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Biomedical subjects

C H Rivard

Publications and source records attributed to C H Rivard.

15 recordsLinked to original sources
PubMed1992

Evaluation of metallic personalized hemiarthroplasty: a canine patellofemoral model.

The purpose of this study was to characterize the response of articular cartilage to weight bearing against a metallic personalized hemiarthroplasty prosthesis. Ten dogs each underwent surgery in which an elastomeric replica of the left femoral patellar groove was made. Using this replica, a 0.5-mm-thick prosthesis was cast in Co-Cr alloy and subsequently the surface was polished to a mirror finish which had a center line average roughness value in the range of human hemiarthroplasty implants. A second surgery was performed to resurface the left trochlea with this prosthesis. Five animals were sacrificed at 3 months and 5 at 6 months. Cartilage damage occurred primarily in the distal region of the patella, and was especially evident at 6 months. Mechanical indentation tests conducted on patellar cartilage in a saline bath at 37 degrees C indicated both increased deformation and residual deformation in the affected areas, indicative of degenerative change. Areas of fibrillation with a depletion of proteoglycans were identified histologically. These areas were only superficial at 3 months but became more extensive at 6 months. Rheological analysis of the synovial fluid of tests joints indicated that a decrease in viscosity occurred from 3 to 6 months, an additional indicator of progressive degeneration. This novel implant model showed that even if a metallic hemiarthroplasty implant had an identical geometry as the joint surface being replaced and had a reasonably smooth surface, cartilage degeneration inevitably resulted.

Animals↗
PubMed1992

Lack of scientific evidence for the treatment of lateral epicondylitis of the elbow. An attempted meta-analysis.

We have reviewed 185 articles published since 1966 to assess the scientific evidence for methods of treatment for lateral epicondylitis of the elbow. Of the 185 articles, 78 discussed treatment, but since the natural history of the syndrome is uncertain we considered only those series with concurrent control groups. Only 18 of these were randomised and controlled studies. We then graded these papers for scientific validity, using the methods of Chalmers et al (1981). The mean score of the 18 articles was only 33%, with a range from 6% to 73%. A minimum of 70% is required for a valid clinical trial, and we therefore concluded that there was insufficient scientific evidence to support any of the current methods of treatment. There were too many methodological differences to allow a quantitative meta-analysis, but our qualitative review established the importance of the natural evolution of the syndrome and of the placebo effect of all treatments. Properly designed, controlled trials are needed.

Acute Disease↗
PubMed1991

[In vitro evaluation of the maximal possible deformation imposable on the median collateral ligaments in rabbits].

With this study, we identified the maximal level of deformation applicable to medial collateral rabbit ligaments in vitro. According to scanning electron microscopy photographs of ligaments fixed at different elongation level 0% (n = 5), 5% (n = 4), 6% (n = 5), 8% (n = 5), 10% (n = 7), 15% (n = 4) and 20% (n = 4), we concluded that a 6% deformation would be optimal. At that level, the collagen fiber undulation are completely unstretched, and still, no collagen ruptures could be observed.

Animals↗
PubMed1991

A computer-controlled apparatus for in vitro mechanical stimulation and characterization of ligaments.

A system has been developed to study in vitro the effects of mechanical stimulation on the biomechanical properties of ligaments. The apparatus is based on a ball screw driven by a microcomputer-controlled stepper motor capable of generating 100 Newtons of traction, the resulting force in the tissue is monitored in real-time acquisition by a load cell. It is programmed to perform virtually any kind of mechanical stimulation or biomechanical characterization tests. Preliminary tests on canine anterior cruciate ligaments indicate that this system is adequate for a variety of mechanical stimulations and characterization assays.

Animals↗
PubMed1990

Study of soft tissue ingrowth into canine porous coated femoral implants designed for osteosarcomas management.

The objective of this project was to characterize soft tissue bonding to porous coated implants such as those that would be used for resection-reconstruction of osteosarcoma cases. We were interested in determining conditions which would provide both mechanical attachment of the implant to the surrounding tissue and produce a vascularized interface. In a bilateral canine implant model, both femoral mid-shafts were replaced with a porous coated cobalt-chrome segmental implant fabricated with average pore sizes of 300 microns or 900 microns. Twelve implants, six of each pore size, were used in six dogs. Two dogs were sacrificed at 2, 4, and 6 months after implantation. The soft tissue-implant interface was characterized mechanically with peel tests and histologically using light microscopy and immunohistochemistry. At all periods, a nonvascularized fibrous membrane surrounded the smaller pore size implants, without ingrowth or mechanical bonding. In contrast, a vascularized membrane developed within and around the larger pore size implants; the attachment strength increasing with implantation time. The vascularity increased in size and quantity with time. This study demonstrates the feasibility of obtaining vascularized soft tissue attachment to tumor replacement implants with appropriate porous coated implant design.

Animals↗
PubMed1990

A scanning electron microscopic study of rabbit ligaments under strain.

For the purpose of determining the critical strain level for ligaments submitted to mechanical stimulation, rabbit medial collateral ligaments (MCLs) were subjected to different predetermined strain levels and then examined by scanning electron microscopy (SEM). Below 10% strain no evidence of disruption of the collagenous entities has been found. At about 10% strain, the ligaments were still intact macroscopically but SEM revealed numerous broken thin collagen fibers. At 20% strain, ruptures of thick collagen fibers bundles (5 to 10 mu in diameter) were found. These findings suggest that when using mechanical stimulation of ligaments, care must be taken to not exceed 10% strain level.

Animals↗
PubMed1990

Ultrastructure of the human interspinous ligament and ligamentum flavum. A preliminary study.

The ultrastructure of ligamenta flava (LF) and interspinous ligaments (ISL) obtained from four patients who underwent surgery for vertebral fracture (control group) and five patients operated for disc herniation was studied. The fine structure of LF was composed of elastic and elaunin fibers. Small diameter collagen fibrils were found between the elastic system fibers. The ISL was constituted predominantly of collagen fibrils. Elastic fibers were seen in the most ventral part of the ligament. In ISL and LF of the control group, the cells were fibroblastic-like cells. Chondrocytes were present only near their attachment sites. The proteoglycans were demonstrated between the collagen fibrils, and they appeared to form a regular interfibrillar linking. In ligaments obtained from patients with disc herniation, several modifications were found. The fibroblasts transformed into chondrocytic cells, which were surrounded by a pericellular matrix rich in proteoglycan filaments. A few cells that had suffered necrosis were found. Alterations in the collagen-proteoglycans arrangement also were evidenced. The proteoglycan filaments were randomly oriented to the collagen fibrils.

Adult↗
PubMed1989

[Study of the microscopic structure of the posterior ligaments of the lumbar spine].

Biopsies of supraspinous ligaments (SSL), interspinous ligaments (ISL) and ligamenta flava (LF), removed at operation from 12 patients aged from 17 to 77 years, were examined by light microscopy, scanning electron microscopy and transmission electron microscopy. The structure of normal ligaments was first established, and then a comparison between normal and pathological ligaments was made. It was found that the SSL and ISL were composed of collagen, while the LF contained predominantly elastic fibres. In normal ligaments, a helical arrangement of the collagen fibrils was found. The fascicles were characterized by a regular waviness. Proteoglycan filaments were demonstrated in the three types of ligaments, forming a regular interfibrillar linking between adjacent collagen fibrils. Degenerative changes were found in most of the ligaments obtained from patients with disc herniation. On light microscopy, metaplasia into fibrocartilage and calcification was commonly seen. Ultrastructurally, the flattened fibroblasts were replaced by chondrocytic cells, and an accumulation of proteoglycans with a random arrangement and a cellular necrosis was encountered. The relevance of these degenerative changes to the mechanical properties and to low back pain is discussed.

Adolescent↗
PubMed1989

Degeneration of the human lumbar spine ligaments. An ultrastructural study.

The fine structural alterations in human lumbar spine ligaments were studied in tissue samples obtained from 8 young patients operated upon for idiopathic scoliosis and from 10 adult patients operated upon for herniated discs. The ultrastructure of the scoliotic ligaments was found to be normal. The majority of cells encountered were the fibroblastic-like cells. The collagen-proteoglycans interaction was similar to that described in other normal soft tissues. However, two forms of degenerative changes were demonstrated in posterior ligaments of patients with herniated discs. Metaplasia of ligamentous tissue into fibrocartilage was a common finding. The fibroblasts were replaced by chondrocytes. A few cells which had suffered necrosis were found. Alterations in the collagen-proteoglycans arrangement were also evidenced. This form of degeneration resembled that commonly associated with wear and tear phenomena. A second form of degeneration due to ageing was found to coexist with the aforementioned alterations.

Adolescent↗
PubMed1989

Studies on the anterior cruciate ligaments: a 10 year experience review.

These different studies through the past 10 years showed us that there is very little future for ligamentous prosthesis because these replacements will never have the nervous feedback mechanisms which are necessary for the upholding of any ligamentous physiology. Those mechanisms allow the ligament to adapt and remodel itself to different stimuli. Our efforts for the years to come will therefore be concentrated on environmental mechanisms, biochemical and biomechanical, which would allow the most physiological ligamentous recovery possible. We therefore believe that from a surgical point of view, we should find new techniques which would allow us to surgically repair an anterior cruciate ligament and to offer immediately after surgery the most adequate environmental factors.

Animals↗
PubMed1988

Neurohistology of lumbar spine ligaments.

A study was conducted to identify neural elements in the posterior ligaments of the lumbar spine by using a modified gold-chloride method. Three morphologic types of mechanoreceptors were identified: Ruffini corpuscles, Ruffini end organs, and pacinian corpuscles. Free nerve endings, which are thought to be responsible for pain production, were also demonstrated within the ligaments.

Adolescent↗
PubMed1986

Effects of hypoxia on the embryogenesis of congenital vertebral malformations in the mouse.

With use of the mouse as the experimental animal and hypoxia as the teratogenic agent, the author produced congenital vertebral malformations identical in form to those found in man. Induced malformations were present in the cartilaginous stage of spine development. During the mesenchymal (prechondral) stage, two different phases of interaction occur between the matrix macromolecules (hyaluronate, glycosaminoglycans) secreted by the notochord and the sclerotomic cells. During the first phase, when the matrix is rich in hyaluronate, sclerotomic cells proliferate and migrate around the notochord in the control embryo. At the same time, in hypoxia-treated embryos, the author observed an inhibition of cell proliferation that was concomitant with a delay in reaching the normal concentration of hyaluronate. During the second phase, after the degradation of the hyaluronate complex, when the matrix is rich in free sulfated GAG, cell differentiation occurred around the notochord in control embryos. At this time, in the hypoxia-treated embryos the author found a delay in the liberation of sulfated GAG from the hyaluronate complex, which markedly changed the normal ratio between the sulfated GAG and nonsulfated GAG. He postulates that this delay in liberation of free sulfated GAG produces the asymmetrical (malformed) cartilage primum by asymmetrical cell differentiation.

Animals↗
PubMedDate not supplied

Congenital kyphosis by segmentation defect: etiologic and pathogenic studies.

Sixteen cases of type II congenital kyphosis were reviewed. As a working hypothesis, we assumed that this pathology should have a behavior similar to scoliosis due to a segmentation defect, if a true unsegmented bar existed. The analysis of different parameters including the number of levels involved, the patient's age, the degree of disc space involvement, and the site of deformity did not confirm this hypothesis. Furthermore, an experimental animal study failed to reproduce this congenital anomaly. It is our belief that kyphosis resulting from a "segmentation defect" represents a developmental defect of the perivertebral structures including the annulus fibrosus, the ring apophysis, and the anterior longitudinal ligament rather than a true intervertebral bar.

Adolescent↗