Development of a twenty-one-component finite element distal hind limb model: stress and strain in bovine digit structures as a result of loading on different floorings.

Finite element modeling is a unique way of introducing technical and material research into medical science. A bovine distal hind limb was scanned using computed tomography for geometric image capture and the data were subsequently divided (segmented) into 4 tissue types: bone, bone marrow, soft tissue, and the horn capsule. Material data from previous studies were integrated into the model. Flexor tendons were assembled as longitudinal structures starting at their cross-sectional areas at the height of the metatarsophalangeal joint, proceeding in the plantaro-distal direction and meeting the distal phalanx at the tuberculum flexorium. Three different flooring situations (full support floor, bearing weight in the abaxial half of the lateral claw and in the dorsal halves of both claws, respectively) were created to evaluate the effects of loading. Full support resulted in von Mises stress levels between 3.5 and 1.5 MPa for the osseous structures and some regions of the segmented soft tissue; stress patterns in the bulb and sole of the claw capsule (1.5 MPa) and in the floor (0.5 MPa) were similar to pressure plate data in vivo and in vitro, with corresponding strain values of 2.4%. Reduced support resulted in higher stresses (up to approximately 8 MPa) in bones, claw capsules, and tendons; high strains ( approximately 11%) were found in the soft tissue, depending on how the floor was constructed. Although the models may still be anatomically improved, stress and strain calculations are possible with results comparable to related research, and the model shows interaction between the 2 digits. This possibly will help with further understanding of the biomechanical function of this 2-digit structure. With respect to clinical interpretation, reduced support to the bovine hind limb increases focal stress peaks in the different tissues, which may indicate a location of potential injury.

Prospective validation study of an algorithm for triage to MRCP or ERCP for investigation of suspected pancreatico-biliary disease.

BACKGROUND: In patients with suspected pancreatico-biliary disease, endoscopic retrograde cholangiopancreatography (ERCP) should be reserved for those requiring therapeutic intervention. However, difficulty arises in identifying patients likely to require therapy in the early phase of diagnostic work-up. An algorithm has been developed by the authors based upon prospective assessment of ERCP patients for triage of patients to magnetic resonance cholangiopancreatography (MRCP) or ERCP with suspected pancreatico-biliary disease. We aimed to validate this algorithm in an independent group of patients using a different group of endoscopists blinded to the algorithm. METHODS: Patients were stratified into different categories by clinical, ultrasound and liver function test findings. The algorithm stratified patients by the likelihood of therapeutic intervention. The accuracy of the algorithm for a therapeutic outcome was assessed by receiver operator characteristics (ROC) curve analysis. RESULTS: Hundred and twenty-five consecutive patients (Oct 2005 to July 2006) were prospectively assessed by MRCP or ERCP according to the algorithm, and the outcomes recorded. Fifty-seven patients were triaged to MRCP and 63 patients were triaged to ERCP. A category was not assessable in five patients. Three patients from the MRCP group required subsequent therapeutic ERCP. Diagnostic ERCP was performed in three patients in the ERCP group. ERCP-related complications occurred in four patients. The algorithm performed well in predicting the requirement for intervention as determined by the area under the ROC curve [0.84 (95%CI 0.76-0.92)]. CONCLUSIONS: Our study confirms that an algorithm-based approach can reproducibly predict those patients requiring therapeutic biliary intervention.

Slatted floors and solid floors: stress and strain on the bovine hoof capsule analyzed in finite element analysis.

An established finite element model of a bovine claw was used to compare mechanical stress levels in a loaded model claw on different types of flooring. The following situations were compared: a claw standing on a solid floor, a claw standing on the edge of a short tie stand, and claws standing on slatted floors with slats of 28 and 40 mm (wide) running parallel and perpendicular to the claw axis. Finite element analysis allowed visualization of stress peaks seen predominantly in the weight-bearing border of the dorsal abaxial wall and of the bulbar region and in the proximal axial wall. Maximum stress values of 13 MPa were found in the model claw loaded on the solid floor and values of 18 to 22 MPa were seen in the model claw loaded on the edge of the solid floor. On slatted floors, stresses increased in the situation in which the claw was not supported under the abaxial wall. Comparison between the other slatted floors showed little difference in amounts of mechanical stress. A clear distinction was detected between the solid floor with full claw contact and the slatted floors. From the point of view of the mechanical stress seen in finite element analysis, a large contact area between claw and floor, as seen in the solid surface floor, is preferable. When use of slatted floors is unavoidable, direction of the slats should run perpendicular to the direction of the walkway to prevent even more mechanical impact in certain footing situations.

A finite element model of the bovine claw under static load for evaluation of different flooring conditions.

AIM: To create a computer-based finite element (FE) model of the bovine claw and to use finite element analysis (FEA) to estimate stress and deformation of a physiologically-shaped model claw under static load, to visualise potential material weakness and to evaluate the effect of different flooring conditions. METHODS: Model geometry was derived using digitalised images from a recently trimmed, sound, hind claw from a 4-year-old Austrian Fleckvieh cow. Material properties of bovine claw horn were defined from preliminary investigations and recently established material data, using a modulus of elasticity from 200 to 600 N/mm2. Meshing of the model was performed with 42,127 elements based on 116,141 nodes. Loading of the model was defined at 756 N per claw on a hard and soft surface. RESULTS: The FE model of the bovine claw under a load of 756 N showed only minimal deformation, most of which took place at the axial wall. Highest stresses were evident in the proximal axial wall, the outer edge of the weight-bearing surface and under the heels. The claw-floor contact image showed a pressure distribution resembling the distal rim of the claw wall. On the hard surface, the maximum stresses were three times higher than those on the soft surface. CONCLUSIONS AND CLINICAL RELEVANCE: FEA allowed visualisation of the effects that loading on different floor surfaces have on the biomechanics of the claw. Uneven preparation of the claw sole resulted in high stresses at and close to irregularities of the sole. Consequences were more severe on harder flooring. The model supports the hypothesis that mechanical factors play a substantial role in the pathogenesis of claw lesions.

Elastic properties of hoof horn on different positions in the bovine claw.

Hind claws of 15 adult, sound Fleckvieh cows were used for material analysis. The elastic modulus was tested in tension tests according to EN ISO 527 and ASTM D 638-03 at a universal material testing machine. Samples were taken from different segments of the bovine claw to find the differences in material properties. Samples orientation was parallel to the horn tubules and transversal, respectively. Dry matter of the test samples was determined at the time of testing. Elastic modulus values were highest with mean = 659.7 N/mm2 at the dorsal wall. Values dropped axial to 416.3 N/mm2, abaxial to 343.9 N/mm2 for longitudinal (parallel) samples and to 433.1 N/mm2 for transversal samples. The elastic modulus of the sole segment was found to be 172.1 N/mm2. No difference was calculated neither between right and left feet, lateral and medial claws, nor between longitudinal and transversal samples.

Nosocomial transmission of hepatitis C virus within a British dialysis centre.

Patients on renal replacement therapy are recognized as a group at increased risk of infection with hepatitis C virus (HCV). While the risk has been reduced by the use of erythropoietin for treatment of anaemia and the introduction of HCV screening of blood products and potential renal transplant donors, new cases of HCV are still being documented, with patients on hospital haemodialysis appearing to be particularly at risk. The exact mode of transmission of HCV within dialysis units is unclear, although there is evidence to support nosocomial transmission between patients. Third generation HCV antibody testing was performed on all dialysis patients when a new case of HCV was identified within our unit. Stored monthly serum samples were then examined retrospectively to determine when patients became HCV RNA and HCV antibody positive. Viral typing was carried out to identify the HCV strains responsible for transmission. Four new cases of HCV infection are described within a single dialysis shift. Viral typing identified two distinct strains of HCV as being responsible for these infections, both of which had previously been identified in dialysis patients within the unit known to have HCV infection. This information, taken in conjunction with knowledge of the location of each patient for dialysis, suggests two separate episodes of nosocomial transmission of HCV between haemodialysis patients. While evidence of nosocomial transmission of HCV is accumulating, with modern dialytic procedures evidence of transmission through the dialysis machine or equipment used for dialysis is lacking. This stresses the importance of strict applications of universal precautions as the key to prevention of further transmission of HCV infection. This information is obviously applicable not only to dialysis units but all units that may potentially come in contact with HCV patients.

Peritoneal mesothelioma with gastric outlet obstruction.

Peritoneal mesothelioma has been increasing in frequency since the 1960s. Although still a rare malignant neoplasm, early diagnosis influences prognosis. More common presenting features include abdominal pain, abdominal distension or a palpable mass; more uncommon presentations have included dysphagia secondary to achalasia, chronic pancreatitis and regional lymphadenopathy. We report two recent cases at the Southern General Hospital in Glasgow.

Madreporite Function and Fluid Volume Relationships in Sea Urchins.

An effort was made to demonstrate an influx of seawater through the madreporites of sea urchins and to evaluate how such an influx, along with osmotic differences and other factors, could contribute to fluid homeostasis. Fluorescent microbeads placed in the medium of Strongylocentrotus droebachiensis were taken up into the pore canals and stone canal and distributed (in small numbers) to the distal tube feet, confirming a slow bulk inflow of seawater through the madreporite, where it is partially purified. Probably none of this fluid stream is diverted to the perivisceral coelom (as it is in asteroids), since experiments with Strongylocentrotus pallidus showed no significant movement of a soluble fluorescent tracer into that compartment. The osmotic concentrations of the perivisceral coelomic fluids in these two species, and in Strongylocentrotus franciscanus, were higher than that of ambient seawater by 2.66 +/- 0.39 mosmol kg-1 (mean +/- SE). That small hyperosmoticity, along with the net hydrostatic pressure differences induced by the flexing peristome, probably stabilizes body fluid volume. Likewise, fluid in the tube feet of S. franciscanus is elevated by 7.94 +/- 1.04 mosmol kg-1 above seawater, which should contribute to their inflation. Blockage of the madreporite does not lead to an obviously reduced activity of the tube feet, but over the long term, an influx through the madreporite is necessary. Specimens of S. droebachiensis with an obstructed madreporite, fed ad libitum, had significantly (P < 0.006) reduced gut contents vs controls after 28 days, indicating impaired movement or feeding; and the body weights (i.e., volumes) of unfed specimens were significantly (P < 0.013) more reduced after 21 days. Compared to starfish, the rigid test of sea urchins reduces the need for an influx of seawater through the madreporite, but some small admission is still essential.

Survey of major genotypes and subtypes of hepatitis C virus using RFLP of sequences amplified from the 5' non-coding region.

A method is described for identifying different genotypes of hepatitis C virus (HCV) by restriction endonuclease cleavage of sequences amplified by PCR from the 5' non-coding region. Using the enzymes HaeIII-RsaI and HinfI-MvaI, followed by cleavage with BstU1 or ScrFI, it was possible to identify and distinguish HCV genotypes 1a, 1b, 2a, 2b, 3a, 3b, 4, 5 and 6. The method was used to investigate the prevalence of these genotypes in 723 blood donors in 15 countries, the largest survey to date, and one which covered a wide range of geographical regions (Europe, America, Africa and Asia). These results, combined with a review of the existing literature, indicate the existence of several distinct regional patterns of HCV genotype distribution, and provide the framework for future detailed epidemiological investigations of HCV transmission.

The Structure and Mode of Function of the Water Vascular System of a Brittlestar, Ophioderma appressum.

Unlike the asteroids, which have large madreporite structures, the ophiuroid Ophioderma appressum possesses only two small hidden madreporite pores. Experiments with labeled amino acids, fluorescent microbeads, and surgical obstruction show that small amounts of seawater do routinely enter these pores and become distributed throughout the water vascular system; but this uptake does not seem essential. The flagellated stone canal draws its fluid from the axial sinus, to which the pores connect through a tortuous ampulla. Thus, the stone canal mainly recirculates fluid from hyponeural (perihemal) passages. That perihemal fluid is augmented by seawater from the pores. As perihemal fluid moves towards the stone canal, it passes by or through the axial organ, where nutritive materials may be removed and passed into the hemal channels. Pressure generated by the stone canal forces flow out to the oral tube feet, polian vesicles, and, through valves, eventually to the arm tube feet. Inflation of the tube feet also might occur through osmotic mechanisms, but their activity was not impeded by raising the external osmotic level with dextran. Observations indicate that negative coelomic pressures must be generated during respiratory movements, and these could lead to sufficient body fluid production (by filtration) that the need for substantive madreporitic inflows would be alleviated.

Environmental conditions for treatment of burned patients by the exposure method.

The influence of the thermal environment on evaporation and heat loss from patients with severe burns treated by exposure has been studied. Simple heat transfer equations can be used to predict changes resulting from alterations in environmental conditions and these have been tested using phantoms. The method relies upon the derivation of surface diffusion resistances to describe the moisture properties of burn wounds. Clinical measurements revealed wide variations in evaporation rates and diffusion resistances for different wounds. Evaporation rates changed by less than 30 per cent during the first 5-6 days following injury, after which evaporation from partial skin thickness wounds gradually fell whereas that from full skin thickness wounds tended to remain higher. Raising ambient temperature can compensate for increased evaporation heat losses. Patients can be treated at ambient temperatures of 32-35 degrees C in the intensive care room with a specially designed airflow system. However, raising the temperatures of standard wards with no special airflow or temperature control facilities often caused patients to sweat, further increasing heat loss.

The Function of the Madreporite in Body Fluid Volume Maintenance by an Intertidal Starfish, Pisaster ochraceus.

The madreporite has been viewed as superfluous and unnecessary because starfish can keep their tube feet inflated by osmotic mechanisms alone. Recent evidence has suggested, however, that the madreporite may be significant in the replenishment of general body fluid. This hypothesis has been tested. The madreporite openings of an intertidal starfish, Pisaster ochraceus, were obstructed with cement, and the animals were used in controlled experiments to compare weight (volume) changes under stable conditions, in response to air drying and recovery, and during adaptations to hyper- and hypoosmotic environments. Over a period of days, normal animals showed positive and negative volume fluctuations of up to about 20% (in part related to posture). Animals with obstructed madreporites generally did not gain weight and were significantly less able to maintain body volume or recover from fluid losses resulting from the stresses applied. The madreporite seemed to contribute little to the initial osmotic responses, but it did participate in subsequent volume readjustments in a hyperosmotic medium that had induced fluid losses. Obstruction of the madreporite did not impede tube foot activity, but may have caused some diversion of general body fluid to the ambulacral system. Rates of seawater uptake through the madreporite of 2.2-2.6 {mu}l g-1 h-1 were calculated from observed maximum mean differences in weight changes.

A study of skin temperatures, sweat rate and heat loss for burned patients.

The influence of the thermal environment on heat losses from patients with severe burns has been studied. Burn wounds were several degrees cooler than intact skin when patients were admitted to hospital. Wound temperatures gradually increased, becoming similar to those of intact skin by three days after injury. Temperatures of intact skin in peripheral regions of burned patients were raised. Evaporation of fluid from wounds of patients with 15-36% burns increased heat loss by 50-120 W, but sweating could increase heat losses by several hundred watts. Patients with large percentage burns tended to sweat less than others with smaller burns, under the same conditions. Patients with over 30% burns could be treated at air temperatures up to 35 degrees C without inducing sweating in the Intensive Care Room, which had forced airflow and good temperature control. Patients treated in standard wards where it was difficult to maintain a constant air temperature were more likely to sweat.

Burn wound evaporation--measurement of body fluid loss by probe evaporimeter and weight change.

A knowledge of the rate of fluid loss from the body is a useful aid in planning treatment of patients with severe burns. Different methods for obtaining this data have been investigated. Evaporation rates recorded from a probe evaporimeter have been compared with gravimetric measurements. The evaporimeter underestimated evaporation, especially at high levels, but could be calibrated against known evaporation rates. Estimates of whole-body fluid loss have been made from calibrated evaporimeter data and results compared with measurements of fluid loss by weight change for three patients. Problems with assessing whole-body evaporation rates in the clinical environment are highlighted. Weight change gives a more accurate assessment of total body fluid loss, but considerable effort is necessary to record all relevant information. Probe evaporimeter measurements are simple to perform and allow local evaporation rates to be estimated, but results should be treated with caution. Evaporation rates from wounds of 17 patients with severe burns have been evaluated in terms of surface diffusion resistances. The diffusion resistances of some burn wounds increased with time, but many did not change significantly during the first ten days after injury, and there was considerable variation with burn type and severity.

Burn wound evaporation--an evaluation of air diffusion resistances governing heat transfer in a clean air unit.

Heat losses from burned patients need to be reduced to avoid placing unnecessary demands on body metabolism. In order to allow more accurate assessments of heat loss, heat transfer has been studied in a clean air unit used for intensive care of burned patients. Evaporation rates have been measured from a phantom representing a recumbent human torso with burn wounds simulated by moist lint strips mounted on the surface. Heat transfer is determined by a complex interaction of free and forced convection, with evaporation rate being greatest on the side of the abdomen in free convection and towards the top in the forced case. Air diffusion resistances have been derived to describe evaporative heat transfer from different parts of a body. Equations have been fitted to data obtained under a wide range of conditions, and will be used to evaluate heat losses from burned patients in order to improve treatment conditions.

A phase II study of sequential methotrexate and 5-fluorouracil in colorectal carcinoma.

Nineteen patients with locally recurrent or metastatic colorectal carcinomas were treated with 3-weekly cycles of methotrexate (MTX) given as a loading dose of 100 mg m-2 and a subsequent 12 h infusion of 400 mg m-2, followed by 5-fluorouracil (5-FU) 900 mg m-2 as a bolus injection on completion of infusion. No objective responses were seen in 14 evaluable patients. One early death was treatment related, and four patients were withdrawn from the study after a single course as toxicity was considered unacceptable. The results suggest that in this regimen of sequential MTX and 5-FU, any synergism may be restricted to drug toxicity as no therapeutic benefit was evident.

Effective use and control of forms in the medical group practice.

At the heart of the medical group practice administrative system is the form. Forms are important information management tools. They have the potential for achieving administrative efficiency and lowering operating costs or, on the other hand, the potential for creating significant paperwork problems. In this thorough presentation, guidelines for implementation and management of an ongoing forms control and management system are provided.