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Biomedical subjects

D Grob

Publications and source records attributed to D Grob.

At least 55 records · Page 3Linked to original sources
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

Effect of cocaine on responses of mouse phrenic nerve-diaphragm preparation.

Effects of 5 to 40 microM cocaine on the compound action potential (AP) and tension responses of the mouse phrenic nerve-diaphragm preparation were monitored following nerve and muscle stimulation at 37 degrees C. Cocaine caused concentration dependent reduction in amplitude of the nerve AP, muscle AP, and tension response to a single nerve stimulus, and greater reduction in amplitude of these responses to repetitive nerve stimuli at 100 Hz for 0.5 sec. Cocaine caused similar reduction in the muscle AP and tension responses to direct muscle stimulation in the presence or absence of curare, and markedly reduced the overshoot, total potential, and maximum rate of rise and fall of intracellularly recorded muscle AP, without affecting the resting potential, or the contracture responses evoked by caffeine. These results indicate that cocaine reduces skeletal muscle function by reducing the excitability of muscle and nerve membranes, without significantly affecting neuromuscular transmission, excitation-contraction coupling or contractility.

Action Potentials↗
PubMed1991

Characterization of in vivo-activated T cell clones from peripheral blood of multiple sclerosis patients.

In vivo-activated interleukin-2 responsive T cell clones were generated from peripheral blood (PBL) of multiple sclerosis patients (MS) and normal subjects (N) by limiting dilution analysis. The frequency with which interleukin-2 responsive cells were cloned from PBL was higher in MS than N. CD8 was the predominant phenotype expressed by both MS (85%) and N (89%) clones. Seven clones from four MS patients but none from five N subjects specifically proliferated against myelin basic protein. These studies demonstrate the existence of MBP-reactive T cells in PBL of MS patients.

Antigens, Surface↗
PubMed1991

Peripheral mechanisms of fatigue in muscles of normal and dystrophic mice.

We evaluated the contribution of different processes to fatigue of normal and dystrophic mouse muscles using an in vitro electromyography chamber. Fatigue was induced by repetitive nerve stimulation at 30 Hz for 0.5 s, every 2.5 s until tension decreased by about 50%. We monitored the compound nerve action potential (AP), compound muscle AP, and isometric tension responses to nerve stimulation, and compound muscle AP and tension responses to direct muscle stimulation. In normal mice, about 50% reduction in nerve-evoked tension occurred by 2.4 min in extensor digitorum longus (EDL), 4.8 min in diaphragm, and 9 min in soleus. Analysis of the responses revealed that the fatigue was caused by failure of more than one process in all muscles, and failure of nerve conduction did not contribute to fatigue in any muscle. Failure of neuromuscular transmission, muscle membrane excitation, and excitation-contraction (E-C) coupling and contractility accounted for 55, 45, and 0%, respectively, of the fatigue in EDL, for 21, 74, and 5% of the fatigue in diaphragm, and for 2, 54, and 44% of the fatigue in soleus. In dystrophic mice, while about 50% reduction in nerve-evoked tension occurred by 8.1 min in EDL and 5.6 min in diaphragm, only 29% reduction in tension occurred by 80 min in soleus. Failure of neuromuscular transmission, muscle membrane excitation, E-C coupling and contractility accounted for 22, 63 and 15% of the fatigue in EDL, for 21, 79, and 0% of the fatigue in diaphragm, and for 15, 59, and 26% of the fatigue in soleus. The proportion of slow-twitch oxidative fibers was more than normal in dystrophic EDL, but the same as normal in dystrophic diaphragm and soleus. The slower onset of fatigue was attributable to lesser failure of neuromuscular transmission in dystrophic EDL, and to lesser failure of E-C coupling and contractility in dystrophic soleus.

Animals↗
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

Functional radiographic diagnosis of the lumbar spine. Flexion-extension and lateral bending.

Several attempts have been made to measure the segmental range of motion in the lumbar spine during flexion-extension with the purpose of gathering additional data for the diagnosis of instability. The previous studies were performed in vitro or in vivo during active motion. The aim of this study was to obtain normal values of passively performed segmental motions. Forty-one healthy adults were examined by means of functional radiographs during flexion-extension and lateral bending. A graphic construction method and a computer-assisted method were used to measure rotations. Comparing with recent in vivo studies, the values obtained for normal angles of rotation were predominately larger. This might be due to the passive examination used in the study. The graphic construction method and computer-assisted method techniques are equally reliable, but the computer-assisted method method yields other important kinematic data, such as translations. It is proposed that passive motion be applied during functional examination of patients with suspected instabilities. However, the large variation of rotational values between individuals in the normal population may limit the clinical usefulness of functional lumbar analysis using this parameter. Future studies should explore the clinical relevance of determining altered segmental mobility in low-back pain patients.

Adult↗
PubMed1991

Clinical validation of functional flexion-extension roentgenograms of the lumbar spine.

The purpose of this study was to determine the clinical validity of functional flexion-extension roentgenograms of the lumbar spine in a defined patient population. One hundred and one adults with low-back pain or functional disorders underwent passive functional flexion-extension examinations. Their roentgenograms were analyzed using a computer-assisted method to determine segmental motion parameters such as rotation and translation of the lumbar vertebrae. The patient population was broken down into five groups with similar pathologies or physical conditions, and their motion parameters compared to a normal population and to each other. It was found that all of the patient groups exhibited significantly hypomobile motion, spread equally among all levels, in comparison to the normal population, except for the group of high-performance athletes, who had significant hypermobility. The uniform spread of hypomobility limits the ability to distinguish with any confidence between the four pathologic groups by their motion. Thus, we believe that the analysis of the segmental motion of the lumbar spine using passive flexion-extension roentgenograms does not aid in differentiating the underlying pathologic condition of patients with low-back pain, and that no useful information can be derived form this procedure, especially in relation to the need for surgical intervention.

Adult↗
PubMed1991

Magnetic stimulation of motor cortex and motor roots for painless evaluation of central and proximal peripheral motor pathways. Normal values and clinical application in disorders of the lumbar spine.

Magnetic stimulation of the motor cortex, motor roots, and proximal nerve trunks was performed in 46 healthy adults and in 73 consecutive patients with disorders of the lumbar spine. In combination with neurography and F-wave recordings, the fractionated stimulation of the motor pathways allowed calculation of conduction times of the pyramidal tract fibers, of the motor roots (ie, caudal fibers), and of the motor fibers of the lumbosacral plexus. Normal values for motor conduction times to the quadriceps, anterior tibial, and extensor digitorum brevis muscles were established. Patients had clinical and radiologic diagnoses of spinal stenosis (n = 43) and nerve root compression syndromes (n = 30). Motor conduction times to lower limb muscles were significantly delayed (above mean normal value +/- 2 x SD) in 65% of the patients with spinal stenosis and 50% of the patients with nerve root compression syndromes. Conduction slowing could be localized within the motor root and caudal fiber segment of the motor pathways in 80% of the patients in whom F-waves could be recorded. This method can be used to verify, quantify, and locate lesions of the motor pathways in conditions such as compression of the spinal cord, the caudal fibers (spinal stenosis), or the motor root passing through the intervertebral canal.

Adult↗
PubMed1991

Transections of the C1-C2 joint capsular ligaments in the cadaveric spine.

The purpose of this study was to examine the mechanical function of the C1-C2 capsular ligaments. Physiologic torques of up to 1.5 Nm were applied to human fresh cadaveric specimens (C0-C1-C2-C3) in three dimensions, and the three-dimensional motion of C1 relative to C2 was recorded. Two groups of cadaveric specimens were used to study the effect of two different sequential ligamentous transections. In the first group (n = 4), the transection of the left capsular ligament was followed by transection of the right capsular ligament. In the second group (n = 10), the transection of the left capsular ligament was preceded by transection of the left and right alar and transverse ligaments. The greatest changes in motion occurred in axial rotation to the side opposite the transection. In the first group, left capsular transections resulted in a significant increase in axial rotation range of motion to the right of 1 degree. After the right capsular ligament was transected, there was a further significant increase of 1.8 degrees to the left and 1.0 degree to the right. Lateral bending to the left also increased significantly by 1.5 degrees after both ligaments were cut. In the second group, with the nonfunctional alar and transverse ligaments, transection of the left capsular ligament resulted in greater increases in range of motion: 3.3 degrees to the right and 1.3 degrees to the left. Lateral bending to the right also increased significantly by 4.2 degrees.

Cadaver↗
PubMed1991

Atlanto-axial fusion with transarticular screw fixation.

We reviewed 161 patients, from four centres in Switzerland, who had undergone posterior fusion of the upper cervical spine with transarticular screw fixation of the atlanto-axial joints. They were followed up for a mean 24.6 months. The vertebral artery and the medulla escaped injury and only 5.9% of the complications were directly related to the screws. The rate of pseudarthrosis was 0.6%.

Adolescent↗
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↗
PubMed1991

[Instability in injury of the alar ligament. A biomechanical model].

Fresh human cadaveric specimens of occiput (C0) to C3 were subjected to 1.5 nm of flexion, extension and bilateral bending and axial torque. The resulting physiological motions were studied in an unconstrained three-dimensional manner. The effects of sequential transections of the left and right alar ligaments on the relative motion of C0-1 and C1-2 were studied. After transection of the left alar ligament, the percentage increases in neutral zones (NZ) and ranges of motion (ROM) were documented at both the C0-1 and C1-2 joints. In the sagittal plane, the most increase was at C1-2 due to the flexion moment, e.g., 47.4% in NZ and 27.6% in ROM. In lateral bending, the left alar transsection resulted in mostly right lateral bending increases and at the C0-1 joint, 37.1% in NZ and 19.6% in ROM. In axial rotation, changes in the total motion of the C0-2 joint complex were more reliable indicators. For left alar transsection, most increases were in right axial rotation, e.g., 25.6% for right rotation versus 11.2% for left rotation in the NZ parameter. Functional loss of the alar ligaments indicates a potential for instability which, however, must be determined in conjunction with other clinical findings, such as neurological dysfunction, pain and deformity.

Adult↗
PubMed1991

[Orthopedic problems of the upper cervical spine in children and adolescents].

Because of relatively low frequency of pathological changes of the upper cervical spine in childhood and adolescence, their management is not well known. Diagnostic problems occur due to the variety of malformations possible, persisting growth plates and ligamentous laxity. Because of this laxity, conservative treatment with immobilization is advocated even in severe dislocations as long as they are reducible. Persistent dislocations, chronic atlantoaxial instability (ADI greater than 5 mm), dens fractures type II and existing or progressing neurological deficits all indicate surgical intervention. Internal fixation allows easier postoperative care. Complications are rare. Patients with orthopedic problems of the upper cervical spine are presented, together with their management.

Adolescent↗
PubMed1991

[Dorsal atlanto-axial screw fixation. A stability test in vitro and in vivo].

Clinical and biomechanical testing of the stability of atlantoaxial fusions was studied. For biomechanical testing, four different techniques for posterior atlantoaxial fusion were tested: (1) wire fixation with one median graft; (2) wire fixation with two bilateral grafts; (3) transarticular screw fixation and two bilateral posterior clamps. Ten fresh human cadaveric specimens were tested. The loads applied were 6 pure moments. The motion of C1 relative to C2 in the intact, injured and mechanically fixed spine were measured and compared. In flexion/extension the difference between Brooks, Magerl and Halifax were not significant, but each was significantly less than the Gallie-system. For the anterioposterior translation the stabilization of all fixation techniques was about equal. In axial rotation measuring the translations between C1 and C2, the screw-fixation technique proved to be the most stable. For lateral bending, there was no significant difference between the different techniques, except for Galliefixation, but the screw-fixation technique allowed the least motion. In additional in vivo tests ten patients with posterior atlantoaxial fusion by the transarticular screw-fixation technique underwent bending X-rays of the upper cervical spine as well as computertomograms. Solid fusion was achieved in all patients. Both investigations proved the reliability of the multidirectional stability of the atlantoaxial screw fixation technique.

Atlanto-Axial Joint↗
PubMed1990

Responses of intercostal muscle biopsies from normal subjects and patients with myasthenia gravis.

In order to evaluate the mechanisms of weakness in muscles of patients with myasthenia gravis (MG), intercostal muscle biopsies were obtained from 9 normal subjects and 6 MG patients, and the compound muscle action potential (AP) and tension responses to nerve and muscle stimulation, and contracture responses on exposure to caffeine, were monitored in vitro. In normal muscle, on stimulation of the nerve or muscle at 30 to 100 Hz, the AP responses showed decrement in amplitude, one-third of which was attributable to failure of neuromuscular transmission and two-thirds to failure of muscle membrane excitation. On stimulation at 1 to 5 Hz, the AP responses showed very little decrement, while the contractile responses showed significant fade in tension, due to failure of E-C coupling or contractility. In muscle from patients with generalized MG, stimulation of the nerve at all frequencies (1 to 100 Hz) caused much greater decrement in APs and fade in tension responses than in normal muscle, due mainly to failure of neuromuscular transmission. However, at 100 Hz, 40% of the decrement in APs was due to failure of muscle membrane excitation, and at 1 to 5 Hz, 40% of the fade in tension was due to failure of E-C coupling or contractility, as in normal muscle. On direct stimulation the contraction and half-relaxation times were slower and the tetanic tension was smaller than in normal muscle, especially in the MG patient with thymoma. Caffeine-induced contractures were smaller in MG muscle than in normal muscle. These results indicate that while the weakness of MG muscle is due mainly to failure of neuromuscular transmission, it is also partly due to reduced E-C coupling or contractility.

Action Potentials↗
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

Detection of HIV antibody and antigen (p24) in residual blood on needles and glass.

There is a significant rate of percutaneous injury with needles during the care of patients with acquired immunodeficiency syndrome (AIDS). Following puncture injury, it is recommended that the source of the contaminating blood be checked, and if human immunodeficiency virus-type 1- (HIV-1)-seropositive, zidovudine prophylaxis be considered. As the source of contaminating blood may be unknown, we studied the detectability of HIV-1 antibody and circulating antigen (p24) in the residual blood from needles and pieces of glass at various intervals following exposure to blood. The residual volume of blood remaining in needles varied from 183 +/- 50 microliters for a 20 G needle to 7.8 +/- 1 microliter for a 27 G needle, and the residual blood on small pieces of glass varied from 23 microliters for a piece weighing 558 mg to 2 microliters for a piece weighing 21 mg. Analysis of washed samples of residual blood from all 20 G through 26 G needles and from broken pieces of glass larger than 0.41 g that had been exposed to HIV-1-seropositive blood and left at room temperature for one hour, one day and one week resulted in positive tests for HIV-1 antibody by enzyme-linked immunosorbent assay (ELISA), immunofluorescence and Western blot assays. The circulating antigen was detected in residual blood of 20 G through 26 G needles, but not from contaminated pieces of glass. This technique could be applied to situations where a healthcare worker pricked him- or herself with a needle or with a piece of glass that had been contaminated with blood of unknown seroreactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Western↗