Biomedical subjects

J Dvorak

Publications and source records attributed to J Dvorak.

At least 127 records · Page 7Linked to original sources

PubMed1991

In vivo flexion/extension of the normal cervical spine.

Twenty-two women (age range 25-49 years, average 30.9 years) and twenty-two men (age range 23-42 years, average 31.6 years), all healthy and asymptomatic, underwent passive flexion/extension examinations of the cervical spine. Functional x-rays were taken and analyzed using a computer-assisted method that quantified intervertebral rotations, translations, and locations of the centers of rotation for each level C1-C2-C6-C7. The aim of the study was to establish values for these parameters for a normal population as related to age and gender. In the process, a statistically significant difference was found in the average value of rotation between male and female groups at the C5-C6 level. A new parameter, the ratio between translation and rotation, was also established and may prove useful for clinical diagnoses. This parameter has a smaller error associated with it than do pure translations and may aid the clinician by helping to account for the large variation in rotatory ranges of motion within the population. This translation/rotation ratio indicated highly significant differences in the lower segments of the cervical spine between gender groups.

Adult↗

PubMed1991

Bone graft translation of four upper cervical spine fixation techniques in a cadaveric model.

The goal of spinal fixation is to promote bony fusion by restricting motion at the site of the bone graft. Therefore, in order to evaluate the efficiency of various cervical fixation techniques, we determined the translations at the posterior arch of C1 for four C1-C2 posterior techniques: Gallie, Brooks, Magerl, and Halifax. Our model was the cadaveric specimen, with extensive soft tissue injury: transection of the alar, transverse, and capsular ligaments. Under three-dimensional physiological loading, we recorded the motion of C1 relative to C2, and calculated the translations at the surface of the graft in three dimensions, 10 specimens being tested intact, injured, and instrumented with each of the techniques. We assumed that translational laxity or neutral zone was the critical motion parameter and evaluated it, quantified herein as the neutral zone, at seven points at the graft site. The three-dimensional neutral zone translations were analyzed by their axial and shear components. We found that there was no significant difference with the fixation techniques in the average axial translation (Brooks: 1.1 mm; Magerl: 1.3 mm; Gallie: 1.5 mm; and Halifax: 0.5 mm). In shear, the Magerl averaged 1 mm, which was significantly less than the Gallie (2.1 mm). The Brooks (1.6 mm) and Halifax (1 mm) were not different from each other, Magerl, or Gallie. We propose that evaluation by translational laxity (neutral zone) at the graft site is a noteworthy concept in biomechanical analysis.

Adult↗

PubMed1991

Circumferential fusion of the lumbar and lumbosacral spine.

Seventy-four patients with circumferential fusion of the lumbosacral spine have been assessed after a mean follow up of 49.8 months. For the ventral procedure, an anterior interbody fusion with tricortical iliac bone graft was performed. The additional dorsal fusion was according to various techniques with mainly transpedicular internal fixation. Forty-six patients underwent a one-stage operation while 28 underwent the ventral and dorsal procedure in different sittings. The results favour the technique of a combined anterior/posterior approach for fusion of the lumbosacral spine in patients with instability and deformity of all three columns, such as fractures and spondylolisthesis of more than 50%. Optimal stability with satisfactory reduction of the deformity may be achieved. The one-stage operation proved to be superior, with less complications and a shorter hospital stay.

Adolescent↗

PubMed1991

A model of the alar ligaments of the upper cervical spine in axial rotation.

Although there are seven vertebrae in the human cervical spine, over 50% of the total axial rotation occurs between the first and second vertebrae, at the atlanto-axial joint. Such motion is possible because of the lack of an intervertebral disc and the shape of the articular facets. The limitation of axial rotation, essential because the spinal cord and vertebral arteries cross this joint, is achieved with ligamentous structures, of which the left and right alar ligaments are primary. When one of the alar ligaments was cut in previous tests of human cadaveric spine (n = 10), the axial rotation to both sides significantly increased. This result does not agree with the long-held hypothesis that axial rotation is limited only by the alar on the side opposite rotation. The purpose of this work was to develop a model of the alar ligaments in axial rotation that is consistent with recent experimental observations. This model predicts that both alars must be intact to limit axial rotation; if one alar is injured, the normal mechanism becomes nonfunctional. The model also predicts the observation that a significant percentage of rotation at the atlanto-axial joint occurs freely, without ligamentous resistance. A physical and a mathematical description of the model is presented. Cadaveric experimental data are demonstrated to support the model.

Biomechanical Phenomena↗

PubMed1991

Flexion, extension, and lateral bending of the upper cervical spine in response to alar ligament transections.

The purpose of this in vitro experimental study was to determine the role of alar ligaments in providing flexion, extension, and lateral bending stability to the upper cervical spine. Ten fresh human cadaver specimens occiput-C3 were studied in a complete unconstrained and three-dimensional manner, first intact and then after sequential cutting of the left and right alar ligaments. At the C0-C1 joint, there were increases in flexion motion with sequential cutting of the alar ligaments but none in extension. For the same joint, cutting of the left alar ligament resulted in a significant increase in neutral zone in right lateral bending but not in left lateral bending, whereas there were no significant increases in the ranges of motion. At the C1-C2 joint, there were significant increases both in flexion and extension due to cutting of the left alar ligament, but subsequent cutting of the right alar ligament resulted in a small increase for flexion only. At this joint, right lateral bending increased due to cutting of the left alar ligament, but the same was not true for the left lateral bending. Subsequent cutting of the right alar ligament resulted in significant increases for both the right and left lateral bending.

Adult↗

PubMed1991

Posterior occipitocervical fusion. A preliminary report of a new technique.

A new technique for occipitocervical fusion is described. The fixation of the upper cervical spine with plates and screws avoids the possible disadvantages of the commonly used wiring technique. By the establishment of a rigid fixation between the occiput and upper cervical spine with a combination of plates and screws, especially with transarticular atlantoaxial screw fixation, reliable, multidirectional, and immediate stability is achieved. The clinical picture and analysis of 14 patients with a variety of pathologies of the upper cervical spine is presented. The satisfactory outcome and solid bony fusion in all 14 patients and the absence of severe complications encourages the continued use of this technique of occipitocervical fusion.

Arthritis, Rheumatoid↗

PubMed1990

[Radiological assessment protocol in injuries of the cervical vertebrae].

Over 3000 cases of soft tissue injuries of the cervical spine are reported annually to SUVA (Swiss accident insurance). Although the majority of the patients are pain-free within 4 weeks, it appears that approximately a quarter of those injured still experience neck pain even years after the accident. The initial radiological assessment should include an AP and a lateral plain X-ray of the cervical spine, and in the case of radicular symptomatology oblique views are also recommended. Should the symptoms persist for more than 6-8 weeks after the accident, functional X-rays in flexion/extension and lateral flexion should also be performed. If no instability can be demonstrated by plain X-rays and symptoms are still present and severe enough to limit the patient's working capacity after 3 to 6 months despite conservative therapy, further neuroradiological investigations, including functional CT's, are indicated. The decision to perform these investigations should lie with an interdisciplinary spinal team. Close cooperation between the clinicians and the radiologists is of utmost importance to ensure that the optimal radiological investigation can be performed on the basis of the clinical findings.

Cervical Vertebrae↗

PubMed1990

[Persistent leg pain].

A 72 year old patient suddenly experienced severe lumbar pain irradiating into the right leg. Later on, weakness of the muscles thigh appeared. A thorough radiological investigation which showed degenerative alterations of the vertebral column did not supply an explanation. After a pathological titer against Borrelia burgdorferi was found in serum and radiculitis was detected on EMG, the diagnosis of Lyme-Borreliosis of the nervous system could be confirmed by analysis of the cerebrospinal fluid. Under intravenous antibiotic treatment with Ceftriaxone (2 to 4 g daily for three weeks) the symptoms regressed completely, and the pathological findings in the CSF regressed. The significance of some findings in CSF in relation to Borreliosis of the CNS.

Aged↗

PubMed1990

[Neuropsychological findings following whiplash injury of the cervical spine].

58 patients with whiplash injury of the cervical spine underwent formal testing with respect to self-rated cognitive impairment and processing of visual and auditory information. The results indicated disturbances in divided attention for auditory information, particularly in patients with so-called cervicoencephalic syndrome. Impaired attentional control was assumed to be relevant to processes of the working memory.

Acoustic Stimulation↗

PubMed1990

Posterior occipito-cervical fusion in rheumatoid arthritis.

The instability of atlanto-axial subluxation remains a challenging problem in patients with rheumatoid arthritis. In order to preserve as much function of the cervical spine as possible, inclusion of the occiput into the fusion should exclusively be performed when there is a radiologically or clinically manifest pathological condition of the atlanto-occipital joint or marked upward migration of the dens axis. In order to prevent irreversible damage to the spinal cord, an early indication of surgical stabilization is recommended. This article presents a retrospective analysis of the clinical and radiological results of occipito-cervical fusion in 26 patients with rheumatoid arthritis using a modified Brattström technique. The complications encountered were mainly due to the use of wire fixation, reinforcement using bone cement and insufficient reduction of atlanto-axial subluxation.

Adult↗

PubMed1990

Histology of the alar and transverse ligaments.

Seven sets of human transverse and alar ligaments, after tensile testing, and eight corresponding ligaments without testing, were examined histologically with respect to their fiber composition and fiber orientation. Various staining techniques were supplemented by polarized light microscopy. Both the transverse and the alar ligaments consist of collagen fibers, with very few elastic fibers in the peripheral layer. In the central portion of the transverse ligament, the collagen fibers cross each other at an angle of approximately 30 degrees. Close to the dens, the transverse ligaments show on their ventral side a transition into fibrocartilage. Except for the immediate site of failure, no differences became evident between tested specimens and controls. The collagen, as the almost exclusive constituent, together with the fiber orientation determine the mechanical properties of these ligaments. This supports the hypothesis that the ligaments could be irreversibly overstretched or even ruptured when the head is rotated and, in addition, flexed by impact trauma, especially in unexpected rear-end collisions.

Aged↗

PubMed1989

[Psychological changes following whiplash injury of the cervical vertebrae].

To evaluate the frequently attributed psychogenic origin of symptoms following "whiplash" injury, 66 patients who had suffered such an injury underwent clinical and psychometric examination. Data were collected on subjective symptoms and their possible psychogenic origin and psychopathology. Personality profile, subjective well-being and cognitive impairment were evaluated. The amount of long-lasting psychopathological alterations was comparatively small. The results do not support the notion of a psychogenic origin for symptoms after "whiplash" injury; personality traits and psychopathology do not explain the nature of the complaints.

Adaptation, Ocular↗

PubMed1989

Functional evaluation of the spinal cord by magnetic resonance imaging in patients with rheumatoid arthritis and instability of upper cervical spine.

Thirty-four patients with atlanto-axial instability due to rheumatoid arthritis were examined with plain x-ray views and functional magnetic resonance imaging (MR), and were neurologically evaluated. Transcranial brain stimulation was performed in 25 patients. In 22 cases, the authors observed inflammatory tissue thicker than 3 mm behind the odontoid peg. The spinal canal diameter was significantly decreased in the flexed position. Nine patients showed signs of cranial migration of the axis. The diameter of the spinal cord was measured to be 7.4 mm in the neutral position, and 6.5 mm in flexion. The difference between the diameter of the neutral and flexed positions was highly significant. Twelve of the 34 patients displayed clinical signs of cervical myelopathy, and 13 showed a significant delay of central motor latency, as calculated from the motor evoked potentials. Surgical intervention, either by a posterior approach only or combined with a transoral dens and inflammatory tissue resection, is recommended in patients with progressive atlanto-axial instability, pathologic clinical and neurophysiologic findings, and a spinal cord diameter of less than 6 mm in flexion. Severe pain and cranial migration of the axis, as measured by the MRI, also justify a surgical intervention.

Adult↗

PubMed1988

Biomechanics of the craniocervical region: the alar and transverse ligaments.

In the treatment of spine fractures and fracture-dislocations, stability of the spine is one of the major objectives. In the craniocervical joint, the alar and transverse ligaments provide much of the stability of the healthy spine. Because the anatomy appears well described, the contribution of each of these structures so far has received little attention. The alar ligament restrains rotation of the upper cervical spine, whereas the transverse ligament restricts flexion as well as anterior displacement of the atlas. A lesion in one or both structures can produce damage to the neural structures and/or cause pain. To investigate the possible role of each of these ligaments, a mechanical and histologic study of the upper cervical spine was made. The bone-ligament-bone complex of the alar and transverse ligaments was subjected to uniaxial mechanical testing in seven specimens. The alar ligaments had an in vitro strength of 200 N, and the transverse ligaments had an in vitro strength of 350 N. Histologic analysis revealed a mainly collagenous nature of these ligaments. Clinical evidence (broken odontoid processes) suggests that the transverse ligament is strong enough to withstand physiologic loads. The alar ligament, on the other hand, due to its lower strength and its axial direction of loading, might be prone to injury and therefore require stabilization of the appropriate vertebra more often than normally is assumed.

Aged↗

PubMed1988

Functional diagnostics of the cervical spine using computer tomography.

35 healthy adults and 137 patients after cervical spine injury were examined by functional CT. The range of axial rotation at the level occiput/atlas, atlas/axis and the segment below were measured in all subjects. A rotation occiput/atlas of more than 7 degrees, and C1/C2 more than 54 degrees could indicate segmental hypermobility, a rotation at the segment C1/C2 less than 29 degrees to hypomobility. According to the postulated normal values based upon a 98% confidence level, out of 137 patients examined after cervical spine injury and with therapy-resistant neck pain, 45 showed signs of segmental hypermobility of the upper cervical spine, 17 showed hyper- or hypomobility at different levels, 10 patients presented segmental hypomobility at C1/C2 level alone. In all patients, according to the clinical assessment, functional pathology was suspected in the upper cervical spine. Surgical correction of rotary instability should be considered as a possible therapeutic procedure after successful diagnostic stabilisation of the cervical spine by minerva cast.

Adolescent↗

PubMed1988

Three-dimensional movements of the upper cervical spine.

Knowledge of the normal movements of the occipito-atlanto-axial joint complex is important for evaluating clinical cases that may be potentially unstable. The purpose of this in vitro study was to quantitatively determine three dimensional movements of the occiput-C1 and C1-C2 joints. Ten fresh cadaveric whole cervical spine specimens (occiput to C7) were studied, using well-established techniques to document the movements in flexion, extension, left and right lateral bending, and left and right axial rotation. Pure moments of a maximum of 1.5 N-m were applied incrementally, and three-dimensional movements of the bones were recorded using stereophotogrammetry. Each moment was applied individually and in three load/unload cycles. The motion measurements were made on the third load cycle. Parameters of neutral zone, elastic zone, and range of motion were computed. Neutral zones for flexion/extension, right/left lateral bending, and right/left axial rotation were, respectively: 1.1, 1.5, and 1.6 (occiput-C1); and 3.2, 1.2, and 29.6 degrees (C1-C2). Ranges of motion for flexion, extension, lateral bending (one side), and axial rotation (one side) were, respectively: 3.5, 21.0, 5.5, and 7.2 degrees (occiput-C1 joint) and 11.5, 10.9, 6.7, and 38.9 degrees (C1-C2 joint). The greatest intervertebral motion in the spine was axial rotation at the C1-C2 joint, with the neutral zone constituting 75% of this motion.

Adult↗

PubMed1988

Functional radiographic diagnosis of the cervical spine: flexion/extension.

The cervical spines of 59 adults were examined by means of functional roentgenograms. They were divided into two groups consisting of 28 healthy adults and 31 patients who had sustained soft tissue injury to the cervical spine and who were complaining of neck pain. Roentgenographic lateral views were taken in active flexion and extension as well as in passive maximal flexion and extension. Measurements using the techniques of Penning and Buetti-Bauml were made by three observers independently. There was a highly significant difference between the active and passive segmental ranges of motion in healthy adults. Based on the normal values obtained in this study, 19 hypermobile segments could be diagnosed during the active examination, while 31 hypermobile segments were found during the passive examination. In addition, the active examination found 60 hypomobile segments, while the passive examination showed only 43 hypomobile segments. The Penning Method of measurement was found to be more reliable than that of Buetti-Bauml. If possible, the functional roentgenogram examination of the cervical spine in the sagittal plane should be performed by including passive movement and the range of motion should be compared with the normal values obtained by passive examination.

Adult↗

PubMed1988

The outcome of surgery for lumbar disc herniation. I. A 4-17 years' follow-up with emphasis on somatic aspects.

Records of 575 patients operated on for the first time for lumbar disc herniation have been reviewed. Four to 17 years after the operation 371 (65%) patients answered a questionnaire on number of reoperations, working capacity, lumbar or sciatic pain as well as necessity of treatment. Of these, 255 (70%) still complained of back pain, and 83 (23%) of this group complained of constant heavy pain; 172 patients (45%) have a residual sciatica; 131 (35%) are still under some kind of treatment; 47 (14%) patients are receiving a disability pension. Repeat operations were performed in 17%. Based on the criteria given by Spine Update 1984 as related to justified or unjustified indication there was no statistical difference in long-term results concerning the above-mentioned criteria of success. The so-called justified indication for disc herniation neurosurgery does not necessarily imply a good long-term result. In the preoperative investigation, not only symptoms and neurological signs, but also the socially and personally defined career of the illness are of importance. The patients with complaints, mainly those receiving a pension, are psychologically conspicuous and show more psychopathological features as monitored by MMPI than the patients without complaints after surgery. Psychological assessment should increasingly be used in the preoperative evaluation, especially in patients who do not present an absolute indication for neurosurgical intervention.

Adolescent↗