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Biomedical subjects

J Dvorak

Publications and source records attributed to J Dvorak.

At least 91 records · Page 5Linked to original sources
PubMed1997

Dynamic elongation of the vertebral artery during an in vitro whiplash simulation.

Clinical signs of whiplash are presently not well understood. Vertebral artery (VA) stretch during trauma is a possible pathomechanism that could explain some aspects of the whiplash symptom complex. This study quantified the VA elongation during whiplash simulation using an in vitro model. Seven fresh human cadaveric specimens (occiput to C7 or T1) were carefully dissected, preserving the osteoligamentous structures. The right VA was replaced with a thin nylon-coated flexible cable. This cable was fixed at one end to the occipital bone and at the other end to a specially designed VA transducer. Physiological motion of the occiput and physiological elongation of the VA were measured with a standard flexibility test. Next the specimen was mounted on a specially designed sled and subjected to 2.5, 4.5, 6.5, and 8.5 g (1 g = 9.81 m/s2) horizontal accelerations. Elongation of the VA was continuously recorded from the start of the trauma. The average (standard deviation) physiological VA elongation was 5.8 (1.6) mm in left lateral bending and 4.7 (1.8) mm in left axial rotation. Flexion and extension did not result in any appreciable elongation of the VA. The maximum VA elongation during the whiplash trauma significantly correlated with the horizontal acceleration of the sled (R2 = 0.7, P < 0.05). The VA exceeded its physiological range by 1.0 (2.1), 3.1 (2.6), 8.9 (1.6), and 9.0 (5.9) mm in the 2.5-, 4.5-, 6.5-, and 8.5-g trauma classes respectively.

Biomechanical Phenomena↗
PubMed1997

[Headache in cervical syndrome].

Headache is a common symptom in patients suffering from cervical spine disorders. The percentage of headaches in association with degenerative changes of the cervical spine ranges from 13 to 79% and that in association with indirect trauma of the cervical spine from 48 to 82%. Based on neuroanatomical and neurophysiological studies, the relationship of the upper cervical spine and the trigeminal nuclei has been demonstrated and serves as an explanation for perceived head pain in cervical spine disorders. As a source of pain, tension in the suboccipital muscles, irritation of the third occipital nerve, and degenerative changes of the C2/C3 joints have been discussed. Bogduk, in his studies, asserts a direct causative role of mechanical derangement of the cervical spine in the pathogenesis of cervicogenic headaches. In 1983, Sjaastad et al. postulated the concept of 'cervicogenic headaches': a migraine-like headache due to certain disorders of the cervical spine, strictly located unilaterally, its manifestations being in the temporal, frontal, and ocular areas, with associated symptoms such as slight lacrimation, conjunctival injections, tinnitus, runny nose, and erythema in the forehead ipsilaterally. As arguments in favour of a cervical origin, Sjaastad mentioned the following features: precipitation of the headaches either by neck movements or by pressure against certain tender spots on the neck, the possibility of homolateral shoulder or arm pain, stiffness and pain of the neck, and reduced mobility of the cervical spine. In 1988, the Headache Classification Committee of the International Headache Society set strict criteria for 'headaches' to be classified as to be of cervical origin.

Cervical Vertebrae↗
PubMed1997

Itraconazole disposition after single oral and intravenous and multiple oral dosing in healthy cats.

OBJECTIVE: To determine the disposition of itraconazole in cats after single IV and oral dosing (as a solution or capsule) and multiple oral (capsule) dosing, and to establish bioavailability after oral administration of the solution. ANIMALS: 6 healthy cats for experiment 1 (E1), and 12 cats for experiment 2 (E2). PROCEDURE: For E1 (nonrandomized crossover design), each cat received a single dose of itraconazole solution (5 mg/kg of body weight) orally, and 1 month later, another dose i.v.. Blood samples were collected for 96 hours. For E2, each cat was given either 5 (group [G] 1) or 10 (G2) mg of itraconazole/kg (capsules) twice daily for 6 weeks. Samples were collected for 96 hours after the first and last dose. Itraconazole was detected by use of high-performance liquid chromatography. RESULTS: For E1, itraconazole plasma drug concentration extrapolated to time zero (IV dose) was 5.2 +/- 1.4 micrograms/ml, and mean residence time (MRT) was 37 +/- 16 hours. For oral dosing, maximal itraconazole concentration was 1.69 +/- 0.864 micrograms/ml, MRT was 48 +/- 17 hours, and bioavailability was 78.8 +/- 28%. For the multiple oral dosing study, MRT (at last dose: 81.1 +/- 97.4 hours for G1, and 63.1 +/- 15.1 hours for G2) was shorter (P = 0.02) at first dose, compared with last dose, for both groups but did not differ between groups. Maximal concentration did not differ between groups at either time. Steady state was achieved at 14 to 21 days. All cats tolerated itraconazole with no evidence of adverse effects. CONCLUSIONS: The oral itraconazole solution is preferred to capsules; a 24-hour dosing interval should be sufficient; 10 mg/kg given daily should generate therapeutic concentrations in most cats; steady-state concentrations may take up to 3 weeks to achieve; and cats appear to tolerate itraconazole well.

Administration, Oral↗
PubMed1996

Consensus summary of the diagnosis and treatment of lumbar disc herniation.

Clinicians must not simply decide that a patient with symptoms and a positive diagnostic test has a reason for a specific treatment, and likewise clinicians must not decide that a patient with symptoms and a negative test does not have a clinically important problem. We must also consider the sensitivity, specificity and predictive value of the diagnostic test and the individual characteristics of the patient. Treatment outcome depends on many factors. Point of service decisions vs population based decisions are obviously different. Each patient presents to the treating practitioner on a given day, at a given time, and it is this picture upon which a plan of care is formulated.

Humans↗
PubMed1996

[Stenosis of the lumbar spine in elderly persons. Surgical decompression].

The degenerative changes in the lumbar vertebral spine frequently appear as encroachment of the lumbar spinal canal. Degenerative changes of the anatomical structures dictate the location of the stenosis, which are divided in central or lateral stenosis of the lumbar spinal canal. According to this localization, more radicular symptoms in a lateral stenosis might be prevalent in contrast to the mixed symptoms of a central stenosis. Operative decompression might be indicated in cases with correlation of clinical symptoms and radiological findings. The operative treatment aims at a satisfactory decompression without creating iatrogenic instability. An additional fusion might be avoided in cases without apparent instability. Adequate operative decompression is most efficient concerning reduction of pain and increasing of walking distance.

Aged↗
PubMed1996

The effectiveness of various cervical orthoses. An in vivo comparison of the mechanical stability provided by several widely used models.

STUDY DESIGN: The amount of motion allowed by various cervical orthoses was compared with the amount of unrestricted neck motion in vivo. OBJECTIVES: To determine how much mechanical stability commonly used cervical orthoses provide to the wearer. SUMMARY OF BACKGROUND DATA: Few studies have compared quantitatively the restriction of motion from cervical orthoses that are commonly prescribed for patients. No studies have used methods allowing measurement of all three rotations throughout the range of motion in passive and active tests. Previous studies may have overstated the amount of restriction provided resulting from the methods used. METHODS: Five subjects were tested for cervical range of motion in flexion-extension, axial, rotation, and lateral bending. Each was tested with no collar, with soft collar, with Philadelphia collar, with Philadelphia collar with thoracic extension, and with sterno-occipital mandibular immobilizer brace. Each test was conducted passively and actively. Measurements were taken with the CA-6000 Spine Motion Analyzer, a highly accurate and precise computerized linkage system that simultaneously records all three rotations in real time. RESULTS: All orthoses restricted motion to some extent. Generally, the collars ranked (from least restrictive to most restrictive): soft, Philadelphia, Philadelphia with extension, and sterno-occipital mandibular immobilizer brace. However, the differences were not usually large, and the collars did not restrict motion as much as previously reported. No collar restricted the motion of any of the subjects to less than 19 degrees of flexion-extension, 46 degrees of axial rotation, or 45 degrees of lateral bending, and most subjects demonstrated significantly more motion. CONCLUSIONS: Although cervical orthoses can be helpful for other reasons, they do not provide a high level of mechanical restriction of motion. Additionally, the restriction they do provide can vary widely between people. Prescribing physicians should consider the relative merits of the various orthoses before deciding whether they will meet a patient's needs. The differences between the collars tested may not be enough to justify one of the more expensive or less comfortable collars.

Adult↗
PubMed1996

Spine update. Impaired cognitive functioning after whiplash injury of the cervical spine.

To enhance the awareness of physicians treating whiplash patients, findings from previous research regarding cognitive functioning of these patients are discussed and recommendations for assessment provided. Cognitive disturbances (i.e., deficient attentional functioning and impairment of memory) are frequent complaints in patients after whiplash injury. However, few prospective studies of nonselected patients have been performed. These studies indicate that impaired cognitive functioning relates either to trauma-induced somatic symptoms (i.e., pain) or psychologic symptoms resulting from problems adjusting to trauma-related somatic symptoms. Accordingly, cognitive disturbances after whiplash show a fair rate of recovery, which parallels recovery from trauma-related somatic symptoms. Current research does not indicate disturbances in higher cognitive functions after whiplash.

Brain Injuries↗
PubMed1996

Direct pediculo-body fixation in cases of spondylolisthesis with advanced intervertebral disc degeneration.

In inveterate cases of grade 2-3 spondylolisthesis (degenerative or spondylolytic), segmental mobility may be reduced by radiologically confirmed disc resorption. Fusion may be indicated in patients with persistent pain. A simple technique for fusion without reduction of the spondylolisthesis is presented. Fixation of the segment is achieved by two cancellous bone screws inserted bilaterally through the pedicles of the lower vertebra into the body of the upper slipped, vertebra. The cases of 16 patients with an average follow-up of 31 months (range 24-27 months) treated with this direct pediculo-body fixation are presented. Clinical evaluation showed significant decrease in pain and, in patients with concomitant spinal stenosis, walking distance without pain improved from between 500 and 1000 m to more than 3000 m. Radiologically, fusion was observed in all cases. The presented technique of internal fixation of a slipped segment in the degenerative lumbar spine represents a simple minimally traumatic procedure with successful clinical and radiological outcome. Additional procedures, such as decompression of the spinal canal, may be performed.

Bone Screws↗
PubMed1996

Foraminal changes with distraction and compression of the L4/5 and L5/S1 segments.

The width of the foramen in the lumbar spine is directly related to the position of the vertebrae. In an MRI study the measurements of the cross-sectional area of the neuroforamen of L4/5 and L5/S1 in neutral position, segmental distraction and compression were calculated. Nine cadaver specimens were investigated and the foraminal width of L4/5 and L5/S1 was measured. In both segments of all specimens the foraminal space significantly enlarged under distraction and decreased under compression. In the L4/5 segment the average relative difference between distraction and compression was 27%.

Adult↗
PubMed1996

[Clinical and technical assessment of the cervical spine].

In analysis of the cervical and cervicobrachial syndrome with or without signs of compression of the nerve root or spinal cord, functional assessment of the cervical spine is of great importance. Comparisons between actively performed and passively induced motion can be verified by using standardized computer-assisted assessment allowing precise documentation of the range of motion and coupled motion. The age-related normal values should be considered. The neurological assessment includes not only the cranial nerves and upper extremities but also lower extremities to avoid overlooking the signs of cervical myelopathy. In patients with compression of nerve roots or the spinal cord neurophysiology might be helpful in identifying or verifying compression. In patients with suspected myelopathy sensory evoked potentials will allow assessment of the function of the ascending spinal pathways and motor evoked potentials, assessment of the function of the descending cortical spinal pathways.

Adult↗
PubMed1996

[Post-traumatic atlanto-axial arthrosis].

Eight patients with post-traumatic chronic cervical syndrome and degenerative changes of the upper cervical spine, were treated with suboccipital fusion. After a mean follow up of 60 months (58-64), the patients were examined. Three patients had died during the follow-up period. A solid fusion was achieved in all cases. Significant reduction of pain and increased quality of life were established.

Adult↗
PubMed1996

[Functional treatment of diseases and injuries of the cervical spine].

The clinical findings and pain symptoms determine the functional treatment of the cervical spine disorders. Acute pain syndromes are to be approached by passive procedures, such as massage, electrotherapy, trigger point treatment. Could the pain reaction be reduced, the mobilizing techniques, including manipulation are indicated, followed by training therapy/reconditioning of shoulder girdle muscles. The patients are also to be instructed to perform home exercise program aiming the stabilization of cervical spine.

Cervical Vertebrae↗
PubMed1995

Differentiation between homoeologous chromosomes 1A of wheat and 1Am of Triticum monococcum and its recognition by the wheat Ph1 locus.

In most allopolyploid plants, only homogenetic chromosome pairing occurs in meiosis, as a result of the recognition of genome differentiation by the genetic system regulating meiotic chromosome pairing. The nature of differentiation between chromosomes of closely related genomes is examined here by investigating recombination between wheat chromosome 1A and the closely related homoeologous chromosome 1Am of Triticum monococcum. The recognition of the differentiation between these chromosomes by the Ph1 locus, which prevents heterogenetic chromosome pairing in wheat, is also investigated. Chromosomes 1A and 1Am are shown to be colinear, and it is concluded that they are differentiated "substructurally." This substructural differentiation is argued to be recognized by the Ph1 locus. In the absence of Ph1, the distribution and frequencies of crossing over between the 1A and 1Am homoeologues were similar to the distribution and frequencies of crossing over between 1A homologues. The cytogenetic and evolutionary significance of these findings is discussed.

Journal Article↗
PubMed1995

The role of motor evoked potentials in psychogenic paralysis.

STUDY DESIGN: This prospective clinical study identified patients in whom paralysis developed after lumbar surgery. OBJECTIVE: To determine whether patients with psychogenic paralysis could be identified using noninvasive techniques. SUMMARY OF BACKGROUND DATA: Before the advent of transcranial magnetic stimulation, no clinically applicable, noninvasive technique was available to confirm the integrity of the corticospinal tract. METHODS: Patients with suspected postoperative psychogenic paralysis were evaluated by clinical examination and neurophysiologic work-up, including transcranial magnetic stimulation. RESULTS: Six patients with psychogenic paralysis were identified in a 15-month period. In each case, motor evoked potentials could be demonstrated from the affected muscle(s), thus obviating the need for further invasive imaging or surgical exploration. CONCLUSIONS: Transcranial magnetic stimulation is a reliable, painless, and noninvasive technique for demonstrating structural integrity of the corticospinal tracts.

Adult↗
PubMed1995

Predictors of bad and good outcomes of lumbar disc surgery. A prospective clinical study with recommendations for screening to avoid bad outcomes.

STUDY DESIGN: Patients were assessed by independent research teams in six different spine centers after indication for discectomy was established. Six- and twelve-month follow-ups were performed. OBJECTIVES: Objectives of this study were to determine somatic subjective symptoms, objective signs, sociodemographic, and psychological factors that influence the outcome of lumbar disc surgery, as well as to develop a screening checklist and score of reliable predictors to distinguish bad and good responders of surgery. METHODS: In addition to symptoms, signs, and neuroradiologic findings, sociodemographic data were obtained. A mobility questionnaire and Beck depression inventory were included in the structured interview. RESULTS: In all, 381 patients were examined. At 6 months 89% and at 12 months, 86% of all operated patients were available for follow-up study. There was no significant difference in the outcome between the 6- and 12-month follow-ups. Of the patients, 51.5% had a good outcome, 28.4% moderate, and 20.1% bad at 12 months follow-up. The calculation of predictor score gave an overall appropriate prediction of 80%, for good outcome 76%, and for bad 79%. CONCLUSION: In addition to clinical and radiologic examination, the Hannover Mobility Questionnaire, the Beck depression inventory, and structured interview should be included for preoperative assessment for disc surgery. If a bad outcome is predicted, it is probably more appropriate not to operate and await natural development of the disc disease or to apply conservative and psychological treatment.

Adolescent↗
PubMed1995

Motor evoked potentials: appropriate positioning of recording electrodes for diagnosis of spinal disorders.

The interpretation of normal and pathological findings of motor evoked potential obtained by the use of transcranial magnetic stimulation depends on adequate examination technique, including the appropriate positioning of the recording electrodes over the muscle. On the basis of knowing the location of the motor end plate zones in muscles, magnetic stimulation of the motor cortex of 30 healthy adults was performed in order to explore the influence of the position of the surface recording electrodes on potential parameters and to establish the standard location of the recording electrodes over the biceps brachii, medial vastus, anterior tibial and abductor hallucis muscles for diagnostic use in spine disorders. The cortical latencies and peak-to-peak amplitudes of the evoked potentials were analysed by varying the location of the recording electrodes and the stimulus intensities. The latencies were significantly shorter when the different electrode lay more proximally over the muscle belly. Reproducible potentials with sharp negative onset and maximum amplitude were recorded with a separation of 5-7.5 cm between the different electrode, located over the motor end plate area, and the different electrode, located over the distal myotendinous junction. This implies that the parameters of evoked potentials depend on the position and separation distance of the recording electrodes over the muscles and that it is possible to record the potentials using a lower stimulus intensity and, above all, on relaxed muscles, which may prove to be applicable for intraoperative monitoring of the spinal cord using magnetic stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Degenerative lumbar spinal stenosis. Decompression with and without arthrodesis.

We prospectively evaluated the results of decompression of the spine, with and without arthrodesis, for the treatment of lumbar spinal stenosis without instability in forty-five patients (twenty-one men and twenty-four women) who had been managed between November 1989 and November 1990. The average age at the time of the operation was sixty-seven years (range, forty-eight to eighty-seven years). The patients were randomly assigned to one of three treatment groups (fifteen patients in each group) according to when they were admitted to the hospital. Group I was treated with decompression with laminotomy and medial facetectomy; Group II, with decompression and arthrodesis of the most stenotic segment; and Group III, with decompression and arthrodesis of all of the decompressed vertebral segments. All of the operations were performed by the same surgeon. The average duration of follow-up was twenty-eight months (range, twenty-four to thirty-two months). All three groups had a significant improvement in the distance that the patients were able to walk at the time of the latest follow-up examination compared with before the operation (p < 0.001 for Group I, p < 0.002 for Group II, and p < 0.005 for Group III). With the numbers available, there were no significant differences in the results among the three groups with regard to the relief of pain (p = 0.25 for Group I compared with Group II, p = 0.36 for Group II compared with Group III, and p = 0.92 for Group I compared with Group III).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗