Robert S. Siffert

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Fractals have been shown to be useful in characterizing texture in a variety of contexts. Use of this methodology normally involves measurement of a parameter H, which is directly related to fractal dimension. In this work the basic theory of fractional Brownian motion is extended to the discrete case. It is shown that the power spectral density of such a(More)
The effect of ultrasound (US) on the rate of fibula osteotomy healing in 139 mature New Zealand white rabbits was assessed in this study. Bilateral midshaft fibular osteotomies were made using a 1-mm Gigli saw. US was noninvasively applied to one limb for 20 minutes daily, while the contralateral limb served as a control. A 2.5-cm PZT transducer was applied(More)
The hip joint presents a coaptive relationship between the head of the femur and the acetabulum. Developmental changes in either component affect the responsive growth of its companion. Normal pressure of the head of the femur in the acetabulum maintains a balance in the proliferation of triradiate and acetabular growth cartilage. Secondary deformities(More)
Ultrasound has been proposed as a means to noninvasively assess bone and, particularly, bone strength and fracture risk. Although there has been some success in this application, there is still much that is unknown regarding the propagation of ultrasound through bone. Because strength and fracture risk are a function of both bone mineral density and(More)
Two hundred patients with a basicervical, intertrochanteric, or subtrochanteric fracture were treated by Ender-pin fixation during a three-year period. Their median age was 73.5 years and there was a 10 per cent mortality rate. Early partial weight-bearing with some external support was allowed for most patients. Minimum shortening and one non-union(More)
A computational model was developed to study the effects of short- and long-term periods of disuse osteopenia and repair to elucidate the interrelationships between bone mass, architecture, and strength. The model is one in which the sequence of structural change events is followed in time. This temporal feature contrasts with studies of real trabecular(More)