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PubMed1994

Trends in firearm suicide among older American males: 1979-1988.

Elderly men are more likely to commit suicide than any other age group in the United States. Moreover, their rate of suicide steadily increased between 1979 and 1988. National Center for Health Statistics (NCHS) Compressed Mortality data were used to perform an age-specific analysis of linear trends. Males 65 and over were the most likely to use firearms followed by those 55-64. In 1988, nearly 8 out of 10 suicides by males 65 and over were committed with a firearm. Firearm-related suicide rates were much lower for blacks than whites 65 and over; however, suicides among blacks were more likely to involve firearms than among whites in this age group. The authors call for a broad public policy effort directed at reducing the availability of firearms.

Adolescent↗

PubMed1995

Reasons for the weak correlation between prostate volume and urethral resistance parameters in patients with prostatism.

In an attempt to increase our understanding of the clinical syndrome of benign prostatic hyperplasia (BPH) an analysis was made of the association between prostate volume as measured by transrectal ultrasound and several reported urodynamically determined urethral resistance parameters. Two types of obstruction can be recognized on the basis of urodynamic data: a compressive type characterized by a high urethral opening pressure and a prolonged isovolumetric contraction phase before urine flow can start, and a constrictive type characterized by a normal opening pressure and an increased slope of the urethral resistance relation. A combination of both types is often seen in BPH. In our study, parameters that selectively quantify compression correlate weakly to moderately with prostate volume, whereas parameters that mainly quantify constriction do not correlate at all with prostate volume. Parameters that combine a measure for compression and constriction correlate less well with prostate volume than parameters that mainly quantify compression. The variation in prostate volume was found to determine the variation in urethral resistance by 15% or less depending on the parameter used, which implies that the different pathophysiological mechanisms that can increase urethral resistance in the complex process of clinical BPH are mainly determined by factors other than the volume of the prostate. Thus, despite the lack of correlation between prostate volume and urethral resistance, pressure-flow studies and the determination of urethral resistance parameters provide a valuable contribution to the understanding of the pathophysiology of voiding dysfunction in men with symptoms of prostatism.

Adult↗

PubMed1998

Distortion-product otoacoustic emission monitoring of cochlear blood flow.

Distortion-product otoacoustic emissions (DPOAEs) have been shown to be ideally sensitive to interruptions of the cochlear blood flow. However, a 15- to 30-second latency typically occurs between cessation of circulation and measurable DPOAE level changes. DPOAEs can also be characterized by phase measures. The aim of the present study was to determine in 10 rabbits the effects on DPOAE phase of repetitively compressing the internal auditory artery. In contrast to the delays measured by DPOAE level, phase changes were detected 1 to 5 seconds after internal auditory artery compression. These data suggest that the essentially "real time" monitoring of cochlear function with DPOAE phase can be used to ensure hearing preservation during surgery involving the porus acousticus and skull base.

Acoustic Stimulation↗

PubMed1997

A model for chronic nerve root compression studies. Presentation of a porcine model for controlled, slow-onset compression with analyses of anatomic aspects, compression onset rate, and morphologic and neurophysiologic effects.

STUDY DESIGN: Compression onset rate, anatomic aspects, and morphologic and neurophysiologic effects in spinal nerve roots were studied in a nerve root compression model in pigs. OBJECTIVES: To analyze the compression onset rate by measuring the gradual reduction of the inner diameter of the constrictor, the motor nerve conduction velocity by electromyography, the morphologic changes by light microscopy, and the gross and vascular anatomy by dissection and ink injections, respectively, in a model for experimental chronic nerve root compression. SUMMARY OF BACKGROUND DATA: Chronic nerve root compression is recognized to be related to back pain syndromes, including sciatica. Various aspects of morphologic and physiologic changes have been studied previously in models for acute compression and chronic nerve root irritation, but a controlled, graded chronic nerve root compression model has not been described. METHODS: An ameroid constrictor was applied around a spinal nerve root just cranial to the dorsal root ganglion. The inner diameter of this constrictor gradually becomes reduced. After 1 week or 4 weeks, electromyographic measurements were performed, and tissue samples were harvested for histologic analyses. The gross and vascular anatomy of the pigs' spinal nerve roots were studied by dissection and ink injections. RESULTS: There was a statistically significant decrease in the nerve conduction velocity in compressed compared with noncompressed spinal nerve roots after 1 week and after 4 weeks. The ameroid constrictors induced nerve fiber damage, endoneural hyperemia, bleeding, and inflammation at the compression zone. There was often a severe reduction in the number of myelinated fibers after 4 weeks. CONCLUSION: A model for controlled, chronic, partial nerve root injury using a gradual compression-onset constrictor is presented. This model allows for induction of a controlled graded chronic nerve root injury and can be used for research on basic pathophysiologic mechanisms and on the effects of various interventions on nerve root injury development.

Animals↗

PubMed1997

Delayed postoperative paraparesis in scoliosis surgery. A case report.

STUDY DESIGN: A case report is presented of an unusual complication of scoliosis surgery that, to the authors' knowledge, has never been reported in the literature. OBJECTIVE: Neurologic complications can occur after an uneventful posterior spinal instrumentation and fusion for scoliosis. Careful observation during the post-operative period is crucial for early detection of impending neurologic deficit. SUMMARY OF BACKGROUND DATA: Nerve compression of the cauda equina has been reported as a complication of different types of surgery in the lumbar spine, but an ascending paraparesis has never been described as a complication of scoliosis surgery. METHODS: A 12-year-old boy with a right thoracic scoliosis measuring 68 degrees and a 72 degrees left lumbar curve underwent Cotrel-Dubousset instrumentation and fusion from T5 to L4. Spinal cord monitoring with somatosensory evoked potentials and motor action potential were recorded and stable through out the entire procedure. Thirty hours later, a rapidly progressive ascending para-paresis developed that required urgent decompression. RESULTS: This patient underwent urgent decompression and removal of the Cotrel-Dubousset instrumentation. After surgery, the clinical picture improved gradually, and at 2-month follow-up he had regained normal strength in his lower limbs except for a grade 4 left extensor hallucis longus. By 4 months postdecompression, he had made a total recovery. CONCLUSIONS: Although clinical examination may be difficult to perform in patients who are unconscious, on large doses of narcotic drugs, or mentally retarded, careful observation during the postoperative period and awareness of this complication can allow early detection of impending reversible neurologic deficit and provision of appropriate treatment.

Child↗

PubMed2005

The monotonic and fatigue properties of osteoporotic thoracic vertebral bodies.

STUDY DESIGN: Measurement of the monotonic and fatigue properties of osteoporotic thoracic vertebral bodies. OBJECTIVES: To determine the loading values at which osteoporotic vertebral bodies are susceptible to failure. SUMMARY OF BACKGROUND DATA: Vertebral compression fractures are the most common osteoporotic fracture. Eighty-three percent of vertebral compression fractures are caused by moderate or less trauma, and there is not a specific traumatic event in 59% of these cases. Fatigue loading can lead to premature failure, although the relationship between loading and cycles to failure is not well established. METHODS: Eighteen osteoporotic thoracic vertebral bodies were tested in monotonic compression to determine the correlation between the bone mineral content and the ultimate compressive load. Seventeen osteoporotic thoracic vertebral bodies were cyclically loaded at varying percentages of the ultimate compressive load until failure to determine the relationship between loading and fatigue life. RESULTS: The bone mineral content was linearly correlated with ultimate compressive load. Based on our regression analysis, a 10% decrease in bone mineral content will lead to an approximate 10% decrease in ultimate compressive load. The percentage of ultimate compressive load was inversely correlated to the logarithm of cycles to failure, with specimens loaded at 60%, 70%, and 80% of ultimate compressive load lasting on average 5.6 x 10, 4.0 x 10, and 31 cycles to failure, respectively. CONCLUSIONS: The bone mineral content is a strong predictor of the ultimate compressive load, while the percentage of the ultimate compressive load is a strong predictor of the cycles to failure for osteoporotic thoracic vertebral bodies.

Adult↗

PubMed2006

Biomechanical evaluation of conventional internal contemporary spinal fixation techniques used for stabilization of complete sacroiliac joint separation: a 3-dimensional unilaterally isolated experimental stiffness study.

STUDY DESIGN: Comparative 3-dimensional biomechanical testing. OBJECTIVE: To compare 5 fixation techniques, 3 using screws or screw and plates and 2 spinal, used for stabilization of complete unilateral sacroiliac dislocation in composite models. SUMMARY OF BACKGROUND DATA: Harrington compression rods have been used for posterior iliosacral stabilization. Recently, the use of compact spinal instrumentation has been introduced for stabilization of iliosacral joint separation to achieve immediate and permanent stability, allowing early mobilization. To the authors' knowledge, no comparative mechanical studies between commonly used internal fixation techniques and contemporary spinal instrumentation have been performed. METHODS: Fifteen identical composite models of the left hemipelvis and sacrum were used to simulate consistently the "worst-case scenario" of complete unilateral sacroiliac dislocation. Subgroups of 3 models each were used to apply 5 (A-E) alternative fixation iliosacral joint fixation techniques: 1 multiaxial 7.5 mm Cotrel-Dubousset screw inserted in the posterior superior iliac spine and connected with a long Cotrel-Dubousset horizontal rod with 6.5 mm multiaxial Cotrel-Dubousset screws inserted bilaterally in the S1 pedicles (technique A); 1 multiaxial 7.5 mm Cotrel-Dubousset titanium pedicle screw inserted in the posterior superior iliac spine and connected with a short horizontal Cotrel-Dubousset-rod to a 6.5 mm multiaxial Cotrel-Dubousset-screw inserted to the ipsilateral S1 pedicle (technique B); 1, 6.5 mm cancellous AO-screw (technique C); 2, 6.5 mm cancellous AO screws (technique D); and 2 dynamic stainless steel compression plates (technique E) placed anteriorly. Constructs were biomechanically tested. The ilium was unilaterally rigidly fixed, the sacrum was put horizontal in the mediolateral direction with a forward tilt of 30 degrees (close to physiologic conditions) in the sagittal plane, and a vertical quasi-static compressive load ranging from 0 to 500 N was applied on the endplate of S1, reproducing a "worst case" loading scenario. Construct stiffness, frontal plus sagittal kinematics, and iliosacral joint gap size for all 5 techniques were measured. RESULTS: The construct stiffness (N/mm +/- standard deviation) ranged for model: A, 121 +/- 18; B, 78 +/- 10; C, 168 +/- 13; D, 193 +/- 42; and E, 145 +/- 4. All other parameters exhibited minor variations between the different techniques of fixation: at the 400 N load level, the maximum iliosacral gap globally ranged 0.9-2.8 mm, the maximum mediolateral sacral tilt ranged 1.3-2.4 degrees, and the maximum anteroposterior sacral tilt ranged 0.6-3.0 degrees. CONCLUSIONS: The iliosacral fixation with 2 6.5 mm AO-cancellous screws for complete sacroiliac dislocation demonstrated the highest stiffness and the short spinal instrumentation the poorest stiffness. All other fixation techniques could be generally considered of equivalent stability value.

Biomechanical Phenomena↗

PubMed2005

Correlation of high-resolution ultrasonographic findings with the clinical symptoms and electrodiagnostic data in carpal tunnel syndrome.

There are several different imaging methods that are helpful in the diagnosis of carpal tunnel syndrome, including traditional radiography, computed tomography (CT), and magnetic resonance imaging (MRI). CT and MRI offer the advantage of providing direct visualization of the structural abnormality of the carpal tunnel and median nerve, but both of these modalities are expensive and time-consuming. Recently, high-resolution ultrasonography has been reported to be effective in the study of the musculoskeletal system. The authors designed a case-control study to assess the diagnostic value of high-resolution ultrasonography. Forty-eight patients, for a total of 96 hands, whose diagnosis was confirmed by self-administered questionnaire and electrodiagnostic tests, underwent high-resolution ultrasonographic studies. The authors compared the sonographic findings with the electromyographic data and the patients' severity scores on the self-questionnaires. Proximal swelling of the median nerve at the entrance to the carpal tunnel was found to correlate with the nerve conduction data. Also, compression of the median nerve under the transverse carpal ligament was found to correlate with the subjective symptoms. Although ultrasonography is not an ideal method of diagnosis for carpal tunnel syndrome, it may be helpful for estimating the symptom severity and nerve conduction deficit.

Adult↗

PubMed1997

Wavelet and wavelet packet compression of electrocardiograms.

Wavelets and wavelet packets have recently emerged as powerful tools for signal compression. Wavelet and wavelet packet-based compression algorithms based on embedded zerotree wavelet (EZW) coding are developed for electrocardiogram (ECG) signals, and eight different wavelets are evaluated for their ability to compress Holter ECG data. Pilot data from a blind evaluation of compressed ECG's by cardiologists suggest that the clinically useful information present in original ECG signals is preserved by 8:1 compression, and in most cases 16:1 compressed ECG's are clinically useful.

Algorithms↗

PubMed1999

Information technology applications in biomedical functional imaging.

In parallel with rapid advances in computer technology, biomedical functional imaging is having an ever-increasing impact on healthcare. Functional imaging allows us to see dynamic processes quantitatively in the living human body. However, as we need to deal with four-dimensional time-varying images, space requirements and computational complexity are extremely high. This makes information management, processing, and communication difficult. Using the minimum amount of data to represent the required information, developing fast algorithms to process the data, organizing the data in such a way as to facilitate information management, and extracting the maximum amount of useful information from the recorded data have become important research tasks in biomedical information technology. For the last ten years, the Biomedical and Multimedia Information Technology (BMIT) Group and, recently, the Center for Multimedia Signal Processing have conducted systematic studies on these topics. Some of the results relating to functional imaging data acquisition, compression, storage, management, processing, modeling, and simulation are briefly reported in this paper.

Algorithms↗

PubMed2002

Quantitative comparison and analysis of brain image registration using frequency-adaptive wavelet shrinkage.

In the field of template-based medical image analysis, image registration and normalization are frequently used to evaluate and interpret data in a standard template or reference atlas space. Despite the large number of image-registration (warping) techniques developed recently in the literature, only a few studies have been undertaken to numerically characterize and compare various alignment methods. In this paper, we introduce a new approach for analyzing image registration based on a selective-wavelet reconstruction technique using a frequency-adaptive wavelet shrinkage. We study four polynomial-based and two higher complexity nonaffine warping methods applied to groups of stereotaxic human brain structural (magnetic resonance imaging) and functional (positron emission tomography) data. Depending upon the aim of the image registration, we present several warp classification schemes. Our method uses a concise representation of the native and resliced (pre- and post-warp) data in compressed wavelet space to assess quality of registration. This technique is computationally inexpensive and utilizes the image compression, image enhancement, and denoising characteristics of the wavelet-based function representation, as well as the optimality properties of frequency-dependent wavelet shrinkage.

Brain↗

PubMedDate not supplied