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Biomedical subjects

M Taylor

Publications and source records attributed to M Taylor.

At least 19 recordsLinked to original sources
PubMed2007

Determination of suitable sample sizes for multi-patient based finite element studies.

Finite element analysis is used extensively to assess joint replacements, but the majority of these are single sample studies. Recent investigations have suggested that such studies are unable to account for natural inter-patient variation in bone geometry and material property distribution. Recent developments in computer tomography based analyses make multiple sample studies possible; the question remains how many femurs are required to perform a study which accounts for such variations. This work investigates the factors that should be considered in answering this question. It explores sample sizing techniques when comparing strain distribution in the intact and implanted femur and when comparing two or more implant designs in a group of femurs. An example analysis of the effect of femoral head resurfacing was undertaken. Two sample sizing calculations were utilised, one based on achieving the desired precision in results, the other based on determining if a significant difference exists between two designs. The analysis shows that reasonable statistical precision can be achieved with a group of femurs. The study was also able to determine a suitable sample size for the analysis of a statistically significant difference between two groups of femurs with varying design parameters. The study concluded that while sample sizing is recommended for an accurate analysis, consideration must be made for the practicality of such a task.

Biomechanical Phenomena↗
PubMed2007

Effect of varus/valgus malalignment on bone strains in the proximal tibia after TKR: an explicit finite element study.

Malalignment is the main cause of tibial component loosening. Implants that migrate rapidly in the first two post-operative years are likely to present aseptic loosening. It has been suggested that cancellous bone stresses can be correlated with tibial component migration. A recent study has shown that patient-specific finite element (FE) models have the power to predict the short-term behavior of tibial trays. The stresses generated within the implanted tibia are dependent on the kinematics of the joint; however, previous studies have ignored the kinematics and only applied static loads. Using explicit FE, it is possible to simultaneously predict the kinematics and stresses during a gait cycle. The aim of this study was to examine the cancellous bone strains during the stance phase of the gait cycle, for varying degrees of varus/valgus eccentric loading using explicit FE. A patient-specific model of a proximal tibia was created from CT scan images, including heterogeneous bone properties. The proximal tibia was implanted with a commercial total knee replacement (TKR) model. The stance phase of gait was simulated and the applied loads and boundary conditions were based on those used for the Stanmore knee simulator. Eccentric loading was simulated. As well as examining the tibial bone strains (minimum and maximum principal strain), the kinematics of the bone-implant construct are also reported. The maximum anterior-posterior displacements and internal-external rotations were produced by the model with 20 mm offset. The peak minimum and maximum principal strain values increased as the load was shifted laterally, reaching a maximum magnitude for -20 mm offset. This suggests that when in varus, the load transferred to the bone is shifted medially, and as the bone supporting this load is stiffer, the resulting peak bone strains are lower than when the load is shifted laterally (valgus). For this particular patient, the TKR design analyzed produced the highest cancellous bone strains when in valgus. This study has provided an insight in the variations produced in bone strain distribution when the axial load is applied eccentrically. To the authors' knowledge, this is the first time that the bone strain distribution of a proximal implanted tibia has been examined, also accounting for the kinematics of the tibio-femoral joint as part of the simulation. This approach gives greater insight into the overall performance of TKR.

Arthroplasty, Replacement, Knee↗
PubMed2006

Commercial sex venues: a closer look at their impact on the syphilis and HIV epidemics among men who have sex with men.

OBJECTIVE: To provide insight into the role of commercial sex venues in the spread of syphilis and HIV among men who have sex with men (MSM). STUDY: A cross sectional study of 1351 MSM who were diagnosed with early syphilis who did and did not encounter sexual partners at commercial sex venues. RESULTS: Overall, 26% MSM diagnosed with syphilis had sexual encounters at commercial sex venues. Of these, 74% were HIV positive, 94% reported anonymous sex, and 66% did not use a condom. Compared to those who did not have a sexual encounter at these venues, they were twice as likely to be HIV positive (OR = 1.91, 95% CI 1.36 to 2.68), six times more likely to have anonymous sex (OR = 6.18, 95% CI 3.37 to 11.32), twice as likely not to use condom (OR = 2.02, 95% CI 1.71 to 2.38), and twice as likely to use non-injecting drugs (OR = 1.65, 95% CI 1.21 to 2.37). CONCLUSIONS: MSM diagnosed with syphilis who frequent commercial sex venues are engaging in high risk behaviours for syphilis and HIV transmission and acquisition. Thus commercial sex venues are one of the focal points of syphilis and HIV transmission and acquisition.

Adult↗
PubMed2006

Current role of radiofrequency ablation for the treatment of colorectal liver metastases.

BACKGROUND AND METHOD: This paper reviews the current status of radiofrequency ablation in the treatment of colorectal liver metastases. Relevant studies with at least ten patients that reported rates of complete tumour ablation, local recurrence, or survival from 1 to 5 years after treatment were included in the review. RESULTS AND CONCLUSION: Only six studies that reported at least 3-year survival were identified, with results ranging from 37 to 58 per cent. Some of these figures are promising, given that the patients were considered to have unresectable disease. However, available evidence is limited and hepatic resection remains the standard of care when feasible; radiofrequency ablation cannot be considered an equivalent. Radiofrequency ablation does, however, appear to have a role in treating unresectable disease, and may also be used in conjunction with resection to extend its limits.

Catheter Ablation↗
PubMed2006

Strain patterns during tensile, compressive, and shear fatigue of human cortical bone and implications for bone biomechanics.

It is a common theme in basic bone biomechanics and in biomechanical applications that much of the behavior can be determined and is dictated by the level of strain, whether this pertains to bone physiology, bone remodeling, osseoinduction, osseointegration, or the development of damage. The development of damage, demonstrated by stiffness loss measurements, has already been reported in detail in the literature. However, the systematic study of the development of "plastic" (residual) strains, which are associated with the inelastic mechanical behavior of bone tissue, has generally been overlooked. The present study compares the rates at which the elastic (e(a)) and plastic components (e(p)) of strain developed during tensile, compressive, and shear fatigue in human cortical bone of six individuals aged between 53 and 79 years. The overall hypothesis of this investigation is that there is a common underlying factor in the damage-related behavior of bone, which may allow us to link together the various aspects of the damage related behavior of bone. The rate of development of plastic strain (Deltae(p)/DeltaN) and the rate of growth in elastic strain amplitude (Deltae(a)/DeltaN) are described as a function of the stress (sigma), and/or stress normalized by the modulus of elasticity (sigma/E). The implications of our findings are discussed with respect to simple models/mechanisms, which may underlie the observed behavior.

Aged↗
PubMed2006

Liposomal encapsulated doxorubicin (Caelyx) in the treatment of relapsed aggressive non-Hodgkin's lymphoma: a phase II study.

Aggressive non-Hodgkin's lymphoma (NHL), such as diffuse large B-cell lymphoma, can be cured in approximately 50% of cases, but those cases that recur and are not amenable to high-dose chemotherapy rely on palliative chemotherapy to improve symptoms and prolong life. Anthracyclines are associated with a high response rate in aggressive NHL but extended treatment results in cardiotoxicity. Liposomal encapsulated doxorubicin has been shown in other tumor types to allow for extended treatment with doxorubicin, but is associated with a low cardiac risk. The present study aimed to assess the response rate, survival and cardiac risk of patients with relapsed aggressive NHL treated with liposomal encapsulated doxorubicin. Eighteen patients with relapsed aggressive NHL were treated with liposomal encapsulated doxorubicin (40 - 50 mg/m2) for a planned six cycles. Some 83% of patients had diffuse large B-cell or mantle cell NHL. Four patients had a partial response (23%), whereas five patients had stable disease. None had a complete response. Eight patients progressed when receiving the liposomal encapsulated doxorubicin therapy. The median survival time was 34 weeks, and the median progression-free survival was 15.7 weeks. Overall survival was 50% at 6 months and 39% at 12 months. Progression-free survival was 33% at 6 months and was 28% at 12 months. The mean ejection fraction pre- and post-liposomal encapsulated doxorubicin treatment remained the same. Only one patient had a drop in ejection fraction to <50%. Liposomal encapsulated doxorubicin offers another choice to patients seeking palliation from their lymphoma recurrence with a response rate of 23% that was well tolerated and had a minimal cardiotoxic risk.

Aged↗
PubMed2006

Use of a vascular access port for the measurement of pulsatile luteinizing hormone in old broiler breeders.

Techniques used to measure circulating hormone concentrations in avian species over extended periods routinely involve cannulation or multiple venipunctures under physical restraint, resulting in sepsis and stress. We adapted a method for serial blood sampling in chickens using a vascular access port (VAP) surgically implanted under the skin of the neck and connected to a catheter inserted in the right jugular vein. The system was used to measure circulating luteinizing hormone (LH) profiles in six, 21-mo-old broiler breeders at the end of their laying period. The VAP were implanted under general anesthesia, and, after a period of recovery, serial blood samples (every 10 min for 6 h) were collected using an extension line connected to a push-pull system. Birds were unrestrained and had free access to food and water. Red blood cells were recovered by centrifugation, reconstituted in saline solution, and returned to the donor bird through the VAP once every 90 min. Luteinizing hormone levels were subsequently measured in plasma by radioimmunoassay. With the exception of 1 hen that developed valvular endocarditis, no sign of disease or infection was observed throughout the study, and the VAP remained functional in all birds for at least 3 mo. Thus, our results suggest that VAP are a safe, reliable, and less stressful technique for serial blood sampling and long-term studies. Radioimmunoassay results revealed that in old birds, circulating LH levels followed a pulsatile pattern, with pulse amplitudes ranging from 1.35 to 2.02 ng/mL and pulse frequencies ranging from 5 to 6 peaks per 6 h. Although not significant, amplitude of LH pulses in out-of-lay hens appeared to be lower than in laying hens.

Aging↗
PubMed2006

Assessment of abstracts submitted to the annual scientific meeting of the Royal Australian and New Zealand College of Radiologists.

The process for selecting abstracts submitted for presentation at annual scientific meetings should ensure both the quality of these meetings and fairness to prospective presenters. The aim of the present study was to review the assessment of radiation oncology abstracts submitted for oral presentation to the 2004 Royal Australian and New Zealand College of Radiologists annual scientific meeting. Selection criteria were developed that were primarily focused on the subjective aspects of abstract quality. All research abstracts were reviewed blindly by five individual reviewers (four radiation oncologists and a statistician), scoring each abstract in five categories. The scores of three reviewers were used to select the top 30 general and top eight trainee entries. For comparison, cluster analysis using the scores of all five reviewers was used to group papers into two ranks. There was a strong correlation in total scores for each paper, between all reviewers. Similarly, the study design subscale was strongly correlated between all reviewers. Abstracts belonging to the first-rank cluster were generally selected. Most trainee entries would have been successful in being accepted into the general programme. The selection process described appears feasible and fair and may improve the quality of meetings.

Abstracting and Indexing↗
PubMed2006

Improving the management and referral of patients with transient ischaemic attacks: a change strategy for a health community.

PROBLEM: Rapid referral and management of patients with transient ischaemic attacks is a key component in the national strategy for stroke prevention. However, patients with transient ischaemic attacks are poorly identified and undertreated. DESIGN AND SETTING: Before and after evaluation of quality improvement programme with controlled comparison in three primary care trusts reflecting diverse populations and organisational structures in an urban district in the North of England. KEY MEASURES FOR IMPROVEMENT: The proportion of patients receiving antiplatelet drugs and safe driving advice on referral to a specialty clinic, and the numbers of referrals, adjusted for age, to the specialist clinic before and after the improvement programme. STRATEGIES FOR CHANGE: Interviews with patient and professionals to identify gaps and barriers to good practice; development of evidence based guidelines for the management of patients with transient ischaemic attacks; interactive multidisciplinary workshops for each primary care trust with feedback of individual audit results of referral practice; outreach visits to teams who were unable to attend the workshops; referral templates and desktop summaries to provide reminders of the guidelines to clinicians; incorporation of standards into professional contracts. EFFECTS OF CHANGE: A significant improvement occurred in identification and referral of patients with transient ischaemic attacks to specialist clinics, with a 41% increase in referrals from trained practices compared with control practices. There were also significant improvements in the early treatment and safety advice provided to patients before referral. LESSONS LEARNT: A strategic approach to effective quality improvement across a diverse health community is feasible and achievable. Careful planning with patient and professional involvement to develop a tailored and multifaceted quality improvement programme to implement evidence based practice can work in very different primary care settings. Key components of the effectiveness of the model include contextual analysis, strong professional support, clear recommendations based on robust evidence, simplicity of adoption, good communication, and use of established networks and opinion leaders.

Communication↗
PubMed2006

Finite element analysis of the resurfaced femoral head.

Failure of the resurfaced femoral head may occur in the short term owing to femoral neck fracture or in the long term owing to aseptic loosening as a result of strain shielding. Resurfacing arthroplasties are not all the same. In particular, there is considerable debate regarding the role of the metaphyseal stem and cementing technique. This study examines the influence of various metaphyseal stem configurations (diameter, percentage length in contact with bone, and bonded versus debonded) and cement mantle thickness on the load transfer within the femoral head. Resurfacing resulted in significant strain shielding in the superior femoral head and elevated strain in the superior femoral neck. Although the increase in strain in the femoral neck was significant, the mean strains were below the yield strain for cancellous bone. Peak strains were observed above the yield strain, but they accounted for less than 1 per cent of the total head-neck bone volume and therefore were unlikely to result in femoral neck fracture. Increasing the stem diameter and increasing the percentage stem length in contact with bone both increased the degree of strain shielding. Bonding the metaphyseal stem produced the most dramatic strain shielding, which also extended into the head-neck junction. In contrast, varying the cement mantle thickness had a negligible effect on the load transfer.

Biocompatible Materials↗
PubMed2006

Rhodococcus and Mycobacterium Tuberculosis: masquerade or mixed infection.

Rhodocci have a morphology similar to that of Mycobacterium tuberculosis (TB), and are indistinguishable from normal diphtheroid flora. Symptoms include fever, productive/non-productive cough and pleuritic chest pain. Rhodococcal infections, being resistant to routine anti-tuberculosis medications, may be misdiagnosed as drug-resistant TB, thus prompting treatment for TB with rifampicin-containing regimens that promote the emergence of resistance. We present here a sputum smear AFB-positive case who, although clinically cured, remains unresolved despite a series of technological investigations as to the cause of infection being purely rhodococci or mixed infection with M. tuberculosis.

Actinomycetales Infections↗
PubMed2005

Finite element analysis of a total ankle replacement during the stance phase of gait.

Total ankle replacement (TAR) designs have still several important issues to be addressed before the treatment becomes fully acceptable clinically. Very little is known about the performance, in terms of the contact pressures and kinematics of TAR when subjected to daily activities such as level gait. For this purpose, an explicit finite element model of a novel 3-component TAR was developed, which incorporated a previously validated mechanical model of the ankle ligament apparatus. The intermediate mobile polyethylene meniscal bearing was modelled as an elastic-plastic continuum while the articulating surfaces of the tibial and talar metal components as rigid bodies. Overall kinematics, contact pressures and ligament forces were analysed during passive, i.e. virtually unloaded, and active, i.e. stance phase of gait, conditions. Simulation of passive motion predicted similar kinematics as reported previously in an analytical four-bar linkage model. The meniscal bearing was observed to move 5.6 mm posteriorly during the simulated stance and the corresponding antero-posterior displacement of the talar component was 8.3 mm. The predicted pattern and the amount (10.6 degrees ) of internal-external rotation of the ankle complex were found to be in good agreement with corresponding in vivo measurements on normal ankles. A peak contact pressure of 16.8 MPa was observed, with majority of contact pressures below 10 MPa. For most ligaments, reaction forces remain within corresponding physiological ranges. A first realistic representation of the biomechanical behaviour of the human ankle when replaced by prosthetic joints is provided. The applied methodology can potentially be applied to other TAR designs.

Ankle Joint↗
PubMed2005

Towards consensus in the long-term management of relapse prevention in schizophrenia.

APPROACH TO DEVELOPING GUIDANCE: When developing guidance for the long-term management of schizophrenia, one approach is to adopt a proactive strategy that sets out clear treatment goals and strategies. This should involve a broad view being taken, embracing overall mental and physical well-being rather than simply the absence of illness. Although relapse prevention is an important goal of any long-term management strategy, there are other aspects that need to be considered, such as reintegration into society, regaining independence and quality of life. CURRENT TREATMENT: To help achieve these goals, a range of interventions can be incorporated into long-term management strategies for schizophrenia, including pharmacological interventions, psychosocial therapies and alliance-building initiatives. The current UK National Institute for Clinical Excellence guidelines already recommend that continuous therapy should be practised using an atypical (second-generation) antipsychotic drug, whenever possible, in preference to older typical drugs. The launch of the first long-acting atypical antipsychotic is an interesting new advance that may benefit many patients with schizophrenia. Psychosocial interventions, particularly family-based therapies, as well as cognitive behavioural and compliance therapies, when used alongside antipsychotics, have been shown to reduce relapse rates dramatically and to assist in social reintegration. In addition, forging collaborative alliances with patients and their carers can help to demystify schizophrenia and empower patients to take responsibility for their illness. CONSENSUS STATEMENT: This article outlines a consensus reached by a panel of leading UK healthcare professionals working with schizophrenia brought together to discuss long-term management strategies.

Antipsychotic Agents↗
PubMed2005

[Ewing's tumor].

Ewing's tumor (ET) is a malignant bone tumor occurring in children and young adults. ET affects mainly bones of the central axis, and almost always involves soft tissue infiltration. The discovery of a unique genetic alteration, which is a reciprocal translocation most frequently resulting in the fusion of the EWS gene situated on chromosome 22 with the FLI-1 gene on chromosome 11, currently places ET among neuroectodermal tumors. Moreover, this translocation is a tumor-specific genetic marker at the basis of defining ET today and is used as a diagnostic and potentially prognostic tool complementary to imaging and histopathological work-up. Since the 1970 s, important progress has been made in the clinical management of ET patients. Multiagent chemotherapy in association with local treatment (surgery and/or radiation) has clearly improved outcome. The introduction of systemic treatment was justified by the frequent sub-clinical diffusion of apparently localized ET. Intensified therapeutic strategies have for the first time cured some metastatic ET patients, but at the cost of major side effects. Treatment is currently adapted as a result of a better definition of prognostic factors as well as a better assessment of its adverse effects. Improvement in global patient care and increased management of specific acute complications associated with ET (often interwoven with iatrogeneous effects) represent an important step towards improving the quality of life for ET patients as well as preventing long term complications. In the light of present studies, the majority of surviving adults today describe their health and quality of life as good. ET is a fascinating example of the progress made not only in the diagnostic and therapeutic approach to cancer but also in the comprehension of the mechanisms behind carcinogenesis, and consequently reflects the revolution of medicine over the last century.

Adolescent↗
PubMed2005

Risk factors for delayed healing and recurrence of chronic venous leg ulcers--an analysis of 1324 legs.

OBJECTIVE: Despite similar disease patterns and treatment, there is great variation in clinical outcome between venous ulcer patients. The aim of this study was to identify independent risk factors for venous ulcer healing and recurrence. METHODS: Consecutive patients assessed by a specialist nurse-led leg ulcer service between January 1998 and July 2003 with an ABPI>0.85 were included in this study. Independent risk factors for healing and recurrence were identified from routinely assessed variables using a Cox regression proportional hazards model. RESULTS: A total of 1324 legs in 1186 patients were studied. The 24-week healing rate was 76% and 1 year recurrence rate was 17% (Kaplan-Meier life table analysis). Patient age (p <0.001, HR per year 0.989, 95% CI 0.984-0.995) and ulcer chronicity (p =0.019, HR per month 0.996, 95% CI 0.993-0.999) were independent risk factors for delayed ulcer healing. Ulcer healing time (p <0.001, HR per week 1.016, 95% CI 1.007-1.026) and superficial venous reflux not treated with surgery (p =0.015, HR 2.218, 95% CI 1.166-4.218) were independent risk factors for ulcer recurrence. CONCLUSIONS: Elderly patients with longstanding ulcers should be targeted for further research and may benefit from adjunctive treatments to improve clinical outcomes. Patients not treated with superficial venous surgery were at increased risk of leg ulcer recurrence.

Age Factors↗
PubMed2005

Obstetric complications in patients with schizophrenia and their unaffected siblings.

OBJECTIVE: We sought to explore whether obstetric complications (OCs) are more likely to occur in the presence of familial/genetic susceptibility for schizophrenia or whether they themselves represent an independent environmental risk factor for schizophrenia. METHODS: The presence of OCs was assessed through maternal interview on 216 subjects, comprising 36 patients with schizophrenia from multiply affected families, 38 of their unaffected siblings, 31 schizophrenic patients with no family history of psychosis, 51 of their unaffected siblings and 60 normal comparison subjects. We examined the familiality of OCs and whether OCs were commoner in the patient and sibling groups than in the control group. RESULTS: OCs tended to cluster within families, especially in multiply affected families. Patients with schizophrenia, especially those from multiply affected families, had a significantly higher rate of OCs compared to normal comparison subjects, but there was no evidence for an elevated rate of OCs in unaffected siblings. CONCLUSION: Our data provides little evidence for a link between OCs and genetic susceptibility to schizophrenia. If high rates of OCs are related to schizophrenia genes, this relationship is weak and will only be detected by very large sample sizes.

Adolescent↗