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.

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.

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.

Hemiarthroplasty of the distal humerus for acute and chronic complex intra-articular injuries.

BACKGROUND: Comminuted intra-articular distal humeral fractures represent a challenging upper extremity injury. This study reviews clinical and radiographic results in patients with distal humeral hemiarthroplasty (DHH). METHODS: DHH with the Latitude prosthesis (Tornier, Saint-Ismier, France) was performed in 8 patients (mean age, 64 years; age range, 33-75 years) for unreconstructible fractures of the distal humerus or salvage of failed internal fixation. Clinical outcomes were assessed with the American Shoulder and Elbow Surgeons elbow instrument; Mayo Elbow Performance Index; and Disabilities of the Arm, Shoulder and Hand questionnaire at a mean of 36 months. Radiologic assessment included radiographs and computed tomography to evaluate olecranon wear and densitometry (dual-energy x-ray absorptiometry). Range of motion, pain, and elbow satisfaction were recorded, and descriptive statistics were used for analysis. RESULTS: Seven patients were available to participate in the follow-up examination. Acute cases (5 patients) scored better than salvage cases (2 patients) on the Mayo Elbow Performance Score (80 points [range, 67-95 points] and 65 points [range, 50-80 points], respectively) and Disabilities of the Arm, Shoulder and Hand score (31 points [range, 2.5-68 points] and 39 points [range, 17-62 points], respectively). The mean arc of elbow flexion and extension was 96° (range, 70°-130°), with mean flexion of 120° (range, 90°-135°) and a mean extension loss of 19° (range, 5°-30°). The mean arc of forearm rotation was 160° (range, 140°-180°). Reoperation was required in 4 patients because of painful retained hardware. Five patients reported pain with activities of daily living. CONCLUSION: DHH should be used with caution until such time as longer-term outcome studies are able to show the efficacy of this procedure.

The outcome of total elbow arthroplasty in juvenile idiopathic arthritis (juvenile rheumatoid arthritis) patients.

BACKGROUND: Elbow prosthetic replacement in patients with juvenile idiopathic arthritis (JIA) can be complicated and technically challenging. Thus, we sought to evaluate the clinical benefit and the prosthetic longevity of primary semiconstrained linked total elbow arthroplasty (TEA) performed to treat these patients. METHODS: Between 1983 and 2005, 29 elbows in 24 patients (20 women and 4 men) had been replaced because of JIA. The mean age was 37 years (range, 24-68 years). Because of underlying deformity, the implant contour was modified for 9 elbows (31%) and a customized implant was inserted in 5 elbows (17%). The mean follow-up duration was 10.5 years (range, 4.6-20.1 years). RESULTS: During the follow-up period, 8 elbows underwent reoperation, including 6 (21%) that underwent implant revision. At most recent follow-up, 22 elbows (76%) subjectively had a satisfactory overall functional result. The mean Mayo Elbow Performance Score was 78 points (range, 50-100 points), with 18 elbows graded as having an excellent or good result. Compared with preoperative range of motion, the mean extension-flexion arc improved from 65° ± 44° to 89° ± 35° (P = .01), mean flexion improved from 113° ± 23° to 126° ± 26° (P = .02), and mean extension improved from 48° ± 25° to 37° ± 26° (P = .08). By use of the Kaplan-Meier survivorship method, the rate of TEA survival from any revision was 96.4% (95% confidence interval, 89.8%-100%) and 79.9% (95% confidence interval, 65.1%-97.5%) at 5 years and 10 years, respectively. CONCLUSION: Primary TEA for JIA patients is technically challenging and frequently requires implant modification or custom designs. These patients might have high complication and revision rates. However, most benefit from the intervention for a long term.

Anatomic shoulder arthroplasty for treatment of proximal humerus malunions.

BACKGROUND: Malunion of proximal humeral fractures complicated by damage to the glenohumeral cartilage and injury to the joint capsule and rotator cuff can include treatment requiring anatomic shoulder arthroplasty. This study defines results and complications of this procedure and identifies factors associated with success or failure. METHODS: From 1976 to 2007, 109 patients underwent shoulder arthroplasty for proximal humerus malunions. Ninety-five met the criteria for analysis with a mean follow-up period of 9.2 years. Fracture types according to the Neer classification were two part in 20, three part in 37, four part in 31, and head splitting in 2, with 16 fracture-dislocations. Hemiarthroplasty was performed in 45 patients, with 50 undergoing total arthroplasty. RESULTS: Pain scores improved from 7.8 to 3.1 (P < .001). The mean active elevation and external rotation improved from 69° to 109° and from 8° and 39°, respectively (P = .001). Of 31 patients with available radiographs, 20 had healed tuberosity osteotomies. Sixteen complications required 10 reoperations, including 6 of 9 patients with severe postoperative instability. There were 57 excellent or satisfactory results by use of the Neer rating. No patient, injury pattern, previous treatment, surgical, or radiologic variation was significantly associated with an increased risk of an unsatisfactory result, except for severe postoperative instability. Kaplan-Meier survivorship for reoperation, in 109 shoulders, was 94.8% (95% confidence interval, 90.5%-99.4%) at 5 years and 90.1% (95% confidence interval, 83.6%-97.1%) at 10 and 15 years. CONCLUSION: Anatomic shoulder arthroplasty improves pain and motion. Surgery is complex. Tuberosity osteotomies often heal. Postoperative instability is the most common complication leading to reoperation and is usually associated with rotator cuff and shoulder capsule injury.

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.

Antimicrobial susceptibility of Propionibacterium acnes isolates from shoulder surgery.

Orthopedic surgeons at our institution have noticed an increase in the number of infections due to Propionibacterium acnes, especially following operations on the shoulder. We collected P. acnes isolates from our hospital microbiology laboratory for 1 year and performed antimicrobial susceptibility testing on 28 strains from the shoulder. Antibiotics with the lowest MIC values against P. acnes (MIC50 and MIC90) included penicillin G (0.006, 0.125), cephalothin (0.047 and 0.094), and ceftriaxone (0.016, 0.045), while others also showed activity. Strains resistant to clindamycin were noted.

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.

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.

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.

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.

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.

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.

Innervation of the supinator muscle and its relationship to two-incision distal biceps tendon repair: an anatomic study.

Reinsertion of the ruptured distal biceps tendon has been performed using either a single-anterior incision or a two-incision approach. A systematic review of these two repair methods has identified a higher incidence of supination weakness following the two-incision approach. The objective of this study was to describe the innervation of the supinator muscle and its implications regarding a two-incision distal biceps repair. Twelve fresh upper extremity specimens from 12 males were dissected with the forearm in full pronation. The number of branches of the posterior interosseous nerve (PIN) to the supinator, their site of exit from the PIN trunk, and their distance from a variety of known anatomic landmarks were recorded. Specimens were characterized as high (<5 mm), moderate (6-10 mm), or low (>10 mm) risk of nerve branch injury depending on the proximity of nerve branches to the bicipital tuberosity. In general, we found the innervation of the supinator to be highly variable. There were from two to nine branches of the PIN which supplied the supinator, with 0-3 arising from the ulnar side of the nerve. Four specimens were at low, five at moderate, and three at high risk of nerve branch injury during dorsal exposure of the bicipital tuberosity. We conclude that there is a substantial amount of variability in the innervation of the supinator, with certain patterns being at higher risk of nerve branch injury if dissection of the supinator is carried out over the bicipital tuberosity.

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.

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.

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.