A Genetically Encoded Fluorescent Biosensor for Intracellular Measurement of Malonyl-CoA.

Malonyl-CoA is the essential building block of fatty acids and regulates cell function through protein malonylation and allosteric regulation of signaling networks. Accordingly, the production and use of malonyl-CoA is finely tuned by the cellular energy status. Most studies of malonyl-CoA dynamics rely on bulk approaches that take only a snapshot of the average metabolic state of a population of cells, missing out on dynamic changes in malonyl-CoA and fatty acid biosynthesis that could be occurring within a single cell. To overcome this limitation, we have developed a genetically encoded fluorescent protein-based biosensor for malonyl-CoA that can be used to capture malonyl-CoA dynamics in single cells. This biosensor, termed Malibu (malonyl-CoA i ntracellular biosensor to understand dynamics), exhibits an excitation-ratiometric change in response to malonyl-CoA binding. We first used Malibu to monitor malonyl-CoA dynamics during inhibition of fatty acid biosynthesis using cerulenin in E. coli , observing an increase in Malibu response in a time- and dose-dependent manner. In HeLa cells, we used Malibu to monitor the impact of fatty acid biosynthesis inhibition on malonyl-CoA dynamics in single cells, finding that two inhibitors of fatty acid biosynthesis, cerulenin and orlistat, which inhibit different steps of fatty acid biosynthesis, increase malonyl-CoA levels. Altogether, we have developed a new genetically encoded biosensor for malonyl-CoA, which can be used to sensitively study malonyl-CoA dynamics in single cells, providing an unparalleled view into fatty acid biosynthesis.

Differences in Primary Total Shoulder Arthroplasty Volume, Reimbursement, Practice Styles, and Patient Populations Based on Surgeon Gender: A Temporal Analysis.

BACKGROUND: Orthopedic surgery has previously been shown to have a shortage of female physicians and a gender pay gap. However, this has not been thoroughly evaluated in the setting of shoulder surgery. The primary purpose of this study was to evaluate differences in total shoulder arthroplasty (TSA) volume, reimbursement, surgeon billing practices, and patient populations between male and female surgeons from 2013 to 2021. METHODS: The Medicare Physician and Other Practitioners database, a publicly available dataset that includes 100% of services billed to Medicare Part B was utilized. The database was queried for all billing episodes of Current Procedural Terminology (CPT) code 23472, which encompasses both anatomic and reverse primary TSA. Procedural volume, average inflation-adjusted reimbursement per TSA, physician billing information, and the patient demographics of each surgeon who performed TSAs were collected. Welch's t-test and Kruskal-Wallis were utilized to compare male and female surgeons each year between 2013 and 2021. RESULTS: Between 2013 and 2021, the proportion of TSAs performed by female surgeons nationally increased from 1.8% to 2.9% (+1.1%). This increase was greatest in the Northeast (2.0% to 6.1%), while a decrease was seen in the Midwest (1.9% to 1.6%). In 2021, there was no significant difference between male and female surgeons in the average inflation-adjusted reimbursement per TSA ($1,144.00 vs $1,143.00, p=0.792) and the average number of TSAs performed per surgeon (26.6 vs 23.1, p=0.105). Female TSA surgeons, on average, had less Medicare beneficiaries (348 vs 462, p<0.001), performed fewer annual services (1,817 vs 3,630, p<0.001), and performed fewer unique services (60 vs 76, p<0.001) compared to male surgeons. A higher proportion of female surgeon's patient populations were non-White (24% vs 22%, p=0.028), female (61% vs 59%, p=0.001), and dual enrolled Medicare-Medicaid patients (13% vs 10%, p<0.001). However, there was no difference in the average patient complexity between male and female TSA surgeons based on hierarchical condition category (HCC) score (1.0783 vs 1.0732, p=0.228). CONCLUSION: Female representation within TSA surgery is increasing nationally, with the greatest representation in the Northeast and West and the lowest representation in the South and Midwest. Although female TSA surgeons perform a similar number of TSAs, receive comparable reimbursement per TSA, and have a similarly complex patient population as their male counterparts, they perform significantly fewer total and unique billable services annually. Additionally, female TSA surgeons tend to see more non-White, women, and dual Medicare-Medicaid enrolled patients.

A cell type-aware framework for nominating non-coding variants in Mendelian regulatory disorders.

Unsolved Mendelian cases often lack obvious pathogenic coding variants, suggesting potential non-coding etiologies. Here, we present a single cell multi-omic framework integrating embryonic mouse chromatin accessibility, histone modification, and gene expression assays to discover cranial motor neuron (cMN) cis-regulatory elements and subsequently nominate candidate non-coding variants in the congenital cranial dysinnervation disorders (CCDDs), a set of Mendelian disorders altering cMN development. We generate single cell epigenomic profiles for ~86,000 cMNs and related cell types, identifying ~250,000 accessible regulatory elements with cognate gene predictions for ~145,000 putative enhancers. We evaluate enhancer activity for 59 elements using an in vivo transgenic assay and validate 44 (75%), demonstrating that single cell accessibility can be a strong predictor of enhancer activity. Applying our cMN atlas to 899 whole genome sequences from 270 genetically unsolved CCDD pedigrees, we achieve significant reduction in our variant search space and nominate candidate variants predicted to regulate known CCDD disease genes MAFB, PHOX2A, CHN1, and EBF3 - as well as candidates in recurrently mutated enhancers through peak- and gene-centric allelic aggregation. This work delivers non-coding variant discoveries of relevance to CCDDs and a generalizable framework for nominating non-coding variants of potentially high functional impact in other Mendelian disorders.

Transcriptomic and proteomic spatial profiling of pediatric and adult diffuse midline glioma H3 K27-Altered.

Diffuse midline glioma, H3 K27-altered (DMG) are highly aggressive malignancies of the central nervous system (CNS) that primarily affect the pediatric population. Large scale spatial transcriptomic studies have implicated that tumor microenvironmental landscape plays an important role in determining the phenotypic differences in tumor presentation and clinical course, however, data connecting overall transcriptomic changes to the protein level is lacking. The NanoString GeoMx™ Digital Spatial Profiler platform was used to determine the spatial transcriptomic and proteomic landscape in a cohort of both pediatric and adult H3 K27-altered DMG biopsy samples. Three fluorescently labeled antibodies targeting immune cells (CD45), epithelial cells (PanCK), tumor cells (H3 K27M) and a nucleic acid stain (SYTO-13) were used to establish regions of interest (ROI) for genomic and proteomic analysis. We found genetic alterations within the tumor which can be delineated across patient age and spatial location. We show that the H3 K27M mutation itself has a profound impact on tumor cells transcriptomics and interestingly we found limited fidelity between overall transcriptome and proteome. Our data also validate a previously described genomic signature at the proteomic level and reveal a special shift in the signature based on the local TME composition.

Holding the Knife on Perceptions of Surgery.

OBJECTIVE: Negative stereotypes associated with surgery by medical students are well documented in literature. Many cite long hours, poor work-life balance, pessimism, mean personalities, and cynicism as pervasive among surgeons and operating room culture. If allowed to persist, these negative perceptions can deter otherwise interested students from pursuing surgical subspecialties. DESIGN: Incorporation of peer-teaching in the third-year clerkship to not only illuminate the hidden curriculum in surgery but adequately prepare students to participate in the operating room is paramount to taking steps to improve student perception as well as success as clerkship students. SETTING: An academic medical center. PARTICIPANTS: Pre-clinical medical students. RESULTS: One-hundred and forty-three third year clerkship students were surveyed with pre- and postinstruments. Students who participated in these pre clerkship peer-teaching sessions reported significant improvements in their ability to identify surgical anatomy (p < 0.001), an increased confidence in answering questions from attendings about anatomy and function as well as in identifying anatomical abnormalities (all p < 0.001). Students also reported significantly improved perceptions about surgeons as teachers and their willingness to support students pursuing surgery. CONCLUSION: This study demonstrates that the incorporation of an immersive orientation prior to the start of the surgery clerkship has significantly positive impacts on the learning experience and confidence of medical students. Increased efforts should be made to introduce students to surgeons, surgical careers, and the operating room prior to the surgery clerkship, being sure to incorporate aspects of the hidden curriculum, to address the negative perceptions that continue to exist regarding surgical fields.

Tissue-resident memory T cells in epicardial adipose tissue comprise transcriptionally distinct subsets that are modulated in atrial fibrillation.

Atrial fibrillation (AF) is the most common sustained arrhythmia and carries an increased risk of stroke and heart failure. Here we investigated how the immune infiltrate of human epicardial adipose tissue (EAT), which directly overlies the myocardium, contributes to AF. Flow cytometry analysis revealed an enrichment of tissue-resident memory T (TRM) cells in patients with AF. Cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) and single-cell T cell receptor (TCR) sequencing identified two transcriptionally distinct CD8+ TRM cells that are modulated in AF. Spatial transcriptomic analysis of EAT and atrial tissue identified the border region between the tissues to be a region of intense inflammatory and fibrotic activity, and the addition of TRM populations to atrial cardiomyocytes demonstrated their ability to differentially alter calcium flux as well as activate inflammatory and apoptotic signaling pathways. This study identified EAT as a reservoir of TRM cells that can directly modulate vulnerability to cardiac arrhythmia.

The ankle-brachial index, gastrocnemius mitochondrial respirometry, and walking performance in people with and without peripheral artery disease.

Background: Mitochondrial abnormalities exist in lower-extremity peripheral artery disease (PAD), yet the association of the ankle-brachial index (ABI) with mitochondrial respiration in gastrocnemius muscle is unknown. The association of gastrocnemius mitochondrial respiration with 6-minute walk distance in PAD is unknown. Objective: To describe associations of the ABI with mitochondrial respiratory function in gastrocnemius muscle biopsies and associations of gastrocnemius mitochondrial respirometry with 6-minute walk distance in people with and without PAD. Methods: People with (ABI ⩽ 0.90) and without (ABI 1.00-1.40) PAD were enrolled. ABI and 6-minute walk distance were measured. Mitochondrial function of permeabilized myofibers from gastrocnemius biopsies was measured with high-resolution respirometry. Results: A total of 30 people with PAD (71.7 years, mean ABI: 0.64) and 68 without PAD (71.8 years, ABI: 1.17) participated. In non-PAD participants, higher ABI values were associated significantly with better mitochondrial respiration (Pearson correlation for maximal oxidative phosphorylation PCI+II: +0.29, p = 0.016). In PAD, the ABI correlated negatively and not significantly with mitochondrial respiration (Pearson correlation for PCI+II: -0.17, p = 0.38). In people without PAD, better mitochondrial respiration was associated with better 6-minute walk distance (Pearson correlation: +0.51, p < 0.001), but this association was not present in PAD (Pearson correlation: +0.10, p = 0.59). Conclusions: Major differences exist between people with and without PAD in the association of gastrocnemius mitochondrial respiration with ABI and 6-minute walk distance. Among people without PAD, ABI and walking performance were positively associated with mitochondrial respiratory function. These associations were not observed in PAD.

Preoperative stereotactic radiosurgery for patients with 1-4 brain metastases: A single-arm phase 2 trial outcome analysis (NCT03398694).

Background: Stereotactic radiosurgery (SRS) following surgical resection is the standard of care for patients with symptomatic oligo brain metastasis (BM), however, it is associated with 10-15% local failure. Targeting a resection cavity is imprecise, thus preoperative radiosurgery where the target is well-defined may be superior, however, the efficacy of preoperative SRS has not yet been tested in a clinical trial. Methods: We conducted a phase 2, single-arm trial of preoperative SRS followed by surgical resection in patients with 1-4 symptomatic oligo BMs (NCT03398694) with the primary objective of measuring 6-month local control (LC). SRS was delivered to all patients utilizing a gamma knife or linear accelerator as per RTOG-9005 dosing criteria [Shaw E, Scott C, Souhami L, et al. Single dose radiosurgical treatment of recurrent previously irradiated primary brain tumors and brain metastases: final report of RTOG protocol 90-05. Int J Radiat Oncol Biol Phys. 2000;47(2):291-298] based on tumor diameter with the exception that the largest lesion diameter treated was 5 cm with 15 Gy with all SRS treatment given in single fraction dosing. Results: The trial screened 50 patients, 48 patients were treated under the protocol and 32 patients completed the entire follow-up period. Of all the patients who completed the follow-up period, the primary endpoint of 6-month LC was 100% (95% CI: 0.891-1.000; P = .005). Secondary endpoints, presented as medians, were overall survival (17.6 months), progression-free survival (5.3 months), distant in-brain failure (40.8% at 1 year), leptomeningeal failure (4.8% at 1 year), and radiation necrosis (7.7% at 1 year). Conclusions: Our data confirms superior local control in patients who received preoperative SRS when compared to historical controls. Further study with a larger randomized cohort of patients is warranted to fully understand the benefits of preoperative SRS.

Urocanic acid as a novel scaffold for next-gen nature-inspired sunscreens: II. Time-resolved spectroscopy under solution conditions.

In recent years the use of synthetic UV filters in commercial skincare formulations has come under considerable scrutiny. Urocanic acid is a naturally occurring UV filter that could serve as a scaffold for developing next-generation biomimetic UV filters. We have carried out time-resolved electronic and vibrational absorption studies on urocanic acid and modified variants in various solvents on timescales spanning eighteen orders of magnitude; from femtoseconds to hours. In combination with quantum chemical calculations these provide vital insight into the photochemical and photophysical properties of urocanic acid and how these are tuned by substitutions and solvents. Moreover, they solve the hitherto conundrum of the wavelength dependence of the photochemistry of trans-urocanic acid in an aqueous environment. Crucially, these studies - together with the accompanying article that reports high-resolution laser spectroscopic studies performed under isolated gas-phase conditions (https://doi.org/10.1039/D4CP02087A) open novel avenues for a rational design of urocanic acid-based UV filters.

The urban-rural gap in older Americans' healthy life expectancy.

PURPOSE: Estimate health-quality-adjusted life expectancy (QALE) for Americans nearing retirement age and assess rural-urban disparities in QALE. METHODS: We used a dynamic microsimulation model based on Health and Retirement Study data to estimate the quantity and health quality of expected future life years for rural and urban Americans ages 59-60 in 2014-2020. FINDINGS: Cohort life expectancy at age 60 (LE) for urban and rural men was 22.9 and 20.9, respectively; for urban and rural women, LE was 25.6 and 25.0, respectively. Adjusting future life years to quality-adjusted life years, QALE was 17.5 versus 15.7 for urban versus rural men, and 19.3 versus 18.7 for women. Compared to a cohort in 1994-2000, the urban-rural QALE gap in 2014-2020 grew substantially for men; changes for women were smaller. Average QALE masked heterogeneity by race/ethnicity, education, and Census region. Counterfactual scenarios suggested eliminating smoking and managing obesity and prevalent heart conditions would be particularly beneficial for increasing rural QALE and reducing the urban-rural gap. CONCLUSIONS: Expected health quality, in addition to longevity, is an important factor when assessing rural disparities in older Americans' future life outcomes. Current chronic disease disparities are expected to translate to a widening urban-rural gap in QALE, particularly for men. Interventions earlier in life may be needed to fully address disparities in QALE at older ages.

A blended genome and exome sequencing method captures genetic variation in an unbiased, high-quality, and cost-effective manner.

We deployed the Blended Genome Exome (BGE), a DNA library blending approach that generates low pass whole genome (1-4× mean depth) and deep whole exome (30-40× mean depth) data in a single sequencing run. This technology is cost-effective, empowers most genomic discoveries possible with deep whole genome sequencing, and provides an unbiased method to capture the diversity of common SNP variation across the globe. To evaluate this new technology at scale, we applied BGE to sequence >53,000 samples from the Populations Underrepresented in Mental Illness Associations Studies (PUMAS) Project, which included participants across African, African American, and Latin American populations. We evaluated the accuracy of BGE imputed genotypes against raw genotype calls from the Illumina Global Screening Array. All PUMAS cohorts had R 2 concordance ≥95% among SNPs with MAF≥1%, and never fell below ≥90% R 2 for SNPs with MAF<1%. Furthermore, concordance rates among local ancestries within two recently admixed cohorts were consistent among SNPs with MAF≥1%, with only minor deviations in SNPs with MAF<1%. We also benchmarked the discovery capacity of BGE to access protein-coding copy number variants (CNVs) against deep whole genome data, finding that deletions and duplications spanning at least 3 exons had a positive predicted value of ~90%. Our results demonstrate BGE scalability and efficacy in capturing SNPs, indels, and CNVs in the human genome at 28% of the cost of deep whole-genome sequencing. BGE is poised to enhance access to genomic testing and empower genomic discoveries, particularly in underrepresented populations.

Corticotropin-Releasing Factor Release From a Unique Subpopulation of Accumbal Neurons Constrains Action-Outcome Acquisition in Reward Learning.

BACKGROUND: The nucleus accumbens (NAc) mediates reward learning and motivation. Despite an abundance of neuropeptides, peptidergic neurotransmission from the NAc has not been integrated into current models of reward learning. The existence of a sparse population of neurons containing corticotropin-releasing factor (CRF) has been previously documented. Here, we provide a comprehensive analysis of their identity and functional role in shaping reward learning. METHODS: Our multidisciplinary approach included fluorescent in situ hybridization (n = ≥3 mice), tract tracing (n = 5 mice), ex vivo electrophysiology (n = ≥30 cells), in vivo calcium imaging with fiber photometry (n = ≥4 mice), and use of viral strategies in transgenic lines to selectively delete CRF peptide from NAc neurons (n = ≥4 mice). Behaviors used were instrumental learning, sucrose preference, and spontaneous exploration in an open field. RESULTS: We showed that the vast majority of NAc CRF-containing neurons are spiny projection neurons (SPNs) comprising dopamine D1-, D2-, or D1/D2-containing SPNs that primarily project and connect to the ventral pallidum and to a lesser extent the ventral midbrain. As a population, they display mature and immature SPN firing properties. We demonstrated that NAc CRF-containing neurons track reward outcomes during operant reward learning and that CRF release from these neurons acts to constrain initial acquisition of action-outcome learning and at the same time facilitates flexibility in the face of changing contingencies. CONCLUSIONS: CRF release from this sparse population of SPNs is critical for reward learning under normal conditions.

Medicaid Reimbursement for Total Hip and Knee Arthroplasty: A State-by-State Analysis Compared With Medicare.

BACKGROUND: Medicare (MCR) reimbursement for arthroplasty procedures has been declining, but little has been reported on Medicaid (MCD) reimbursement. We sought to determine MCD reimbursement rates using state MCD data for nine arthroplasty procedure codes and compare them to MCR rates. METHODS: The Centers for Medicare & Medicaid Services physician fee schedule was used to collect MCR reimbursement rates, and state MCD fee schedules were accessed to collect MCD rates for nine procedures encompassing primary and revision hip and knee arthroplasty surgery. State MCR and MCD rates were compared to determine the mean dollar difference and dollar difference per relative value unit. A cost of living adjustment was performed using the Medicare Wage Index for each state. Coefficients of variation were calculated for each state to determine overall variability between the two systems. RESULTS: The mean reimbursement rates for MCD were lower for eight of the nine codes used in the study. Medicaid reimbursed physicians an average of 11.3% less overall and 23.1% less when adjusted for cost of living. The amount of variability in the MCR rates was low with a consistent coefficient of variation of 0.06, but was higher in the MCD rates with a range of 0.26 to 0.29 in the unadjusted rates and 0.34 to 0.37 in the adjusted rates. There was a mean $6.73 decreased reimbursement per relative value unit for MCD procedures. CONCLUSIONS: For the most common arthroplasty procedures, MCD reimbursed physicians less than MCR on average. MCD also demonstrated increased variability when compared to MCR rates between states.

Simultaneous Optical Imaging of Gastric Slow Waves and Contractions in the In Vivo Porcine Stomach.

Gastric peristalsis is governed by electrical "slow waves" generally assumed to travel from proximal to distal stomach (antegrade propagation) in symmetric rings. While alternative slow wave patterns have been correlated with gastric disorders, their mechanisms and how they alter contractions remain understudied. Optical electromechanical mapping, a developing field in cardiac electrophysiology, images electrical and mechanical physiology simultaneously. Here, we translate this technology to the in-vivo porcine stomach. Stomachs were surgically exposed and a fluorescent dye (di-4-ANEQ(F)PTEA) that transduces the membrane potential (Vm) was injected through the right gastroepiploic artery. Fluorescence was excited by LEDs and imaged with one or two 256x256 pixel cameras. Motion artifact was corrected using a marker-based motion tracking method and excitation ratiometry, which cancels common-mode artifact. Tracking marker displacement also enabled gastric deformation to be measured. We validated detection of electrical activation and Vm morphology against alternative non-optical technologies. Non-antegrade slow waves and propagation direction differences between the anterior and posterior stomach were commonly present in our data. However, sham experiments suggest they were a feature of the animal preparation and not an artifact of optical mapping. In experiments to demonstrate the method's capabilities, we found that repolarization did not always follow at a fixed time behind activation "wavefronts," which could be a factor in dysrhythmia. Contraction strength and the latency between electrical activation and contraction differed between antegrade and non-antegrade propagation. In conclusion, optical electromechanical mapping, which simultaneously images electrical and mechanical activity, enables novel questions regarding normal and abnormal gastric physiology to be explored.

Racial and ethnic differences in unmet needs among older adults receiving publicly-funded home and community-based services.

BACKGROUND: Unmet need for home and community-based services (HCBS) may disparately impact older adults from racial and ethnic minoritized groups. We examined racial and ethnic differences in unmet need for HCBS among consumers ≥65 years using publicly funded HCBS. METHODS: We analyzed the National Core Indicators-Aging and Disability survey data (2015-2019) from 21,739 community-dwelling HCBS consumers aged ≥65 years in 23 participating states. Outcome measures included self-reported unmet need in six service types (i.e., personal care, homemaker/chore, delivered meals, adult day services, transportation, and caregiver support). Racial and ethnic groups included non-Hispanic Black, Asian, non-Hispanic White, Hispanic, and multiracial groups. Logistic regression models examined associations between race and ethnicity and unmet need, adjusting for sociodemographic, health, and HCBS program (i.e., Medicaid, Older Americans Act [OAA], Program for All-Inclusive Care for the Elderly [PACE]) characteristics, and use of specific service types. RESULTS: Among 21,739 respondents, 23.3% were Black, 3.4% were Asian, 10.8% were Hispanic, 58.8% were non-Hispanic White, and 3.7% were multiracial or identified with other races/ethnicities. Asian and Black consumers had higher odds of reporting unmet need in personal care than White consumers (adjusted odds ratio [aOR], 1.45, p value < 0.01; and aOR, 1.25, p < 0.001, respectively). Asian and Black consumers had significantly higher odds of unmet need in adult day services versus White consumers (aOR, 1.94, p < 0.001 and aOR, 1.39, p < 0.001, respectively). Black consumers had higher odds of unmet need versus non-Hispanic White consumers in meal delivery and caregiver support services (aOR, 1.29; p < 0.01; and aOR 1.26, p < 0.05, respectively). Race and ethnicity were not significantly associated with experiencing unmet need for homemaker/chore or transportation services. CONCLUSIONS: Future research should identify driving forces in disparities in unmet need to develop culturally appropriate solutions.

Commentary on Chen et al. (2022): The need for continued methodological research on leveraging information in secondary endpoints for more efficient RCTs.

Chen et al. (2022) recently proposed a set of estimating equations that incorporate data from secondary endpoints to improve precision in parameter estimates related to a primary endpoint. We were motivated to translate their methodology to the context of randomized controlled trials to gain precision in treatment effect estimation using data from secondary endpoints. Our results suggest that this estimator cannot gain efficiency in this context because of random treatment assignment, especially when there is a treatment effect on secondary endpoints, and that further methodological work in this area is needed.

Integrating Phylogenies with Chronology to Assemble the Tree of Life.

Reconstructing the global Tree of Life necessitates computational approaches to integrate numerous molecular phylogenies with limited species overlap into a comprehensive supertree. Our survey of published literature shows that individual phylogenies are frequently restricted to specific taxonomic groups due to the expertise of investigators and molecular evolutionary considerations, resulting in any given species present in a minuscule fraction of phylogenies. We present a novel approach, called the chronological supertree algorithm (Chrono-STA), that can build a supertree of species from such data by using node ages in published molecular phylogenies scaled to time. Chrono-STA builds a supertree of organisms by integrating chronological data from molecular timetrees. It fundamentally differs from existing approaches that generate consensus phylogenies from gene trees with missing taxa, as Chrono-STA does not impute nodal distances, use a guide tree as a backbone, or reduce phylogenies to quartets. Analyses of simulated and empirical datasets show that Chrono-STA can combine taxonomically restricted timetrees with extremely limited species overlap. For such data, approaches that impute missing distances or assemble phylogenetic quartets did not perform well. We conclude that integrating phylogenies via temporal dimension enhances the accuracy of reconstructed supertrees that are also scaled to time.

Regional Differences in Primary Total Knee Arthroplasty Utilization, Physician Reimbursement, and Patient Characteristics.

Background: The primary purpose of this study was to evaluate how utilization, physician reimbursement, and patient populations have changed for primary total knee arthroplasty (TKA) from 2013 to 2021 at both a regional and national level within the Medicare population. Methods: The Medicare Physician and Other Practitioners database was queried for all episodes of primary TKA between years 2013 and 2021. TKA utilization per 10,000 beneficiaries, inflation-adjusted physician reimbursement per TKA, and patient demographics of each TKA surgeon were extracted each year. Data were stratified geographically, and Kruskal-Wallis tests were utilized. Results: Between 2013 and 2021, TKA utilization per 10,000 beneficiaries increased at the greatest rate in the Northeast (+15.1%). In 2021, TKA utilization was highest in the Midwest (97.6/10,000; P < .001). The Midwest had the greatest decline in average physician reimbursement per TKA between 2013 and 2021 (-26.3%) and the lowest average reimbursement ($988.70, P < .001) in 2021. Alternatively, the Northeast had the smallest decline in average TKA reimbursement (-22.6%). Nationally, the average number of beneficiaries per TKA surgeon declined (-6.8%), while the average number of TKAs per surgeon (+5.7%) and average services per beneficiary (+24.3%) both increased. The average number of patient comorbidities and proportion of patients with dual Medicare-Medicaid eligibility decreased over time across all regions. Conclusions: This study demonstrates that TKA utilization is increasing and average physician reimbursement per TKA is declining at varying rates across the country, with the Northeast and Midwest most affected. These findings should be addressed in policy discussions to ensure equitable arthroplasty care.