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Biomedical subjects

G Drouin

Publications and source records attributed to G Drouin.

At least 73 records · Page 4Linked to original sources
PubMed1988

Nonlinear gross response analysis of a lumbar motion segment in combined sagittal loadings.

A 3-D nonlinear mathematical model is used to analyze the mechanical response of a lumbar L2-3 motion segment including the posterior elements when subjected to combined sagittal plane loads. The loadings consist of axial compression force, anterior and posterior shear forces, and flexion and extension moments. The facet articulation is modelled as a general moving contact problem and the ligaments as a collection of uniaxial elements. The disk nucleus is considered as an inviscid fluid and the annulus as a composite of collagenous fibers embedded in a matrix of ground substance. The presence of axial compression force reduces the segmental stiffness in flexion whereas a reverse trend is predicted in extension. In the presence of axial compression with and without sagittal shear force, flexion considerably increases the intradiscal pressure while extension reduces it. In other words, under an identical compression force, disk pressure is predicted to be noticeably larger in flexion than in extension. The segmental mechanical response in extension loadings is markedly influenced by the changes in the relative geometry of the articular surfaces at the lower regions. Finally, the deformation of the bony structures plays a significant role in the segmental mechanics under relatively large loads.

Biomechanical Phenomena↗
PubMed1988

An evaluation of the hemiplegic subject based on the Bobath approach. Part I: The model.

An evaluation, based on the Bobath approach to treatment has been developed. A model, substantiating this evaluation is presented. In this model, the three stages of motor recovery presented by Bobath have been extended to six, to better follow the progression of the patient. Six parameters have also been identified. These are the elements to be quantified so that the progress of the patient through the stages of motor recovery can be followed. Four of these parameters are borrowed from the Bobath approach, that is: postural reaction, muscle tone, reflex activity and active movement. Two have been added: sensorium and pain. An accompanying paper presents the evaluation protocol along with the operational definition of each of these parameters.

Disability Evaluation↗
PubMed1988

An evaluation of the hemiplegic subject based on the Bobath approach. Part III. A validation study.

Sixty-two hemiplegic subjects were treated with the Bobath approach for a period of three months. During this time they were evaluated on three occasions. The testing battery consisted of a Bobath evaluation, the Brunnstrom scale, the Fugl-Meyer test, the Upper Extremity Functional Test (UEFT) and the Present Pain Intensity (PPI) of the McGill pain questionnaire. A Friedman analysis of variance showed that, except for pain, all the protocols used disclosed significant progress (p less than 0.001) over time in terms of motor recovery. Except for pain, the results of the Bobath evaluation were significantly correlated (Spearman's Rho, p less than 0.001) with the results of the other testing procedures. It is concluded that the new Bobath evaluation proposed in a previous paper is as sensitive in depicting progress in motor recovery over time as are the other testing procedures used. Furthermore, this new evaluation seems to be measuring similar properties to the other tests. However, pain (PPI) appears not to be an important dependent variable.

Adult↗
PubMed1988

An evaluation of the hemiplegic subject based on the Bobath approach. Part II: The evaluation protocol.

A protocol of evaluation of the hemiplegic patient based on the Bobath approach to treatment is presented. Six parameters are evaluated: sensorium, muscle tone, reflex activity, active movement, postural reactions and pain. The first and last of these are included because of their possible effects on the motor recovery process of the hemiplegic patient. The other four are directly borrowed from the Bobath modality of treatment. For each of these parameters, the procedures are given for its evaluation along with its respective rating scales. These scales are of an ordinal nature ranging from 0 to 3. It is suggested that this new evaluation protocol is fully compatible with the therapeutic modality developed by Bobath and as well is adequate to quantify patient progress in the principle aspects treated by this well used rehabilitation approach.

Disability Evaluation↗
PubMed1987

Unusual ribosomal RNA gene organization in copepods of the genus Calanus.

Ribosomal RNA genes in the nuclear genomes of eukaryotes are generally found in tandemly repeated units encoding 18 S, 5.8 S and 28 S rRNA (in that order). 5 S rRNA genes typically lie outside these units, most often in tandem clusters coding exclusively for 5 S rRNA. Inclusion of 5 S genes within the 18 S-5.8 S-28 S repeat unit is known only for certain protozoa and fungi. Here we report that, in the copepod Calanus finmarchicus, single 5 S genes are included within many or all of the 18 S-5.8 S-28 S repeat units. Sequence analyses of regions cloned from two of these repeat units show that they indeed include 5 S genes (which are distal to 28 S genes) and that these are transcribed from opposite strands.

Animals↗
PubMed1987

Load-bearing role of facets in a lumbar segment under sagittal plane loadings.

In the present work, the load-bearing role of the facet joints in a lumbar I2-3 segment is quantitatively determined by means of a three dimensional nonlinear finite element program. The analysis accounts for both material and geometric nonlinearities and treats the facet articulation as a nonlinear moving contact problem. The disc nucleus is considered as an inviscid incompressible fluid and the annulus as a composite of collagenous fibres embedded in a matrix of ground substance. The spinal ligaments are modelled as a collection of nonlinear axial elements. The loadings consist of axial compression and sagittal plane shears and bending moments, acting alone or combined. The results show that in pure compression, the external axial force is transmitted primarily by the intervertebral disc. The facet joints carry only a small percentage of the force. However, the facet joints carry large forces in extension, whereas in small flexion they carry none. Addition of compression tends to increase these contact forces in extension while it has no effect on them in flexion. In extension, the forces on the facet joints are transmitted by both the articular surfaces and the capsular ligaments. Although in small flexion the facets carry no load, large contact forces are predicted to develop as the segment is flexed beyond 7-8 degrees. These forces are of the same magnitude as those computed under large extension rotation and are oriented nearly in the horizontal plane with negligible component in the axial direction. The horizontal components of the contact forces generated during articulation are often larger than the axial components which directly resist the applied compressive force. The axial components of the contact forces, therefore, grossly underestimate the total forces acting on the facets. The transfer of forces from one facet to the adjacent one occurs through distinct areas in flexion and in extension loadings. That is, on the superior articular surface, the contact area shifts from the upper tip in large flexion to the lower margin in extension. On the inferior articular surface, the contact area shifts from the upper and central regions in large flexion to the lower tip in extension.

Humans↗
PubMed1987

In situ mechanical behavior of posterior spinal ligaments in the lumbar region. An in vitro study.

The posterior ligaments: ligamentum flavum, articular, interspinous and supraspinous ligaments of twenty five fresh cadaveric intervertebral segments, from T11-T12 to L4-L5, extracted from fourteen spines were tested in tension. A progressive dissection method was used, that is, each segment was tested after first resecting the disk with the ligaments intact and a force-elongation curve obtained. Then one ligament was cut and the test repeated, and so on. The most restrictive ligament was found to be the ligamentum flavum followed by the articular, interspinous, and supraspinous ligaments.

Aged↗
PubMed1987

Shoulder subluxation in hemiplegia: a radiologic correlational study.

A tridimensional (3-D) x-ray method of evaluation of the shoulder was contrasted with six clinical and radiologic techniques used to evaluate shoulder subluxation, in 50 hemiplegic subjects. The 3-D evaluation is obtained through a mathematical computation associating two x-rays of the same shoulder, one taken at 0 degree (anteroposterior) and the other at a 45 degrees oblique view. A vector is thus obtained quantifying the separation from the apex of the humeral head to the inferior border of the glenoid fossa. The Y component (cephalocaudal) of this vector is used to represent the inferior displacement of the humeral head. The six other techniques of evaluation were: a) palpation, or the number of finger breadths inserted between the acromial process and the head of the humerus; b) anthropometry, or the distance between the acromial process and the lateral epicondyle of the humerus; c) templates, or the use of four schemas representing different degrees of separation of the humeral head from the glenoid fossa; d) a measure of the relation of the center of the humeral head to the center of the glenoid fossa; e) the vertical distance between the center of the humeral head and the center of the glenoid fossa; and f) the vertical distance between the apex of the humeral head and the inferior border of the glenoid fossa. Correlation coefficients contrasting the 3-D x-ray technique and the six other measures ranged from .738 to .995. The high level of precision and reliability of the 3-D measure indirectly validated the other measurement techniques.

Female↗
PubMed1987

Rotation of the scapula and shoulder subluxation in hemiplegia.

Inferior subluxation of the shoulder in hemiplegia was measured using a tridimensional (3-D) x-ray technique. This technique gave the true vertical distance separating the apex of the humeral head and the inferior margin of the glenoid cavity. Both shoulders of each subject were evaluated and the difference used as a measure of subluxation. This measure was then compared to the orientation of the scapula relative to the vertical, to the abduction, and to the relative abduction of the arm. Relative abduction is defined as the angle between the humerus and the glenoid fossa. It has been suggested that these factors are associated with inferior subluxation in hemiplegia. Results of this study of 50 volunteer stroke patients indicated that the affected and nonaffected shoulders were different (subluxed) in terms of the vertical position of the humerus vis-à-vis the scapula. The orientation of the glenoid cavities was also different, the subluxed one facing less downward. The angle of abduction of the arm of the affected side was significantly greater than on the nonaffected side, but the relative abduction of the arm was on the same order of magnitude for both sides. There was no significant relationship between the orientation of the scapula and the severity of the subluxation. The abduction of the humerus was weakly (r = .24) related to the subluxation, which partly explained the weak association found between the relative abduction of the arm and the subluxation. It was concluded that the position of the scapula and the relative abduction of the arm cannot be considered important factors in the occurrence of inferior subluxation in hemiplegia.

Female↗
PubMed1986

The prosthetic replacement of the cruciate ligament.

In the design of a ligament replacement, the elastic behavior of the ligament as well as the failure strength of the natural ligament should be reproduced. The implantation sites and alignment are very important in order to reduce the mechanical loads on the prosthesis.

Humans↗
PubMed1984

Torsion and bending imposed on a new anterior cruciate ligament prosthesis during knee flexion: an evaluation method.

A new composite prosthesis was recently proposed for the anterior cruciate ligament. It is implanted in the femur and the tibia through two anchoring channels. Its intra-articular portion, composed of a fiber mesh sheath wrapped around a silicone rubber cylindrical core, reproduces satisfactorily the ligament response in tension. However, the prosthesis does not only undergo elongation. In addition, it is submitted to torsion in its intra-articular portion and bending at its ends. This paper presents a new method to evaluate these two types of deformations throughout a knee flexion by means of a geometric model of the implanted prosthesis. Input data originate from two sources: (i) a three-dimensional anatomic topology of the knee joint in full extension, providing the localization of the prosthesis anchoring channels, and ii) a kinematic model of the knee describing the motion of these anchoring channels during a physiological flexion of the knee joint. The evaluation method is independent of the way input data are obtained. This method, applied to a right cadaveric knee, shows that the orientation of the anchoring channels has a large effect on the extent of torsion and bending applied to the implanted prosthesis throughout a knee flexion, especially on the femoral side. The study suggests also the best choice for the anchoring channel axes orientation.

Biomechanical Phenomena↗