SARS-CoV-2 Infection Depends on Cellular Heparan Sulfate and ACE2.

We show that SARS-CoV-2 spike protein interacts with both cellular heparan sulfate and angiotensin-converting enzyme 2 (ACE2) through its receptor-binding domain (RBD). Docking studies suggest a heparin/heparan sulfate-binding site adjacent to the ACE2-binding site. Both ACE2 and heparin can bind independently to spike protein in vitro, and a ternary complex can be generated using heparin as a scaffold. Electron micrographs of spike protein suggests that heparin enhances the open conformation of the RBD that binds ACE2. On cells, spike protein binding depends on both heparan sulfate and ACE2. Unfractionated heparin, non-anticoagulant heparin, heparin lyases, and lung heparan sulfate potently block spike protein binding and/or infection by pseudotyped virus and authentic SARS-CoV-2 virus. We suggest a model in which viral attachment and infection involves heparan sulfate-dependent enhancement of binding to ACE2. Manipulation of heparan sulfate or inhibition of viral adhesion by exogenous heparin presents new therapeutic opportunities.

Novel classification system for periprosthetic distal femoral fractures: a consideration for comminution.

PURPOSE: Comminution is an aspect of periprosthetic distal femoral fractures (PDFFs) that can influence postoperative outcomes and treatment selection, but is not included in current classification systems. We propose a new classification system for PDFFs based on comminution and cortical reads. This study aims to prove its reliability and efficacy to predict fracture severity and guide treatment. METHODS: A retrospective chart review of patients treated with single or dual locking plates for PDFFs was performed. Two fellowship-trained orthopedic joint reconstruction specialists used available imaging to classify each PDFF as either type 1 (minimal or no comminution allowing for reconstruction of medial and lateral cortices), type 2 (comminution reasonably allowing for reconstruction of either medial or lateral cortex), and type 3 (extensive comminution not allowing reasonable reconstruction of medial or lateral cortex). Each PDFF was then analyzed for radiographic outcomes including lateral distal femoral angle (LDFA) and the posterior distal femoral angle (PDFA). RESULTS: Interobserver reliability assessed by Cohen's Kappa statistic was 0.707, and average intraobserver reliability was 0.843, showing substantial reliability. Type 3 PDFFs had greater varus deformity than type 1 (p = 0.0457) or 2 (0.0198). CONCLUSION: The proposed classification system accounts for comminution, demonstrates strong interobserver and intraobserver reliability, and can be used to guide treatment in regard to single versus dual plating. LEVEL OF EVIDENCE: Retrospective comparative study, Level IV.

Are our actions matching our words? A review of trainee ethnic and gender diversity in orthopaedic surgery.

Background: There is a lack of physician ethnic and gender diversity amongst surgical specialties. This study analyzes the literature that promotes diversity amongst surgical trainees. Specifically, this study sought to answer (i) how the number of publications regarding diversity in orthopaedic surgery compares to other surgical specialties, (ii) how the number of publications amongst all surgical subspecialties trends over time and (iii) which specific topics regarding diversity are discussed in the surgical literature. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used to query articles from PubMed, Web of Science, Embase and the Cumulative Index to Nursing and Allied Health Literature. Broad inclusion criteria for both ethnic and gender diversity of any surgical specialty were utilized. Results: Our query resulted 1429 publications, of which 408 duplicates were removed, and 701 were excluded on title and abstract screening, leaving 320 to be included. The highest number of related publications was in orthopaedic surgery (n = 73) followed by general surgery (n = 56). Out of 320 total articles, 260 (81.3 %) were published after 2015, and 56 of 73 (76.7 %) orthopaedic-specific articles were published after 2015. Conclusion: Orthopaedic surgery published the most about ethnic and gender diversity, however, still remains one of the least diverse surgical specialties. With the recent increase in publications on diversity in surgical training, close attention should be paid to ethnic and gender diversity amongst surgical trainees over the coming years. Should diversity remain stagnant, diversification efforts may need to be restructured to achieve a diverse surgeon workforce. Key message: Orthopaedic surgery is the surgical subspecialty that publishes the most about trainee ethnic and gender diversity followed by general surgery. With most of this literature being published over the last eight years, it is imperative to pay close attention to the ethnic and gender landscape of the surgeon workforce over the coming years.

Socioeconomic Factors Correlation With Idiopathic Scoliosis Curve Type and Cobb Angle Severity.

INTRODUCTION: Race and socioeconomic status correlate with disease outcomes and treatment in patients with idiopathic scoliosis (IS) to varying degrees, although there is no clear association with Cobb angle and curve type. The purpose of this study was to assess socioeconomic factors and their association with Cobb angles in patients with IS. METHODS: A retrospective chart review was completed with the radiographic analysis of 89 patients diagnosed with IS and spinal curves >10° between the ages of six and 18. Associations between the Cobb angles and socioeconomic categorical variables were analyzed using a nonparametric Kruskal-Wallis test and continuous variables using a Spearman Rank correlation.  Results: There were no significant associations between proximal thoracic, main thoracic, or thoracolumbar/lumbar Cobb angles and sex, insurance type, race, access to healthy food, financial difficulty, or income. BMI and proximal thoracic Cobb angle (ρ = 0.2375, p=0.0268) had a significant positive correlation, and BMI and income (ρ = -0.2468, p=0.0228) shared a significant negative correlation. CONCLUSIONS: The severity of IS proximal thoracic Cobb angles was positively associated with BMI and income. Other socioeconomic factors such as age, race, sex, access to food, insurance, and financial difficulties related to scoliosis treatment were not correlated with Cobb angle severity. The data presented suggest that patients with IS have varying degrees of curve type and severity that overall do not correlate with various socioeconomic factors. Validating which factors are predictive of curve severity could lead to early intervention preventing further morbidity of IS.

Alternative and Adjunct Treatments for Scoliosis: A Google Trends Analysis of Public Popularity Compared With Scientific Literature.

Purpose As Google searches have often been found to provide inaccurate information regarding various treatments for orthopedic conditions, it becomes important to analyze search trends to understand what treatments are most popularly considered and the quality of information available. We sought to compare the public interest in popular adjunct/alternative scoliosis treatments to the published literature on these topics and assess any temporal trends in the public interest in these treatments. Methods The study authors compiled the most common adjunct/alternative treatments for scoliosis on PubMed. Chiropractic manipulation, Schroth exercises, physical therapy, pilates, and yoga, along with "scoliosis," were each entered into Google Trends, collected from 2004 to 2021. A linear regression analysis of covariance (ANCOVA) was done to determine whether there was a linear relationship between Google Trends' popularity and PubMed publication data. The seasonal popularity of the terms was assessed using locally estimated scatterplot smoothing (LOESS) regression. Results Google Trends and publication frequency linear regression curves were different for chiropractic manipulation (p < 0.001), Schroth exercises (p < 0.001), physical therapy (p < 0.001), and pilates (p = 0.003). Chiropractic manipulation (p < 0.001), Schroth exercises (p = 0.003), and physical therapy (p < 0.001) had positive trends, and yoga (p < 0.001) had a negative trend. Chiropractic manipulation and yoga were more popular in the summer and winter months. Conclusion Google Trends can provide orthopedic surgeons and other healthcare professionals with valuable information on which treatments are gaining popularity with the public, so physicians may specifically inform themselves prior to patient encounters, leading to more productive shared decision-making.

Cannabis Use Among Lower-Extremity Arthroplasty Patients Does Not Lead to Worse Postoperative Outcomes.

INTRODUCTION: Smoking and general categorizations of substance use are linked with increased postoperative complications following total knee arthroplasty (TKA) and total hip arthroplasty (THA). There is a lack of similar evidence on how cannabis use may affect outcomes after arthroplasty. The present study aims to compare postoperative outcomes in cannabis users versus non-cannabis users who underwent THA/TKA. We hypothesize that cannabis users will have no difference in primarily the complication rate, revision rate, and secondarily post-operative Patient-Reported Outcomes Information System (PROMIS) scores, hospital stay, or pain compared to matched controls. METHODS: Billing codes were used to generate lists of hip/knee arthroplasty patients from 2013 to 2019 at our institution. In the case group, cannabis use was confirmed via chart review. Cannabis-using patients were matched appropriately with non-users by (1) the same arthroplasty procedure; (2) BMI ± 3.5; (3) age ± 3 years; (4) sex. Data on postoperative outcomes were collected from charts and compared between groups using either a Chi-square test for qualitative variables or a paired t-test for quantitative variables. RESULTS: A total of 24 patients with an average age of 57.1 and a BMI of 30.6 were confirmed to have isolated cannabis use. They were matched to 24 patients with an average age of 57.6 and a BMI of 31.4. There were no significant differences in the complication rate (4.2% vs 4.2%, p=1.00), the revision rate (0% vs 4.2%, p=0.31), days of hospital stay (2.7 vs 3.3, p=0.22), or postoperative pain (4.7 vs 4.9, p=0.86). Similarly, there were no significant differences in all PROMIS score measures. DISCUSSION/CONCLUSIONS: Current research shows that cannabis use may lead to increased revision arthroplasty and decreased mortality, with mixed findings regarding post-surgical complications. The present study suggests that cannabis-using patients have no difference in postoperative complication rate, revision rate, PROMIS scores, hospital stay, or pain compared to matched controls.

Comminuted periprosthetic distal femoral fractures have greater postoperative extension malalignment.

INTRODUCTION: Comminution is a significant aspect of periprosthetic distal femoral fracture characterization and may influence post-surgical outcomes. Existing classification systems that guide treatment decisions do not take into account comminution and current literature is unclear on which surgical approach is optimal. We hypothesize that fractures with comminution will have poorer quality post-reduction alignment, especially with a lateral approach. MATERIALS AND METHODS: 37 study patients were identified with billing codes designating a distal femoral periprosthetic fracture. A retrospective chart review was performed to categorize fractures by absence or presence of comminution and medial parapatellar versus lateral surgical approach. These patients underwent an imaging evaluation for the primary outcome of reduction quality including the anatomic lateral distal femoral angle (LDFA) and the posterior distal femoral angle (PDFA). Differences in radiographic outcomes were analyzed with Wilcoxon/Kruskal-Wallis tests, and analysis by approach was through Fisher's exact test. RESULTS: Patients with comminuted fractures had significantly greater extension of the fragment (PDFA = 95.4° vs 90.0°, p = 0.018) and similar coronal alignment (LDFA = 85.3° vs 86.3°, p = 0.83) of the knee compared to non-comminuted fractures after surgical reduction. This difference was more prominent amongst those treated with a lateral approach (PDFA = 96.1° vs 89.4°, p = 0.032) than with a medial approach (PDFA = 93.7° vs 91.5°, p = 0.41) (Table 1). DISCUSSION: Current classification systems and treatment guidelines for periprosthetic distal femoral fractures do not adequately address several issues that may influence treatment outcomes, especially comminution. Comminuted fractures had greater post-reduction extension malalignment, falling outside the recommended PDFA range of 87-90°, especially with a lateral approach. Consideration should be given to surgical approach and techniques to reduce excessive extension when treating comminuted periprosthetic distal femoral fractures.

Differences of Search Engine Digital Footprints Between Podiatrists and Foot and Ankle Orthopaedic Surgeons: A Need to Join the Digital Era.

BACKGROUND: Search engines generate lists of the most relevant websites using a keyword or phrase query and are integral in guiding consumer preferences. Digital information is important in the field of medicine, influencing what patients learn about their conditions and who they choose as providers. When two types of healthcare providers, such as podiatry and foot and ankle orthopaedic surgeons (FAOSs), share an overlapping consumer market, whichever group has a larger digital footprint receives increased digital engagement. METHODS: The Google search engine was used to query nine common foot and ankle-associated terms using a "search term + zip code" format for 150 zip codes divided into urban, suburban, and rural population densities. The first 10 results of each search were classified into one of five categories. Site content was classified as podiatry-oriented, other MD/DO-oriented, or FAOS-oriented. Separately, a ratio between podiatrists and FAOSs was calculated for each population density group. Data were then normalized using this ratio and reanalyzed with the Wilcoxon signed-rank test with significance at P < 0.05. RESULTS: Of 13,500 total search results, 4,992 (36.9%) were podiatry-oriented, 2,109 (15.6%) were other MD/DO-oriented, and 436 (3.2%) were FAOS-oriented. All geographic areas featured a higher number of podiatry than FAOS-oriented sites. FAOSs have more results per provider in urban areas (P < 0.001), although podiatrists had more in suburban and rural areas (P < 0.001, P < 0.001). Podiatrists have greater digital engagement in descriptive search terms. "Ankle replacement" has greater FAOS engagement in all three geographic areas. DISCUSSION: Foot and ankle-related Internet search terms results are overwhelmingly composed of podiatry-oriented sites. Per provider, regional differences are demonstrated, with FAOS having more sites in urban areas only. FAOS scope-of-practice terms such as "ankle replacement" still retain greater engagement by FAOSs. Search engine optimization and saturation strategies should be considered. LEVEL OF EVIDENCE: Level 3 (observational study).

Biologically Derived Neoproteoglycans for Profiling Protein-Glycosaminoglycan Interactions.

Glycosaminoglycans (GAGs) are a class of highly negatively charged membrane-associated and extracellular matrix polysaccharides involved in the regulation of myriad biological functions, including cell adhesion, migration, signaling, and differentiation, among others. GAGs are typically attached to core proteins, termed proteoglycans (PGs), and can engage >500 binding proteins, making them prominent relays for sensing external stimuli and transducing cellular responses. However, their unique substructural protein-recognition domains that confer their binding specificity remain elusive. While the emergence of glycan arrays has rapidly enabled the profiling of ligand specificities of a range of glycan-binding proteins, their adaptation for the analysis of GAG-binding proteins has been considerably more challenging. Current GAG microarrays primarily employ synthetically defined oligosaccharides, which capture only a fraction of the structural diversity of native GAG polysaccharides. Augmenting existing array platforms to include GAG structures purified from tissues or produced in cells with engineered glycan biosynthetic pathways may significantly advance the understanding of structure-activity relationships in GAG-protein interactions. Here, we demonstrate an efficient and tunable strategy to mimic cellular proteoglycan architectures by conjugating biologically derived GAG chains to a protein scaffold, defined as neoproteoglycans (neoPGs). The use of a reactive fluorogenic linker enabled real-time monitoring of the conjugation reaction efficiency and tuning of the neoPG valency. Immobilization of the reagents on a 96-well array platform allowed for efficient probing of ligand binding and enzyme-substrate specificity, including growth factors and the human sulfatase 1. The neoPGs can also be used directly as soluble probes to evaluate GAG-dependent growth factor signaling in cells.

Spatially controlled glycocalyx engineering for growth factor patterning in embryoid bodies.

Growth factor (GF) patterning in stem cell spheroids, such as embryoid bodies (EBs), has been sought to guide their differentiation and organization into functional 3D tissue models and organoids. Current approaches relying on exposure of EBs to gradients of GFs suffer from poor molecular transport in the spheroid microenvironment and from high cost of production and low stability of recombinant GFs. We have developed an alternative method for establishing GF gradients in EBs utilizing stem cell surface engineering with membrane-targeting heparan sulfate-glycomimetic co-receptors for GFs. We have capitalized on the ability of amphiphilic lipid-functionalized glycopolymers with affinity for FGF2 to assemble into nanoscale vesicles with tunable dimensions and extracellular matrix penetrance. Upon size-dependent diffusion into EBs, the vesicles fused with the plasma membranes of stem cells, giving rise to concentric gradients of cells with enhanced FGF2-binding. The extracellular matrix-assisted cell surface remodeling process described is the first example of spatially-targeted glycocalyx engineering in multicellular systems to control GF localization. The glycopolymer structure, vesicle dimensions, and remodeling conditions determine the level of FGF2 adhesion and gradient slope. The increased chemical and thermal stability of the synthetic glycomimetics and the tunability of their GF-binding profile, which is defined by their glycosylation and may be extended to other recombinant or endogenous morphogens beyond FGF2, further increase the versatility of this method.

SARS-CoV-2 Infection Depends on Cellular Heparan Sulfate and ACE2.

We show that SARS-CoV-2 spike protein interacts with cell surface heparan sulfate and angiotensin converting enzyme 2 (ACE2) through its Receptor Binding Domain. Docking studies suggest a putative heparin/heparan sulfate-binding site adjacent to the domain that binds to ACE2. In vitro, binding of ACE2 and heparin to spike protein ectodomains occurs independently and a ternary complex can be generated using heparin as a template. Contrary to studies with purified components, spike protein binding to heparan sulfate and ACE2 on cells occurs codependently. Unfractionated heparin, non-anticoagulant heparin, treatment with heparin lyases, and purified lung heparan sulfate potently block spike protein binding and infection by spike protein-pseudotyped virus and SARS-CoV-2 virus. These findings support a model for SARS-CoV-2 infection in which viral attachment and infection involves formation of a complex between heparan sulfate and ACE2. Manipulation of heparan sulfate or inhibition of viral adhesion by exogenous heparin may represent new therapeutic opportunities.

Embryonic Stem Cell Engineering with a Glycomimetic FGF2/BMP4 Co-Receptor Drives Mesodermal Differentiation in a Three-Dimensional Culture.

Cell surface glycans, such as heparan sulfate (HS), are increasingly identified as co-regulators of growth factor signaling in early embryonic development; therefore, chemical tailoring of HS activity within the cellular glycocalyx of stem cells offers an opportunity to control their differentiation. The growth factors FGF2 and BMP4 are involved in mediating the exit of murine embryonic stem cells (mESCs) from their pluripotent state and their differentiation toward mesodermal cell types, respectively. Here, we report a method for remodeling the glycocalyx of mutant Ext1-/- mESCs with defective biosynthesis of HS to drive their mesodermal differentiation in an embryoid body culture. Lipid-functionalized synthetic HS-mimetic glycopolymers with affinity for both FGF2 and BMP4 were introduced into the plasma membrane of Ext1-/- mESCs, where they acted as functional co-receptors of these growth factors and facilitated signal transduction through associated MAPK and Smad signaling pathways. We demonstrate that these materials can be employed to remodel Ext1-/- mESCs within three-dimensional embryoid body structures, providing enhanced association of BMP4 at the cell surface and driving mesodermal differentiation. As a more complete understanding of the function of HS in regulating development continues to emerge, this simple glycocalyx engineering method is poised to enable precise control over growth factor signaling activity and outcomes of differentiation in stem cells.