undergoing primary shoulder arthroplasty with prior ipsilateral nonarthroplasty shoulder surgery is unknown. The aim of this study was to determine the incidence and predictors of positive cultures in these patients.

Methods

We performed a retrospective review of patients with prior ipsilateral shoulder surgery with intraoperative cultures taken at the time of primary shoulder arthroplasty. We evaluated culture results, demographics, and number of prior surgeries. Regression analysis was used to determine patient-related risk factors that predict positive cultures.

Results

A total of 682 patients underwent primary shoulder arthroplasty, 83 had at least 1 prior ipsilateral shoulder surgery: 65.1% male, mean age 64.2 ± 10.9 years. For the cohort of 83 patients, an average of 3.2 ± 1.2 tissue samples were obtained for each patient, with a mean of 0.84 ± 1.14 tissue cultures being positive (range 0-5). Thirty-seven of the 83 patients (44.5%) had at least 1 positive culture, with Cutibacterium acnes the most frequent organism (31/37; 83.4%). An average of 1.9 ± 0.96 tissue cultures resulted positive (range 1-5) for the 37 patients who had positive cultures, 40.5% (15/37) had only 1 positive tissue culture (12/15 C acnes, 2/15 Staphylococcus epidermidis, and 1/15 vancomycin-resistant enterococcus). Male sex and history of prior shoulder infection were predictive of culture positivity (odds ratios: 2.5 and 20.9, respectively). Age, race, medical comorbidities, number of prior shoulder surgeries, and time from index shoulder surgery were not predictive of culture positivity.

Conclusion

About 45% of patients with no clinical signs of infection and a history of prior ipsilateral shoulder surgery undergoing primary shoulder arthroplasty grew positive intraoperative cultures. The significance of these findings remains unclear with regard to risk of periprosthetic infection and how these patients should be managed.

Ten-day culture incubation time can accurately detect bacterial infection in periprosthetic infection in shoulder arthroplasty

Background

Cutibacterium acnes is the most commonly isolated organism involved in periprosthetic shoulder infections. C acnes has traditionally been difficult to isolate, and much debate exists over appropriate culture methods. Recently, our institution initiated a 10-day culture method using a Brucella blood agar medium to enhance anaerobic growth specifically for C acnes in shoulder specimens.

Methods

A retrospective review of shoulder cultures from 2014-2017 of patients undergoing workup for possible infected shoulder arthroplasty was performed. Cultures were obtained in patients either preoperatively or intraoperatively at the time of revision. Presence of infection was determined based on at least 1 positive culture and treatment with either prolonged antibiotics, placement of an antibiotic spacer at the time of revision, or repeat surgical débridement.

Results

The records of 85 patients with 136 cultures were reviewed. Eighty-two patients had full records with at least 1-year clinical follow-up. Fifty-eight cultures were positive, with C acnes as the most commonly recovered organism (57% of positive cultures). Clinical follow-up of patients with negative cultures found no incidence of missed periprosthetic infection.

Conclusions

Use of a 10-day culture incubation method to enhance anaerobic bacterial growth is able to accurately detect periprosthetic infection in the shoulder including those related to C acnes. Our results suggest that by adopting more uniform culture methods, a shorter culture incubation time may be adequate. Ultimately, prospective studies with rigorous microbiologic methods are needed to best understand the clinical significance of unexpected positive bacterial cultures in shoulder arthroplasty.

Calcium sulphate mixed with antibiotics does not decrease efficacy against Cutibacterium acnes (formerly Propionibacterium acnes), in vitro study

Background

This study explored the in vitro efficacy of antibiotics mixed with calcium sulfate (ACS) against Cutibacterium acnes (C. acnes).

Methods

C. acnes isolates from orthopaedic infection sites were tested for antimicrobial susceptibility with ACS. Minimal inhibitory concentrations (MIC) were determined with a gradient diffusion method (Etest® strips).

Results

When tested with Etest®, all 22 isolates were susceptible to penicillin, ceftriaxone, vancomycin, and two were resistant to clindamycin (MICs of 4 and 8 mg/L). Penicillin and rifampin had the largest inhibition zone diameters.

Conclusions

Antibiotics retained activity against C. acnes when mixed with calcium sulfate.

Next-generation sequencing for diagnosis of infection: is more sensitive really better?

BACKGROUND

The utility of next-generation sequencing (NGS) in differentiating between active infection and contaminant or baseline flora remains unclear. The purpose of this study is to compare NGS with culture-based methods in primary shoulder arthroplasty.

METHODS

A prospective series of primary shoulder arthroplasty patients with no history of infection or antibiotic use within 60 days of surgery was enrolled. All patients received standard perioperative antibiotics. After skin incision, a 10 × 3-mm sample of the medial skin edge was excised. A 2 × 2-cm synovial tissue biopsy was taken from the rotator interval after subscapularis takedown. Each sample set was halved and sent for NGS and standard cultures.

RESULTS

Samples from 25 patients were analyzed. Standard aerobic/anaerobic cultures were positive in 10 skin samples (40%, 95% confidence interval [CI] 20%-60%) and 3 deep tissue samples (12%, 90% CI 1%-23%]). NGS detected ≥1 bacterial species in 17 of the skin samples (68%, 95% CI 49%-87%) and 7 deep tissue samples (28%, 95% CI 9%-47%). There was a significant difference (P < .03) in the mean number of bacterial species detected with NGS between the positive standard culture (1.6 species) and the negative standard culture groups (5.7 species).

CONCLUSION

NGS identified bacteria at higher rates in skin and deep tissue samples than standard culture did in native, uninfected patients undergoing primary procedures. Further research is needed to determine which NGS results are clinically relevant and which are false positives before NGS can be reliably used in orthopedic cases.

Propionibacterium acnes Osteomyelitis after Intraosseous Cannulation in a Child

Propionibacterium acnes osteomyelitis secondary to intraosseous (IO) cannulation is not well documented in literature. We report here an extremely rare incident of P. acnes tibial osteomyelitis at the IO access site, in a 4-year-old child, who presented 3 months after an episode of fluid resuscitation for streptococcal toxic shock syndrome necessitating irrigation and debridement and prolonged antibiotic therapy. We advocate for heightened awareness of osteomyelitis in patients with continued pain after IO cannulation. Low-grade persistent symptoms may be caused by less virulent organisms and may dictate need for early magnetic resonance imaging studies for diagnosis and treatment planning.

Cerebral empyema and abscesses due to Cutibacterium acnes

INTRODUCTION

Cutibacterium acnes is a commensal bacterium of the skin, frequently reported in prosthetic shoulder or spinal implant infections, but rarely in cranial and intracranial infections.

METHODS

We retrospectively reviewed patients with intracranial samples positive to Cutibacterium acnes managed in the neurosurgical units of our hospital of Lyon, France, between 2008-2016.

RESULTS

We included 29 patients, of whom 23 had empyema (with or without abscess), 17 had cranial osteomyelitis, and six only had abscess. Prior neurosurgery was reported in 28 patients, and the remaining patient had four spontaneous abscesses. Twelve patients had polymicrobial infections, including methicillin-susceptible Staphylococcus in 11 cases. The clinical diagnosis was difficult because of indolent and delayed symptoms: a CT scan or MRI was required. Thirteen patients (52%) had material at the infection site. All patients with bone flap implant or bones from biological banks had a bone flap-associated infection. Drainage was surgically performed in 25 cases or by CT scan-guided aspiration in four cases. All patients received an adapted antibiotic therapy (from three weeks to six months). The outcome was favorable in 28 patients. Three patients relapsed during the antibiotic therapy, requiring further surgery.

CONCLUSION

Cutibacterium acnes can be responsible for postoperative empyema and cerebral abscesses, with particular indolent forms, which make their diagnosis difficult. They are often polymicrobial and associated with bone flap osteomyelitis. Their outcome is favorable after drainage and adapted antibiotic therapy.

Vancomycin pre-soaking of the graft reduces postoperative infection rate without increasing risk of graft failure and arthrofibrosis in ACL reconstruction

PURPOSE

To investigate whether pre-soaking the graft in vancomycin during anterior cruciate ligament reconstruction (ACLR) reduces the postoperative infection rate and if this technique is associated with an increased rate of complications, including graft failure or arthrofibrosis.

METHODS

A retrospective review of a prospective database was performed in 1779 patients who underwent ACLR over a period of 5 years, analysing the rate of postoperative deep knee infection. Group 1 and 2 both received perioperative IV antibiotics, while only group 2 underwent ACLR with grafts pre-soaked in a 5 mg/ml vancomycin solution. To analyse possible side effects associated with vancomycin use, 500 patients out of the overall study population (100 patients per year) were randomly selected and retrospectively interviewed for further postoperative complications including graft failure and arthrofibrosis as well as subjective evaluation of their knee by completing the IKDC form with a minimum mean follow-up of 37 months.

RESULTS

In group 1, 22 out of 926 (2%) patients suffered a postoperative deep knee infection. In contrast, there were no postoperative infections in the second group of 853 patients (0%). 16 of 22 infections (73%) were caused by coagulase-negative Staphylococcus. Statistical analysis revealed a significantly reduced postoperative infection rate when bathing the autograft in vancomycin (p < 0.01). Analysis of the random sample revealed a significant decrease of graft failure with 8 reruptures in 257 patients (3%) in the vancomycin group compared to 16 cases of graft failure in 167 patients (10%) in the control group (p < 0.05). No differences were found in the rate of postoperative arthrofibrosis, Tegner or subjective outcome scores.

CONCLUSION

Prophylactic vancomycin pre-soaking of autografts during ACLR appears to be a viable, cost-effective and safe option to reduce the rate of deep infection compared to systemic antibiotics alone.

LEVEL OF EVIDENCE

III.

Diagnostic Arthroscopy for Detection of Periprosthetic Infection in Painful Shoulder Arthroplasty

PURPOSE

To analyze the utility of arthroscopic biopsies for detection of periprosthetic infection in painful shoulder arthroplasty without objective signs of infection.

METHODS

A retrospective analysis of all patients who underwent a diagnostic arthroscopy for painful shoulder arthroplasty from June 2012 through July 2018 was performed. Patients with a subsequent revision shoulder arthroplasty after diagnostic arthroscopy were included. Arthroscopic tissue culture results were compared with the culture results of intraoperative tissue samples obtained at the time of open revision surgery. A minimum of 3 tissue samples from synovia and bone-prosthesis interface with signs of synovitis or abnormal appearance was routinely collected. Cases with 2 or more positive cultures for the same microorganism obtained at open revision surgery were considered as true presence of infection. The study protocol was reviewed and approved by the institutional ethics committee.

RESULTS

Twenty-three cases in 22 patients were included in this study. Five of these 23 cases were classified as true infection based on the samples obtained during open revision surgery, and 16 cases had a positive culture in diagnostic arthroscopy. Cutibacterium acnes was isolated in each case. Classifying any microbiologic growth in the arthroscopic biopsies as positive resulted in a sensitivity and negative predictive value of 100%, specificity of 39%, and positive predictive value of 31.3% for the detection of a periprosthetic shoulder infection (PPSI). If at least 2 positive samples with the same microbiologic growth in the arthroscopic biopsies were considered as positive, sensitivity and negative predictive value dropped to 80% and 94.4%, respectively, but the specificity and positive predictive value increased to 94.4% and 80%, respectively.

CONCLUSIONS

Diagnostic arthroscopy is a useful diagnostic tool in patients with suspicion but no clear evidence of PPSI. Arthroscopically obtained tissue biopsies for culture offer a high sensitivity and specificity in the diagnosis of PPSI if at least 2 cultures positive for the same microorganism are considered as infection.

LEVEL OF EVIDENCE

Level III.

Factors to Consider When Assessing the Diagnostic Accuracy of Synovial Leukocyte Count in Periprosthetic Joint Infection

Synovial white blood cell (WBC) count and the percentage of polymorphonuclear leucocytes (PMN%) is one of the diagnostic criteria to diagnose a periprosthetic joint infection (PJI). Although the test is widely available, the diagnostic accuracy of proposed cut-off levels are influenced by several factors, such as: the affected joint, co-morbid conditions, the causative microorganism and the gathering and processing of samples in the laboratory. In this narrative review we provide an overview on how and to what extent these factors can affect the synovial WBC count and PMN% in synovial fluid.

Hydrogen peroxide skin preparation reduces Cutibacterium acnes in shoulder arthroplasty: a prospective, blinded, controlled trial

BACKGROUND

The purpose of this study was to determine whether preoperative skin preparation with hydrogen peroxide reduces intraoperative culture positivity for Cutibacterium acnes in shoulder arthroplasty.

METHODS

This was a prospective, controlled, parallel/noncrossover, nonrandomized, single-blinded trial registered at clinicaltrials.gov. We included a consecutive series of patients scheduled to undergo primary anatomic or reverse total shoulder arthroplasty. The first group of patients underwent a standard skin preparation and the second group underwent the same preparation with the addition of hydrogen peroxide. We then took skin, dermis, glenohumeral joint, and air (negative control) aerobic and anaerobic culture swabs. We blinded the laboratory analyzing the samples. An a priori power analysis determined that 56 patients would be needed to see a 50% reduction in culture positivity rates. We also conducted a post hoc gender-stratified analysis.

RESULTS

Between January 2017 and October 2018, the authors performed 124 primary shoulder arthroplasties, of which we included 65 and collected samples on 61. There were no demographic differences. There were fewer patients within the peroxide group with triple-positive cultures (skin, dermis, and joint) (0% vs. 19%, P = .024) and positive cultures from the joint (10% vs. 35%, P = .031). In our subgroup analysis, these differences were only significant in males. The vast majority of positive cultures were with C. acnes.

CONCLUSION

Although larger, randomized studies are needed, adding hydrogen peroxide to the preoperative skin preparation may be a low-cost, low-risk method to reduce deep tissue contamination with C. acnes, particularly within males.

Proceedings from the 2018 International Consensus Meeting on Orthopedic Infections: prevention of periprosthetic shoulder infection

The Second International Consensus Meeting on Orthopedic Infections was held in Philadelphia, Pennsylvania, in July 2018. Over 800 international experts from all 9 subspecialties of orthopedic surgery and allied fields of infectious disease, microbiology, and epidemiology were assembled to form a consensus workgroup. The following proceedings on the prevention of periprosthetic shoulder infection come from 16 questions evaluated by delegates from the shoulder section.

Delayed implant infection with Cutibacterium acnes (Propionibacterium acnes) 30 years after silicone sheet orbital floor implant

Purpose: To report a case of delayed implant infection with Cutibacterium acnes (C. acnes, previously known as Propionibacterium acnes) 30 years after silicone sheet orbital floor implant.Methods: Case report with orbital imaging.Results: A 61-year-old male with a history of traumatic orbital floor fracture right eye (OD) repaired using a silicone sheet orbital floor implant 30 years prior, presented with 6 months of painless blepharoptosis and diplopia OD. On examination, there was 3 mm right upper eyelid blepharoptosis and hyperglobus. There was no globe proptosis, dysmotility, or compression and no cutaneous erythema, hyperthermia, discharge, or tenderness to palpation. Orbital magnetic resonance imaging (MRI) revealed a cystic mass in the inferior orbit in the region of the floor implant, measuring 25 mm in diameter and 10 mm in thickness. By MRI, T1-weighted images revealed a hypointense signal within the mass and T2-weighted images showed hyperintense signal with a flat hypointensity centrally representing the floor implant. Microbiologic cultures grew C. acnes.Conclusions: C. acnes can manifest several decades after placement of an orbital prosthetic implant, leading to delayed infection.

Application of dermal chlorhexidine antisepsis is ineffective at reducing Proprionibacterium acnes colonization in shoulder surgery

BACKGROUND

Chlorhexidine as a skin surface antiseptic has been shown to be ineffective with respect to reducing Proprionibacterium acnes colonization within the dermis. The purpose of the present study was to determine whether the application of aqueous chlorhexidine solution to the dermal layer decreased P. acnes colonization during open shoulder surgery.

METHODS

The present study enrolled 50 patients who were undergoing open shoulder surgery. Patients received standard antimicrobial preparation. Three dermal swabs were taken from each patient: swab 1 following skin incision; swab taken 2 minutes to 5 minutes post-application of aqueous chlorhexidine to the dermis; and swab 3 taken 60 minutes post-application.

RESULTS

Mean age was 57.5 years (22 males, 28 females). There were 21 patients (42%) with P. acnes present on any dermal swab. There were significantly more P. acnes positive cultures identified at swab 3 compared to swab 1 (p = 0.043). In nine patients with positive P. acnes at cultures swab 1, eight also isolated P. acnes after at swabs 2 or 3. Males were significantly more likely to have P. acnes on any swab (p < 0.001). Positive P. acnes cultures were significantly more common in patients ≤50 years (p < .001). None of the patients had any clinical signs of infection at a minimum of 1 year following surgery.

CONCLUSIONS

Dermal application of aqueous chlorhexidine during open shoulder surgery fails to eradicate or reduce P. acnes on deep cultures.

Cutibacterium acnes and the shoulder microbiome

BACKGROUND

Advances in DNA sequencing technologies have made it possible to detect microbial genome sequences (microbiomes) within tissues once thought to be sterile. We used this approach to gain insights into the likely sources of Cutibacterium acnes (formerly Propionibacterium acnes) infections within the shoulder.

METHODS

Tissue samples were collected from the skin, subcutaneous fat, anterior supraspinatus tendon, middle glenohumeral ligament, and humeral head cartilage of 23 patients (14 male and 9 female patients) during primary arthroplasty surgery. Total DNA was extracted and microbial 16S ribosomal RNA sequencing was performed using an Illumina MiSeq system. Data analysis software was used to generate operational taxonomic units for quantitative and statistical analyses.

RESULTS

After stringent removal of contamination, genomic DNA from various Acinetobacter species and from the Oxalobacteraceae family was identified in 74% of rotator cuff tendon tissue samples. C acnes DNA was detected in the skin of 1 male patient but not in any other shoulder tissues.

CONCLUSION

Our findings indicate the presence of a low-abundance microbiome in the rotator cuff and, potentially, in other shoulder tissues. The absence of C acnes DNA in all shoulder tissues assessed other than the skin is consistent with the hypothesis that C acnes infections are derived from skin contamination during surgery and not from opportunistic expansion of a resident C acnes population in the shoulder joint.

Anterior cruciate ligament reconstruction complicated by Propionibacterium acnes infection: case series

Anterior cruciate ligament (ACL) reconstruction is one of the most commonly performed orthopaedic procedures. While generally successful, failure resulting in revision surgery is reported to be between 1.9 - 4.9%. However, when not related to traumatic re-injury, failure mechanism is poorly understood. One potential but understudied mechanism of ACL reconstruction failure is infection. We describe three patients with previous ACL reconstructions who later developed infection with Propionibacterium acnes. Two cases presented with knee pain and swelling, and one presented with instability. While only two of the three cases received antibiotic treatment, all three cases were free of knee and infectious symptomatology at most recent follow-up. P. acnes infection may represent one potential mechanism for biologic failure of ACL reconstruction and anaerobic operative cultures may be used to identify its presence.

Culture positivity in primary total shoulder arthroplasty

BACKGROUND

The clinical significance of positive cultures in shoulder surgery remains unclear. This study determined the rate and characteristics of positive intraoperative cultures in a cohort of patients undergoing primary shoulder arthroplasty.

METHODS

From February 2015 to March 2016, 94 patients, without prior surgery, underwent primary shoulder arthroplasty. Before surgery, all shoulders were prospectively enrolled and consented to obtain standardized intraoperative cultures. All patients received standard preoperative antibiotic prophylaxis. Standardized fluid and tissue locations were sampled and sent for aerobic and anaerobic cultures and held for 13 days. Patients and surgeon were blinded to the culture results.

RESULTS

Average age at surgery was 70.5 years (range, 50-91 years), and 41 patients (47%) were male. At least 1 positive culture was found in 33 shoulders (38%), with 17 patients (19%) having ≥2 positive cultures. Cutibacterium (formerly Propionibacterium) acnes was the most common organism (67%), followed by coagulase-negative Staphylococcus (21%), Staphylococcus aureus (3%), and other organisms (18%). The rate of positive culture was higher in men (51%) than in women (26%, P = .016). Cutibacterium acnes was more common in men with positive cultures (95% vs. 17%, P < .001) and coagulase-negative Staphylococcus and Staphylococcus epidermidis were more common in women with positive cultures (42% vs. 10%, P = .071).

CONCLUSION

Positive deep tissue cultures develop in a high percentage of patients undergoing primary shoulder arthroplasty despite antibiotic prophylaxis. The long-term clinical implication of this finding requires further study, especially with regard to the risk of late failures of shoulder arthroplasty.

Imaging of Shoulder Arthroplasties

OBJECTIVE

In this article, we review the preoperative imaging features used for planning shoulder arthroplasty as well as review the various shoulder arthroplasty component types, discussing the expected normal imaging features and specific complications to look for with each.

CONCLUSION

Given the increasing use of shoulder arthroplasty, it is important to understand the imaging features of the various shoulder arthroplasty complications.

Preoperative Doxycycline Does Not Reduce Propionibacterium acnes in Shoulder Arthroplasty

BACKGROUND

Propionibacterium acnes (P. acnes) is the most common bacteria associated with infection after shoulder arthroplasty. These bacteria can be grown on culture of skin after standard preoperative skin preparation and antibiotics. The purpose of this study was to determine whether adding preoperative intravenous doxycycline reduces the prevalence of positive P. acnes cultures of skin and deep tissues at the time of prosthetic joint implantation during shoulder arthroplasty.

METHODS

This was a randomized controlled trial. An a priori power analysis determined that a sample size of 56 patients was necessary. Patients scheduled to undergo shoulder arthroplasty were randomized to receive either standard perioperative cefazolin or a combination of doxycycline and cefazolin. Tissue specimens for culture were then taken from the skin edge, and swabs of the superficial dermal tissue and glenohumeral joint were obtained. All cultures were maintained for 14 days to allow for P. acnes detection. Groups were compared to determine if the addition of doxycycline reduced the rate of culture positivity.

RESULTS

Fifty-six patients were enrolled and randomized. Twenty-one (38%) had ≥1 positive cultures for P. acnes, with no significant difference between the group treated with cefazolin alone (10 [37%] of 27 patients) and the combined doxycycline and cefazolin group (11 [38%] of 29 patients) (p = 0.99). The greatest numbers of culture-positive samples were obtained from the skin (30%), followed by dermal tissue (20%) and the glenohumeral joint (5%). Patients who had ≥1 positive cultures were younger than those who did not (mean age [and standard deviation], 64.9 ± 7.7 versus 69.4 ± 7.7 years; p = 0.041), had a greater tendency to be male (16 [76%] of 21 versus 17 [49%] of 35; p = 0.053), and had a lower Charlson Comorbidity Index (3.35 ± 1.3 versus 4.09 ± 1.4; p = 0.051). There were no significant differences between the culture-positive and culture-negative groups in terms of body mass index (BMI) (p = 0.446) or arthroplasty type, with positive cultures found for 8 of the 29 anatomic shoulder arthroplasty procedures compared with 13 of the 27 reverse shoulder arthroplasty procedures (p = 0.280). There were no doxycycline-related adverse events.

CONCLUSIONS

In this randomized controlled trial, doxycycline did not significantly decrease P. acnes culture positivity of the skin, dermis, or glenohumeral joint of patients undergoing shoulder arthroplasty. The addition of prophylactic intravenous antibiotics to cover P. acnes may not be an effective method to reduce postoperative and periprosthetic shoulder joint infections.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Cutibacterium acnes prosthetic joint infection: Diagnosis and treatment

Cutibacterium acnes is a commensal skin bacterium, regularly implicated in prosthetic joint infection, particularly of the shoulder. Diagnosis has been improved by progress in bacteriological techniques: longer culture time, liquid medium culture, MALDI-TOF mass spectrography, and universal 16S rRNA PCR, associated by some authors to sonication of ablated implants. C. acnes pathogenicity involves many virulence factors, notably including biofilm formation. C. acnes may lead to infection that is clinically evident or, frequently, relatively asymptomatic. C. acnes is an anaerobic Gram-positive bacterium, susceptible to many antibiotics that are regularly used in bone and joint infection: beta-lactams, quinolone, rifampicin and clindamycin. It shows increasing resistance to clindamycin and natural resistance to metronidazole. Treatment is medical and surgical, associating synovectomy or complete 1- or 2-step revision depending on time to treatment, and antibiotic therapy. Antibiotic therapy is typically for three months with an initial 2-6 weeks' intravenous phase. Prognosis is generally favorable with well-conducted treatment. Late discovery of positive samples after apparently aseptic implant change is an at-risk situation, usually managed by antibiotic therapy, but with late initiation and hence increased risk of failure. Adverse secondary progression requires repeat revision under good conditions.

Increased Shoulder Arthroscopy Time Is Associated With Overnight Hospital Stay and Surgical Site Infection

PURPOSE

The purpose of this study was to characterize the rates of short-term postoperative complications, readmissions, and overnight hospital stays as a function of shoulder arthroscopy procedure time. A secondary aim of this current study was to identify baseline patient risk factors for adverse outcomes.

METHODS

This study used the American College of Surgeons National Surgical Quality Improvement Program registry from 2012 to 2015. Shoulder arthroscopy cases were categorized based on operative time, either <45 minutes, between 45 and 90 minutes, or >90 minutes. The rates of 30-day postoperative complications, readmissions, and overnight hospital stays were compared with bivariate and multivariate analysis.

RESULTS

In total, 33,095 shoulder arthroscopy procedures were identified. Of these, 7,027 (21.2%) were <45 minutes, 16,610 (50.2%) were between 45 and 90 minutes, and 9,458 (28.6%) were >90 minutes. Multivariate analysis identified increased the risk of superficial surgical site infections (SSIs) for procedures lasting between 45 and 90 minutes (odds ratio [OR] = 3.63; P = .036) and for procedures >90 minutes (OR = 4.40; P = .019), compared with procedures <45 minutes. Furthermore, there was an increased risk of overnight hospital stay for patients who had a shoulder arthroscopy lasting between 45 and 90 minutes (OR = 1.33) and >90 minutes (OR = 2.14), compared with procedures <45 minutes. A body mass index >30 kg/m² was an independent predictor of both overnight hospital stay and superficial SSI (P = .020). Age >60, female gender, American Society of Anesthesiologists class ≥3, and a history of diabetes mellitus, hypertension, or chronic obstructive pulmonary disease were additional predictors of overnight hospital stay (P < .001 for all comparisons, unless otherwise noted).

CONCLUSIONS

Increased shoulder arthroscopy procedure time is associated with adverse short-term outcomes, particularly superficial SSI and overnight hospital stay. This information may be useful for patient counseling and postoperative risk stratification, as operative time is an easily measured surrogate for surgical complexity or difficulty.

LEVEL OF EVIDENCE

Retrospective cohort study, Level III.

Do Elevated Inflammatory Markers Associate With Infection in Revision Shoulder Arthroplasty?

Background

Serologic erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) measurements, which have been successfully utilized in the lower extremity, are thought to lack adequate sensitivity in the diagnosis of infection after shoulder arthroplasty. The purpose of this study is to determine the diagnostic performance of preoperative white blood cell (WBC) count, ESR, and CRP in the diagnosis of infection in the setting of revision shoulder arthroplasty with the gold standard of infection being defined as a later diagnosis of infection.

Patients and methods

A national insurance database between the years of 2007 and 2015 (PearlDiver, Warsaw, IN) was queried for those patients who underwent revision shoulder arthroplasty using a combination of procedural (common procedural terminology codes 23472 and 23474) and diagnostic codes (International Classification of Diseases [ICD]-9 code 81.97 and equivalent ICD-10 codes). This database contains demographics, laboratory data, and complication data to allow identification of patients with an infection within 1 year postoperatively.

Results

The database contained 1392 patients who met criteria. Among these, the best diagnostic performance was with a combined test which was positive if CRP, ESR, or WBC was positive with a sensitivity of 7% to 42%, a specificity of 92%, a positive predictive value of 8% to 45%, a negative predictive value of 91%, and an accuracy of 84% to 85%. On multivariate analyses, predictors included an abnormal ESR (odds ratio 2.4, P = .05) and male gender (3.8, <.001).

Conclusions

Those patients with an abnormal preoperative ESR have significantly increased odds of a subsequent infection following revision shoulder arthroplasty. ESR, CRP, and WBC in combination are specific but insensitive. Level of Evidence: Diagnostic, Level III

Acute Peritonitis Caused by Propionibacterium Acnes in a Peritoneal Dialysis Patient

Propionibacterium acnes is a gram-positive human skin commensal that is involved in the pathogenesis of acne and prefers anaerobic growth conditions. It has been considered as a low virulence pathogen in different clinical conditions. We present the case of acute peritonitis caused by Propionibacterium acnes in a peritoneal dialysis patient.

Routine cultures for seemingly aseptic revision shoulder arthroplasty: are they necessary?

Propionibacterium acnes has recently gained attention as the leading cause of periprosthetic joint infections (PJIs) after shoulder arthroplasty. Unlike PJIs in the lower extremity, PJIs after shoulder arthroplasty usually have an indolent course and are notoriously difficult to diagnose. Most of the time, the diagnosis is made after positive intraoperative cultures are taken at the time of revision surgery. Adding even more complexity to the diagnosis is the high rate of P acnes-positive cultures taken at the time of primary shoulder surgery. In many cases the preoperative workup yields no suspicion for infection; however, intraoperative cultures are taken to completely eliminate the potential of an ongoing indolent infection. Concerns over how to interpret positive P acnes culture results and the high rate of culture positivity in primary shoulder arthroplasty, as well as the potentially high rate of contamination, have led surgeons to wonder about the utility of obtaining intraoperative cultures at the time of revision shoulder arthroplasty. We present evidence for and against the practice of obtaining routine intraoperative cultures at the time of seemingly aseptic revision shoulder arthroplasty.

Is previous nonarthroplasty surgery a risk factor for periprosthetic infection in primary shoulder arthroplasty?

BACKGROUND

The purpose of this study was to determine the risk of periprosthetic infection after primary shoulder arthroplasty (SA) in patients undergoing previous nonarthroplasty shoulder surgery compared with those without previous surgery.

MATERIALS AND METHODS

All patients undergoing primary SA at our institution between 1970 and 2012 were included in this study. The cohort consisted of 4577 patients treated with 2890 total SAs, 1233 hemiarthroplasties, and 454 reverse SAs; 813 (18%) patients had undergone prior nonarthroplasty shoulder surgery on the operative side. Patients with and without previous surgery were compared for postoperative periprosthetic infection. Univariate and multivariable analyses were used.

RESULTS

Deep postoperative infection of the shoulder was diagnosed in 68 patients (1.49%). Of the 813 patients who had undergone previous surgery, 20 (2.46%) developed a deep postoperative infection. However, of the 3764 patients who did not have previous shoulder surgery, 48 patients (1.28%) sustained deep shoulder infection. This difference was significant in both the univariate (P = .0094) and multivariate analyses (P = .0390). In addition, older age and female gender were significantly associated with a lower risk of deep postoperative infection (P = .0150 and P = .0074, respectively). A higher number of previous surgeries was also significantly associated with an increased risk of deep postoperative infection (P = .0272).

CONCLUSIONS

The risk of infection after primary SA is significantly higher in patients with a history of prior non-arthroplasty-related surgery. This finding should be discussed with the patients before their surgery, and potential preoperative and intraoperative workup should be undertaken to identify at-risk patients.