Birmingham hip resurfacing: a systematic review of outcomes at minimum 10-years follow-up.

Although controversy surrounding the use of metal-on-metal (MoM) arthroplasty implants continues to exist, satisfactory clinical and radiological outcomes have been reported following Birmingham Hip Resurfacing (BHR) at long-term follow-up, leading to an Orthopaedic Data Evaluation Panel (ODEP) rating of 13A. The purpose of this study was to systematically review the literature to evaluate the functional outcomes, radiological outcomes and revision rates following BHR at a minimum of 10 years follow-up. Using the PRISMA guidelines, two independent reviewers performed a literature search using Pubmed, Embase and Scopus databases. Only studies reporting on outcomes of BHR with a minimum of 10 years' follow-up were considered for inclusion. A total of 12 studies including 7132 hips (64.8% males), with mean follow-up of 11.5 years (10-15.3), met our inclusion criteria. Of included patients, 94.3% of patient underwent BHR for osteoarthritis at a mean age was 52.0 years (48-52). At final follow-up, 96% of patients reported being satisfied with their BHR, with mean Harris Hip Scores of 93.6 and Oxford Hip Scores of 16.5. Rates of radiological femoral neck narrowing of greater than 10% and non-progressive radiological loosening were reported as 2.0% and 3.8% respectively. At final follow-up, the overall revision rate was 4.9% (334/7132), deep infection rate was 0.4%, metal allergy/insensitivity rate was 1.6%, metal reaction rate was 0.3%, rate of peri-prosthetic fracture was 0.9% and aseptic loosening rates were 1.6%. This systematic review demonstrates that BHR results in satisfactory clinical outcomes, acceptable implant survivorship, low complication rates and modest surgical revision rates in the long-term at minimum 10-year follow-up.

Strength can be controlled by edge dislocations in refractory high-entropy alloys.

Energy efficiency is motivating the search for new high-temperature (high-T) metals. Some new body-centered-cubic (BCC) random multicomponent "high-entropy alloys (HEAs)" based on refractory elements (Cr-Mo-Nb-Ta-V-W-Hf-Ti-Zr) possess exceptional strengths at high temperatures but the physical origins of this outstanding behavior are not known. Here we show, using integrated in-situ neutron-diffraction (ND), high-resolution transmission electron microscopy (HRTEM), and recent theory, that the high strength and strength retention of a NbTaTiV alloy and a high-strength/low-density CrMoNbV alloy are attributable to edge dislocations. This finding is surprising because plastic flows in BCC elemental metals and dilute alloys are generally controlled by screw dislocations. We use the insight and theory to perform a computationally-guided search over 107 BCC HEAs and identify over 106 possible ultra-strong high-T alloy compositions for future exploration.

Yield strength and misfit volumes of NiCoCr and implications for short-range-order.

The face-centered cubic medium-entropy alloy NiCoCr has received considerable attention for its good mechanical properties, uncertain stacking fault energy, etc, some of which have been attributed to chemical short-range order (SRO). Here, we examine the yield strength and misfit volumes of NiCoCr to determine whether SRO has measurably influenced mechanical properties. Polycrystalline strengths show no systematic trend with different processing conditions. Measured misfit volumes in NiCoCr are consistent with those in random binaries. Yield strength prediction of a random NiCoCr alloy matches well with experiments. Finally, we show that standard spin-polarized density functional theory (DFT) calculations of misfit volumes are not accurate for NiCoCr. This implies that DFT may be inaccurate for other subtle structural quantities such as atom-atom bond distance so that caution is required in drawing conclusions about NiCoCr based on DFT. These findings all lead to the conclusion that, under typical processing conditions, SRO in NiCoCr is either negligible or has no systematic measurable effect on strength.

A growing challenge: The rise of femoral periprosthetic fractures - An 11-year observational study.

INTRODUCTION: The demand for joint arthroplasty has risen as our elderly population increases and ages. With this so to has the number of patients suffering periprosthetic fractures (PPF). The aim of our study was to quantify the burden of PPF and provide an up to date reference of the epidemiology of PPF in Ireland. We also sought to assess length of stay (LOS), resource utilisation and mortality associated with this cohort of patients. METHODS: An eleven-year retrospective observational study was conducted of a consecutive series of patients treated for a femoral PPF. Costs were obtained from activity based tariffs provided by the hospital inpatient enquiry system and mortality was confirmed using the national death events publication system. RESULTS: Over the 11-year study period 174 procedures for a femoral PPF were performed. Mean age of patients was 77.6 years (SD 11.1 years) with 44.7% male. Median ASA grade was 3 (range 1-4) and mean LOS was 19 days. There was a 700% increase in patients undergoing surgery for a PPF over the study period. The mean cost of care was €24,413 in 2017. Thirty-day mortality was 2.9% while one-year mortality was 12.4%. CONCLUSIONS: PPF occur in an elderly comorbid cohort of patients. Care of these patients now makes up a considerable part of the orthopaedic workload and consumes a significant portion of healthcare resources. Patients should be treated in tertiary referral centres with surgeons skilled in their management. Better access to rehabilitation is needed.

Mechanistic origin and prediction of enhanced ductility in magnesium alloys.

Pure magnesium exhibits poor ductility owing to pyramidal [Formula: see text] dislocation transformations to immobile structures, making this lowest-density structural metal unusable for many applications where it could enhance energy efficiency. We show why magnesium can be made ductile by specific dilute solute additions, which increase the [Formula: see text] cross-slip and multiplication rates to levels much faster than the deleterious [Formula: see text] transformation, enabling both favorable texture during processing and continued plastic straining during deformation. A quantitative theory establishes the conditions for ductility as a function of alloy composition in very good agreement with experiments on many existing magnesium alloys, and the solute-enhanced cross-slip mechanism is confirmed by transmission electron microscopy observations in magnesium-yttrium. The mechanistic theory can quickly screen for alloy compositions favoring conditions for high ductility and may help in the development of high-formability magnesium alloys.

A Simple and Easy Intramedullary Lavage Method to Prevent Embolism During and After Reamed Long Bone Nailing.

Reaming of the long bones is widely practiced because it allows for improved healing and early mobilization in patients needing surgical debridement of bone tissue. The insertion of reamed intramedullary nails can cause complications such as bone necrosis, cortical blood supply damage, and fat or bone marrow embolism. We describe a novel way to limit the amount of material in the canal before nail insertion to limit the chances of embolism.

Cast aluminium single crystals cross the threshold from bulk to size-dependent stochastic plasticity.

Metals are known to exhibit mechanical behaviour at the nanoscale different to bulk samples. This transition typically initiates at the micrometre scale, yet existing techniques to produce micrometre-sized samples often introduce artefacts that can influence deformation mechanisms. Here, we demonstrate the casting of micrometre-scale aluminium single-crystal wires by infiltration of a salt mould. Samples have millimetre lengths, smooth surfaces, a range of crystallographic orientations, and a diameter D as small as 6 µm. The wires deform in bursts, at a stress that increases with decreasing D. Bursts greater than 200 nm account for roughly 50% of wire deformation and have exponentially distributed intensities. Dislocation dynamics simulations show that single-arm sources that produce large displacement bursts halted by stochastic cross-slip and lock formation explain microcast wire behaviour. This microcasting technique may be extended to several other metals or alloys and offers the possibility of exploring mechanical behaviour spanning the micrometre scale.

Medium term review of the ASR implant system: A single surgeon series.

INTRODUCTION: Both ASR hip resurfacings and stemmed ASR XL arthroplasties have failed at high rates in several published series. We assessed a single surgeon series of these arthroplasties looking to identify factors associated with their failure. METHODS: All surgeries were performed by one surgeon. Patients were evaluated clinically, radiologically and with serial cobalt and chromium ion analysis. RESULTS: 274 implants were analysed - 152 ASR resurfacings and 122 ASR XL implants. Thirty revisions were performed. CONCLUSION: The failure rate of the ASR implant in our series is unacceptably high - its use in routine hip arthroplasty cannot be supported.

Early results of the LPS™ limb preservation system in the management of periprosthetic femoral fractures.

INTRODUCTION: Achieving skeletal fixation in the presence of progressive bone loss is a surgical challenge, especially in cases of periprosthetic fracture (PPF). Unpredictable fracture patterns and preexisting bone loss frequently combine in this patient group. Megaprosthetic arthroplasty allows for immediate mobilisation and shorter periods of rehabilitation. We describe the clinical outcomes of a cohort of LPS™ megaprostheses performed for PPF by a single surgeon at our institution. METHODS: Between July 2013 and November 2015, 23 patients underwent endoprosthetic femoral replacement of which 16 were performed for PPF or bone loss. Patient demographics, surgical indication, operative details, implant composition, blood loss, survival, and revision surgery details were recorded in a prospectively maintained database. Patients underwent serial clinical and X-ray evaluations at 6 weeks, 3 months and 6 months post surgery with yearly reviews thereafter. RESULTS: The PPF cohort consisted of 9 males and 7 females with a mean age of 75 and a mean follow up of 19.2 months. The mean Oxford score prior to fracture was 41 (range 12-48), and 39 (range 13-48, p = 0.6) post megaprosthesis insertion. Postoperative dislocation of the megaprosthesis occurred in two patients (12.5%), with no postoperative infections recorded. CONCLUSION: We report minimal postoperative changes in functional outcome scores. The results of revision arthroplasty with LPS™ proximal femur megaprosthesis were satisfactory in 15/16 patients at a mean follow-up of 19.2 months. We recommend the use of megaprostheses in patients with markedly deficient bone stock for whom other available reconstructive procedures are unavailable.

Mechanism and energetics of 〈c + a〉 dislocation cross-slip in hcp metals.

Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated [Formula: see text] dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of [Formula: see text] dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal [Formula: see text] dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension-compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals.

The origins of high hardening and low ductility in magnesium.

Magnesium is a lightweight structural metal but it exhibits low ductility-connected with unusual, mechanistically unexplained, dislocation and plasticity phenomena-which makes it difficult to form and use in energy-saving lightweight structures. We employ long-time molecular dynamics simulations utilizing a density-functional-theory-validated interatomic potential, and reveal the fundamental origins of the previously unexplained phenomena. Here we show that the key 〈c + a〉 dislocation (where 〈c + a〉 indicates the magnitude and direction of slip) is metastable on easy-glide pyramidal II planes; we find that it undergoes a thermally activated, stress-dependent transition to one of three lower-energy, basal-dissociated immobile dislocation structures, which cannot contribute to plastic straining and that serve as strong obstacles to the motion of all other dislocations. This transition is intrinsic to magnesium, driven by reduction in dislocation energy and predicted to occur at very high frequency at room temperature, thus eliminating all major dislocation slip systems able to contribute to c-axis strain and leading to the high hardening and low ductility of magnesium. Enhanced ductility can thus be achieved by increasing the time and temperature at which the transition from the easy-glide metastable dislocation to the immobile basal-dissociated structures occurs. Our results provide the underlying insights needed to guide the design of ductile magnesium alloys.

Computational Design of Strain in Core-Shell Nanoparticles for Optimizing Catalytic Activity.

Surface strains in core-shell nanoparticles modify catalytic activity. Here, a continuum-based strategy enables accurate surface-strain-based screening and design of core-shell systems using minimal input as a means to enhance catalytic activity. The approach is validated here for Pt shells on Cu(x)Pt(1-x) cores and used to interpret experimental results on the oxygen reduction reaction in the same system. The analysis shows that precise control of particle sizes and shell thicknesses is required to achieve peak activity, rationalizing the limited increases in activity observed in experiments. The method is also applied to core-shell nanorods to demonstrate its wide applicability.

Intrapartum fever, epidural analgesia and histologic chorioamnionitis.

OBJECTIVE: Our objective was to determine whether epidural analgesia and histologic chorioamnionitis were independent predictors of intrapartum fever. STUDY DESIGN: This secondary analysis, retrospective cohort study included term parturients with placental examination during 2005. Logistic regression used fever (⩾38 °C) as the dependent variable. Significance was defined as P⩽0.05. RESULT: There were 488 (76%) of 641 term parturients with placental examination and epidural. Independent predictors of intrapartum fever were epidural odds ratio (OR)=3.4, confidence interval (CI): 1.70, 6.81, histologic chorioamnionitis OR=3.18, 95% CI: 2.04, 4.95, birthweight OR=2.07, 95%CI: 1.38, 3.12, vaginal exams OR=1.15, 95% CI:1.06, 1.24, duration ruptured membranes OR=1.03, 95% CI: 1.01,1.05, parity⩾1 OR=0.44: 0.29, 0.66 and thick meconium OR=0.35: 95%CI: 0.24, 0.85. CONCLUSION: Epidural analgesia and histologic chorioamnionitis were independent predictors of intrapartum fever. Modification of labor management may reduce the incidence of intrapartum fever.

Mechanical work makes important contributions to surface chemistry at steps.

The effect of mechanical strain on the binding energy of adsorbates to late transition metals is believed to be entirely controlled by electronic factors, with tensile stress inducing stronger binding. Here we show, via computation, that mechanical strain of late transition metals can modify binding at stepped surfaces opposite to well-established trends on flat surfaces. The mechanism driving the trend is mechanical, arising from the relaxation of stored mechanical energy. The mechanical energy change can be larger than, and of opposite sign than, the energy changes due to electronic effects and leads to a violation of trends predicted by the widely accepted electronic 'd-band' model. This trend has a direct impact on catalytic activity, which is demonstrated here for methanation, where biaxial tension is predicted to shift the activity of nickel significantly, reaching the peak of the volcano plot and comparable to cobalt and ruthenium.

Quantum-to-continuum prediction of ductility loss in aluminium-magnesium alloys due to dynamic strain aging.

Negative strain-rate sensitivity due to dynamic strain aging in Aluminium-5XXX alloys leads to reduced ductility and plastic instabilities at room temperature, inhibiting application of these alloys in many forming processes. Here a hierarchical multiscale model is presented that uses (i) quantum and atomic information on solute energies and motion around a dislocation core, (ii) dislocation models to predict the effects of solutes on dislocation motion through a dislocation forest, (iii) a thermo-kinetic constitutive model that faithfully includes the atomistic and dislocation scale mechanisms and (iv) a finite-element implementation, to predict the ductility as a function of temperature and strain rate in AA5182. The model, which contains no significant adjustable parameters, predicts the observed steep drop in ductility at room temperature, which can be directly attributed to the atomistic aging mechanism. On the basis of quantum inputs, this multiscale theory can be used in the future to design new alloys with higher ductility.

Diffusion on demand to control precipitation aging: application to Al-Mg-Si alloys.

We demonstrate experimentally that a part-per-million addition of Sn solutes in Al-Mg-Si alloys can inhibit natural aging and enhance artificial aging. The mechanism controlling the aging is argued to be vacancy diffusion, with solutes trapping vacancies at low temperature and releasing them at elevated temperature, which is supported by a thermodynamic model and first-principles computations of Sn-vacancy binding. This "diffusion on demand" solves the long-standing problem of detrimental natural aging in Al-Mg-Si alloys, which is of great scientific and industrial importance. Moreover, the mechanism of controlled buffering and release of excess vacancies is generally applicable to modulate diffusion in other metallic systems.

Second to fourth digit ratio confirms aggressive tendencies in patients with boxers fractures.

BACKGROUND: Upper limb second to fourth digit ratio (2D:4D) has been shown to be dependent on prenatal androgen exposure. A longer relative fourth digit to second digit is indicative of increased intrauterine testosterone exposure prenatally and the converse is also true for oestrogen exposure. The 2D:4D ratio has implications in the sporting, academic, financial and sexual arenas. The purpose of this study was to examine the association between smaller finger length ratios (2D:4D) and boxers fractures, in both men and women, by comparing the 2D:4D ratios in 150 boxers fractures and comparing them to matched controls. Boxers fractures are an injury classically incurred during acts of aggression and we postulated that this cohort of patients would have a smaller 2D:4D ratio in comparison to the normal population mean ratio. METHODS: One hundred and fifty radiographs from patients with boxers fractures secondary to aggressive actions were analysed and the 2D:4D ratio was calculated. A further 150 X-rays from patients not involved in aggressive activities were used as a control group and the 2D:4D ratio was calculated in the same manner. We then performed statistical analysis to compare the 2D:4D ratios between our two groups. RESULTS: As predicted, the 2D:4D in males was smaller than females in all of the groups. However, our results showed that those presenting with a boxers fracture due to an aggression related injury had a statistically significant smaller 2D:4D ratio when compared to the normal population. CONCLUSION: Boxers fractures are injuries that typically occur from an aggressive act. It is well documented that a low 2D:4D ratio is reflective of an increased prenatal exposure to androgens, particularly testosterone. We have shown that boxers fractures are associated with a smaller 2D:4D ratio than the normal population, thus suggesting that persons exposed to high levels of prenatal androgens are more likely to exhibit aggressive tendencies in adulthood. Our results suggest that smaller digit ratios may predict a predisposition to acts of aggression, and as such result in an increased likelihood of sustaining an injury such as a boxers fracture. This relationship seems to be present independently of gender.

Micromotion and friction evaluation of a novel surface architecture for improved primary fixation of cementless orthopaedic implants.

A new surface architecture (OsteoAnchor) for orthopaedic stem components has been developed, which incorporates a multitude of tiny anchor features for embedding into the bone during implantation. It was tested for its ability to provide improved primary fixation compared to existing surface coatings. Friction testing was performed on bovine trabecular bone. It was found that OsteoAnchor provided up to 76% greater resistance to transverse motion under simultaneous normal loading compared to the porous tantalum. Micromotion testing was performed on stem components implanted in cadaver ovine femurs. The micromotion amplitudes for the OsteoAnchor stem were significantly lower than for a corresponding plasma sprayed stem. These results demonstrate that OsteoAnchor has the potential to provide improved primary fixation for stem components in joint replacement operations.

Accuracy of signs of clinical chorioamnionitis in the term parturient.

OBJECTIVE: Uniform histopathologic guidelines were applied to diagnose chorioamnionitis and estimate the accuracy of clinical signs in term parturients. STUDY DESIGN: A retrospective cohort study utilized slides from term parturient placentas with Amniotic Fluid Infection Nosology Committee guidelines as the gold standard. Sensitivity, specificity and accuracy for fever, maternal tachycardia and fetal tachycardia were calculated. RESULT: Of 641 placentas, 367 (57.3%) had histologic chorioamnionitis and 274 (42.7%) were negative. Fever had a sensitivity of 42%, specificity of 86.5% and accuracy of 61%. Fever, maternal tachycardia and fetal tachycardia had a sensitivity of 18.3%, specificity of 98.2% and accuracy of 52.4%. CONCLUSION: Histologic chorioamnionitis, frequently asymptomatic, is a common finding in placentas examined from term parturients. Clinical signs are not accurate in the diagnosis. Adoption of uniform pathologic guidelines will facilitate research into the clinical significance of these lesions in the future.

Atomic mechanism and prediction of hydrogen embrittlement in iron.

Hydrogen embrittlement in metals has posed a serious obstacle to designing strong and reliable structural materials for many decades, and predictive physical mechanisms still do not exist. Here, a new H embrittlement mechanism operating at the atomic scale in α-iron is demonstrated. Direct molecular dynamics simulations reveal a ductile-to-brittle transition caused by the suppression of dislocation emission at the crack tip due to aggregation of H, which then permits brittle-cleavage failure followed by slow crack growth. The atomistic embrittlement mechanism is then connected to material states and loading conditions through a kinetic model for H delivery to the crack-tip region. Parameter-free predictions of embrittlement thresholds in Fe-based steels over a range of H concentrations, mechanical loading rates and H diffusion rates are found to be in excellent agreement with experiments. This work provides a mechanistic, predictive framework for interpreting experiments, designing structural components and guiding the design of embrittlement-resistant materials.