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Biomedical subjects

D Amiel

Publications and source records attributed to D Amiel.

At least 145 records · Page 8Linked to original sources
PubMed1981

The importance of controlled passive mobilization on flexor tendon healing. A biomechanical study.

The effects of controlled passive motion on primary tendon repair were studied using the canine forepaw flexor apparatus as experimental model. The animals were divided into seven groups based on duration(3 to 12 weeks post repair) and mode of immobilization and partial mobilization. The repaired tendons were subjected to biomechanical evaluation of their gliding function and tensile strength characteristics. The results showed positive effects of controlled passive motion on tendon repair. The rate of tendon repair was significantly improved over those animals that were continuously immobilized. At 12 weeks, the repaired flexors from the motion group had regained over one-third of the ultimate tensile load as compared to their contralateral intact controls. Of equal importance is that these repaired tendons maintained good gliding function within the sheath during the repair process. The gliding function of these tendons was also significantly better than those subjected to continuous immobilization.

Animals↗
PubMed1981

The effect of prolonged physical training on the properties of long bone: a study of Wolff's Law.

UNLABELLED: Five one-year-old immature swine were subjected to twelve months of exercise training. Four matched swine with no training served as controls. After they were killed, four-millimeter-wide strips of bone taken from the anterior, medial, posterior, and lateral quadrants of the central femoral diaphysis were subjected to four-point bending tests to failure. It was found that although exercise did not change the mechanical properties of the cortical bone, it resulted in significant increases in the averaged femoral cross-sectional properties: 17 per cent in cortical thickness, 23 per cent in cortical cross-sectional area, and 21 per cent and 27 per cent in maximum and minimum area moments of inertia, respectively. These changes were due primarily to reduction in the diameter of the medullary canal. The analyses of bone composition showed that the bone density and biochemical contents of the control and exercised animals were similar, but the total volume and the dry, ash, and calcium weights of the exercised bone were significantly higher. These combined results suggest that prolonged exercise has a significant effect on the quantity of the bone, but not on its quality. CLINICAL RELEVANCE: It has long been recognized that stress deprivation from immobilization in plaster casts results in profound bone atrophy, and it is generally accepted that a minimum level of activity is necessary for homeostasis of bone. These results show that exercise at a level comparable to that prescribed in running fitness programs for humans (65 to 80 per cent of maximum heart rate) can not only maintain homeostasis, but produce actual hypertrophy of bone. This work further suggests the importance of graduated, prolonged, supervised rehabilitation programs in overcoming osteoporotic states.

Animals↗
PubMed1980

The biomechanical and biochemical properties of swine tendons--long term effects of exercise on the digital extensors.

Positive effects on the tensile characteristics of swine digital extensors were found following twelve months of exercise training. Compared to sedentary controls, the tendons from the exercised animals became stronger as a material and exhibited hypertrophy. These biomechanical results were supported by biochemical analyses of tendon composition. Exercise increased the concentration of collagen as well as the total weights of the tendons. For determining stress and strain in tendon material, we used specially designed instruments to measure the tendon cross-sectional area, and a video dimensional analyzer system to measure accurately its "non-contact" tensile strain. With these newly developed apparatus, the mechanical properties of the tendons were accurately determined so that the effects of exercise training could be compared.

Animals↗
PubMed1980

The effect of immobilization on the types of collagen synthesized in periarticular connective tissue.

The distribution of collagen types was studied in control and immobilized periarticular connective tissue to test the hypothesis that inflammatory tissue is the basis of the contracture process. The hypothesis derives from the fact that Type III collagen is prominent in inflammatory processes. The content of Type I and Type III collagen was determined by standard differential salt precipitation of the pepsin solubilized collagen, followed by resolution of the subunits on CM-cellulose. Analysis of the peptide fragments produced by cyanogen bromide was performed and their distribution determined by SDS gel electrophoresis. The collagen of control and immobilized periarticular connective tissue proved to be entirely Type I. Type III was not present. The periarticular connective tissue contracture process, therefore, is different from the intraarticular process in which fibrofatty connective tissue proliferation is prominent.

Amino Acids↗
PubMed1980

Dupuytren's contracture. An electron microscopic, biochemical, and clinical correlative study.

Fascial specimens were obtained from twenty-four patients treated operatively for Dupuytren's contracture. The nodules and cords were examined by electron microscopic and biochemical techniques. The clinical course and response to operative treatment were then correlated with the tissue findings. Electron microscopic analysis revealed myofibroblasts in the nodules of seven of twenty-four patients. Fibroblasts containing prominent microtubules were found in ten patients. The fascia contained type-III collagen, increased amounts of collagen per unit of dry weight, and an increase in reducible cross-links of collagen. While the nodules were noted to contain a greater increase in reducible cross-links than the cords, there was little variation in the biochemical findings from patient to patient. Clinical recurrence was not related to the age of the patient at onset, duration, or severity of disease. Recurrence was related to the electron microscopic findings of myofibroblasts in the nodules and fibroblasts containing prominent microtubules in the fascia of these patients.

Aged↗
PubMed1977

Effect of low dosage schedule of D-penicillamine on collagen cross-linking in a nine week immobilized rabbit knee.

Rabbits immobilized with one leg pinned in a fully flexed position, were treated with 60 mg of D-penicillamine/kg three times a week for 9 weeks. After this period of immobilization the animals were sacrificed and the periarticular connective tissue collagen reduced with [3H] NaBH4 for determination of collagen cross-links. There was a significant decrease in the formation of cross-links in the control and immobilized knee in the treated animals as compared to the untreated animals. Penicillamine also blocked the increase in DHLNL, HLNL and HHMD previously demonstrated in immobilized rabbit knees. This is the first demonstration that in vivo administration of penicillamine directly inhibits cross-linking reactions in collagen.

Animals↗
PubMed1977

Collagen cross-linking alterations in joint contractures: changes in the reducible cross-links in periarticular connective tissue collagen after nine weeks of immobilization.

A significant increase in the NaBH4 reducible intermolecular cross-links in the 9 week immobilized rabbit periarticular connective tissue was found. Dihydroxylysinonorleucine, hydroxylysinonorleucine, and histidinohydroxymerodesmosine were the major cross-links which increased during the period of immobilization. No change in the hydroxlysine/lysine ratio between the immobilized and control periarticular connective tissue collagen was detected during the 9 weeks of enforced immobilization of the rabbit knee. Since the collagen mass in the immobilized periarticular connective tissue does not change, or at most is reduced 10%, we suggest that there is an increase in collagen cross-links expressed both in per unit weight of collagen and on the basis of collagen mass per knee due to the lack of physical stress and motion.

Amino Acids↗
PubMed1977

Polyarticular disability: a functional assessment.

The purpose of this study was to design and evaluate a system for the functional evaluation of patients with polyarticular disease. A single assessment can be done in approximately 15 minutes. Extensive prior preparation is not required. The evaluation is reproducible and the numerical characterization agrees well with a physician's overall assessment of functional impairment. The subscores can be used independently of the total score to focus on specific areas of disability. Use of the evaluation in other institutions has produced a high degree of reliability. Statistical evaluation has demonstrated areas of weakness that have been eliminated or modified to increase reliability of the system.

Activities of Daily Living↗
PubMed1976

The effects of rigidity of internal fixation plates on long bone remodeling. A biomechanical and quantitative histological study.

The effect of rigidity of internal fixation plates on long bone remodeling was studied using two types of plates with considerable differences in stiffness. The plated bones were subjected to bioengineering quantitative histological, and cortical thickness studies after 9 and 12 months. The biomechanical results, together with the quantitative histological measurements of the macroscopic architecture, showed that tissue characteristics of the plated bones were similar. However, because of the larger cortical area, the less regidly plated femora can sustain significantly higher loads and energy before failure. Cortical thickness measurements also showed that rigid plate immobilization results in thinning of the cortex of the underlying bone. The experimental results suggest that cortical bone remodels according to functional stress demands, and the osteoporosis secondary to rigid plate protection is consequent to thinking of its cortex.

Animals↗
PubMed1976

A comparison of cortical bone atrophy secondary to fixation with plates with large differences in bending stiffness.

Two internal-fixation plates with large differences in bending stiffness were applied to pairs of intact femora of six adult mongrel dogs to study the osteoporosis induced by rigid fixation. After nine and twelve months of plate application a significant, increased amount of bone atrophy was seen on the rigidly plated side. Biomechanical measurements of specimens from various segments of both femoral diaphyses showed the bones to have similar mechanical properties (as tissue), but different structural properties (as organ). These findings suggest that the osteoporosis due to rigid plate fixation occurs by thinning of the cortex rather than by reduction of the mechanical properties of the osseous tissue.

Animals↗
PubMed1976

Comparison of stainless steel and composite plates in the healing of diaphyseal osteotomies of the dog radius: report on a short term study.

The rigid fixation of fractures is generally accepted as the best method to achieve union when open treatment of a fracture is undertaken. This has led to the development of plates that have a greater overall dimension and stiffness compared to earlier plate models, as exemplified by the Lane or Eggers type of plate. In our experience the more rigid plate generally leads to satisfactory union, but also carries with it the risk of refracture, either through a screw hole or across the original fracture after plate removal. Experiments by Uhtoff and Dubuc on experimental animals showed that plate induced osteopenia existed when a rigid plate was applied to an intact or osteomized canine femur. These results provide a possible explanation for the occurrence of late fracture. The study to be described is based on the hypothesis that a rigid plate applied to bone induced localized immobilization osteopenia, which ultimately weakens the bone and leads to the development of late fracture. The study was designed to compare a plate made of stainless steel, which exhibited mechanical stiffness comparable to that of devices presently in use, with a plate made of a composite material, which exhibited decreased stiffness by nearly one order of magnitude. It had been demonstrated by engineering analysis that the less stiff plate would allow the bone to experience normal loading, and it was thought that this loading would modulate the rate and pattern of bone remodeling, thereby resulting in bone of greater strength and size as compared to a more rigidly plated bone.

Alloys↗
PubMed1976

Lavage of septic joints in rabbits: effects of chondrolysis.

Septic joints were produced in rabbits which were then treated with systemic procaine penicillin. One group of animals also had surgical lavage at four and seven days after bacterial inoculation. In the infected joints there was a significant loss of hexosamine by five days and of collagen by nine days. Lavage delayed the loss of collagen.

Animals↗
PubMed1975

Quantitative histological evaluation of early fracture healing of cortical bones immobilized by stainless steel and composite plates.

Internal fixation devices of less bending stiffness than conventional plates made of stainless steel or vitallium were compared with conventional plates in a study of fracture healing. The material for this investigation was a fine graphite fiber reinforced methyl methacrylate resin composite with a modulus of elasticity approximately ten times less than that of stainless steel. Osteotomies were performed on canine radii. Internal fixation was accomplished by means of a composite plate on the left side, and a stainless steel plate on the right. Clinical assessment, as well as biomechanical and quantitative histological techniques, were used to compare osteotomy healing of the two sides. At four months, all osteotomies had healed and the bioengineering tests showed radii from the two sides had equivalent strength. However, significantly less cortical porosity was found in the side with the composite plate (6.8 per cent), as compared to that of the stainless steel plated side (14 per cent). These results suggest that a less stiff fixation plate may have some advantage in the treatment of long bone fracture if there is no implant failure, and if union rates are equivalent.

Animals↗
PubMed1975

Value of 17beta-oestradiol in prevention of contracture formation.

Male and female rabbits were treated with 17beta-oestradiol during the 9-week development of a contracture in the left hind limb. The right hind limb served as the paired control. Untreated (absolute control) animals received saline injections. After 9 weeks biochemical analyses of water, hexosamine, soluble and total collagen, as well as biomechanical measurements of joint stiffness, were performed on the dissected knees. In all cases 17beta-oestradiol reduced the measured stiffness in the contractures by approximately 50% as compared to the contractures of the untreated animals. 17beta-oestradiol, in addition, partially prevented the loss of water and hexosamine which occurs in untreated contractures. 17beta-oestradiol administration also decreased the content of soluble collagen fractions in the periarticular connective tissue of both the control and experimental knees. The relationship of these biochemical findings to their mechanical consequences is discussed, and the results are related to a working hypothesis of stress- and motion-dependent homoeostasis within periarticular connective tissue.

Animals↗