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.

Prognostic importance of a clinical profile and exercise test in medically treated patients with coronary artery disease.

To identify predictors of mortality in medically treated patients with symptomatic coronary artery disease, 30 variables were analyzed in 4,083 patients. Regression analysis demonstrated that seven variables were independent predictors of survival. A high risk subgroup (annual mortality rate above 5%) was identified, consisting of patients with either a congestive heart failure score of 3 to 4 or 1 mm or greater ST segment depression and final exercise stage of 1 or less. When all 30 variables were analyzed conjointly, the left ventricular contraction pattern (p less than 0.0001) and the number of diseased coronary vessels (p less than 0.003) proved to be the most important predictors of survival. In a subgroup of 572 patients with three vessel coronary disease and preserved left ventricular function, the probability of survival at 4 years ranged from 53% for patients only able to achieve stage 1/2 of exercise to 100% for patients able to exercise into stage 5 (p less than 0.004). Thus, in patients with defined coronary pathoanatomy, clinical and exercise variables primarily relating to the functional state of the left ventricle are helpful in assessing prognosis.

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.

Effects of three cobra venoms on blood coagulation, platelet aggregation, and fibrinolysis.

The effects of the venoms of Naja melanoleuca, Naja nigricollis, and Ophiophagus hannah on blood coagulation, platelet aggregation, and fibrinolysis were studied in vitro. All three venoms were shown to be anticoagulant. This action appeared to be due to an effect on both the extrinsic and blood thromboplastin mechanisms. Platelet aggregation in Chandler's tubes and adenosine diphosphate reactivity were inhibited by the three venoms, although in the case of Ophiophagus hannah venom they were inhibited only with intermediate concentrations. The three venoms possessed proteolytic properties, but when incorporated into purified caseinolytic systems and euglobulin clot lysis systems inhibition of plasmin activity was observed.

Effects of the venom of the rhinoceros horned viper (Bitis nasicornis) on blood coagulation, platelet aggregation, and fibrinolysis.

The venom of the rhinoceros horned viper (Bitis nasicornis) has been studied in vitro and has been shown to be anticoagulant. This action appeared to be due to an effect on both the extrinsic and intrinsic blood thromboplastin mechanisms. The venom was also proteolytic and in purified caseinolytic systems activated plasminogen, enhanced the activation of plasminogen by streptokinase, and potentiated the action of plasmin. In the euglobulin clot lysis system high concentrations of venom produced inhibition. The crude venom increased platelet adhesiveness but in high concentrations delayed the snowstorm effect in the Chandler's tube system and inhibited platelet adenosine diphosphate reactivity. Passage through carboxymethylcellulose yielded six fractions. One possessed anticoagulant activity, inhibited plasmin, and increased the optical density of platelet-rich plasma. The other five fractions shortened the plasma recalcification time but had no effect on plasmin activity. Four fractions aggregated platelets and enhanced platelet adenosine diphosphate reactivity.

Effect of feeding fat on fibrinolysis, Stypven time, and platelet aggregation in Africans, Asians, and Europeans.

The effects of acute fat feeding on fibrinolytic activity, platelet aggregation, and Stypven time in 10 Africans and 10 Asians are presented and compared with the results previously obtained in 10 Europeans. These indicated that the inhibition of fibrinolytic activity seen in Europeans does not occur in either Africans or Asians although the Stypven time was shortened in all three groups. Platelet aggregation, as measured by the Chandler's tube technique, was inhibited by fat feeding in Europeans but was unchanged in Africans and Asians. The results also indicate that the fibrinolytic activity of Africans and Asians is greater than that of Europeans.

Effect of feeding fat on fibrinolysis, stypven time, and platelet aggregation in elderly Africans.

The effects of acute fat feeding on fibrinolytic activity, platelet aggregation, and stypven time in six elderly Africans are presented. These indicate that there is no alteration in the pattern of response seen in Africans with advancing age.

Effect of gaboon viper (Bitis gabonica) venom on blood coagulation, platelets, and the fibrinolytic enzyme system.

The action of the venom of the gaboon viper (Bitis gabonica) on blood coagulation, platelets, and the fibrinolytic enzyme system was studied. The results confirm that the venom of Bitis gabonica has a marked anticoagulant action in vitro. The venom appears to impair clot formation by a direct proteolytic action on fibrinogen, releasing soluble breakdown products.

Hypocalcaemia of acute pancreatitis: the effect of hypoalbuminaemia.

Hypoalbuminaemia has been consistently observed in a prospective study of 130 patients with acute pancreatitis. A study was initiated, therefore, to find out if the hypocalcaemia of acute pancreatitis could be explained by the associated hypoalbuminaemia. 64.4% of all serum calcium results were in the apparently hypocalcaemic range. A comparable incidence of hypoalbuminaemia was observed. The 'uncorrected' total serum calcium and serum albumin showed a similar pattern in their daily changes and also a significant correlation overall. When correction of serum calcium was made for albumin levels, only 10.9% of all results represented varying degrees of 'true' hypocalcaemia. Mortality and severity of acute pancreatitis related as closely to hypoalbuminaemia as to uncorrected hypocalcaemia. It is concluded that a low serum albumin should be regarded as the most common cause of a low serum calcium in acute pancreatitis. Routine albumin administration is proposed, a procedure which has been shown to be associated with improved mortality rate and morbidity in this disease.

Accidental injuries among naval personnel by occupation, duty status, and pay grade.

The relative incidence of accidental injury for Navy enlisted men during 1974-1977 was analyzed for 68 occupations, three pay grade or job responsibility levels, and duty status (on or off duty) at the time of the injury. Thirteen "blue-collar", predominantly sea-going or construction occupations, were significantly higher than the Navy injury rate norm and 26 "white-collar" occupations, typically in clerical, supply, administrative or technical specialties, were significantly lower than the Navy norm. An inverse linear relationship was found between injury rate and job responsibility for all occupations combined. This relationship varied by occupation, however, suggesting that experience and familiarity with the work environment may not moderate risks to the same degree in all occupational fields. Occupations with high on-duty injury rates tended to have high off-duty rates as well, suggesting at least some common causal factors.

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.

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.