Greater Mental Health Burden is Associated With Poor Postoperative Pain Control and Increased Opioid Utilization Following Total Shoulder Arthroplasty.

Background: Prolonged opioid use is associated with higher complications and worse patient-reported outcomes following total shoulder arthroplasty (TSA). Identified risk factors for prolonged postoperative use are related to several medical comorbidities, gender, diagnoses of anxiety or depressive disorders, and preoperative opioid use. In this study, we hypothesized that patient-reported mental health characteristics can help to identify patients at risk of worse postoperative pain control, worse sleep, and higher opioid utilization following TSA. Methods: Ninety-three consecutive patients were asked to fill out 2 mental health questionnaires prior to undergoing TSA. Following surgery, patients filled out a daily pain diary to track their daily pain, pain medication use, and quality and duration of their sleep for 30 days. Preoperative opioid use and postoperative refill were determined by the New York State Prescription Monitoring Program. Mixed-model linear regressions were conducted. Significance was defined as p < 0.05. Results: Postoperative opioid refill was associated with female gender, preoperative opioid therapy, higher inpatient opioid use, worse anxiety, depression, somatization, and pain catastrophizing scores. The number of days using opioids postoperatively was associated with worse pain catastrophizing scale (PCS) and somatization scores (patient health questionnaire-15). Preoperative opioid therapy was associated with worse somatization scores, whereas no opioids used after surgery were associated with better somatization scores. Worse sleep quality and duration were associated with worse PCS scores. Conclusion: A greater mental health burden is associated with worse postoperative pain control and higher opioid utilization during the acute postoperative period. This is especially evident in the pain catastrophizing and somatization domains.

Reverse shoulder arthroplasty using an onlay humeral prosthesis, offset humeral tray, and augmented glenoid baseplate: surgical technique and review of the impact of prosthesis design on scapular fractures following reverse shoulder arthroplasty.

Reverse total shoulder arthroplasty (RSA) has become the most utilized form of arthroplasty of the shoulder. Acromial stress fractures and scapular spine stress fractures are rare, yet well-recognized complications of RSA with ongoing studies identifying whether patient factors or prosthetic designs serve as risk factors. Specifically, it remains unclear if or how the position of the humeral tray (inlay or onlay) in RSA affects rates of periscapular fractures. The purpose of this article is to describe our technique for RSA using an onlay prosthesis, a variable-offset humeral tray, and an augmented glenoid baseplate, as well as to review the published results of acromial and scapular spine fractures after RSA based on humeral implant design.

Optimizing glenoid bone preservation in reverse total shoulder arthroplasty using augmented baseplates.

Background: As techniques and implants for reverse total shoulder arthroplasty (rTSA) evolve, a greater emphasis is being placed on preserving glenoid bone stock and optimizing shoulder biomechanics. Augmented baseplates preserve glenoid bone and improve shoulder range of motion by lateralizing the center of rotation of the glenosphere, while also reducing postoperative complications after rTSA. The technique for bone preservation with use of augmented baseplates in the absence of bone loss and the outcomes of a series of cases are contained in this report. Materials and Methods: A retrospective chart review was conducted for 37 patients with Walch type A1/Sirveaux E0 glenoids who underwent primary rTSA using a bone preserving technique with an augmented baseplate between January 2018 and January 2019 at a single site by a single surgeon. The primary outcome measures were range of motion, strength, and patient-reported clinical outcomes (pain and function rated on a visual analog scale; single assessment numeric evaluation; American Shoulder and Elbow Surgeons score; and disabilities of the arm, shoulder, and hand score). Preoperative radiographs were analyzed for the presence of glenoid bone loss and postoperative radiographs were assessed for evidence of component loosening and scapular notching. A repeated measures design was used, and preoperative and postoperative comparisons were made using parametric t-tests. Results: At an average follow-up of 23.3 ± 6.3 months, there was a significant improvement in active forward flexion and abduction and nonsignificant improvement in external rotation. There was no radiographic evidence of glenoid notching in any of the patients and optimal glenoid inclination was observed. Patient-reported outcome scores after an average of 25.2 ± 10.0 months indicated a significant improvement in pain, function, and scores for the American Shoulder and Elbow Surgeons and disabilities of the arm, shoulder, and hand assessments. There were no substantial postoperative radiographic findings, intra/postoperative complications, or revisions/reoperations. Conclusion: rTSA with augmented baseplates for glenoid bone preservation in patients with minimal or no bone loss is effective for preserving glenoid bone stock and significantly improves the range of motion and patient-reported outcomes after approximately 2 years.

Outcomes of Reverse Total Shoulder Arthroplasty for Proximal Humerus Fracture Using Uncemented Stems, a Single Center Study.

Background: To evaluate the clinical, functional, radiographic, and survival outcomes in patients undergoing reverse total shoulder arthroplasty (RSA) with uncemented stem fixation for proximal humerus fractures. Materials and Methods: This is a retrospective cohort study that evaluated a consecutive series of patients with proximal humerus fractures undergoing RSA. Clinical data, radiographs, and re-operation rates were reviewed in patients selected for uncemented stem fixation. The same parameters were compared to the remainder of the cohort undergoing cemented stem fixation. Results: The uncemented group (n = 16, median total follow-up = 108 weeks) and cemented group (n = 12, median total follow-up = 223 weeks, p = 0.110) did not differ statistically in pre-operative demographic, post-operative outcomes or incidence of complications. Two patients (12.5%) in the uncemented group required a reoperation (Week 52 and 180) versus none in the cemented group. Conclusion: Uncemented stem fixation in RSA for proximal humerus fractures does not yield worse results than cemented stem fixation in properly selected patients. Prospective non-inferiority trials comparing outcomes are recommended.

Reverse total shoulder arthroplasty baseplate stability with locking vs. non-locking peripheral screws.

BACKGROUND: There are many options for glenosphere baseplate fixation commercially available, yet there is little biomechanical evidence supporting one type of fixation over another. In this study, we compared the biomechanical fixation of a reverse total shoulder glenoid baseplate secured with locking or non-locking peripheral screws. METHODS: Both a non-augmented mini baseplate with full backing support and an augmented baseplate were testing after implantation in solid rigid polyurethane foam. Each baseplate was implanted with a 30 mm central compression screw and four peripheral screws, either locking or non-locking (15 mm anterior/posterior and 30 mm superior/inferior). A 1 Hz cyclic force of 0-750 N was applied at a 60o angle for 5000 cycles. Throughout the test, the displacement of the baseplate was measured using a 3D Digital Image Correlation System. FINDINGS: The amount of migration measured in the both the non-augmented and augment cases shows no significant differences between locking and non-locking cases at the final cycle count (non-augment: 5.66 +/- 2.29 µm vs. 3.71 +/- 1.23 µm; p = 0.095, augment: 15.43 +/- 8.49 µm vs. 12.46 +/- 3.24 µm; p = 0.314). Additionally, the amount of micromotion measured for both sample types shows the same lack of significant difference (non-augment: 10.79 +/- 5.22 µm vs. 10.16 +/- 7.61 µm; p = 0.388, augment: 55.03 +/- 10.13 µm vs. 54.84 +/- 10.65 µm; p = 0.968). INTERPRETATION: The presence of locking versus non-locking peripheral screws does not make a significant difference on the overall stability of a glenoid baseplate, in both a no defect case with a non-augmented baseplate and a bone defect case with an augmented baseplate.

What do positive and negative Cutibacterium culture results in periprosthetic shoulder infection mean? A multi-institutional control study.

BACKGROUND: Deep tissue culture specimens obtained at the time of revision shoulder arthroplasty are commonly positive for Cutibacterium. Clinical interpretation of positive cultures can be difficult. This was a multi-institutional study evaluating the accuracy of cultures for Cutibacterium using positive control (PC) and negative control (NC) samples. The relationship between time to culture positivity and strength of culture positivity was also studied. METHODS: Eleven different institutions were each sent 12 blinded samples (10 PC and 2 NC samples). The 10 PC samples included 2 sets of 5 different dilutions of a Cutibacterium isolate from a failed total shoulder arthroplasty with a probable periprosthetic infection. At each institution, the samples were handled as if they were received from the operating room. Specimen growth, time to culture positivity, and strength of culture positivity (based on semiquantitative assessment) were reported. RESULTS: A total of 110 PC samples and 22 NC samples were tested. One hundred percent of specimens at the 4 highest dilutions were positive for Cutibacterium. At the lowest dilution, 91% of samples showed positive findings. Cutibacterium grew in 14% of NC samples. Cutibacterium grew in PC samples at an average of 4.0 ± 1.3 days, and all of these samples showed growth within 7 days. The time to positivity was significantly shorter (P < .001) and the strength of positivity was significantly higher (P < .001) in true-positive cultures compared with false-positive cultures. CONCLUSIONS: This multi-institutional study suggests that different institutions may report highly consistent rates of culture positivity for revision shoulder arthroplasty samples with higher bacterial loads. In contrast, with lower bacterial loads, the results are somewhat less consistent. Clinicians should consider using a shorter time to positivity and a higher strength of positivity as adjuncts in determining whether a tissue culture sample is a true positive.

Factors affecting internal rotation following total shoulder arthroplasty.

Background: Reverse shoulder arthroplasty (RSA) was developed in the late twentieth century to provide a stable arthroplasty option for patients with rotator cuff deficiency arthropathy. Since its inception, there have been changes in materials, design, and positioning. One of the persistent clinical issues has been difficulty with internal rotation (IR) and the associated difficulty with behind the back activities. Implant design, positioning, and the available soft tissues may influence IR after RSA. The purpose of this systematic review is to assess factors that impact IR following RSA. Methods: The literature search, based on PRISMA guidelines, used 4 databases: Pubmed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials. We included clinical trials that compared different implantation and design modifications and assessed IR. Results: Of the 617 articles identified in the initial search, 46 satisfied the inclusion criteria. The articles explored multiple factors of RSA and their effects on IR, including humeral and glenoid components and muscle function and integrity. Among humeral factors affecting rotation, there was a broad consensus that: IR decreases as retroversion increases, humeral neck-shaft angle less than 155° improves IR, lateralized humeral offset does not improve IR, and shallow cups improve IR. Insert thickness was not associated with a reproducible effect. Of the studies evaluating the effect of glenoid components, there was majority agreement that glenosphere lateralization improved IR, and there were mixed results regarding the effects of glenosphere size and tilt. Others included one study in each: glenoid overhang, retroversion, and baseplate. One study found an association between teres minor insufficiency and improved IR, with mixed results in the presence of fatty infiltration in both teres minor and subscapularis. Most studies noted subscapularis repair had no effect on IR. Conclusion: Prosthetic variables affecting IR are not widely studied. Based on the existing literature, evidence is conflicting. More research needs to be undertaken to gain a greater understanding regarding which factors can be modified to improve IR in RSA patients.

Stemless anatomic total shoulder arthroplasty: surgical technique and review of the literature.

Stemless anatomic total shoulder arthroplasty (aTSA) is a promising option for the treatment of degenerative disease in patients. This novel technique avoids the stem-related complications associated with the traditional stemmed aTSA. Stemless aTSA offers additional benefits such as decreased operative time, preservation of bone stock, improved radiographic outcomes, and easier revision. Moreover, loading of the metaphyseal region rather than the diaphysial region with traditional stemmed implants can decrease stress shielding. When compared to stemmed-implants, stemless aTSA has demonstrated similar outcomes and complication rates. The purpose of this article is to analyze published outcomes and complications following the utilization of stemless aTSA. Additionally, key aspects of the surgical technique that may promote optimal results in stemless aTSA implantation are presented.

Hybrid fixation in anatomic shoulder arthroplasty: surgical technique and review of the literature.

Hybrid constructs have been used as a primary fixation technique in primary anatomic total shoulder arthroplasty for more than a decade. A highly porous metal central peg, metal cage, or coatings attached to the surface of cemented polyethylene glenoid component have been used with the concept of providing an additional adjunct in promoting osseointegration, preventing glenoid component loosening, and promoting longer-term success. The purpose of this article is to analyze the published results, complications, as well as rate of revision using this form of glenoid fixation. In addition, key aspects of the surgical technique that may be considered to facilitate optimal results when hybrid fixation is considered in total shoulder arthroplasty are also reviewed.

Reverse Total Shoulder Arthroplasty Baseplate Stability in Superior Bone Loss With Augmented Implant.

BACKGROUND: Glenoid bone loss is commonly encountered in cases of rotator cuff tear arthropathy and can create challenges during reverse shoulder arthroplasty. In this study, we sought to investigate the biomechanical properties of a new treatment option for superior glenoid defect, an augmented reverse total shoulder baseplate. METHODS: Three conditions were examined: non-augmented baseplate without defect, non-augmented baseplate with defect, and augmented baseplate with defect. The augmented baseplates included a 30-degree half wedge which also matched the created superior defect. The samples were cyclically loaded at a 60° simulated abduction angle to mimic baseplate loosening. The migration and micromotion of the baseplate were measured on the superior edge using a 3D Digital Image Correlation System. RESULTS: The migration measured in the augmented baseplate showed no significant difference when compared to the no defect or defect cases. In terms of micromotion, the augmented baseplate showed values that were between the micromotions reported for the no defect and defect conditions, but not by a statistically significant amount. CONCLUSION: This study provides biomechanical evidence that augmented baseplates can reduce the amount of micromotion experienced by the RSA construct in the presence of significant superior glenoid bone deficiency, but do not fully restore stability to that of a full contact non-augmented baseplate.

Prospective, Blinded, Randomized Controlled Trial of Stemless Versus Stemmed Humeral Components in Anatomic Total Shoulder Arthroplasty: Results at Short-Term Follow-up.

BACKGROUND: Stemless humeral components for anatomic total shoulder arthroplasty (aTSA) have several reported potential benefits compared with stemmed implants. However, we are aware of no Level-I, randomized controlled trials (RCTs) that have compared stemless implants with stemmed implants in patients managed with aTSA. We sought to directly compare the short-term clinical and radiographic outcomes of stemless and stemmed implants to determine if the stemless implant is noninferior to the stemmed implant. METHODS: We performed a prospective, multicenter, single-blinded RCT comparing stemless and short-stemmed implants in patients managed with aTSA. Range-of-motion measurements and American Shoulder and Elbow Surgeons (ASES), Single Assessment Numeric Evaluation (SANE), and Constant scores were obtained at multiple time points. Device-related complications were recorded. Radiographic evaluation for evidence of loosening, fractures, dislocation, or other component complications was performed. Statistical analysis for noninferiority was performed at 2 years of follow-up for 3 primary end points: ASES score, absence of device-related complications, and radiographic signs of loosening. All other data were compared between cohorts at all time points as secondary measures. RESULTS: Two hundred and sixty-five shoulders (including 176 shoulders in male patients and 89 shoulders in female patients) were randomized and received the allocated treatment. The mean age of the patients (and standard deviation) was 62.6 ± 9.3 years, and 99% of the shoulders had a primary diagnosis of osteoarthritis. At 2 years, the mean ASES score was 92.5 ± 14.9 for the stemless cohort and 92.2 ± 13.5 for the stemmed cohort (p value for noninferiority test, <0.0001), the proportion of shoulders without device-related complications was 92% (107 of 116) for the stemless cohort and 93% (114 of 123) for the stemmed cohort (p value for noninferiority test, 0.0063), and no shoulder in either cohort had radiographic signs of loosening. Range-of-motion measurements and ASES, SANE, and Constant scores did not differ significantly between cohorts at any time point within the 2-year follow-up. CONCLUSIONS: At 2 years of follow-up, the safety and effectiveness of the stemless humeral implant were noninferior to those of the stemmed humeral implant in patients managed with aTSA for the treatment of osteoarthritis. These short-term results are promising given the potential benefits of stemless designs over traditional, stemmed humeral components. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Pathogenic genetic variations of C. acnes are associated with clinically relevant orthopedic shoulder infections.

Many surgeons continue to face the clinical dilemma of interpreting a positive aspiration or unexpected positive Cutibacterium acnes (C. acnes) culture. There are factors that complicate the interpretation of positive cultures including variations in both frequency of false positive cultures and virulence properties. As indices of virulence, hemolytic strains, from previously confirmed clinically infected shoulders, were compared with non-hemolytic isolates determined to be contaminants, by RNA-sequencing (RNA-Seq). Six C. acnes isolates from patients who underwent revision total shoulder arthroplasty (TSA) were identified based on previously described infection criteria. Three C. acnes isolates from each group underwent RNA-Seq. Differential gene expression analysis, principal component analysis (PCA), and heatmap analysis were used to determine the gene variation and patterning between the definite infection and probable contaminant isolates. Differential gene expression analysis identified genes that were differentially expressed between the isolates classified as definite infection and isolates classified as probable contaminants. PCA using a 500 gene subset of identified genes was able to find combinations of these genes that separated out the definite infection and probable contaminants isolates. The heatmap demonstrated similar gene expression in the three Definite Infections isolates, and significantly different expression when compared with the probable contaminant isolates. Clinical significance: C. acnes revision TSA isolates classified as definite infection and probable contaminant demonstrated a similar gene expression pattern to each respective group and different gene expression pattern when compared between groups. These findings indicate distinct differences in C. acnes strains associated with clinically relevant orthopedic TSA infections.

Effect of Blue Light and Photosensitizers on Cutibacterium acnes on Shoulder Periprosthetic Joint Infection Isolates.

Introduction: Cutibacterium acnes is gaining recognition as a leading pathogen after orthopaedic shoulder procedures. Photodynamic therapy, a combination of light and a photosensitizer, has demonstrated antimicrobial activity against C. acnes in the treatment of acne vulgaris. We sought to evaluate the effect of photodynamic therapy using blue light and photosensitizers on C. acnes isolates from shoulder prosthetic joint infections. Methods: C. acnes strains isolated from 19 patients with shoulder PJI were exposed to blue light alone (415 nm) or in combination with photosensitizers (fluorescein, riboflavin and demeclocycline). C. acnes strains were divided into 4 categories: Highly Sensitive (HS), Sensitive (S), Weakly Sensitive (WS), Resistant to blue light. Results: 13 of 19 C. acnes strains (68%) were S or HS to blue light alone. Of these 19 strains tested, 11 were tested with blue light and fluorescein or blue light plus riboflavin. Fluorescein (1 µg/mL) enhanced the effect of blue light in 6 of 11 strains (55%). Blue light plus riboflavin (10 µg/mL) resulted enhanced killing in 3 of 11 strains (27%), but produced a paradoxical photoprotective effect in 4 of 11 strains (36%), resulting in a net decrease compared to blue light alone. Demeclocycline, however, enhanced the effect of blue light in 16 of 17 strains (94 %). Conclusions: Blue light with the addition of photosensitizers killed C. acnes from periprosthetic shoulder infections in vitro, with demeclocycline having the most pronounced effect.

Hemolysis Is a Diagnostic Adjuvant for Propionibacterium acnes Orthopaedic Shoulder Infections.

INTRODUCTION: The purpose of this study was to further evaluate the pathogenicity of hemolytic and nonhemolytic phenotypes of Propionibacterium acnes (P acnes) isolates from shoulders of orthopaedic patients. METHODS: Thirty-one patient records were reviewed, which had a positive P acnes shoulder culture from joint aspiration fluid and/or intraoperative tissues for demographics, clinical course, culture, and laboratory data. Patients were categorized as definite infection, probable infection, or probable contaminant. Antibiotic resistance patterns and hemolysis characteristics were subsequently analyzed. RESULTS: Hemolysis demonstrated 100% specificity with a positive predictive value of 100% and 80% sensitivity with a negative predictive value of 73% for determining definite and probable infections. Hundred percent of the patients in the hemolytic group and only 27% of patients in the nonhemolytic group were classified as infected. Presenting inflammatory markers were markedly higher in the hemolytic group. Clindamycin resistance was found in 31% of the hemolytic strains, whereas no antibiotic resistance was observed in the nonhemolytic group. CONCLUSION: Hemolytic strains of P acnes exhibit enhanced pathogenicity to their host by eliciting a more prominent systemic inflammatory response, increased antibiotic resistance, and a more challenging clinical course. Hemolysis may serve as a specific marker for assisting in diagnosing true infection with P acnes. LEVEL OF EVIDENCE: Level III retrospective comparative study.

Running Out of Room: Managing Humeral and Glenoid Bone Loss in Shoulder Arthroplasty.

Glenoid bone loss is frequently encountered in arthritic conditions. The Walch classification is commonly used to categorize glenoid bone loss into several different types. Preoperative CT can assist in identifying the type and extent of bone loss for development of the appropriate treatment plan. Restoration of glenoid alignment and soft-tissue balancing is essential in shoulder arthroplasty, which can be achieved through a variety of techniques including high side reaming, augmented components, and bone grafting. Reverse total shoulder arthroplasty, another viable option to address severe bone deficiency, may be performed in conjugation with bone grafting or augmented components. Extensive bone loss may also be addressed in a staged procedure or avoided with isolated humeral head replacement. Humeral bone loss also remains a challenge in patients undergoing shoulder arthroplasty, which may be addressed with an allograft-prosthesis composite or an isolated metal prosthesis. Further investigation into the use of different biomaterials, ceramics, endosteal fixation, and modular components is needed. There are promising results with computer-assisted component implantation.

Antibiotic Prophylaxis and Prevention of Surgical Site Infection in Shoulder and Elbow Surgery.

Infection after orthopedic procedures is a devastating and serious complication associated with significant clinical and financial challenges to the health care system and unfortunate patient. The time and resource-intensive nature of treating infection after orthopedic procedures has turned attention toward enhancing prevention and establishing quality improvement measures. Prevention strategies throughout the perioperative period include host optimization, risk mitigation, reducing bacterial burden and proper wound management. Understanding the most common offending organisms of the shoulder, Propionibacterium acnes and coagulase negative Staphylococcus species, and their hypothesized mechanism of infection is crucial to selecting appropriate preventative measures.

Reverse total shoulder glenoid baseplate stability with superior glenoid bone loss.

BACKGROUND: Superior wear of the glenoid bone is common in patients with rotator cuff arthropathy. This can become a treatment challenge for patients who require shoulder arthroplasty. In reverse shoulder arthroplasty (RSA), glenoid bone loss may affect the stability of baseplate fixation. The primary purpose of this biomechanical laboratory study was to assess the initial fixation stability of RSA glenosphere baseplates in the presence of variable amounts of superior glenoid bone loss. MATERIALS AND METHODS: High-density solid rigid polyurethane foam (30 pounds/cubic foot) was machined to model the glenoid with variable superior defects that provided different levels of support (100%, 90%, 75%, and 50%) for the glenosphere baseplate. The samples were cyclically loaded (0-750 N at 1 Hz for 5000 cycles) at a 60° glenohumeral angle. The micromotion and migration of the baseplate were calculated from displacement data captured during the loading tests with an array of 3 linear variable differential transformers mounted around the baseplate. RESULTS: Micromotion was significantly greater in samples with 50% defects compared with those with smaller defects. Migration was significantly greater after testing for all defect sizes. CONCLUSIONS: Initial fixation of RSA glenosphere baseplates was significantly reduced in models with 50% bone loss on the superior edge compared with models with less bone loss in this high-density bone foam model.

Propionibacterium acnes Host Inflammatory Response During Periprosthetic Infection Is Joint Specific.

BACKGROUND: Propionibacterium acnes (P. acnes) has become increasingly recognized as a cause of periprosthetic joint infection (PJI). QUESTIONS/PURPOSES: It is not currently known if the clinical presentation of P. acnes varies depending on the joint being infected. METHODS: We retrospectively reviewed patients infected with P. acnes after total hip, knee, and shoulder arthroplasty from two institutions. Patients were classified as having a PJI based on the Musculoskeletal Infection Society criteria and were excluded if they had a polymicrobial culture. Patient demographics, preoperative laboratory values, and microbiology data were analyzed. RESULTS: Eighteen knees, 12 hips, and 35 shoulders with a P. acnes PJI were identified. Median ESR was significantly higher in the knee (38.0 mm/h, IQR 18.0-58.0) and hip (33.5 mm/h, IQR 15.3-60.0) groups compared to the shoulder group (11.0 mm/h, IQR 4.5-30.5). C-reactive protein levels were higher in the knee (2.0 mg/dl, IQR 1.3-8.9) and hip (2.4 mg/dl, IQR 0.8-4.9) groups compared to the shoulder group (0.7 mg/dl, IQR 0.6-1.5). Median synovial fluid WBC was significantly higher in the knee group than shoulder group (19,950 cells/mm3, IQR 482-60,063 vs 750 cells/mm3, IQR 0-2825, respectively). Peripheral blood WBC levels were similar between groups, as was mean time of P. acnes growth in culture. Clindamycin resistance was present in all groups. CONCLUSION: The manner in which a patient with P. acnes PJI presents is joint specific. Inflammatory markers were significantly higher in the knee and hip groups compared to the hip and shoulder groups, and long hold anaerobic cultures up to 14 days are necessary to accurately identify this organism.

Propionibacterium acnes Susceptibility and Correlation with Hemolytic Phenotype.

BACKGROUND: Many studies have noted an increase in the number of recognized cases of invasive infections due to Propionibacterium acnes, especially after shoulder replacement surgery. The increase in the number of recognized cases of P. acnes, a nonspore-forming, anaerobic, Gram-positive organism, appears due to both an increase in the number of shoulder operations being performed and more specimens being sent for anaerobic cultures. Nevertheless, the optimal surgical and antibiotic management of P. acnes remains controversial. METHODS: We tested the susceptibility of 106 P. acnes strains from sterile body sites collected at the Erie County Medical Center between 2012 and 2015, using Etest gradient antibiotic strips. RESULTS: P. acnes is very susceptible to the penicillins and the first-generation cephalosporins. We noted an association between hemolytic phenotype on Brucella Blood Agar and clindamycin resistance. CONCLUSIONS: Antimicrobial susceptibility testing of P. acnes should no longer just be confined to the research laboratory but expanded and incorporated into routine microbiological evaluation of P. acnes. This would improve patient care as well as help clarify the relationship between hemolysis and clindamycin resistance.