A patterned human neural tube model using microfluidic gradients.

The human nervous system is a highly complex but organized organ. The foundation of its complexity and organization is laid down during regional patterning of the neural tube, the embryonic precursor to the human nervous system. Historically, studies of neural tube patterning have relied on animal models to uncover underlying principles. Recently, models of neurodevelopment based on human pluripotent stem cells, including neural organoids1-5 and bioengineered neural tube development models6-10, have emerged. However, such models fail to recapitulate neural patterning along both rostral-caudal and dorsal-ventral axes in a three-dimensional tubular geometry, a hallmark of neural tube development. Here we report a human pluripotent stem cell-based, microfluidic neural tube-like structure, the development of which recapitulates several crucial aspects of neural patterning in brain and spinal cord regions and along rostral-caudal and dorsal-ventral axes. This structure was utilized for studying neuronal lineage development, which revealed pre-patterning of axial identities of neural crest progenitors and functional roles of neuromesodermal progenitors and the caudal gene CDX2 in spinal cord and trunk neural crest development. We further developed dorsal-ventral patterned microfluidic forebrain-like structures with spatially segregated dorsal and ventral regions and layered apicobasal cellular organizations that mimic development of the human forebrain pallium and subpallium, respectively. Together, these microfluidics-based neurodevelopment models provide three-dimensional lumenal tissue architectures with in vivo-like spatiotemporal cell differentiation and organization, which will facilitate the study of human neurodevelopment and disease.

Outcome Reporting in Total Ankle Arthroplasty: A Systematic Review.

Total ankle arthroplasty is an increasingly utilized treatment for ankle arthritis due to decreasing failure rates and improved outcomes. However, the literature on this procedure remains heterogeneous with large variability in outcome reporting methods. PRISMA guidelines were used to systematically review outcome reporting measures used in prospective studies and randomized control trials on total ankle arthroplasty published in 15 high-impact journals between Jan 1, 2009-May 1, 2020. A total of 43 studies were included and outcome measures were grouped into seven categories: pain, subjective function, patient satisfaction, complications, objective function, implant survivorship, and imaging. The most common topic of study was implant design followed by differences in outcomes when comparing total ankle arthroplasty and arthrodesis. The most commonly reported outcome measure was post-surgical complications. No study reported on all seven categories, while 22 (51.2%) studies reported on four or more. Subjective measures had significant variability with fifteen different Patient Reported Outcome Measures used across the studies. While the included studies were quite comprehensive, there was little consistency in reporting outcomes after total ankle arthroplasty. With improving outcomes and techniques in total ankle arthroplasty, and thus an expected increase in utilization and number of published studies, efforts should be made to use commonly employed outcome reporting methods to facilitate comparison of results across studies.

Biomechanical Comparison of Tape Versus Suture in Simulated Achilles Tendon Midsubstance Rupture.

As sutures have progressed in strength, increasing evidence supports the suture tendon interface as the site where most tendon repairs fail. We hypothesized that suture tape would have a higher load to failure versus polyblend suture due to its larger surface area. Eleven matched pairs of cadaveric Achilles tendons were sutured with 2 mm wide braided ultrahigh molecular weight polyethylene tape (Tape) or 2 mm wide braided ultrahigh molecular weight polyethylene suture (Suture) using a Krackow repair method. All Achilles repair constructs were cyclically loaded, after which they were loaded to failure. Change in suture footprint height, clinical and ultimate load to failure, and location of failure was recorded. Clinical loads to failure for Tape and Suture were 290.4 ± 74.8 and 231.7 ± 70.4 Newtons, respectively (p= .01). Ultimate loads to failure for Tape and Suture were 352.9 ± 108.1 and 289.8 ± 53.7 Newtons, respectively (p = .11). Cyclic testing resulted in significant changes in footprint height for both Tape and Suture, but the 2 sutures did not differ in terms of the magnitude of change in footprint height (p = .52). The suture tendon interface was the most common site of failure for both Tape and Suture. Our results suggest that Tape may provide added repair strength in vivo for Achilles midsubstance rupture.

Multigenerational silencing dynamics control cell aging.

Cellular aging plays an important role in many diseases, such as cancers, metabolic syndromes, and neurodegenerative disorders. There has been steady progress in identifying aging-related factors such as reactive oxygen species and genomic instability, yet an emerging challenge is to reconcile the contributions of these factors with the fact that genetically identical cells can age at significantly different rates. Such complexity requires single-cell analyses designed to unravel the interplay of aging dynamics and cell-to-cell variability. Here we use microfluidic technologies to track the replicative aging of single yeast cells and reveal that the temporal patterns of heterochromatin silencing loss regulate cellular life span. We found that cells show sporadic waves of silencing loss in the heterochromatic ribosomal DNA during the early phases of aging, followed by sustained loss of silencing preceding cell death. Isogenic cells have different lengths of the early intermittent silencing phase that largely determine their final life spans. Combining computational modeling and experimental approaches, we found that the intermittent silencing dynamics is important for longevity and is dependent on the conserved Sir2 deacetylase, whereas either sustained silencing or sustained loss of silencing shortens life span. These findings reveal that the temporal patterns of a key molecular process can directly influence cellular aging, and thus could provide guidance for the design of temporally controlled strategies to extend life span.

Plant-made E2 glycoprotein single-dose vaccine protects pigs against classical swine fever.

Classical Swine Fever Virus (CSFV) causes classical swine fever, a highly contagious hemorrhagic fever affecting both feral and domesticated pigs. Outbreaks of CSF in Europe, Asia, Africa and South America had significant adverse impacts on animal health, food security and the pig industry. The disease is generally contained by prevention of exposure through import restrictions (e.g. banning import of live pigs and pork products), localized vaccination programmes and culling of infected or at-risk animals, often at very high cost. Current CSFV-modified live virus vaccines are protective, but do not allow differentiation of infected from vaccinated animals (DIVA), a critical aspect of disease surveillance programmes. Alternatively, first-generation subunit vaccines using the viral protein E2 allow for use of DIVA diagnostic tests, but are slow to induce a protective response, provide limited prevention of vertical transmission and may fail to block viral shedding. CSFV E2 subunit vaccines from a baculovirus/insect cell system have been developed for several vaccination campaigns in Europe and Asia. However, this expression system is considered expensive for a veterinary vaccine and is not ideal for wide-spread deployment. To address the issues of scalability, cost of production and immunogenicity, we have employed an Agrobacterium-mediated transient expression platform in Nicotiana benthamiana and formulated the purified antigen in novel oil-in-water emulsion adjuvants. We report the manufacturing of adjuvanted, plant-made CSFV E2 subunit vaccine. The vaccine provided complete protection in challenged pigs, even after single-dose vaccination, which was accompanied by strong virus neutralization antibody responses.

Plantar Fascia Release Through a Single Lateral Incision in the Operative Management of a Cavovarus Foot: A Cadaver Model Analysis of the Operative Technique.

Plantar fascia release and calcaneal slide osteotomy are often components of the surgical management for cavovarus deformities of the foot. In this setting, plantar fascia release has traditionally been performed through an incision over the medial calcaneal tuberosity, and the calcaneal osteotomy through a lateral incision. Two separate incisions can potentially increase the operative time and morbidity. The purpose of the present study was threefold: to describe the operative technique, use cadaveric dissection to analyze whether a full release of the plantar fascia was possible through the lateral incision, and examine the proximity of the medial neurovascular structures to both the plantar fascia release and calcaneal slide osteotomy when performed together. In our cadaveric dissections, we found that full release of the plantar fascia is possible through the lateral incision with no obvious damage to the medial neurovascular structures. We also found that the calcaneal branch of the tibial nerve reliably crossed the osteotomy in all specimens. We have concluded that both the plantar fascia release and the calcaneal osteotomy can be safely performed through a lateral incision, if care is taken when completing the calcaneal osteotomy to ensure that the medial neurovascular structures remain uninjured.

Factors Predicting Length of Hospital Stay and Extended Care Facility Admission After Hindfoot Arthrodesis Procedures.

Delayed identification of patients requiring admission to extended care facilities (ECFs) can lead to greater healthcare costs through an increased length of hospital stay (LOHS). Previous studies of hip and knee arthroplasty identified factors associated with a likely discharge to an ECF. These issues have not been extensively studied for major hindfoot procedures. We conducted a retrospective review of 198 cases treated during a 3-year period to identify the risk factors for an extended LOHS and ECF admission after ankle arthrodesis, triple arthrodesis, pantalar arthrodesis, and subtalar arthrodesis. The primary outcomes were LOHS and ECF admission. The independent predictors included age, sex, body mass index, housing status, American Society of Anesthesiologists class, diabetes and/or diabetic neuropathy, health insurance, fixation type, and perioperative infection. Stepwise multiple regression analysis was used to determine which variables were related to a longer LOHS. Nonparametric discriminant function analysis was used to identify the preoperative factors that best predicted ECF admission. A longer LOHS was significantly related to postoperative ECF admission, Centers for Medicare and Medicaid Services (CMS) insurance, diabetic neuropathy, external fixation, and infection. ECF admission was required for 34 of 198 patients (17.2%). Discriminant analysis found that older age, living alone, external fixation, and CMS insurance predicted a greater probability of ECF admission. The function accurately classified 94% of ECF admissions and 80% of non-ECF admission patients. ECF admission and CMS insurance extended the LOHS, likely owing to the administrative process of arranging an ECF discharge. If externally validated, the function we have derived could provide preoperative identification of likely ECF discharge candidates and reduce costs by shortening the LOHS.

Hospital-Based Acute Care After Total Hip and Knee Arthroplasty: Implications for Quality Measurement.

BACKGROUND: Although hospital readmissions are being adopted as a quality measure after total hip or knee arthroplasty, they may fail accurately capture the patient's postdischarge experience. METHODS: We studied 272,853 discharges from 517 hospitals to determine hospital emergency department (ED) visit and readmission rates. RESULTS: The hospital-level, 30-day, risk-standardized ED visit (median = 5.6% [2.4%-13.7%]) and hospital readmission (5.0% [2.6%-9.2%]) rates were similar and varied widely. A hospital's risk-standardized ED visit rate did not correlate with its readmission rate (r = -0.03, P = .50). If ED visits were included in a broader "readmission" measure, 246 (47.6%) hospitals would change perceived performance groups. CONCLUSION: Including ED visits in a broader, hospital-based, acute care measure may be warranted to better describe postdischarge health care utilization.

Salmonella uses energy taxis to benefit from intestinal inflammation.

Chemotaxis enhances the fitness of Salmonella enterica serotype Typhimurium (S. Typhimurium) during colitis. However, the chemotaxis receptors conferring this fitness advantage and their cognate signals generated during inflammation remain unknown. Here we identify respiratory electron acceptors that are generated in the intestinal lumen as by-products of the host inflammatory response as in vivo signals for methyl-accepting chemotaxis proteins (MCPs). Three MCPs, including Trg, Tsr and Aer, enhanced the fitness of S. Typhimurium in a mouse colitis model. Aer mediated chemotaxis towards electron acceptors (energy taxis) in vitro and required tetrathionate respiration to confer a fitness advantage in vivo. Tsr mediated energy taxis towards nitrate but not towards tetrathionate in vitro and required nitrate respiration to confer a fitness advantage in vivo. These data suggest that the energy taxis receptors Tsr and Aer respond to distinct in vivo signals to confer a fitness advantage upon S. Typhimurium during inflammation by enabling this facultative anaerobic pathogen to seek out favorable spatial niches containing host-derived electron acceptors that boost its luminal growth.

A Standardized Set of MoClo-Compatible Inducible Promoter Systems for Tunable Gene Expression in Yeast.

Small-molecule control of gene expression underlies the function of numerous engineered gene circuits that are capable of environmental sensing, computation, and memory. While many recently developed inducible promoters have been tailor-made for bacteria or mammalian cells, relatively few new systems have been built for Saccharomyces cerevisiae, limiting the scale of synthetic biology work that can be done in yeast. To address this, we created the yeast Tunable Expression Systems Toolkit (yTEST), which contains a set of five extensively characterized inducible promoter systems regulated by the small-molecules doxycycline (Dox), abscisic acid (ABA), danoprevir (DNV), 1-naphthaleneacetic acid (NAA), and 5-phenyl-indole-3-acetic acid (5-Ph-IAA). Assembly was made to be compatible with the modular cloning yeast toolkit (MoClo-YTK) to enhance the ease of use and provide a framework to benchmark and standardize each system. Using this approach, we built multiple systems with maximal expression levels greater than those of the strong constitutive TDH3 promoter. Furthermore, each of the five classes of systems could be induced at least 60-fold after a 6 h induction and the highest fold change observed was approximately 300. Thus, yTEST provides a reliable, diverse, and customizable set of inducible promoters to modulate gene expression in yeast for applications in synthetic biology, metabolic engineering, and basic research.

Anthropomorphic Characterization of Ankle Joint.

Even though total ankle replacement has emerged as an alternative treatment to arthrodesis, the long-term clinical results are unsatisfactory. Proper design of the ankle device is required to achieve successful arthroplasty results. Therefore, a quantitative knowledge of the ankle joint is necessary. In this pilot study, imaging data of 22 subjects (with both females and males and across three age groups) was used to measure the morphological parameters of the ankle joint. A total of 40 measurements were collected by creating sections in the sagittal and coronal planes for the tibia and talus. Statistical analyses were performed to compare genders, age groups, and image acquisition techniques used to generate 3D models. About 13 measurements derived for parameters (TiAL, SRTi, TaAL, SRTa, TiW, TaW, and TTL) that are very critical for the implant design showed significant differences (p-value < 0.05) between males and females. Young adults showed a significant difference (p-value < 0.05) compared to adults for 15 measurements related to critical tibial and talus parameters (TiAL, TiW, TML, TaAL, SRTa, TaW, and TTL), but no significant differences were observed between young adults and older adults, and between adults and older adults for most of the parameters. A positive correlation (r > 0.70) was observed between tibial and talar width values and between the sagittal radius values. When compared with morphological parameters obtained in this study, the sizes of current total ankle replacement devices can only fit a very limited group of people in this study. This pilot study contributes to the comprehensive understanding of the effects of gender and age group on ankle joint morphology and the relationship between tibial and talus parameters that can be used to plan and design ankle devices.

Fabrication of Microfluidic Devices for Continuously Monitoring Yeast Aging.

For several decades, aging in Saccharomyces cerevisiae has been studied in hopes of understanding its causes and identifying conserved pathways that also drive aging in multicellular eukaryotes. While the short lifespan and unicellular nature of budding yeast has allowed its aging process to be observed by dissecting mother cells away from daughter cells under a microscope, this technique does not allow continuous, high-resolution, and high-throughput studies to be performed. Here, we present a protocol for constructing microfluidic devices for studying yeast aging that are free from these limitations. Our approach uses multilayer photolithography and soft lithography with polydimethylsiloxane (PDMS) to construct microfluidic devices with distinct single-cell trapping regions as well as channels for supplying media and removing recently born daughter cells. By doing so, aging yeast cells can be imaged at scale for the entirety of their lifespans, and the dynamics of molecular processes within single cells can be simultaneously tracked using fluorescence microscopy. Key features This protocol requires access to a photolithography lab in a cleanroom facility. Photolithography process for patterning photoresist on silicon wafers with multiple different feature heights. Soft lithography process for making PDMS microfluidic devices from silicon wafer templates.

Implementation of a Multidisciplinary Preoperative Protocol for Geriatric Hip Fractures Improves Time to Surgery at a Level III Trauma Center.

Introduction: Hip fractures are common among the elderly, and delays in time to surgery (TTS) and length of stay (LOS) are known to increase mortality risk in these patients. Preoperative multidisciplinary protocols for hip fracture management are effective at larger trauma hospitals. The purpose of this study is to evaluate the effect of a similar multidisciplinary preoperative protocol for geriatric hip fracture patients at our Level III trauma center. Materials and Methods: In this single-center retrospective study, patients aged 65 and older who were admitted from March 2016 to December 2018 (pre-protocol group, Cohort #1, n = 247) and from August 2021 to September 2022 (post-protocol group, Cohort #2, n = 169) were included. Demographic information, TTS, and LOS were obtained and compared using Student's t-test and Chi-square testing. Results: There was a significant decrease in TTS in Cohort #2 compared to Cohort #1 (P < .001). There was a significant increase in LOS in Cohort #2 compared to Cohort #1 (P < .05), but when comparing a subset of Cohort #2 (Subgroup 2B, patients admitted from May to September 2022 when the effects of COVID-19 were likely dissipated) to Cohort #1, there was no significant difference in LOS (P = .13). For patients admitted to skilled nursing facilities (SNF), LOS in Cohort #2 was significantly longer than in Cohort #1 (P = .001). Discussion: In general, Level III hospitals have fewer perioperative resources compared to larger Level I hospitals. Despite this fact, this multidisciplinary preoperative protocol effectively reduced TTS which improves mortality risk in elderly patients. LOS is a multifactorial variable, and we believe the COVID-19 pandemic was a significant confounder that reduced available SNF beds in our area which prolonged the average LOS in Cohort #2. Conclusion: A multidisciplinary preoperative protocol for geriatric hip fracture management can improve efficiency of getting patients to surgery at Level III trauma centers.

A Microfluidic Platform for Screening Gene Expression Dynamics across Yeast Strain Libraries.

The relative ease of genetic manipulation in S. cerevisiae is one of its greatest strengths as a model eukaryotic organism. Researchers have leveraged this quality of the budding yeast to study the effects of a variety of genetic perturbations, such as deletion or overexpression, in a high-throughput manner. This has been accomplished by producing a number of strain libraries that can contain hundreds or even thousands of distinct yeast strains with unique genetic alterations. While these strategies have led to enormous increases in our understanding of the functions and roles that genes play within cells, the techniques used to screen genetically modified libraries of yeast strains typically rely on plate or sequencing-based assays that make it difficult to analyze gene expression changes over time. Microfluidic devices, combined with fluorescence microscopy, can allow gene expression dynamics of different strains to be captured in a continuous culture environment; however, these approaches often have significantly lower throughput compared to traditional techniques. To address these limitations, we have developed a microfluidic platform that uses an array pinning robot to allow for up to 48 different yeast strains to be transferred onto a single device. Here, we detail a validated methodology for constructing and setting up this microfluidic device, starting with the photolithography steps for constructing the wafer, then the soft lithography steps for making polydimethylsiloxane (PDMS) microfluidic devices, and finally the robotic arraying of strains onto the device for experiments. We have applied this device for dynamic screens of a protein aggregation library; however, this methodology has the potential to enable complex and dynamic screens of yeast libraries for a wide range of applications. Key features • Major steps of this protocol require access to specialized equipment (i.e., microfabrication tools typically found in a cleanroom facility and an array pinning robot). • Construction of microfluidic devices with multiple different feature heights using photolithography and soft lithography with PDMS. • Robotic spotting of up to 48 different yeast strains onto microfluidic devices.

Evaluation of a Novel Multidisciplinary Preoperative Workup Strategy for Geriatric Hip Fractures.

OBJECTIVE: To determine the financial and clinical impact of a standardized, multidisciplinary team for surgical clearance and optimization in geriatric hip fracture patients. DESIGN: Retrospective case series. SETTING: Level-1 trauma center. PATIENTS: One hundred twenty-four geriatric patients (age >65 years old) in the preprotocol group (cohort 1; January 2017-December 2018) and 98 geriatric patients in the postprotocol group (cohort 2; October 2019-January 2021) with operative hip fractures. INTERVENTION: Implementation of a multidisciplinary team protocol consisting of Anesthesiology, Internal Medicine and Orthopedic Surgery departments for the assessment of medical readiness and optimization for surgical intervention in geriatric hip fractures. MAIN OUTCOME MEASURES: Rate of cardiology consultation, need for cardiac workup (echocardiography stress testing, heath catheterization), time to medical readiness (TTMR), time to surgery, case-cancellation rate, length of stay (LOS), and total hospitalization charges. RESULTS: Following implementation of the new protocol, there were significant ( P < 0.001) decreases in TTMR (19 vs. 11 hours), LOS (149 vs. 120 hours), case cancellation rate, and total hospital charges ($84,000 vs. $62,000). There were no significant differences with respect to in-hospital complications or readmission rates/mortality rates at 1 year. CONCLUSIONS: Following implementation of a protocolized, multidisciplinary approach to optimizing geriatric fracture patients, we were able to demonstrate a reduction in unnecessary preoperative testing, TTMR for surgery, case cancellation rate, LOS, and total hospitalization charge-without a concomitant increase in complications or mortality. This study highlights that standardization of the perioperative care for geriatric hip fracture patients can provide effective patient care while also lowering financial and logistical burden in care for these injuries. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Patterning of brain organoids derived from human pluripotent stem cells.

The emerging technology of brain organoids deriving from human pluripotent stem cells provides unprecedented opportunities to study human brain development and associated disorders. Various brain organoid protocols have been developed that can recapitulate some key features of cell type diversity, cytoarchitectural organization, developmental processes, functions, and pathologies of the developing human brain. In this review, we focus on patterning of human stem cell-derived brain organoids. We start with an overview of general procedures to generate brain organoids. We then highlight some recently developed brain organoid protocols and chemical cues involved in modeling development of specific human brain regions, subregions, and multiple regions together. We also discuss limitations and potential future improvements of human brain organoid technology.

Age-dependent aggregation of ribosomal RNA-binding proteins links deterioration in chromatin stability with challenges to proteostasis.

Chromatin instability and protein homeostasis (proteostasis) stress are two well-established hallmarks of aging, which have been considered largely independent of each other. Using microfluidics and single-cell imaging approaches, we observed that, during the replicative aging of Saccharomyces cerevisiae, a challenge to proteostasis occurs specifically in the fraction of cells with decreased stability within the ribosomal DNA (rDNA). A screen of 170 yeast RNA-binding proteins identified ribosomal RNA (rRNA)-binding proteins as the most enriched group that aggregate upon a decrease in rDNA stability induced by inhibition of a conserved lysine deacetylase Sir2. Further, loss of rDNA stability induces age-dependent aggregation of rRNA-binding proteins through aberrant overproduction of rRNAs. These aggregates contribute to age-induced proteostasis decline and limit cellular lifespan. Our findings reveal a mechanism underlying the interconnection between chromatin instability and proteostasis stress and highlight the importance of cell-to-cell variability in aging processes.

Regulatory protein HilD stimulates Salmonella Typhimurium invasiveness by promoting smooth swimming via the methyl-accepting chemotaxis protein McpC.

In the enteric pathogen Salmonella enterica serovar Typhimurium, invasion and motility are coordinated by the master regulator HilD, which induces expression of the type III secretion system 1 (T3SS1) and motility genes. Methyl-accepting chemotaxis proteins (MCPs) detect specific ligands and control the direction of the flagellar motor, promoting tumbling and changes in direction (if a repellent is detected) or smooth swimming (in the presence of an attractant). Here, we show that HilD induces smooth swimming by upregulating an uncharacterized MCP (McpC), and this is important for invasion of epithelial cells. Remarkably, in vitro assays show that McpC can suppress tumbling and increase smooth swimming in the absence of exogenous ligands. Expression of mcpC is repressed by the universal regulator H-NS, which can be displaced by HilD. Our results highlight the importance of smooth swimming for Salmonella Typhimurium invasiveness and indicate that McpC can act via a ligand-independent mechanism when incorporated into the chemotactic receptor array.

Inter- and intraobserver reliability in the radiographic evaluation of adult flatfoot deformity.

BACKGROUND: Adult acquired flatfoot is a complex deformity with numerous radiographic measurements described to define it. The purpose of this study was to evaluate the inter- and intraobserver reliability of six radiographic measurements using digital and conventional radiographs. MATERIALS AND METHODS: Three digital weightbearing radiographs consisting of anteroposterior, lateral, and hindfoot alignment views were obtained at presentation for 20 consecutive patients. Six radiographic measurements were made for each patient: talus/second metatarsal angle, calcaneal pitch angle, talus/first metatarsal angle, medial cuneiform/fifth metatarsal distance, tibial/calcaneal displacement, and calcaneal angulation. Each radiograph was evaluated on multiple occasions by a senior orthopaedic surgery resident, a junior orthopaedic surgery resident, and a third-year medical student. Inter- and intraobserver reliability was determined using measurements made on digital radiographs. RESULTS: Interobserver reliabilities were 0.830 for talus/second metatarsal angle, 0.948 for calcaneal pitch angle, 0.781 for talus/first metatarsal angle, 0.991 for medial cuneiform/fifth metatarsal distance, 0.870 for tibial/calcaneal displacement, and 0.834 for calcaneal angulation. Interobserver reliability was similar for digital and conventional radiographs, and intraobserver reliability increased with observer experience. CONCLUSION: Adult acquired flatfoot deformity is a complex condition that is difficult to quantify radiographically. The medial cuneiform/fifth metatarsal distance and the calcaneal pitch angle were found to have the highest interobserver reliability. Intraobserver reliability increased with observer experience.

Biomechanical Behavior of a Variable Angle Locked Tibiotalocalcaneal Construct.

This paper examines the mechanics of the tibiotalocalcaneal construct made with a PHILOS plating system. A failed device consisting of the LCP plate and cortical, locking, and cannulated screws was used to perform the analysis. Visual, microstructure, and fractographic examinations were carried out to characterize the fracture surface topology. These examinations revealed the presence of surface scratching, inclusions, discoloration, corrosion pits, beach marks, and cleavage and striations on the fracture surface. Further examination of the material crystallography and texture revealed an interaction of S, Ni, and Mo-based inclusions that may have raised pitting susceptibility of the device made with Stainless Steel 316L. These features suggest that the device underwent damage by pitting the corrosion-fatigue mechanism and overloading towards the end to fail the plate and screws in two or more components. The screws failed via conjoint bending and torsion fatigue mechanisms. Computer simulations of variable angle locking screws were performed in this paper. The material of construction of the device was governed by ASTM F138-8 or its ISO equivalent 5832 and exhibited inconsistencies in chemistry and hardness requirements. The failure conditions were matched in finite element modeling and those boundary conditions discussed in this paper.