John A. Glaser

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BACKGROUND Sacroiliac (SI) joint pain is a prevalent, underdiagnosed cause of lower back pain. SI joint fusion can relieve pain and improve quality of life in patients who have failed nonoperative care. To date, no study has concurrently compared surgical and non-surgical treatments for chronic SI joint dysfunction. METHODS We conducted a prospective(More)
OBJECT In this clinical review of ankylosing spondylitis, the authors emphasize the fragility of the spine and the degree of neurological deficit that can result from minor injury. The management of thoracolumbar fractures complicating ankylosing spondylitis is discussed. METHODS Six thoracic and five lumbar fractures were identified in a review of(More)
This paper presents analytical tools aimed at improving and simplifying the development of frequency-controlled dimming electronic ballasts. A modified phasor transformation is proposed that converts a frequency-modulated signal into an equivalent time-varying phasor. The proposed transformation is applied to develop a complete small-signal phasor model of(More)
This paper provides a direct dynamic modeling approach for envelope signals in resonant inverters driven by modulated inputs (AM or FM). Based on the sinusoidal approximation, this approach decomposes the modulated input into its fundamental component plus two dominant sidebands. The system response is then found by the summation of the responses to the(More)
DESIGN Independent retrospective review of a single surgeon's experience with a new technique of SI fixation. OBJECTIVE Examine results of percutaneous fixation of the SI joint with porous coated triangular titanium implants. BACKGROUND Diagnosis and treatment of a dysfunctional sacroiliac joint is challenging as well as controversial. Recently,(More)
BACKGROUND Sacroiliac joint (SIJ) dysfunction is a prevalent cause of chronic, unremitting lower back pain. OBJECTIVE To concurrently compare outcomes after surgical and nonsurgical treatment for chronic SIJ dysfunction. METHODS A total of 148 subjects with SIJ dysfunction were randomly assigned to minimally invasive SIJ fusion with triangular titanium(More)
The cases of all patients treated with halo-vests for cervical trauma at the University of Virginia since 1977 were analyzed retrospectively. A standardized chart and radiographic review protocol were used to identify complications associated with the use of the orthosis. Two hundred and forty-five patients satisfied the criteria for inclusion in the study.(More)
—This paper presents analytical tools aimed at improving and simplifying the development of frequency-controlled dimming electronic ballasts. A modified phasor transformation is proposed that converts a frequency-modulated signal into an equivalent time-varying phasor. The proposed transformation is applied to develop a complete small-signal phasor model of(More)
Little information exists about the ability of the Hoffmann sign to predict cervical spinal cord compression. The objective of this study was to determine the correlation between the Hoffmann sign and cervical spinal cord compression in a consecutive series of patients seen by a single spine surgeon. All new patients with complaints related to their(More)
Weakness of the neck extensors can lead to "dropped head syndrome", a condition of progressive cervical kyphosis in which a patient is unable to hold their head up against the force of gravity. This condition can be associated with structural abnormalities of the spine as found in ankylosing spondylitis and vertebral fractures. Neuromuscular disorders, such(More)