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Seminars in Nuclear Medicine, VOL XXVIII, NO 1, 62-77, January 1998

Disorders of the ankle and foot are common and may pose a significant clinical problem. Acute injuries of the ankle and foot are routinely evaluated by radiographs and, if inconclusive, by magnetic resonance imaging (MRI) or computed tomagraphy (CT). In subacute or chronic injuries, where prolonged pain is unexplained, bone scintigraphy may play a significant role. The bone scan may differentiate soft tissue from bone pathology, and, being a sensitive test, it may indicated the region that needs further specific radiologic examination. It may also indicate the clinical significance of a radiologic finding. Moreover, in some clinical settings bone scintigraphy can be specific in the diagnosis. Careful attention to the technique enhances the efficiency of bone scintigraphy and SPECT allows better ivestigation of the hindfoot. The importance of ankle and foot injuries in the orthopedic practice and the better understanding of subacute and chronic injuries in athletes and in the general population has led to an increased use of specific tests such as MRI, CT, and bone scintigraphy. With improved technique and instrumentation it is no longer sufficient to indicate a focal abnormality in the ankle or foot on bone scintigraphy. More precise information about perfusion, blood pool, and specific location of a lesion can be obtained by high resolution and tomographic images. The role of bone scintigraphy in the diagnosis of such disorders will be presented with a focus on subacute traumatic injuries and related disorders, as well as its role in systemic inflammatory disorders that often involve the ankle and foot.

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The lower limb of a paraplegic patient can be analyzed as a dynamically determinate system, since the muscles there are isolated from voluntary control. Hence, when activated by functional electrical stimulation (FES), the only nonzero active muscle forces are those of the actually stimulated muscles. This unique situation allows the calculation of the muscle force from the externally measured torques and the correlation of this direct muscle output to parameters of another nature, such as metabolic or myoelectric. In the present work the authors have studied the relation between force and myoelectric activity of the FES-activated quadriceps muscles of paraplegics during the course of fatigue. Stimulation was provided by means of surface electrodes. The electromyographic (surface EMG) activity was represented by the peak-to-peak (PTP) amplitude of the M-wave signal obtained. It was important to suppress the stimulus artifact preceding the EMG signal and the authors, therefore, designed an amplifier capable of monitoring the artifact-free signal. The surface EMG and the force were sampled on line for analysis. The PTP amplitudes were correlated with the corresponding force values, simultaneously measured and a parallel decay in these two parameters was noticed. An exponential curve was found adequate to express the relationship between force and EMG PTP. The results obtained indicate the conditions under which surface EMG can be used to noninvasively monitor the quadriceps muscle fatigue during stimulation

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