Cyclic fatigue of hydroxyapatite-coated titanium alloy implant material--effect of crystallinity.

Titanium alloy (ASTM F-136) rods were coated with hydroxyapatite (HA) of 3 levels of crystallinity, which were determined by X-ray diffraction (XRD) analysis to be 60.5%, 52.8%, and 47.8%. Fourier Transform Infrared (FTIR) spectroscopy analysis showed the removal of the hydroxyl and carbonate groups as compared to the original HA powder. It appears that these changes are caused by the high temperature plasma spray coating process. Cyclic fatigue testing in a lactated Ringer's solution to 5 million cycles showed no statistical difference in calcium dissolution among the 3 crystalline levels, whereas phosphorus dissolution was lowest from the highest crystalline coating sample. The mechanical properties, however, did not change in response to fatigue loading.

Psychometric prediction of driving performance among the disabled.

A battery of psychometric and performance tests was administered to 25 subjects who were classified into able-bodied (n = 8), brain-injured (n = 10), and spinal cord injured groups (n = 7). All disabled subjects were regarded by their referring rehabilitation therapists as potential candidates for driver assessment. Data were analyzed to identify which measures were useful in differentiating among the groups and predicting driving performance. Results indicated that psychometric measures can be useful in predicting driving performance among disabled drivers. Nearly all the measures in the battery were significant predictors of driving ability, and some were highly predictive. The best was the oral version of the Symbol Digit Modalities test, which by itself accounted for 70% of the variance of the full-sized-vehicle driving score. Adding a second variable into a two-step multiple regression further increased the correlation between predictors and driving, accounting for almost 80% of the variance in driving score. These findings support the feasibility of developing a simple test battery to determine which disabled candidates are ready for in-vehicle assessment, and which candidates are not ready without further evaluation of cognitive and performance skills.

A small-scale vehicle for assessing and training driving skills among the disabled.

A small-scale vehicle (SSV) was developed to assess and train skills of disabled individuals who wish to become licensed to drive. The SSV incorporates power-assisted adjustable-effort steering and braking functions, variable-speed control, modular interchangeable hand control units, standard foot-control units, and a variety of safety and instrumentation features. This vehicle offers numerous advantages over traditional modes of assessment and training. These advantages include its lower price and operating costs as compared to a full-sized vehicle; its adaptability to left- or righthanded clients; and the provision of a specially adapted vehicle for vehicle for practice driving and regaining skills and self-confidence away from public thoroughfares. The SSV is one component in the Center's driving assessment and education curriculum that follows a graded progression, beginning with use of a driving simulator, to driving the SSV, to driving a full-sized vehicle.

Clinical evaluation of six intraocular lens calculation formulas.

We examined the results of posterior chamber intraocular lens (IOL) implantation and evaluated six commonly used IOL power calculation formulas (original Binkhorst, modified Binkhorst, Colenbrander, Shammas, Hoffer, and SRK regression) to determine which ones produce the most accurate and predictable results. We found that the accuracy of the various formulas depends upon several factors, including the surgeon's technique, the type and style of posterior chamber IOL implanted, and the axial length of the eye being operated on. Furthermore, we found that the results using the different formulas vary in a consistent pattern. Surgeons must therefore evaluate their cases periodically to determine which formulas and IOL styles will provide their patients with the most accurate and satisfying results.