Mechanism and Prediction of Hydrogen Embrittlement in fcc Stainless Steels and High Entropy Alloys.

The urgent need for clean energy coupled with the exceptional promise of hydrogen (H) as a clean fuel is driving development of new metals resistant to hydrogen embrittlement. Experiments on new fcc high entropy alloys present a paradox: these alloys absorb more H than Ni or SS304 (austenitic 304 stainless steel) while being more resistant to embrittlement. Here, a new theory of embrittlement in fcc metals is presented based on the role of H in driving an intrinsic ductile-to-brittle transition at a crack tip. The theory quantitatively predicts the H concentration at which a transition to embrittlement occurs in good agreement with experiments for SS304, SS316L, CoCrNi, CoNiV, CoCrFeNi, and CoCrFeMnNi. The theory rationalizes why CoNiV is the alloy most resistant to embrittlement and why SS316L is more resistant than the high entropy alloys CoCrFeNi and CoCrFeMnNi, which opens a path for the computationally guided discovery of new embrittlement-resistant alloys.

Perioperative Mortality After Cemented or Uncemented Hemiarthroplasty for Displaced Femoral Neck Fractures-A Systematic Review and Meta-analysis.

BACKGROUND: Debate surrounds the use of cemented or uncemented prostheses for the treatment of displaced femoral neck fractures (FNF). Many guidelines recommend the use of the cemented hemiarthroplasty (CHA). Proponents of CHA point out the increased re-operation rate while proponents of uncemented hemiarthroplasty (HA) highlight the increased mortality rate in the perioperative period. The aim of this study was to systematically review the literature to evaluate perioperative mortality after HA for displaced FNFs. METHODS: A systematic review and meta-analysis was performed of MEDLINE, Cochrane Library, and Embase databases evaluating perioperative mortality after HA for displaced FNFs. Randomized control trials and observational studies were included comparing current-generation stem designs. A meta-analysis was performed on studies that directly compared the different modes of fixation. RESULTS: Twenty-two studies were included (seven randomized control trials and 15 observational studies), with a total of 183,167 HAs for treatment of a displaced FNF. Fourteen studies were included in the meta-analysis. There was a higher cumulative odds of death within the first 48 hours in those with CHA compared with uncemented HA (OR: 1.64; 95% CI: 1.35, 2.00; P ≤ .01). No difference was found in mortality at 7 days, 30 days, and one year. CONCLUSION: CHA is associated with an increased mortality rate within the first two days of surgery with no difference at 7 days, 30 days, and one year. Surgeons should consider tailoring their stem choice based on the physiological status of the patient when planning HA for FNFs. Techniques to reduce the risk of bone cement implantation syndrome should be used.

Cemented Proximal Femoral Replacement for the Management of Non-Neoplastic Conditions: A Versatile Implant but Not Without Its Risks.

BACKGROUND: The demand for revision arthroplasty continues to grow. Proximal femoral bone loss poses a significant challenge to surgeons and proximal femoral replacements (PFRs) are one option to address this problem. The aim of our study is to assess the reoperation, complication, and mortality rates following PFR for treatment of non-neoplastic conditions. METHODS: A retrospective observational study was conducted of a consecutive group of patients treated with a PFR for non-neoplastic conditions between 2010 and 2018. Mortality was confirmed using the Irish national death events publication service. RESULTS: Over the 8-year study period, 79 PFRs in 78 patients were performed. Mean age of patients was 78.3 years (standard deviation 11.9), of which 37.2% were male. Periprosthetic fracture was the most common indication for PFR (63.3%). The 30-day mortality rate was 7.6% (6 patients), of which bone cement implantation syndrome occurred in 4 patients. One-year mortality was 12.7%. Complications occurred in 22.8%. CONCLUSION: A cemented PFR is a versatile prosthesis in the armamentarium of a revision arthroplasty surgeon that allows immediate full weight-bearing. However, it may appropriately be considered a last resort procedure that poses specific risks that must be explained to patients and family. We present the short-term outcomes on one of the largest series of PFR to date.

Impact of Type 2 Diabetes Mellitus on Human Bone Marrow Stromal Cell Number and Phenotypic Characteristics.

Human bone marrow-derived mesenchymal stromal cells (MSCs) have been investigated in numerous disease settings involving impaired regeneration because of the crucial role they play in tissue maintenance and repair. Considering the number of comorbidities associated with type 2 diabetes mellitus (T2DM), the hypothesis that MSCs mediate these comorbidities via a reduction in their native maintenance and repair activities is an intriguing line of inquiry. Here, it is demonstrated that the number of bone marrow-derived MSCs in people with T2DM was reduced compared to that of age-matched control (AMC) donors and that this was due to a specific decrease in the number of MSCs with osteogenic capacity. There were no differences in MSC cell surface phenotype or in MSC expansion, differentiation, or angiogenic or migratory capacity from donors living with T2DM as compared to AMCs. These findings elucidate the basic biology of MSCs and their potential as mediators of diabetic comorbidities, especially osteopathies, and provide insight into donor choice for MSC-based clinical trials. This study suggests that any role of bone marrow MSCs as a mediator of T2DM comorbidity is likely due to a reduction in the osteoprogenitor population size and not due to a permanent alteration to the MSCs' capacity to maintain tissue homeostasis through expansion and differentiation.

Placental thickness on ultrasound and neonatal birthweight.

Objective To investigate the relationship between maximal placental thickness during routine anatomy scan and birthweight at delivery. Methods This retrospective descriptive study analyzed 200 term, singleton deliveries in 2016 at Penn State Hershey Medical Center. We measured maximal placental thickness in the sagittal plane from the ultrasound images of the placenta obtained at the 18-21-week fetal anatomy screen. The relationship between placental thickness and neonatal birthweight was assessed using Pearson's correlation coefficient (r) with 95% confidence interval (CI). Logistic regression was used to assess the association between placental thickness and secondary binary outcomes of neonatal intensive care unit (NICU) admission and poor Apgar scores. Two-sample t-tests, or exact Wilcoxon rank-sum test for non-normally distributed data, were used to assess for differences attributable to medical comorbidities (pre-gestational diabetes, gestational diabetes, chronic hypertension, gestational hypertension, preeclampsia and eclampsia). Results Placental thickness had a positive correlation with neonatal birthweight [r=0.18, 95% CI=(0.05, 0.32)]. The mean placental thickness measured 34.2±9.7 mm. The strength of the correlation remained similar when adjusting for gestational age (r=0.20) or excluding medical comorbidities (r=0.19). There was no association between placental thickness and NICU admission, Apgar scores <7 or medical comorbidities. Conclusion Our study demonstrated a positive correlation between sonographic placental thickness and birthweight. Future prospective studies are warranted in order to further investigate whether a clinically significant correlation exists while adjusting for more covariates.

Breaking Bad: A Comparative Descriptive Analysis of Periprosthetic Fractures Around Cemented and Uncemented Femoral Stems.

BACKGROUND: Periprosthetic fractures are most commonly classified according to the Vancouver classification system and more recently the Unified Classification System. The aim of this study is to provide a descriptive analysis of fracture patterns in femoral periprosthetic fractures (PPFs) by femoral stem fixation. METHODS: A retrospective observational study of all femoral PPFs over a 10-year period at our institution was conducted. Presenting radiographs were examined to assess the fracture pattern. RESULTS: Over the 10-year period, 138 femoral PPFs that underwent operative treatment were examined. Mean age of patients was 78 years with 45.7% male and median American Society of Anaesthesiologists grade 3. The femoral stem fixation was cemented in 83 patients and uncemented in 55 patients. Uncemented femoral stems most commonly caused a simple oblique fracture pattern (69.1%) with a more comminuted pattern seen in cemented fixation (59%). CONCLUSION: Fracture patterns differ according to femoral stem fixation. A simple "sickle-like" oblique fracture pattern was more commonly seen in uncemented stems while cemented tapered stems resulted in a comminuted "axe splitting" pattern.

Extended trochanteric osteotomy (ETO) fixation for femoral stem revision in periprosthetic fractures: Dall-Miles plate versus cables.

BACKGROUND: Extended trochanteric osteotomy (ETO) is a well-established surgical technique used for femoral stem retrieval in revision hip arthroplasty procedures. Fixation of ETO is commonly achieved through wire, cable or cable-plate fixation. No evidence exists to date to suggest which method is superior when used in an acute traumatic setting. METHODS: Thirty cases of acute periprosthetic fracture requiring femoral stem revision with an ETO were identified over a 10-year period. Each case had a loose femoral prosthesis which was revised using an ETO approach. Nineteen of these were fixed using cables only, and 11 were fixed using a cable-plate construct. Radiographic outcomes measured included greater trochanter migration, osteolysis, union, time to union and overall success using the Beals and Tower classification. Clinical outcomes were assessed using the modified Harris Hip Score. RESULTS: Twenty-three Vancouver B/C-type fractures were identified. The remaining seven consisted of other fracture types with a loose femoral stem requiring revision through ETO. Mean follow-up was 32 months in the cable group and 12 months in the cable-plate group. The cable-plate construct performed better than cables alone. Mean migration rates were 1.7 mm lower in the cable-plate group (p < 0.05). Beals and Tower classification of radiographic outcomes was significantly better in the cable-plate group (p < 0.01). Modified Harris Hip Scores were better in this group also (p < 0.05). CONCLUSION: When utilising an ETO approach for femoral stem revision in acute periprosthetic fractures, superior clinical and radiographic outcomes can be achieved if fixation involves a cable-plate system instead of cables only.

Retrospective Multicenter Analysis of the Accuracy of Clinical Examination by Community Physicians in Diagnosing Developmental Dysplasia of the Hip.

OBJECTIVES: To determine among general practitioners (GPs) the most common clinical findings that raised concern for developmental dysplasia of the hip (DDH) and necessitated an orthopedic outpatient referral. In addition, we assessed the sensitivity and specificity of the most common of these clinical findings. STUDY DESIGN: We performed a multicenter retrospective review of all referrals by GPs to local orthopedic outpatient departments for DDH over a 12-month period. All patients had undergone pelvic radiographs, and the acetabular index (AI) was measured. The AI was used as a reference test to assess the accuracy of the clinical examination in diagnosing DDH. Sensitivity and specificity of each clinical sign was calculated. RESULTS: Twenty-six of 174 (14.9%) referred patients were diagnosed with DDH, defined as an AI score > 30. The most common indication for referral, per the GP letter was asymmetrical skin folds (97 patients, 45.8%), followed by hip click (42 patients, 19.8%), and limb shortening (34 patients, 16%). Sensitivities and specificities, respectively, among findings were asymmetric skin folds 46.2% (95% CI 26.6%-66.6%) and 42.6% (95% CI 34.5%-51.0%), hip click 23.1% (95% CI 9.0%-43.6%) and 75.7% (95% CI 67.9%-82.3%), limb shortening 30.8% (95% CI 14.3%-51.8%) and 82.4% (75.3%-88.2%), and reduced abduction 19.2% (95% CI 6.6%-39.4%) and 91.9% (95% CI 86.3%-95.7%). Using logistic regression analysis, no clinical sign was found to be a statistically significant indicator of an abnormal AI. CONCLUSIONS: Clinical examination by GPs does not reliably detect radiographically-defined DDH. None of the clinical findings by the GP showed an acceptable level of sensitivity. Absence of reduced abduction and limb shortening are relevant negatives given the high level of specificity of these signs.

Ultrasound Examination for Infants Born Breech by Elective Cesarean Section With a Normal Hip Exam for Instability.

INTRODUCTION: Because of the risk of developmental dysplasia of the hip in infants born breech-despite a normal physical exam-the American Academy of Pediatrics (AAP) guidelines recommend ultrasound (US) hip imaging at 6 weeks of age for breech females and optional imaging for breech males. The purpose of this study is to report US results and follow-up of infants born breech with a normal physical exam. METHODS: The electronic medical record for children born at 1 hospital from 2008 to 2011 was reviewed. Data were analyzed for sex, birth weight, breech position, birth order, ethnicity, US and x-ray results, follow-up, and cost. RESULTS: A total of 237 infants were born breech with a normal physical examination, all delivered by cesarean section. Of the infants, 55% were male and 45% female. About 151 breech infants (64%) with a normal Barlow and Ortolani exam had a precautionary hip US as recommended by the AAP performed at an average of 7 weeks of age. Eighty-six breech infants (35%) did not have an US and were followed clinically. Of the 151 infants that had an US, 140 (93%) were read as normal. None had a dislocated hip. Two patients had a normal physical exam but laxity on US. These 2 patients were the only infants treated in a Pavlik harness. A pediatric orthopaedic surgeon followed those with subtle US findings and no laxity until normal. CONCLUSIONS: The decision by the AAP to recommend US screening at 6 weeks of age for infants with a normal physical exam but breech position was based on an extensive literature review and expert opinion. Not all pediatricians are following the AAP guidelines. The decision to perform an US should be done on a case-by-case basis by the examining physician. A more practical, cost-effective strategy would be to skip the US if the physical exam is normal and simply obtain an AP pelvis x-ray at 4 months. LEVEL OF EVIDENCE: Level III-this is a case-control study investigating the outcomes of infants on data drawn from the electronic medical record.

Fetal Metabolic Alkalosis Resulting from Maternal Vomiting.

We describe a pregnant patient with severe compulsive water ingestion and vomiting that lead to metabolic alkalosis and preterm delivery. A 21-year-old patient was hospitalized multiple times throughout pregnancy for symptoms initially thought to be related to hyperemesis gravidarum. Overtime, it became apparent that the patient induced vomiting by rapidly drinking large volumes of water. At 32 weeks' gestation, rapid ingestion of water caused 3 days of vomiting with findings of hyponatremia, hypokalemia, hypochloremia, metabolic alkalosis, and compensatory respiratory acidosis. Fetal monitoring showed minimal variability and recurrent decelerations; subsequent biophysical profile score of 2/10 prompted urgent cesarean section. A male newborn was delivered and cord blood gases reflected neonatal metabolic alkalosis and electrolyte imbalances identical to those of the mother. Compensatory hypoventilation in both mother and fetus were treated with assisted ventilation. With saline administration and repletion of electrolytes, metabolic alkalosis resolved for both patients within days. Metabolic alkalosis was transplacentally acquired by the fetus. This case demonstrates the development of metabolic alkalosis in a pregnant woman caused by vomiting severe enough to prompt preterm delivery for nonreassuring fetal status. It also demonstrates fetal dependence on both placenta and mother to maintain physiologic acid-base and electrolyte balance.

Midtrimester fetal herpes simplex-2 diagnosis by serology, culture and quantitative polymerase chain reaction.

The acquisition of herpes simplex virus (HSV) in utero comprises a minority of neonatal herpes infections. Prenatal diagnosis is rare. We describe a midtrimester diagnosis of fetal HSV-2 infection. Ultrasound at 20 weeks for elevated maternal serum α-fetoprotein (MSAFP) showed lagging fetal growth, echogenic bowel, echogenic myocardium, and liver with a mottled pattern of echogenicity. Amniocentesis demonstrated normal karyotype, elevated AFP and positive acetylcholinesterase. Culture isolated HSV-2 with an aberrant growth pattern. Maternal serology was positive for HSV-2. Quantitative DNA polymerase chain reaction (PCR) showed 59 million copies/ml. Fetal autopsy demonstrated widespread tissue necrosis but only sparse HSV-2 inclusions. Fetal HSV-2 infection can be suspected when an elevated MSAFP accompanies ultrasound findings suggesting perinatal infection. Maternal HSV serology, amniotic fluid culture and quantitative PCR are recommended for diagnostic certainty and counseling.

Mesenchymal Stem Cell Identification After Delayed Cord Clamping.

We sought to determine the feasibility of identifying and quantifying mesenchymal stem cells (MSCs) from umbilical cord blood (UCB) after delayed cord clamping in preterm and term births. We obtained 3 mL of UCB at various gestational ages after delayed cord clamping. UCB separated by density gradient centrifugation within 4 h of delivery was passed through magnetic bead micro-columns to exclude the CD34 + cell population. The samples were incubated with fluorescent-tagged mesenchymal cell marker antibodies CD 29, CD44, CD73, CD105, and hematopoietic cell marker CD45. The cell populations were analyzed by flow cytometry. Viable cells were assessed with 7-aminoactinomycin-D. The results were expressed in median (minimum to maximum) MSCs and compared between preterm and term samples. A total of 12 UCB samples (32-40 weeks) were obtained, 10 of which demonstrated MSCs, accounting for 0.0174% (0-14.7%) of the viable UCB mononuclear cells. MSCs comprised 0.148% (0.0006-1.59%) and 0.116% (0-14.7%) of the viable UCB mononuclear cells in the term (n = 5), 38.4 ± 1.3 weeks, and preterm (n = 7) samples, 34.6 ± 1.1, respectively, p = 0.17. There was an overall median of 96 (0-39,574) MSCs. There was no difference in the median numbers of MSCs identified between term and preterm UCB samples, 3384 (23-6042) and 36 (0-39,574), respectively, p = 0.12. Mesenchymal stem cells were identified and quantified in 5 of 7 preterm and all 5 term UCB 3-mL samples obtained after delayed cord clamping.

Placental pathology reports: A qualitative study in a US university hospital setting on perceived clinical utility and areas for improvement.

OBJECTIVE: To explore how placental pathology is currently used by clinicians and what placental information would be most useful in the immediate hours after delivery. STUDY DESIGN: We used a qualitative study design to conduct in-depth, semi-structured interviews with obstetric and neonatal clinicians who provide delivery or postpartum care at an academic medical center in the US (n = 19). Interviews were transcribed and analyzed using descriptive content analysis. RESULTS: Clinicians valued placental pathology information yet cited multiple barriers that prevent the consistent use of pathology. Four main themes were identified. First, the placenta is sent to pathology for consistent reasons, however, the pathology report is accessed by clinicians inconsistently due to key barriers: difficult to find in the electronic medical record, understand, and get quickly. Second, clinicians value placental pathology for explanatory capability as well as for contributions to current and future care, particularly when there is fetal growth restriction, stillbirth, or antibiotic use. Third, a rapid placental exam (specifically including placental weight, infection, infarction, and overall assessment) would be helpful in providing clinical care. Fourth, placental pathology reports that connect clinically relevant findings (similar to radiology) and that are written with plain, standardized language and that non-pathologists can more readily understand are preferred. CONCLUSION: Placental pathology is important to clinicians that care for mothers and newborns (particularly those that are critically ill) after birth, yet many problems stand in the way of its usefulness. Hospital administrators, perinatal pathologists, and clinicians should work together to improve access to and contents of reports. Support for new methods to provide quick placenta information is warranted.

Implant system for large osteochondral defects.

Issues with current treatments for osteochondral defects such as mosaicplasty and autologous chondrocyte implantation (ACI) are lack of donor material, problems associated with donor sites, necessity of second surgical intervention and cell expansion, difficult site preparation and implant fitting to match the surrounding tissue. This study presents the development of a patient specific implant system for focal osteochondral defects that addresses these issues. Using computer aided design and manufacturing techniques, computed tomography scans are utilized to design the implant and templates that facilitate site preparation to allow for precise and easy implantation of the designed perfectly fitting tissue replacement. Functionality of the system and accurate restoration of a defect is demonstrated by digital before/after comparison and with a prototype. With the presented implantation system larger defects in curved joint surfaces can be restored to an optimal shape in an easier procedure than for instance mosaicplasty. The proposed system potentially allows for later replacement of worn implants.

Quantitative prediction of solute strengthening in aluminium alloys.

Despite significant advances in computational materials science, a quantitative, parameter-free prediction of the mechanical properties of alloys has been difficult to achieve from first principles. Here, we present a new analytic theory that, with input from first-principles calculations, is able to predict the strengthening of aluminium by substitutional solute atoms. Solute-dislocation interaction energies in and around the dislocation core are first calculated using density functional theory and a flexible-boundary-condition method. An analytic model for the strength, or stress to move a dislocation, owing to the random field of solutes, is then presented. The theory, which has no adjustable parameters and is extendable to other metallic alloys, predicts both the energy barriers to dislocation motion and the zero-temperature flow stress, allowing for predictions of finite-temperature flow stresses. Quantitative comparisons with experimental flow stresses at temperature T=78 K are made for Al-X alloys (X=Mg, Si, Cu, Cr) and good agreement is obtained.

Does Proximal Femoral Morphology Impact Morbidity and Mortality? A Cohort Study of Uncemented Hemiarthroplasties in the Treatment of Femoral Neck Fractures.

BACKGROUND: To assess outcomes after uncemented hemiarthroplasty stems in the treatment of intracapsular femoral neck fractures over an 11-year period. Mortality rates were assessed, and whether proximal femoral geometry and stem alignment were factors in intraoperative or postoperative periprosthetic fracture (PPF) needs to be identified. MATERIALS AND METHODS: A retrospective single-center observational study was conducted of all patients who underwent intracapsular femoral neck fracture treatment using an uncemented prosthesis between January 2008 and December 2018. Primary endpoints included mortality rate, Dorr classification, prosthesis alignment, intraoperative fracture, and reoperation rate for any reason. Subanalysis on collared and uncollared implants was also conducted. Multivariate logistic regression was performed based on Dorr classification for stem alignment, fracture incidence, reoperation rate, implant sizing, and patient mortality. RESULTS: A total of 536 patients received an uncemented hemiarthroplasty in the study period. The mean patients age was 80.4 years, of which 71% were female. The 30-day mortality rate was 5.2%, with no deaths on day zero or day one. Twenty patients (3.7%) sustained an intraoperative calcar fracture, and 14 patients a PPF (2.6%) at a mean of 1.3 years from surgery. Dorr C type femurs were more likely to develop a PPF (P = .001), while valgus stem alignment was associated with PPF (P = .049). CONCLUSIONS: This implant has low reoperation rates, low early postoperative mortality, and low 30-day mortality. This large single-center study provides up-to-date information using a contemporary stem in patients with multiple comorbidities. Dorr C femoral morphology and valgus stem malalignment were risk factors for postoperative fractures.

Origin of plasticity length-scale effects in fracture.

Fracture in metals is controlled by material behavior around the crack tip where size-dependent plasticity, now widely demonstrated at the micron scale, should play a key role. Here, a physical origin of the controlling length scales in fracture is identified using discrete-dislocation plasticity simulations. Results clearly demonstrate that the spacing between obstacles to dislocation motion controls fracture toughness. The simulations support a continuum strain-gradient plasticity model and provide a physical interpretation for that model's phenomenological length scale. Analysis of a dislocation pileup under a stress gradient predicts the yield stress to increase with increasing obstacle spacing, physically rationalizing the simulations.