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Biomedical subjects

D Amiel

Publications and source records attributed to D Amiel.

At least 109 records · Page 6Linked to original sources
PubMed1990

Influences of flexor sheath continuity and early motion on tendon healing in dogs.

The healing response of flexor tendons treated with either sheath reconstruction or sheath excision, and early passive motion rehabilitation was investigated in a canine model. Flexor sheath repair, sheath excision, and autogenous sheath grafting were compared for biomechanical characteristics, and biochemical and ultrastructural alterations at the repair site at intervals over a 12-week period. No significant differences could be found in tendons treated with either sheath repair or sheath excision by biomechanical, biochemical, or morphologic assessments. Although ultimate load and linear slope values increased significantly in both groups at each interval (p less than 0.05 for each comparison), there were no significant differences in angular rotation of the distal interphalangeal joint over time. Biochemical findings showed high levels of reducible Schiffbase crosslinks through 12 weeks, indicating a repair process undergoing active remodeling. Ultrastructural studies showed active fibrinogenesis and early evidence of longitudinal alignment of collagen fibrils in the extracellular matrix. In the sheath graft group, strength characteristics did not increase over time, and there was a high degree of disorganization of collagen fibril orientation. These findings demonstrate that reconstruction of the tendon sheath, either by suture or autogenous graft, does not improve significantly the biomechanical, biochemical, or morphologic characteristics of repaired tendons treated with early motion rehabilitation.

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PubMed1990

Collagenase activity in anterior cruciate ligament: protective role of the synovial sheath.

To evaluate the protective role of the synovial sheath of the anterior cruciate ligament (ACL), we have developed a synovectomy model that exposes the ACL substance to the intra-articular environment with and without hemarthrosis. Histology and the level of collagenase activity were studied to assess intrinsic ligament alterations. The treatment groups studied were as follows: ACLs of sham-operated knees receiving arthrotomy only, ACLs of knees receiving arthrotomy and acute hemarthrosis, ACLs of knees that underwent synovectomy, and ACLs of knees that underwent both synovectomy and acute hemarthrosis. All animals were killed 10 days postoperatively for gross, histological, and biochemical assessment. Histologically at 10 days ACLs experiencing synovectomy and ACLs having synovectomy plus hemarthrosis revealed marked hypocellular areas. Biochemical results indicate that synovectomy is the treatment mainly responsible for the observed increase in ACL collagenase activity. Hemarthrosis alone clearly had no effect, although hemarthrosis coupled with synovectomy appeared to further increase the amount of active collagenase present in the ACLs. This study indicates that, with exposure of the ACL substance to the synovial fluid or with hemarthrosis after synovectomy, there is an increase in the degradative activity of the ACL. The protective role of the synovial sheath suggests that the synovial sheath injury associated with acute ACL rupture may allow for exposure of the ligament substance to the degradative effects of the synovial environment and associated hemarthrosis.

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PubMed1990

Effects of surgical treatment and immobilization on the healing of the medial collateral ligament: a long-term multidisciplinary study.

The long-term effects of surgical repair and immobilization on the healing of the transected medial collateral ligament (MCL) were studied biomechanically, biochemically and histologically in a canine model. Twelve adult canines were divided into two experimental groups and studied at 48 weeks postoperatively. For Group I, the transected MCL of the left knee was not repaired, and the joint was not immobilized. For Group II, the MCL was repaired and the joint was immobilized for six weeks. The right knee of each canine was sham-operated and served as the control. Histologically, the collagen fibers were less aligned in both of the experimental groups than in the controls. Furthermore, there were minimal differences in collagen and fibroblast alignment between the groups, although poorer alignment was observed for Group I at 12 weeks. Biochemically, the levels of types I and III collagen, reducible collagen cross-links and total collagen concentration for both groups returned to normal levels. Biomechanically, Group I achieved better results than Group II in terms of varus-valgus (V-V) knee rotation and ultimate load of the femur-MCL-tibia complex (FMTC), as these values returned to the level of controls. However, the mechanical properties of the healing MCLs did not compare well with the controls; the tensile strength was only 62% and 45% of controls for Groups I and II, respectively, at 48 weeks. These results suggest that conservative treatment (i.e., no surgical intervention) with early mobilization is better than surgical treatment with immobilization for an isolated Grade III MCL injury.

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PubMed1990

Cartilage resurfacing of the rabbit knee. The use of an allogeneic demineralized bone matrix-autogeneic perichondrium composite implant.

A full-thickness articular-cartilage defect was created in the medial femoral condyles of 32 adult rabbits. The defects were filled with demineralized bone or a composite of demineralized bone and perichondrium. Results of cartilage repair were assessed after 12 weeks of implantation. We conclude that demineralized bone matrix used as a subchondral matrix in a cartilage repair model 1) stimulates and induces subchondral bone ingrowth, 2) provides a surface on which cartilage repair can proceed, and 3) can be utilized as a platform on which perichondrium can be fixed to provide a cellular source for cartilage repair. Repair tissue that developed from perichondrium was thicker, more closely resembled normal articular cartilage, and was of a less fibrous nature than the repair tissue that developed de novo on the demineralized bone matrix.

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PubMed1990

Long-term storage effects on canine osteochondral allografts.

We have studied long-term (to 60 days) effects of 4 degrees C storage in culture media on the histologic, mechanical, and chemical properties of the cartilage from osteochondral shell allografts from the dog. The structural integrity of the cartilage matrix was intact up to 60 days of storage, for the mechanical properties represented by the aggregate modulus and apparent permeability remained normal. These data are supported by normal safranin-O staining as well as normal glycosaminoglycan content and total collagen concentration. However, chondrocyte viability, as assessed by 35SO4 uptake and hematoxylin and eosin preparations, decreased dramatically with time. We believe that the longer storage to 60 days is not indicated, unless conditions can be modified to maintain cell viability.

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PubMed1989

Early histologic, metabolic, and vascular assessment of anterior cruciate ligament autografts.

A rabbit model for anterior cruciate ligament (ACL) reconstruction using autogenous patellar tendon was utilized to study the early events of autograft cellular dynamics. Biochemical, autoradiographic, histological, and vascular injection techniques demonstrated that the native autograft cell population rapidly necroses. This repopulation occurs without a vascular contribution; cells entering the autograft are reliant upon synovial fluid nutrition.

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PubMed1989

Injury of the anterior cruciate ligament: the role of collagenase in ligament degeneration.

Rapid degeneration of the anterior cruciate ligament (ACL) has been observed following acute ACL rupture. An understanding of this process might explain some of the poor clinical results of primary ACL repair. We created a surgical rabbit model of acute ACL injury and developed an in vitro assay for collagenase activity in the ACL and menisci. Microscopic evaluation revealed a rapidly degenerative process in injured ACLs, with loss of cellularity and matrix organization. This was associated with a significant increase in collagenase activity and a decrease in total collagen of the injured ACLs as compared with sham-operated controls. These findings confirm the observation that cut ACL ligament ends rapidly degenerate. This degenerative process might be partly due to a response of cells intrinsic to the ACL to injury. Left unchecked, this process may be detrimental to surgical attempts for primary ACL repair.

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PubMed1989

Hyaluronan in flexor tendon repair.

This study assesses the effect of a preparation of hyaluronan (hyaluronic acid) applied topically at the time of flexor tendon repair in a well-established model. The hypothesis is that hyaluronic acid applied topically at the time of flexor tendon repair will decrease adhesions, and will improve clinically the gliding function of the repaired flexor tendon. After transection and repair of the second and fifth flexor tendons of the left forepaw of four mongrel dogs, the second flexor tendon was treated with hyaluronic acid of molecular weight 3.6 x 10(6) daltons applied topically between the synovial sheath and the repair site. The left forepaws were completely immobilized for 5 weeks to optimize the formation of adhesion ingrowth. After death, the repaired tendons and sheaths were removed en bloc, fixed, and dissected. Gross inspection and histologic evaluation of all tendons showed that the quality and quantity of adhesions from the wound repair to the synovial sheath appeared to have been consistently affected by hyaluronan. Hyaluronic acid had a beneficial effect on both the repair site and synovial sheath by decreasing the peripheral inflammatory response and promoting a contact healing process via epitenon and endotenon cell involvement in the repair process.

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PubMed1989

Quantitative assessment by competitive ELISA of fibronectin (Fn) in tendons and ligaments.

A method utilizing the enzyme-linked immunosorbent assay (ELISA) is presented for quantitating fibronectin in periarticular soft tissues from rabbits. The concentrations of fibronectin were determined in the medial collateral ligament, anterior cruciate ligament, posterior cruciate ligament, and patellar tendon. The anterior cruciate and posterior cruciate ligaments, surrounded by a synovial sheath, had similar amounts of fibronectin that were each over twice as high as that found in either medial collateral ligament or patellar tendon which have no sheath covering.

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PubMed1989

Collagenases from periarticular ligaments and tendon: enzyme levels during the development of joint contracture.

Our laboratories have previously demonstrated that normal rabbit periarticular ligaments, anterior cruciate ligaments (ACL), medial collateral ligaments (MCL) and patellar tendon (PT) secrete collagenase. In this current study we examined these connective tissues following an immobilization period of 4 weeks. In the ligaments producing collagenase, activity was expressed only in the control, not in the immobilized joint. Control and experimental patellar tendon samples produce collagenolytic activity, suggesting that the expression of enzyme is less affected in tendons as compared to ligaments. Characterization of these collagenases was carried out using an antiserum directed against rabbit synovial collagenase. We demonstrated that ligament (ACL) and tendon (PT) collagenases cross react with this antibody in a double immunodiffusion assay. Protein blots of PT, ACL and MCL collagenases identified one major species (Mr = 45,000) and a minor species (Mr = 50,000) of immunoreactive proteins in all three connective tissues. Differences between control and experimental enzyme levels appear to be due to less collagenase protein being produced by immobilized ligaments.

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PubMed1989

Medical collateral ligament healing subsequent to different treatment regimens.

The response of transected canine medical collateral ligaments (MCL) to clinical treatment regimens was investigated. These regimens included no surgical repair with no immobilization and surgical repair with various periods of immobilization. The biomechanical, biochemical, and histological properties of the healing MCL were examined 6 and 12 wk postoperatively. At 6 wk, all healing MCLs had increased cellularity with decreased levels of total collagen and increased amounts of reducible Schiff base cross-links and type III collagen. Biomechanically, the varus-valgus (V-V) knee laxity was significantly increased, and no group achieved normal structural or mechanical properties. At 12 wk the histological appearance of the MCL became more normal but still had increased cellularity. Biochemically, the total collagen levels in experimental MCLs were not statistically different from the controls, but these MCLs still had high amounts of type III collagen and an even higher number of reducible cross-links. From knees in which the MCL was not treated, the V-V knee laxity and the ultimate loads of the femur-MCL-tibia complex achieved normal values. However, the stress-strain properties for these MCLs and those treated with repair and immobilization did not completely recover.

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PubMed1989

A histological and biochemical assessment of the cartilage matrix obtained from in vitro storage of osteochondral allografts.

Fresh osteochondral allografts were stored at 4 degrees C in tissue culture media at variable time periods (3, 7, 14 and 28 days). Sterilely dissected tibial plateaus with a standardized 1/2 cm subchondral bone "shell" were obtained from canines 1-3 hrs post mortem. X-rays were taken to determine maturity of the animals. Only mature animals (closed epiphyses) were considered for the study. Histologically, safranin 0 (metachromatic stain for glycosaminoglycans) was observed in all experimental specimens. H&E stained sections showed at all time periods of 3, 7, 14 and 28 days that the cell morphology and arrangements were similar in the superficial and deep areas of the cartilage obtained from the stored osteochondral allograft when compared to the control articular cartilage. The cells were in lacunae and arranged in clusters. Biochemically, glycosaminoglycans and collagen content showed no difference at the 95% level of confidence during the duration of the study (28 days) when compared to the 0 day control cartilage. Collagen typing, based on the assessment by HPLC of the CNBr peptides showed the major presence of type II collagen (no evidence of dedifferentiation was observed). No type I was found to be present. Some apparent variations in the proportions of minor collagen components were noted--e.g. at 14 days the cartilage appeared to contain increased amounts of type XI but little or no type IX collagen (HMW, LMW) when compared to the day 0 control. At 28 days a shift to a larger amount of type IX collagen occurs, especially in the LMW component, with a small amount of type XI collagen when compared to normal day 0 articular cartilage. Cell viability, i.e., the ability of the allograft tissue to incorporate 35SO4 in the synthesis of glycosaminoglycans, was intact up to 28 days of storage.

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PubMed1988

Collagenase production by rabbit ligaments and tendon.

Three periarticular connective tissues from normal rabbits were examined for collagenolytic activity. Enzyme activity was secreted by cultures of anterior cruciate ligament (ACL), medial collateral ligament (MCL) and patellar tendon (PT). A lag period of six days or more was often observed prior to the detection of active collagenase. We attributed this to the presence of an excess of inhibitor in the early days of culture. We quantitated the amount of enzyme and inhibitor produced in 13 days. The levels of collagenase in the ACL and MCL were comparable. The PT, however, consistently secreted more enzyme than the two periarticular (ACL and MCL) ligaments. The reaction products were analyzed for all three collagenases and compared to those generated by the rabbit skin enzyme. We observed the characteristic TCA and TCB collagen fragments for MCL and PT enzymes. Collagen cleavage by the ACL cultures resulted in a product with a molecular weight intermediate between the alpha 2 chain and the TCA piece. These data suggest that quantitative and qualitative differences exist in the ability of these similar connective tissues to degrade collagen.

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PubMed1988

The chondrogenesis of rib perichondrial grafts for repair of full thickness articular cartilage defects in a rabbit model: a one year postoperative assessment.

The purpose of this study was to investigate the results or rib perichondrial grafting after the creation of a full thickness articular cartilage defect. In a rabbit model, rib perichondrium was used to repair defects created in the femoral condyle. The formation of repair tissue (neocartilage) and its chondrogenesis into a tissue resembling articular cartilage was found over time. The gross, histological and biochemical characteristics of the neocartilage were evaluated at intervals of 6, 12, 18, 26 and 52 weeks post transplant, and compared to normal articular cartilage. The neocartilage was characterized by the early formation of relatively large amounts of glycosaminoglycans. A steady increase in the proportion of type II collagen over the time periods was also observed. Improved attachment of the neocartilage to host tissues was seen over the period of 6 to 52 weeks. Successful grafts were seen to proliferate to fill the articular defect and to undergo a chondrogenesis over a post transplant time period of one year.

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PubMed1987

Collagen alteration in medial collateral ligament healing in a rabbit model.

The purpose of this study was to evaluate changes over time in surgically ruptured medial collateral ligament (MCL) with respect to collagen synthesis, collagen degradation and collagen type. Our method involved prelabeling collagen in growing rabbits using 3H-proline followed by surgical injury to the MCL. Animals were sacrificed at intervals up to 40 weeks post-injury. At each time point total hydroxyproline, changes in collagen mass, and collagen synthesis and degradation were determined and related to the unruptured control MCL. A separate semiquantitative determination of collagen type was also performed on the midsubstance of each healing and control ligament. Results showed an increase in total collagen mass and a decrease in collagen concentration in all healing ligaments. Concommitantly, an increase in the collagen turnover rate was observed. Relative turnover was greatest at 3 to 6 weeks after injury and returned toward the normal rate by 40 weeks. Type I collagen was partially replaced by type III, probably as a result of increased synthesis during scar formation. The mechanism for collagen remodeling (replacement of mass and concentration in an organized fashion) in untreated rabbit MCL scar appears functional by virtue of its chronicity but, due to a shift in collagen type, it may also be qualitatively inadequate.

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PubMed1987

Effects of immobilization on joints.

Stress deprivation alters the morphologic, biochemical, and biomechanical characteristics of various components of synovial joints. Prominent among the protean changes that result are proliferation of fibrofatty connective tissue within the joint space, adhesions between synovial folds, adherence of fibrofatty connective tissue to cartilage surfaces, atrophy of cartilage, "ulceration" at points of cartilage-cartilage contact, disorganization of cellular and fibrillar ligament alignment, weakening of ligament insertion sites owing to osteoclastic resorption of bone and Sharpey's fibers, regional osteoporosis of the involved extremity, increased force requirement for joint cycling, and increased ligament compliance. Reduced load-to-failure and reduced energy-absorbing capacity of the bone-ligament-bone complex progresses to about one-third that of controls. Collagen mass declines by about 10%. Collagen turnover increases with accelerated degradation and synthesis. Formation of reducible collagen crosslinks increases. Content of proteoglycan, notably hyaluronic acid, falls and water content is correspondingly reduced. An understanding of the functional implications of these extensive perturbations in the phenomenon of joint immobilization is essential for progress in orthopedics.

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PubMed1986

Synovial fluid nutrient delivery in the diathrial joint: an analysis of rabbit knee ligaments.

The role of synovial fluid in providing nutrition to rabbit knee ligaments and menisci was evaluated by intraarticular injection of a labeled collagen precursor, tritiated proline. Incorporation of this substrate as tritiated hydroxyproline was measured in collateral and cruciate ligaments and menisci. The injectate volume (0.35 ml) did not appreciably change the overall joint pressure as measured by a wick catheter; therefore, no alteration of synovial membrane diffusion characteristics resulted. The concentration of the injected proline (0.52 mg%) was well below that normally present in serum (2.65 mg%). Therefore, incorporation of this substrate was not driven by a concentration gradient and represented normal uptake of synovial fluid and physiological incorporation of label as measured by the presence of tritiated hydroxyproline. Autoradiography was performed on all ligaments and menisci, and demonstrated concentration of the isotope and its metabolite (tritiated proline and tritiated hydroxyproline, respectively) in and around fibroblasts. This study indicates that rabbit knee ligaments and menisci can derive nutrition from a synovial fluid source.

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