Biomedical subjects

D Amiel

Publications and source records attributed to D Amiel.

At least 127 records · Page 7Linked to original sources

PubMed1986

Flexor tendon repair.

Healing canine flexor tendons treated with either total immobilization, delayed protected mobilization, or early protected mobilization was studied by biomechanical, microangiographic, biochemical, and histologic techniques at intervals through 12 weeks. The healing characteristics of the early mobilization tendons showed higher tensile strengths and improved gliding function than the delayed mobilization and immobilization tendons. Protected passive motion brought about accelerated changes in peritendinous vessel density and configuration, as well as increased repair site total DNA content. While adhesions obliterated the space between the tendon surface and the tendon sheath of the immobilized repairs, the mobilized tendons demonstrated coverage of the repair site by cells from the epitenon by 10 days, and a smooth, gliding surface that was maintained free of adhesions through 42 days. A series of in vitro studies demonstrated the cellular processes involved in the repair: phagocytosis of cellular debris and collagenous fragments by cells from the epitenon, and collagen synthesis primarily by endotenon cells.

Animals↗

PubMed1986

The phenomenon of "ligamentization": anterior cruciate ligament reconstruction with autogenous patellar tendon.

Reconstruction of the anterior cruciate ligament (ACL) with patellar tendon (PT) is a common procedure for the symptomatic ACL-deficient knee. Questions regarding graft incorporation, viability, and nutrition of the transplanted tissue are of concern. This relates to the graft's response to its new intrasynovial milieu and new physical forces. These factors were studied in a rabbit model of ACL reconstruction using PT and were evaluated with histological and biochemical parameters with respect to time. A histological and biochemical metamorphosis of the grafted PT occurred in this study. Autografts demonstrated a gradual assumption of the microscopic properties of normal ACL; by 30 weeks postoperatively, cell morphology was ligamentous in appearance. Normally, type III collagen is not observed in PT, however, a gradual increase in its concentration was seen in the grafts; by 30 weeks its concentration (10%) was the same as in normal ACL. Similarly, glycosaminoglycans content increased from its normally low level in PT to that found in native ACL. Collagen-reducible crosslink analysis demonstrated that grafted tissue changed from the normal PT pattern of low dihydroxylysinonorleucine (DHLNL) and high histidinohydroxymerodesmosine (HHMD) to the pattern seen in normal ACL (high DHLNL and low HHMD) by 30 weeks. These data suggest that when PT is placed in the anatomic and environmental milieu of the ACL, a "ligamentization" of the grafted tissue results; also the autograft initially depends on synovial fluid nutrition, as revascularization occurs after 6 weeks.

Animals↗

PubMed1986

Origin of replacement cells for the anterior cruciate ligament autograft.

A rabbit model for anterior cruciate ligament (ACL) reconstruction using autogenous avascular patellar tendon (PT) was utilized to study the early events of graft incorporation. Histological observations demonstrated that autografts were centrally acellular with a peripheral rim of cells at 2 weeks, a central focal proliferation of cells at 3 weeks, and a cellular homogeneous distribution by 4-weeks postoperation. Graft necrosis followed by cellular proliferation suggested that a different population of cells other than the native PT fibroblasts may be inhabiting the graft. The extrinsic contribution of cells was studied by selective destruction of native PT cells with liquid nitrogen immersion prior to reconstruction of the ACL. The intrinsic contribution of cells was evaluated by sequestration of the PT graft in a semipermeable membrane before it was used to reconstruct the ACL. Histological analysis of tissue that was liquid N2 treated, used as an autograft, and then harvested 3-weeks postoperation revealed fibroblastic incorporation of the graft. In contrast, no cells were observed in semipermeable membrane sequestered autografts. These data suggest that autogenous ACL autografts of PT origin are repopulated by cells of external origin. In vitro control studies that were carried out in parallel demonstrated that PT fibroblasts could survive in tissue culture, but not in the synovial environment of the ACL. This suggests that fibroblasts from different sources have different, tissue-specific nutritional requirements.

Animals↗

PubMed1986

Nutrition of cruciate ligament reconstruction by diffusion. Collagen synthesis studied in rabbits.

The reconstructed anterior cruciate ligament was studied in the rabbit using the medial third of the patellar tendon. Tritiated proline, 100 microCi/kg body weight, was injected intra-articularly to insure detection of the metabolic conversion product 3H-hydroxyproline in the avascular graft. During the immediate postoperative period, nutrients were found to derive from the synovial fluid through a process of diffusion, demonstrating that synovial nutrition occurs prior to revascularization of the graft.

Animals↗

PubMed1985

Collagen types in neocartilage tissue resulting from rib perichondrial graft in an articular defect--a rapid semi-quantitative methodology.

A method for estimating type II to type I collagen ratios in small tissue samples has been developed. The cyanogen bromide peptides of the tissue collagens were analyzed by SDS-gel electrophoresis. Marker peptides representative of each collagen type were established and their relative amounts determined by integration of the stained peptide bands following gel scans. Marker peptide ratios were then computed for each of several standard type II/type I mixtures and these peptide ratios were mathematically correlated with the corresponding type II/type I collagen ratios. A linear relationship between marker peptide ratio and collagen type ratio was established. This relationship was applied to the analyses of type II/type I ratios in samples of rib perichondrium and neocartilage derived from perichondrial graft repairs of full thickness femoral condyle defects. The results indicated that perichondrial grafts synthesize both types II and I collagens and that the proportion of type II increases with increasing post-transplant time.

Animals↗

PubMed1985

Normal ligament properties and ligament healing.

There is still a long way to go to achieve the goals of ligament replacement through modification of normal, intrinsic ligament healing processes. We are learning about the biology of ligamentous tissues, including the problem of regeneration, and that in itself is an all-important first step toward seeking solutions.

Biomechanical Phenomena↗

PubMed1985

Value of hyaluronic acid in the prevention of contracture formation.

Joint stiffness secondary to immobilization was inhibited by intra-articular hyaluronic acid injection in an experimental joint contracture in rabbits. Biochemical and biomechanical parameters were used to evaluate the joint stiffness after nine weeks of immobilization. In all treatments, hyaluronic acid reduced the measured stiffness in the contracture by approximately 50% as compared to the contractures of the untreated rabbits. In addition, hyaluronic acid prevented the loss of glycosaminoglycans (GAGs) (as measured by hexosamine), which normally occurs in untreated contractures. The results are related to a working hypothesis that intra-articular injections of drugs such as hyaluronic acid (Healon-R) will stimulate hyaluronic acid synthesis within the matrices of periarticular connective tissue (PCT). If the spacing and lubricating properties of the glycosaminoglycans could be maintained in the stress-deprived state, the "centripetal collapse" of the fibrillar matrix could be avoided, anomalous cross-links could be minimized, and more normal joint mechanics could be retained.

Animals↗

PubMed1985

Rib perichondrial grafts for the repair of full-thickness articular-cartilage defects. A morphological and biochemical study in rabbits.

The purpose of this study was to investigate the use of perichondrial grafts in articular cartilage defects and to characterize the newly formed cartilage. In a rabbit model, rib perichondrium was used to repair full-thickness defects in the femoral condyle. The quality of repair was then evaluated histologically and biochemically at six and twelve weeks after grafting. Unacceptable results were obtained in 50 per cent of the rabbits. These failures were due to condylar fracture in 20 per cent, failure of graft attachment in 20 per cent, and infection in 10 per cent. The technique of grafting must be improved to increase the percentage of successful grafts in which neocartilage with a relatively normal chemical composition fills the articular cartilage defect. Successful grafts proliferate to fill the full-thickness defect with neocartilage, which has biochemical characteristics that are similar to those of hyaline cartilage.

Animals↗

PubMed1984

Tendons and ligaments: a morphological and biochemical comparison.

The purpose of this study was to compare selected rabbit tendons and ligaments morphologically and biochemically. Five representative structures from each of six age- and sex-matched rabbits were compared. Biochemical analyses included total collagen, reducible collagen cross-links, quantitative collagen typing, DNA, and glycosaminoglycans. Histological and chemical differences were demonstrated between the tendons and the ligaments. Smaller differences were also found between the individual ligaments (collateral and cruciate) and between the two tendons (patellar and Achilles) that were examined. These findings suggest that ligaments are more metabolically active than tendons, having more plump cellular nuclei, higher DNA content, larger amounts of reducible cross-links, and the presence of more type III collagen, as compared with tendons. They also contain slightly less total collagen than tendons and more glycosaminoglycans. We conclude that the tendons and ligaments studied have unique histological and biochemical characteristics, despite their gross similarities. Relatively increased metabolic activity in ligaments, implied by our findings, may be species specific, age related (transient), or may truly represent a structural expression of functional need for more rapid adaptation. Further investigation of other similarities or differences between particular ligaments (or tendons) is indicated, and attention is directed toward the importance of such variables in development of models for tendon and ligament studies.

Animals↗

PubMed1984

Characterization of arthroplasty tissue after 14 years post-cup arthroplasty: a morphological and biochemical assessment.

The cup arthroplasty has been reported to cause the formation of a fibrocartilaginous joint surface, which may result in a painless, functional joint. The joint surface of a 38-year-old man with a failed cup arthroplasty implanted for 14 years was examined histologically and biochemically. The joint surface tissue of this patient resembled fibrous connective tissue, with major types of collagen being Type I and Type III. No evidence of cartilaginous transformation in the healing scar was demonstrated, despite several years of successful functioning of the cup arthroplasty.

Adult↗

PubMed1984

Technical aspects of perichondrial grafting in the rabbit.

A screening process to determine the most appropriate model for the study of cartilage growth from perichondrium obtained from the rabbit's left tenth costal cartilage has resulted in the following observations: (1) best growth is achieved when fixation of the graft is secure and conformity to the recipient bed is complete; (2) immobilization enhances fixation, but permits fibrous tissue growth onto the graft, and (3) diminishing periods of immobilization enhance perichondrial growth, but have a deleterious effect on fixation.

Animals↗

PubMed1984

Physiology and therapeutic value of passive joint motion.

Despite the long history of therapeutic experience with different types and amounts of passive joint motion, its effects and the principles of its use remain controversial. Through empiric success, a spectrum of passive motion has evolved for various clinical purposes, including joint diagnosis; correction of joint deformities; mobilization of stiff joints; stimulation of joint healing; neuromuscular re-education; and prevention of immobilization complications (e.g., contracture formation, connective tissue atrophy, relative healing inhibition, and associated stasis abnormalities). However, the potential abuses of passive motion (e.g., causing additional tissue trauma, mobilizing unprotected joints, and stretching the wrong joints or tissues) have created serious doubts as to the value of this therapy and raised important questions concerning the lack of proper definition (e.g., force, direction, speed, and duration) and the unknown margins of safety. Clinical and experimental evidence supports the probable effectiveness of passive joint motion on joint and tissue levels, but without a better quantitative understanding of the mechanisms of action, dose-responsiveness, specific tissue effects, and, most important, their controls. Thus, passive motion will continue to be used suboptimally with inconsistent results. When these clinical and research deficiencies are corrected, passive motion will attain its proper place as a powerful and reliable orthopedic tool.

Connective Tissue↗

PubMed1983

Healing of the medial collateral ligament of the knee. A morphological and biochemical assessment in rabbits.

Complete midsubstance injuries of medial collateral ligaments of matched New Zealand white rabbits were allowed to heal without repair or immobilization for various lengths of time. Morphological and biochemical parameters were used to evaluate healing as compared with normal unoperated and sham operated ligaments. Results showed incomplete healing at the longest term follow-up (14 weeks) with significant biochemical abnormalities. Although there was a trend toward normal, recovery from injury was much slower than previously reported.

Animals↗

PubMed1982

Effects of early intermittent passive mobilization on healing canine flexor tendons.

The response of healing canine flexor tendons to motion was investigated using protected passive mobilization techniques. Early motion, delayed motion, and immobilization groups were compared over a 12-week period for their strength and excursion characteristics. Tendons which were mobilized early showed progressively greater ultimate load and linear slope values at each time interval tested. The ultimate load of the immediately mobilized tendons, those tested at 3 weeks, was twice as great, and the linear slope values were almost three times greater than the immobilized repairs at 3 weeks. Similar differences were noted at each time interval through 12 weeks. The differences in angular rotation of the distal interphalangeal joint following the application of a small load were also significant. At 12 weeks, the angular rotation of the tendons of the immobilization group averaged only 19% +/- 2% of their intact contralateral controls. The delayed mobilization tendons produced values of 67% +/- 8%, and the immediate mobilization tendons produced 95% +/- 10% of the control joint motion. These findings indicate that early protected passive mobilization augments the physiologic processes that determine the strength and excursion of repaired flexor tendons.

Animals↗

PubMed1982

The effect of immobilization on collagen turnover in connective tissue: a biochemical-biomechanical correlation.

Immobilization of the knee joint for 9 weeks results in a reduction of the mechanical properties in the lateral collateral ligament. Specifically, ligament stiffness is reduced in this tissue. No statistical change in collagen mass was detected for the medial collateral ligament (MCL) or patellar tendon. An increase in collagen turnover (synthesis and degradation) was, however, found in the immobilized medial collateral ligament and patellar tendon. It is thus proposed that stiffness reduction is due to a change in the ligament substance itself, rather than a result of tissue atrophy.

Animals↗

PubMed1982

The effect of delayed internal fixation on healing of the osteotomized dog radius.

Delay in surgical intervention has been reported to enhance the process of fracture healing. Quantitative observations or experimental osteotomies were made to investigate the mechanical for such enhancement. Eight mongrel dogs with bilateral radial osteotomies were prepared with immediate plate fixation on the right side, and with delayed fixation two weeks later on the left side. The response to delayed fixation was measured radiographically, mechanically, and by measurement of new bone formation using a quantitative tetracycline incorporation method. A clearly discernible stimulation of new bone formation occurred early in the osteotomy healing process. Delayed fixation has a transient stimulatory effect on the healing process of bone.

Animals↗

PubMed1981

The effects of exercise on the biomechanical and biochemical properties of swine digital flexor tendons.

The digital flexor tendons of the miniature swine were studied after 12 mo of running exercise. Using a newly developed methodology whereby the properties of tendon substance and tendon-bone composite are measured simultaneously, it was found that training augments the strength of the tendon insertion site, but has minimal effect on the tendon substance. Biochemical analyses also showed that the collagen concentration in the tendon substance remains unchanged following exercise. There was also moderate, but not significant, tendon hypertrophy. The present results on flexor tendon differ from those previously obtained for the swine digital extensors [6]. Such difference in response to functional stress may be attributed to the biochemical composition and mechanical properties of these tissues.

Animals↗

PubMed1981

The biochemical response of rabbit articular cartilage matrix to an induced talcum synovitis.

Transient synovitis is a commonly occurring affliction in the hips of young children. The results of an experimental model of this condition produced in the immature rabbit's hip showed that there is a significant response in the articular cartilage. Thus, the cartilage rapidly thickens, becomes more hydrated and reveals an initial decrease in glycosaminoglycan concentration. Three weeks following the induction of synovitis, the concentrations of water, glycosaminoglycan and collagen are similar to the control side. The increase of articular cartilage mass is due, not only to an increased hydration, but also to increased matrix production under the stimulus of the synovitis. A similar response by the immature cartilage might be expected following a transient synovitis in a child's hip.

Animals↗