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Biomedical subjects

M Browne

Publications and source records attributed to M Browne.

At least 19 recordsLinked to original sources
PubMed2006

A comparison of paediatric soccer, gaelic football and rugby injuries presenting to an emergency department in Ireland.

OBJECTIVES: Children presenting with sport related injuries (SRIs) as a result of soccer, rugby and gaelic football are frequently seen in an emergency medicine (EM) setting in Ireland. A comparison of the demographics of injuries in these three sports has however not previously been performed. The purpose of this study was to provide up-to-date data on the nature of these SRIs. METHOD: Data was collected retrospectively on all children (<17 years of age), injured in these three sports, presenting to an emergency medicine department over 6 months, and was entered into a database for analysis. RESULTS: Retrospective analysis was performed on 23,000 charts, and 409 SRIs were identified over a 6-month period. None of the children reported using any form of protective gear, and 27% reported a previous presentation to the emergency department with a SRI. Most injuries were as a result of soccer (56%), with 24% occurring in gaelic football, and 20% occurring in rugby. The predominant mechanism of injury was different in each sport, in soccer-falls (38%), in gaelic football-collisions with objects (balls) (37%), and in rugby-collision with persons (55%). Although the predominant type of injury in soccer and gaelic football was a fracture, accounting for 50% and 42% of injuries, respectively, in rugby however, skin/soft tissue injuries presented more commonly, accounting for 44% of injuries. When the general site of injury was investigated, the upper limb accounted for the majority of SRIs in each sport. In the management of SRIs, oral analgesics were prescribed in 50%, however, it was observed that no use was made of topical, intramuscular or rectal analgesic routes of administration. In addition it was observed that RICE/general injury advice was given in only 27%, physiotherapy was requested in 2%, and no injury prevention advice was given to any child. Overall, 8% required admission. CONCLUSIONS: The data provided from this study may raise awareness of the nature of SRIs affecting children in each of these three sports, and may be useful in formulating much needed injury prevention strategies.

Adolescent↗
PubMed2005

Microtomography assessment of failure in acrylic bone cement.

Micromechanical studies of fatigue and fracture processes in acrylic bone cement have been limited to surface examination techniques and indirect signal analysis. Observations may then be mechanically unrepresentative and/or affected by the presence of the free surface. To overcome such limiting factors the present study has utilised synchrotron X-ray microtomography for the observation of internal defects and failure processes that occurred within a commercial bone cement during loading. The high resolution and the edge detection capability (via phase contrast imaging) have enabled clear microstructural imaging of both strongly and weakly absorbing features, with an effective isotropic voxel size of 0.7 microm. Detailed assessment of fatigue damage processes in in vitro fatigue test specimens is also achieved. Present observations confirm a link with macroscopic failure and the presence of larger voids, at which crack initiation may be linked to the mechanical stress concentration set up by adjacent beads at pore surfaces. This study does not particularly support the suggested propensity for failure to occur via the inter-bead matrix; however crack deflections at matrix/bead interfaces and the incidence of crack arrest within beads do imply locally increased resistance to failure and potential improvements in global crack growth resistance via crack tip shielding.

Biocompatible Materials↗
PubMed2004

Quantitative measurement of the stresses induced during polymerisation of bone cement.

When bone cement cures, residual stresses due to bulk and thermal shrinkage will result. Present finite element (FE) simulations of implanted constructs often do not account for these stresses as an initial condition; this may lead to overestimations of the fatigue life of the cement. In the present study, an instrumented stem equipped with strain gauges and a thermocouple was employed to experimentally quantify the residual stresses induced as a result of bone cement curing within a simulated bone/cement/stem construct. Residual stresses as high as 10 MPa were observed in the cement mantle. Residual stresses of this magnitude are potentially high enough to initiate damage within the cement mantle or at the stem/cement interface immediately post-implantation. The acoustic emission technique has demonstrated that cracking and sliding mechanisms are occurring during curing, resulting in partial relaxation of these stresses. The implications for FE simulations of the implanted construct are discussed.

Bone Cements↗
PubMed2004

Investigation of fatigue crack growth in acrylic bone cement using the acoustic emission technique.

Failure of the bone cement mantle has been implicated in the loosening process of cemented hip stems. Current methods of investigating degradation of the cement mantle in vitro often require sectioning of the sample to confirm failure paths. The present research investigates acoustic emission as a passive experimental method for the assessment of bone cement failure. Damage in bone cement was monitored during four point bending fatigue tests through an analysis of the peak amplitude, duration, rise time (RT) and energy of the events emitted from the damage sections. A difference in AE trends was observed during failure for specimens aged and tested in (i) air and (ii) Ringer's solution at 37 degrees C. It was noted that the acoustic behaviour varied according to applied load level; events of higher duration and RT were emitted during fatigue at lower stresses. A good correlation was observed between crack location and source of acoustic emission, and the nature of the acoustic parameters that were most suited to bone cement failure characterisation was identified. The methodology employed in this study could potentially be used as a pre-clinical assessment tool for the integrity of cemented load bearing implants.

Acoustics↗
PubMed2004

Application of an interface failure model to predict fatigue crack growth in an implanted metallic femoral stem.

A novel computational modelling technique has been developed for the prediction of crack growth in load bearing orthopaedic alloys subjected to fatigue loading. Elastic-plastic fracture mechanics has been used to define a three-dimensional fracture model, which explicitly models the opening, sliding and tearing process. This model consists of 3D nonlinear spring elements implemented in conjunction with a brittle material failure function, which is defined by the fracture energy for each nonlinear spring element. Thus, the fracture energy criterion is implicit in the brittle material failure function to search for crack initiation and crack development automatically. A degradation function is employed to reduce interfacial fracture properties corresponding to the number of cycles; thus fatigue lifetime can be predicted. Unlike other failure modelling methods, this model predicts the failure load, crack path and residual stiffness directly without assuming any pre-flaw condition. As an example, fatigue of a cobalt based alloy (CoCrMo) femoral stem is simulated. Experimental fatigue data was obtained from four point bending tests. The finite element model simulated a fully embedded implant with a constant point load. Comparison between the model and mechanical test results showed good agreement in fatigue crack growth rate.

Femur↗
PubMed2004

Fatigue characterization of a polymer foam to use as a cancellous bone analog material in the assessment of orthopaedic devices.

Analog materials are used as a substitute to cancellous bone for in vitro biomechanical tests due to their uniformity, consistency in properties and availability. To date, only the static material properties of these materials have been assessed, although they are often used in fatigue tests. Cancellous bone exhibits complex material behavior when subjected to fatigue loads, including modulus degradation, accumulation of permanent strain and increasing hysteresis. Analog materials should exhibit similar fatigue behavior to cancellous bone if they are to be used in cyclic loading tests. In our study, a polymer foam (commercial name HEREX C70.55) has been studied for its static and fatigue behavior and compared with that of cancellous bone. In compression, the foam exhibited qualitatively similar mechanical behavior, but the degree of modulus degradation and accumulation of permanent strain was lower than expected for cancellous bone. In general, the tensile properties of the foam were greater than found in compression, the opposite to the mechanical behavior of cancellous bone. The methodology employed here could form the basis of selecting suitable analog materials for cancellous bone in the future.

Biomechanical Phenomena↗
PubMed2002

Low-probability event-detection and separation via statistical wavelet thresholding: an application to psychophysiological denoising.

OBJECTIVES: The aim of this paper is to introduce and test a general, wavelet-based method for the automatic removal of noise and artefact from psychophysiological data. METHODS: Statistical wavelet thresholding (SWT) performs blind source separation by transforming data to the wavelet domain, and subsequent filtering of wavelet coefficients based on a statistical framework. The observed wavelet coefficients are modelled using a Gaussian distribution, from which low-probability outliers are attenuated based on their z-scores. RESULTS: The technique was applied to both simulated and real event-related potentials (ERP) data. SWT applied to artificial data displayed increased signal-to-noise ratio (SNR) improvements as noise amplitude increased. ERP averages of filtered experimental data displayed a correlation of 0.93 with operator-filtered data, compared with a correlation of 0.56 for unfiltered data. The energy of operator-designated contaminated trials was attenuated by a factor of 7.46 relative to uncontaminated trials. SNR improvement was observed in simulated tests. CONCLUSIONS: Variations of SWT may be useful in situations where one wishes to separate uncommon/uncharacteristic structures from time series data sets. For artefact removal applications, SWT appears to be a valid alternative to expert operator screening.

Artifacts↗
PubMed2001

Ischaemic optic neuropathy following bilateral neck dissection.

Two cases of ischaemic optic neuropathy, which occurred as a complication of oncological neck surgery, are reported. These cases are submitted because of the apparent scarcity in the literature of this complication after head and neck surgery. They are also unusual because they presented with different clinical manifestations of ischaemic optic neuropathy after separate forms of bilateral neck dissection. A literature review identifies a small number of similar cases and risk factors and preventative measures are discussed.

Carcinoma, Squamous Cell↗
PubMed2001

Expandable metal stents in the palliation of malignant dysphagia and oesophageal-respiratory fistulae.

The use of self expandable metal stents in the palliation of malignant dysphagia and oesophago-respiratory fistulae has increased in recent years. The aim of this study was to report a comprehensive 4 year audit of a Specialist Unit's experience with the expandable stent. 200 expandable metal stents were deployed for palliation of non operable malignant dysphagia or fistulae. Per-operative, early (<30 days) and late (>30 days) complications specific to the stent were documented. Stents were successfully positioned in all patients. There was no mortality associated with the insertion and no perforation. Dysphagia was palliated initially in 93 per cent of cases. The mean dysphagia score improved significantly from 3.2 to 1.5 (p<0.01). This significant benefit persisted at 3 months and 6 months of follow-up. The commonest complication was stent migration (5.5%) and 23 patients (11%) required a second stent insertion. Oesophago-respiratory fistulae were successfully palliated in all cases. This study demonstrates the effectiveness of self expandable metallic stents in the palliation of non operable malignant dysphagia and oesophago-respiratory fistulae. The minimal risk of significant complications and low incidence of reintervention should establish this approach as first line palliation in these patients.

Aged↗
PubMed2000

Adaptive wavelet filtering for analysis of event-related potentials from the electro-encephalogram.

A challenging task in psychophysiology is the extraction of event-related potentials (ERPs) from the background electro-encephalogram. The task is made more difficult by the properties of ERPs, which typically consist of multiple features of variable latency, localised in time and frequency. A novel technique is described for analysis of ERPs, adaptive wavelet filtering (AWF), which is proposed as an alternative to trial averaging. Band-limited detail representations of each trial are obtained using wavelet analysis. The Woody adaptive filter is then used to align trials with respect to the evoked response. In a simulation study, the AWF extracts 39% of higher-frequency signal variance from background noise, compared with less than 1% for standard averaging and the Woody filter. The AWF is applied to a data-set of 448 ERPs, comprising right-finger button presses from eight subjects. Average split-half reliability of the AWF on scales up to 12 Hz was 0.51.

Electroencephalography↗
PubMed2000

Implementation of a large-scale ENU mutagenesis program: towards increasing the mouse mutant resource.

Systematic approaches to mouse mutagenesis will be vital for future studies of gene function. We have begun a major ENU mutagenesis program incorporating a large genome-wide screen for dominant mutations. Progeny of ENU-mutagenized mice are screened for visible defects at birth and weaning, and at 5 weeks of age by using a systematic and semi-quantitative screening protocol-SHIRPA. Following this, mice are screened for abnormal locomotor activity and for deficits in prepulse inhibition of the acoustic startle response. Moreover, in the primary screen, blood is collected from mice and subjected to a comprehensive clinical biochemical analysis. Subsequently, secondary and tertiary screens of increasing complexity can be used on animals demonstrating deficits in the primary screen. Frozen sperm is archived from all the male mice passing through the screen. In addition, tail tips are stored for DNA. Overall, the program will provide an extensive new resource of mutant and phenotype data to the mouse and human genetics communities at large. The challenge now is to employ the expanding mouse mutant resource to improve the mutant map of the mouse. An improved mutant map of the mouse will be an important asset in exploiting the growing gene map of the mouse and assisting with the identification of genes underlying novel mutations-with consequent benefits for the analysis of gene function and the identification of novel pathways.

Animals↗
PubMed2000

Effect of mechanical surface pretreatment on metal ion release.

The degree of metal ion dissolution from Ti-6Al-4V alloy hip replacement stems subjected to various mechanical and chemical surface pretreatments was analysed in vitro. High-dissolution rates were observed for nitric acid passivated samples that had been mechanically surface treated to increase the implant surface area. Significantly lower ion release levels were observed for mechanically treated samples which had been aged in de-ionised water. The application of an hydroxyapatite coating decreased the metal ion release from the nitric acid passivated samples (compared to the uncoated sample) and increased the metal ion dissolution from the aged samples. The dissolution behaviour of the samples is explained in terms of the diffusion processes occurring at the stem/solution interface and the morphological and chemical characteristics of the surface treated stems.

Alloys↗
PubMed2000

A systematic, genome-wide, phenotype-driven mutagenesis programme for gene function studies in the mouse.

As the human genome project approaches completion, the challenge for mammalian geneticists is to develop approaches for the systematic determination of mammalian gene function. Mouse mutagenesis will be a key element of studies of gene function. Phenotype-driven approaches using the chemical mutagen ethylnitrosourea (ENU) represent a potentially efficient route for the generation of large numbers of mutant mice that can be screened for novel phenotypes. The advantage of this approach is that, in assessing gene function, no a priori assumptions are made about the genes involved in any pathway. Phenotype-driven mutagenesis is thus an effective method for the identification of novel genes and pathways. We have undertaken a genome-wide, phenotype-driven screen for dominant mutations in the mouse. We generated and screened over 26,000 mice, and recovered some 500 new mouse mutants. Our work, along with the programme reported in the accompanying paper, has led to a substantial increase in the mouse mutant resource and represents a first step towards systematic studies of gene function in mammalian genetics.

Animals↗
PubMed2000

Optimization of routine plasma homocysteine monitoring.

An elevated plasma homocysteine (Hcy) level is now considered to be an important risk factor in arterial and venous thromboembolic events. As a result of this relatively recent finding, there has been a dramatic increase in the number of requests for Hcy measurement. In our laboratory, this demand has been met by employing an automated immunoassay and improving the pre-analytical handling of blood samples. An automated fluorescent polarization immunoassay (FPIA) gave similar results to a reference high-pressure chromatographic (HPLC) method (r2 = 0.98, enzyme immunoassay = 0.998 HPLC - 0.3) and excellent between-run reproducibility (coefficient of variation <3%). The new assay also required less specialized technical input, and improved the sample throughput two-fold. Pre-analytical stability of plasma Hcy concentrations in blood samples is crucial to the accuracy of Hcy monitoring. This stability was improved 10-fold by adopting the anticoagulant acidic citrate instead of ethylenediamine tetraacetic acid for Hcy screening by FPIA. Acidic citrate dramatically inhibits time-related plasma contamination by red-cell Hcy, resulting in improved accuracy and a reduced number of 'spoiled' specimen discards.

Drug Monitoring↗
PubMed2000

Professional roller hockey injuries.

OBJECTIVE: To study the incidence and types of injuries sustained by professional roller hockey players in practices and games, and to compare these statistics with those from ice hockey. DESIGN: This injury survey used a strict definition of injury, standardized reporting strategies, and diagnosis by a team physician as standards by which to analyze the characteristics of roller hockey injuries. SETTING: The injuries were recorded after the players had been examined by a team physician at the game or practice site or in the physician's office. PARTICIPANTS: During three seasons for one roller hockey team and one season for another team, an average of 22 players per team participated in the study. Due to personnel changes, the team rosters were modified between seasons. Each player injury was included in the study. An injury was defined as any physical impairment caused during a practice or game that eliminated the player from that practice or game or the next day's practice session or contest, or any physical ailment that necessitated a physical examination by the team physicians. MAIN OUTCOME MEASURE: Injury data were categorized and injury rates were calculated. RESULTS: 122 injuries were recorded during four professional roller hockey seasons, resulting in an overall participation injury rate of 14.4 per 1,000 player hours. The game injury rate was 304.9 per 1,000 player hours. The players were 105.1 times more likely to be injured during a game than during practice. Preseason practices produced 4.5 times more injuries than regular season practices. In comparison, sample data from the only other published study of roller hockey injuries and from several studies of ice hockey have indicated game injury rates of 139.0 (roller hockey), 119.0, 96.1, 78.4, 78.8, and 66.0 per 1,000 player hours, respectively. CONCLUSION: Results of this study demonstrate that roller hockey produces a higher rate of both contact and noncontact injuries than ice hockey; this contradicts the findings of the only other published research study on injuries in roller versus ice hockey. This increased incidence of injury may be due in part to the differences in surfaces, and can prove hazardous to even the recreational roller hockey player or in-line skater.

Adolescent↗
PubMed1999

Community hospitals. Cornish hops.

A joint health and social services trial initiative to facilitate transfers from acute hospitals to four community hospitals in east Cornwall has increased placements. Discharge planning from the community hospitals has also been improved with the appointment of a specialist social worker. Staff involved believe the project has improved communication between agencies.

Adult↗