Development of a home ankle exerciser.

A portable, lightweight home ankle exerciser was designed and built by the Biomedical Engineering Department of University Hospital in London, Ontario, Canada. The ankle exerciser incorporates several unique features that overcomes the drawbacks of exercise equipment presently available. For optimal muscle strengthening, the resistance offered by the device matches the strength curve of the ankle muscles. The magnitude of the resistance can be widely varied to accommodate any subject. Resistance is generated by a slip clutch rather than by springs or weights which can be cumbersome and potentially dangerous. One of the considerations in the design of the ankle exerciser was to monitor subject compliance with the exercise regimen. This is accomplished with a battery-operated monitoring unit mounted on the device. The exerciser is instrumented with a battery-powered torque transducer and digital display unit that enables the subject and assessor to monitor the exercise resistance level at a glance.

Ongoing use of an affective rating scale in the treatment of a mentally retarded individual with a rapid-cycling bipolar affective disorder.

Empirically tracking cyclic variations in the behavior of mentally retarded individuals with bipolar affective disorders is difficult because disturbances in mood are difficult to operationally define and quantify. The following report presents a case study in which a moderately retarded man's mood and energy were rated by direct care staff who completed a mood rating scale two times each day. The resulting weekly summaries of the data were plotted on a graph which indicated the cyclic fluctuations in symptom areas related to his bipolar disorder. This information was of great value in assessing therapeutic interventions and in designing habilitative activities congruent with shifts in the behavioral patterns.

Polyarthritis and angioimmunoblastic lymphadenopathy.

Angioimmunoblastic lymphadenopathy (AILD) is a lymphoproliferative disorder with well established clinical and histological features, one of the clinical manifestations being a peripheral polyarthritis. A case of AILD with a symmetrical non-erosive peripheral polyarthritis is described, including the findings in the synovial fluid and histology of the synovium. There was a marked reduction in the number of peripheral blood T lymphocytes bearing the CDT8 phenotype in both the peripheral blood and synovial fluid. The arthritis was difficult to control, requiring large doses of corticosteroids, which produced significant side effects. Levamisole 150 mg, one day each week, was effective in controlling the arthritis and returning the numbers of CDT8 lymphocytes to normal. The aetiology of AILD is unknown, though a defect in T cell regulation, in particular T cell suppression, with a secondary B cell proliferation has been postulated. The demonstration of reduced numbers of lymphocytes bearing the CDT8 phenotype in this patient supports that theory.

Compressive behavior after simulated service conditions of some foamed materials intended as orthotic shoe insoles.

The compressive characteristics of a group of foamed plastics and rubbers, suitable for use as orthotic shoe insoles, were assessed for any changes incurred as a result of exposure to a series of simulated service conditions. The service conditions considered in this study were heat (accelerated aging), sustained deflection (compression set), and cyclic loading. Since the stress/strain characteristics computed from the load/deformation curves were non-linear, it was necessary to develop a new procedure for comparing the relative compressive characteristics. The results from this study identified a group of preferred materials whose virgin compressive characteristics have been judged to be the most suitable, and which exhibited the least change following exposure to the three simulated service conditions.

A physical model for the formation of evaginations: a prospective precursor to the creation of saccular aneurysms.

The actual spatial geometry of separate regions of normal and enlarged fenestrations from the internal elastic lamina of human cerebral arteries have been replicated in sheets of latex rubber from scanning electron microscope (SEM) photomicrographs. Geometrical models which assume a constant diameter for the fenestrations, a constant ligament efficiency for the regions of fenestrations and a uniform array of rows and columns have also been created in sheets of latex rubber. The stress (load per unit of cross-sectional area) and strain (percent elongation) were computed for each of the samples during uniaxial stretching. The elongation of the sample representing the region of enlarged fenestrations increased an average of 47% compared to the similar representation of normal fenestrations, at the same increments of stress. This suggests that regions of enlarged fenestrations would form a bulge, indicative of an evagination of the internal elastic lamina. The model configurations demonstrate very similar stress/strain characteristics to the replications. This finding justified the use of the modelling technique using equivalent ligament efficiencies, to represent the actual spatial geometry. During elongation, the average area of the enlarged fenestrations increased at a rate which was an order of magnitude greater than the normal fenestrations. Since a number of observations associated with the development of intracranial saccular aneurysms can be correlated to a region of enlarged fenestrations, the region of enlarged fenestrations may be a defect in the internal elastic lamina which could play a prominent role in the development of intracranial saccular aneurysms.

The use of ligament efficiency to model fenestrations in the internal elastic lamina of cerebral arteries. I--modelling scheme.

The spatial geometry of fenestrations (windows) in the internal elastic lamina from human cerebral arteries is being characterized by a single parameter termed 'ligament efficiency', which is a ratio of the solid band of material to the centre-to-centre spacing between two or more holes. As a result, the apparent random distribution of fenestrations with variable diameters may be represented as a uniform array of holes with a single diameter. The actual arrangement of fenestrations from three separate tissue specimens were replicated in thin latex sheets by transposing the image of the fenestrations from photomicrographs obtained with the scanning electron microscope. In a similar manner, the uniform array of holes with an equivalent ligament efficiency are modelled in latex sheets. The tensile (stress-strain) properties of the latex sheets representing the replication and model configurations were comparable for all three specimens, even though their individual ligament efficiencies were different. The close similarity between the elastic characteristics for the two configurations, verifies the application of ligament efficiency to represent the spatial geometry of a perforated material such as the fenestrated internal elastic lamina.

The use of ligament efficiency to model fenestrations in the internal elastic lamina of cerebral arteries. II--analysis of the spatial geometry.

During uniaxial extension of the latex model, the holes (both marked on the sheet and perforated) demonstrated a distinctive change in their shape, from circular to elliptical. Measurements of the axial and transverse diameters of a consistent row of holes, along with the width of the sample at distinct elongations were converted into an area, ligament efficiency (transverse and axial) and shape factor (eccentricity). Values for the expansion ratio of the holes and necking of the latex sheet were also computed. The perforations expanded more rapidly than with the holes only marked on the solid material, which translated into a more rapid increase for the axial diameter, area and eccentricity, while the axial ligament efficiency decreased more rapidly. The transverse diameter and transverse ligament efficiency remained essentially constant. Necking of the latex sheet was consistent for all of the specimens (both solid and perforated). The relative expansion ratios paralleled the relative changes for the standardized stresses presented in Part I.

An optimization procedure for the alignment of marker points to assess dimensional changes.

The process of dehydration and drying associated with the preparation of tissue specimens for examination by the scanning electron microscope usually results in dimensional changes in the form of shrinkage. A new method has been devised which requires specification of the location of marker points which have been affixed in a random pattern to the surface of the specimen. A new computer programme has been developed which acquires the coordinate pairs of the marker points, optimizes the alignment between the location of the marker points for the wet (fresh or fixed) and processed (dehydration with an intermediate fluid, and/or drying) conditions of the specimen, and computes the proportional dimensional changes in two mutually-perpendicular directions, as well as along the direct path between the origin and each of the marker points. Techniques for using the programme to assess whether the shrinkage may be planar-orthotropic or planar-anisotropic are suggested.

Fenestrations in the internal elastic lamina at bifurcations of human cerebral arteries.

Measurements of fenestrations (or windows) in the internal elastic lamina at the bifurcation of human cerebral arteries, were obtained from photomicrographs (scanning electron microscope). Thirteen of 28 bifurcations revealed regions of enlarged fenestrations among the normal fenestrations in the vicinity of the apex. The mean diameter of the enlarged fenestrations (7.0 +/- 0.34 SEM micrometer) was significantly greater than the mean diameter (2.1 +/- 0.13 SEM micrometer) of the normal fenestrations. The number of fenestrations per sq mm was less (2606 +/- 284 SEM per sq mm) for the enlarged fenestrations than for the normal fenestrations (4518 +/- 397 SEM per sq mm). The proportion of the area of internal elastic lamina comprised of fenestrations increased to 15.0 +/- 1.1 SEM percent for the enlarged fenestrations from a mean of 1.8 +/- 0.16 SEM percent for the normal fenestrations. Fenestrations from bifurcations without enlarged fenestrations, demonstrated characteristics similar to the normal fenestrations. More than 80% of the specimens exhibited a gap in the internal elastic lamina in the apical region of the bifurcation. Based on a comparison of stress concentration factors, we propose that the presence of enlarged fenestrations represents a weakness in the internal elastic lamina at the bifurcation apex which may contribute to the initiation of microaneurysms.

The pneumatic tourniquet: a biomechanical and electrophysiological study.

The pneumatic tourniquet is used routinely in extremity surgery, not only to prevent unnecessary blood loss, but also to increase the safety of the operative procedure. The mechanical part of this study shows that the system can fail in either of two major ways, each causing serious problems. The tourniquet may be inadequate if the pressure delivered to the cuff is not accurately displayed on the gauge or if the pre-set pressure is not maintained for the duration of the operative procedure. In our hospital, three of seven tourniquets (43%) in daily use showed significant errors in this regard. The electrophysiological part of this study indicates that nerve conduction does not necessarily return to preoperative levels immediately postoperatively, and that the conduction block is generally at the level of the cuff. Our observations confirm those of others and implicate both direct pressure as well as ischemia as the cause of the problem.