Surface Roughness of CoCr and ZrO2 Femoral Heads with Metal Transfer: A Retrieval and Wear Simulator Study

Metal transfer to femoral heads may result from impingement against the metallic acetabular shell following subluxation/dislocation, or when metallic debris enters the articulation zone. Such transfers roughen the head surface, increasing polyethylene wear in total hip replacements. Presently, we examined the surface roughness of retrieved femoral heads with metallic transfer. Profilometry revealed roughness averages in regions of metal transfer averaging 0.380 μm for CoCr and 0.294 μm for ZrO2 which were one order of magnitude higher than those from non-implanted controls. Scanning electron microscopy (SEM) revealed adherent transfers on these retrievals, with titanium presence confirmed by electron dispersive spectroscopy. Due to the concern for increased wear, metal transfer was induced on non-implanted heads, which were then articulated against flat polyethylene discs in multidirectional sliding wear tests. Increased polyethylene wear was associated with these specimens as compared to unaltered controls. SEM imaging provided visual evidence that the transfers remained adherent following the wear tests. Pre- and post-test roughness averages exceeded 1 μm for both the CoCr and ZrO2 heads. Overall, these results suggest that metal transfer increases the surface roughness of CoCr and ZrO2 femoral heads and that the transfers may remain adherent following articulation against polyethylene, leading to increased polyethylene wear

A MADYMO STUDY OF PELVIC AND LOWER EXTREMITY INJURY IN FRONTAL CRASHES

ABSTRACT Recent studies suggest that there is increased risk to the pelvis and lower extremities for unbelted, front seat occupants when airbags deploy in frontal collisions. Among belted drivers, women and small adults are more likely to experience fractures of the knee-thigh-hip complex and lower leg. The occupant kinematics and impact mechanics for varying sized drivers under belted and unbelted conditions, with a deploying airbag, have not been well-investigated. The present study used occupant kinematic computer software (MADYMO) to investigate injury likelihood for the pelvis, femur and lower leg in simulations of FMVSS 208 test conditions (30 mph, rigid barrier, frontal crash) for a mid-size sedan with airbag deployment. The pelvic force criterion (PFC), femur force criterion (FFC), and Tibia index (TI) were calculated as injury predictors for 50 th percentile male and 5 th percentile female drivers, belted and unbelted, with variations in instrument panel angle and stiffness as well as hip abduction. The results indicated, most notably, that the unbelted 5 th percentile female submarined beneath the airbag and experienced TI values that exceeded the current tolerance in nearly every unbelted simulation. Injury scores for the left leg were generally higher for both dummies, due to leg entrapment and the intruding floor pan. Hip abduction of 20 degrees led to excessive hip forces in the 50 th percentile male. Seatbelts were effective at reducing injury measures in both dummies, most notably the TI score of the 5 th percentile female

Temporary epicardial cardiac resynchronisation versus conventional right ventricular pacing after cardiac surgery: study protocol for a randomised control trial

Background: Heart failure patients with stable angina, acute coronary syndromes and valvular heart disease may benefit from revascularisation and/or valve surgery. However, the mortality rate is increased- 5-30%. Biventricular pacing using temporary epicardial wires after surgery is a potential mechanism to improve cardiac function and clinical endpoints. Method/design: A multi-centred, prospective, randomised, single-blinded, intervention-control trial of temporary biventricular pacing versus standard pacing. Patients with ischaemic cardiomyopathy, valvular heart disease or both, an ejection fraction ≤ 35% and a conventional indication for cardiac surgery will be recruited from 2 cardiac centres. Baseline investigations will include: an electrocardiogram to confirm sinus rhythm and measure QRS duration; echocardiogram to evaluate left ventricular function and markers of mechanical dyssynchrony; dobutamine echocardiogram for viability and blood tests for renal function and biomarkers of myocardial injury- troponin T and brain naturetic peptide. Blood tests will be repeated at 18, 48 and 72 hours. The principal exclusions will be subjects with permanent atrial arrhythmias, permanent pacemakers, infective endocarditis or end-stage renal disease. After surgery, temporary pacing wires will be attached to the postero-lateral wall of the left ventricle, the right atrium and right ventricle and connected to a triple chamber temporary pacemaker. Subjects will be randomised to receive either temporary biventricular pacing or standard pacing (atrial inhibited pacing or atrial-synchronous right ventricular pacing) for 48 hours. The primary endpoint will be the duration of level 3 care. In brief, this is the requirement for invasive ventilation, multi-organ support or more than one inotrope/vasoconstrictor. Haemodynamic studies will be performed at baseline, 6, 18 and 24 hours after surgery using a pulmonary arterial catheter. Measurements will be taken in the following pacing modes: atrial inhibited; right ventricular only; atrial synchronous-right ventricular; atrial synchronous-left ventricular and biventricular pacing. Optimisation of the atrioventricular and interventricular delay will be performed in the biventricular pacing group at 18 hours. The effect of biventricular pacing on myocardial injury, post operative arrhythmias and renal function will also be quantified

High Natality Rates of Endangered Steller Sea Lions in Kenai Fjords, Alaska and Perceptions of Population Status in the Gulf of Alaska

Steller sea lions experienced a dramatic population collapse of more than 80% in the late 1970s through the 1990s across their western range in Alaska. One of several competing hypotheses about the cause holds that reduced female reproductive rates (natality) substantively contributed to the decline and continue to limit recovery in the Gulf of Alaska despite the fact that there have been very few attempts to directly measure natality in this species. We conducted a longitudinal study of natality among individual Steller sea lions (n = 151) at a rookery and nearby haulouts in Kenai Fjords, Gulf of Alaska during 2003–2009. Multi-state models were built and tested in Program MARK to estimate survival, resighting, and state transition probabilities dependent on whether or not a female gave birth in the previous year. The models that most closely fit the data suggested that females which gave birth had a higher probability of surviving and giving birth in the following year compared to females that did not give birth, indicating some females are more fit than others. Natality, estimated at 69%, was similar to natality for Steller sea lions in the Gulf of Alaska prior to their decline (67%) and much greater than the published estimate for the 2000s (43%) which was hypothesized from an inferential population dynamic model. Reasons for the disparity are discussed, and could be resolved by additional longitudinal estimates of natality at this and other rookeries over changing ocean climate regimes. Such estimates would provide an appropriate assessment of a key parameter of population dynamics in this endangered species which has heretofore been lacking. Without support for depressed natality as the explanation for a lack of recovery of Steller sea lions in the Gulf of Alaska, alternative hypotheses must be more seriously considered

Carnosine:can understanding its actions on energy metabolism and protein homeostasis inform its therapeutic potential?

The dipeptide carnosine (β-alanyl-L-histidine) has contrasting but beneficial effects on cellular activity. It delays cellular senescence and rejuvenates cultured senescent mammalian cells. However, it also inhibits the growth of cultured tumour cells. Based on studies in several organisms, we speculate that carnosine exerts these apparently opposing actions by affecting energy metabolism and/or protein homeostasis (proteostasis). Specific effects on energy metabolism include the dipeptide's influence on cellular ATP concentrations. Carnosine's ability to reduce the formation of altered proteins (typically adducts of methylglyoxal) and enhance proteolysis of aberrant polypeptides is indicative of its influence on proteostasis. Furthermore these dual actions might provide a rationale for the use of carnosine in the treatment or prevention of diverse age-related conditions where energy metabolism or proteostasis are compromised. These include cancer, Alzheimer's disease, Parkinson's disease and the complications of type-2 diabetes (nephropathy, cataracts, stroke and pain), which might all benefit from knowledge of carnosine's mode of action on human cells. © 2013 Hipkiss et al.; licensee Chemistry Central Ltd

Active Immersion in Scientific Literature: Gateway to Critical Thinking

The presentation will report the impact of teaching freshman Science and Technology Honors students to read and critically evaluate scientific literature using a modification of Hoskins\u27 CREATE ( C onsider, R ead, E lucidate the hypotheses, A nalyze and interpret the data and T hink of the next E xperiment) methodology. Upperclassmen in the Science and Technology Honors Program were recruited to be research liaisons to freshman teams. Research liaisons assisted freshman teams in understanding the research focus of the lab and identified a research paper from the lab. Freshman students developed concept maps, prepared cartoons of key methods used in the paper, and analyzed the presentation of data in a key figure. Changes in critical thinking during the semester were measured by the quality of the questions students posed to each other during presentations. Students\u27 confidence in understanding, conducting, evaluating and discussing scientific research increased significantly from the beginning to the end of the semester

FINITE ELEMENT SIMULATION OF PELVIC FRACTURES IN A UAB-CIREN CRASH CASE OF AN AUTOMOTIVE SIDE IMPACT SBC2013-14251

(UAB) is the only Level I Trauma Center in the state of Alabama. Roughly 3,500 patients are admitted each year from the Birmingham Regional Emergency Medical Services System (BREMSS) region, which has a population of approximately 1.3 million. The UAB Crash Injury Research Engineering Network (CIREN) Center has agreed to enroll cases and work with CIREN engineering resources to determine injury causation. The co-authors are currently working with the UAB CIREN Center in an effort to apply a validated finite element (FE) model to predict pelvic fractures in CIREN case studies. Pelvic injuries occur in over 10% of automotive side impact crashes, with over 15,000 pelvic fractures occurring annually in the United States alone METHODS UAB CIREN Case #490103596 was selected for study using a simulation with an existing car FE model from the National Crash Analysis Center (NCAC) and the PLEX model developed for the Global Human Body Models Consortium (GHMBC). The coded injury indices were 856118848-856118849-856118852, indicating pelvis fractures of the left anterior/front/ventral region and the left posterior/back/dorsal region due to the 22 mm driver side door intrusion. Model Development and Validation Geometries for the pelvis and lower extremity were generated from CT scan data (GE LightSpeed, 0.98 mm resolution, slice thickness of 1.25 mm) of a living 26-yearold, average male in a seated position The PLEX model was positioned in a detailed Ford Taurus model, including the seat cushion, from the NCAC archiv