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PURPOSE: To compare intraocular pressure (IOP) at one year with the InnFocus MicroShunt(®) with or without cataract surgery with according to placement and concentration of mitomycin C (MMC) DESIGN: A retrospective two-center, two-surgeon study (France and Dominican Republic). PATIENTS AND METHODS: Adults with POAG requiring filtering surgery. One MicroShunt(®) was placed in one eye of each patient. The effect of concentration and site of application of MMC was assessed by IOP and medication reduction at one year. RESULTS: Eighty-seven eyes were studied with one-year follow-up. Twenty-three eyes treated with 0.4 mg/mL MMC close to the limbus demonstrated a 55% reduction in IOP from 23.8 ± 5.3 at baseline to 10.7 ± 2.8 mmHg at one year. Topical glaucoma medication/patient was reduced 85% from 2.4 ± 0.9 to 0.3 ± 0.8. Thirty-one eyes treated with 0.2mg/mL MMC close to the limbus demonstrated a 52% reduction in IOP from 27.9 ± 6.7 at baseline to 13.3 ± 3.3 mmHg at one year. Topical glaucoma medication/patient was reduced 88% from 2.5 ± 1.4 to 0.5 ± 1.0. Thirty-three eyes treated with 0.4 mg/mL MMC deep in the pocket demonstrated a 38% reduction in IOP from 25.4 ± 7.9 at baseline to 15.7 ± 4.6 mmHg at one year. Topical glaucoma medication/patient was reduced 72% from 2.9 ± 1.0 to 0.8 ± 1.3. There were no sight-threatening long-term adverse events. CONCLUSION: The InnFocus MicroShunt(®) is a filtering surgery whose efficacy is related to the location of application and concentration of MMC used.

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Approximately 50,000 abdominal aortic aneurysms (AAAs) are surgically repaired annually in the United States. Endovascular grafts (EVGs) combine a stent and a vascular graft offering great potential for reduced morbidity, mortality, and hospital stay because of minimally invasive endoluminal placement through catheters. Because most AAAs extend into one or both iliac arteries, a bifurcated EVG (bEVG) was developed, consisting of a proximal aortic trunk divided into two distinct lumens or sockets to receive two smaller diameter leg (iliac) components. All components were composed of Didcott self-expanding braided wire stents integrally attached to porous spun polycarbonate urethane liners. Successful placement of the bEVGs (trunks 10-12 mm and legs 5-6 mm diameter) by a 10 Fr introducer through the femoral arteries into the infrarenal aorta and external iliac arteries of 9 of 11 dogs was achieved. Subsequently, 11 of 12 bEVGs were successfully placed to exclude a saccular aneurysm exceeding three aortic diameters created by a fascia lata pouch extending from the aorta into the left external iliac artery, of which 7 were patent at 1 to 4 months. These findings establish design feasibility of the bEVG as well as the utility of the canine experimental model.

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We evaluated a prototype composite collagenous anterior cruciate ligament replacement device designed to possess the advantages of biological grafts and synthetic materials. Collagenous anterior cruciate ligament prostheses were made by embedding 225 reconstituted type I collagen fibers in a type I collagen matrix, and placing polymethylmethacrylate bone fixation plugs on the ends. The collagenous prosthesis was used to replace the anterior cruciate ligament of 31 mature rabbits. At 4 and 20 weeks postimplantation, histologic and mechanical studies were performed on the developing neoligament tissue, and compared to values for the contralateral sham-operated control. At 4 weeks, neoligament tissue infiltrated the collagen fibers of the prostheses. The tibial bone tunnel attachment site contained new bone approaching the fibrous neoligament. The glutaraldehyde-treated prosthetic fibers appeared intact, while the carbodiimide-treated prosthetic fibers began to resorb. The ultimate load and ultimate tensile strength of femur-neoligament-tibia complexes had decreased. At 20 weeks, glutaraldehyde-treated fibers appeared partially intact; in contrast, the carbodiimide-treated prostheses appeared to be completely degraded, and were replaced by organized, crimped neoligament tissue. The ultimate tensile strength and ultimate load increased substantially due to deposition and remodeling of neoligament tissue. The neoligament ultimate load was 2 to 4 times the initial load value of the prosthesis. Implantation of a resorbable, composite collagenous anterior cruciate ligament prosthesis encourages the development of functional neoligament tissue. Studies are underway to optimize the mechanical and biological properties of the prostheses.

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Compression-molded disks of two tyrosine-derived polymers [poly(desaminotyrosyl-tyrosine-hexyl ester carbonate) and poly(desaminotyrosyl-tyrosine hexyl ester iminocarbonate)], two polymers derived from Bisphenol A [poly(Bisphenol A iminocarbonate) and poly(Bisphenol A N-phenyliminocarbonate)], and two clinically used standard materials [poly(D,L-lactic acid) and high-density polyethylene] were implanted subcutaneously in the back of Sprague-Dawley rats. The tissue response elicited by these materials was evaluated histologically at 7, 30, and 120 days postimplantation, based on the total cell density (including fibroblasts, monocytes, giant cells, and macrophages) at the implantation site. The tissue response observed for the two tyrosine-derived polymers was mild, comparable to the two standard materials, medical-grade poly(L-lactic acid) and high density polyethylene. The two Bisphenol A-containing polymers elicited significantly more severe tissue responses. These results indicate that the use of derivatives of the natural amino acid L-tyrosine in the synthesis of degradable implant materials improved the tissue compatibility of these materials relative to chemically related polymers that contain Bisphenol A, an industrial diphenol. The tyrosine-derived polyiminocarbonate and polycarbonate are therefore promising candidates for a detailed evaluation of their biocompatibility, including long-term implantation studies in higher mammals.

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It is widely accepted that the mechanical properties of implants must match those of the surrounding connective tissue to prevent stress concentration and premature failure. The purpose of this paper is to review the structure-mechanical property relationships that exist for connective tissue. The mechanical properties of connective tissue depend on the content of collagen, elastic tissue, and proteoglycans, as well as the geometric arrangement of the fibrous components, age, and location of the specimen. To a first approximation the geometry and loading pattern of the collagen networks in these tissues dominate the mechanical response at high strains. The behavior of the elastic fiber networks dominate the low-strain mechanical response in tissues where energy and shape recovery are critical. Proteoglycans are involved in resisting tissue compressive forces. Since the stiffness of connective tissue increases with age, it is necessary to attempt to match this property by designing implants that have similar behaviors to insure that stress concentration does not occur at the interface between the implant and host.

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We previously reported on the short-term biocompatibility of a reconstituted type-I collagen prosthesis that had been tested in the Achilles tendons of rabbits. Preliminary results indicated that, by ten weeks after implantation, carbodiimide-cross-linked implants had been replaced by neotendon in a manner that was similar to that of autogenous tendon grafts that had been used as controls. Also by ten weeks after implantation, glutaraldehyde-cross-linked collagen implants were encapsulated and appeared to have caused an acute inflammatory response. In the present study, carbodiimide and glutaraldehyde-cross-linked collagen implants and autogenous grafts that served as controls were implanted for fifty-two weeks as a replacement for a three-centimeter section of the Achilles tendon of rabbits. The absence of a crimp in a cross-linked implant and the presence of a crimp in normal tendon and in tendon that formed after an implant had been resorbed made it possible to distinguish between a cross-linked implant and new host tendon that had replaced the implant after it was resorbed. New collagen that had replaced the implant and autogenous (control) tendon graft were compared with normal Achilles tendon with respect to the angle and length of the crimp. The autogenous grafts and the carbodiimide-cross-linked collagen implants had been completely resorbed and replaced by neotendon. The neotendon that was present fifty-two weeks after implantation was similar, but not identical, to normal tendon. In contrast, the glutaraldehyde-cross-linked implant was essentially inert, had not been resorbed, and was surrounded by a capsule of collagenous connective tissue. The neotendon in the capsule was also similar, but not identical, to normal tendon. There were more cells in the capsule than in the autogenous grafts or in the carbodiimide-cross-linked implants. The results of the present study indicate that rapid repair is achieved with a carbodiimide-cross-linked collagenous implant that has a structure and mechanical properties that are similar to those of an autogenous tendon graft and that biodegrades at a similar rate. Prolonged biodegradation of a glutaraldehyde-cross-linked collagenous implant results in formation of a capsule and only limited formation of neotendon.

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Reconstituted collagen fibres have potential applications in repair of soft and hard tissues. Preliminary studies conducted in our laboratory suggest that discontinuous reconstituted type I fibres have strengths similar to those of fibres teased from tendons. The purpose of this paper is to report a method for continuous collagen fibre production and the properties of fibres produced. Ultimate tensile mechanical properties and biocompatibility of continuous type I collagen fibres were studied and compared with the properties of fibres produced manually (discontinuous fibres). In general, continuously made cyanamide cross-linked fibres show slightly inferior mechanical properties and faster biodegradation rates compared with manually made fibres because of minor differences in the fibreformation protocol introduced by design constraints. However, continuous and discontinuous fibres crosslinked with glutaraldehyde had comparable properties. These results demonstrate that production of 50 microns diameter continuous collagen fibre is possible.

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Reconstituted type I collagen was processed into fibers which were subsequently severely dehydrated and cyanamide cross-linked. Fibers prepared by this method were stronger and more resistant to degradation than uncrosslinked fibers. When used as a tendon replacement prosthesis, morphological events occurred which were observed by light, scanning, transmission electron microscopy and electron histochemistry. Resorption was the initial host response to the prosthesis and involved gradual biodegradation. Formation of a host-replacement tendon was the second response. Increased collagen fibril diameters and a transition in the proteoglycan/collagen fibril interactions occurred in the newly developing connective tissue between 3 and 10 weeks postimplantation. These extracellular matrix transitions were major events occurring during wound healing and led to the assembly of a mature connective tissue. When used as a tendon prosthesis, these collagen fibers rapidly resorb while allowing simultaneous formation of aligned connective tissue. The fibers may have other applications in the fields of Orthopaedic Surgery, Neurosurgery and Biomaterials Research.

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A reconstituted collagen tendon prosthesis was developed and implanted in rabbit Achilles tendons. The prosthesis was prepared by extruding type-I collagen into fibers and crosslinking it either with glutaraldehyde or with dehydrothermal treatment followed by exposure to carbodiimide. A tendon prosthesis was assembled by coating a longitudinal array of the fibers with uncrosslinked collagen. In one leg of the rabbit, the Achilles tendon was replaced with the synthetic tendon; in the contralateral leg of the animal, the tendon was excised, devascularized, and anastomosed as an autogenous graft. The autogenous tendon grafts were seen to be infiltrated centrally by fibroblasts and capillaries ten weeks postoperatively and to have been partially replaced by repair tissue twenty weeks postoperatively. Three weeks after implantation, all collagen implants were noted to have been infiltrated with fibrous tissue. At ten weeks, reorganization of collagenous tissue was observed in and around the prostheses, and the carbodiimide-crosslinked implants had been resorbed and replaced by normal-appearing neotendon. The implants that had been treated with glutaraldehyde were resorbed more slowly and were surrounded by more inflammatory cells, compared with the prostheses that had been treated with carbodiimide. Neotendon in the glutaraldehyde-treated prostheses matured more slowly. When the implants were examined at intervals after the operation, their mechanical properties approached those of fresh tendon. The initial strength of the carbodiimide-treated implants was lower than that of the fresh autogenous grafts. Twenty weeks after implantation, the strength and modulus of the carbodiimide-treated implants approached those of fresh tendon.(ABSTRACT TRUNCATED AT 250 WORDS)

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This study involves comparison of the mechanical properties of reconstituted collagen fibres with those of collagen fibres obtained from rat tail tendons. Reconstituted collagen fibres were cross-linked in the presence of glutaraldehyde vapour for 2 and 4 d or using a combination of severe dehydration and carbodiimide treatment. Ultimate tensile strengths for reconstituted fibres cross-linked with glutaraldehyde ranged from 50 to 66 MPa while those cross-linked by severe dehydration and carbodiimide treatment had ultimate tensile strengths between 24 and 31 MPa. Rat tail tendon fibres had tensile strengths that ranged from 33 to 39 MPa. These results indicate that high-strength collagen fibres can be reconstituted in vitro and that these fibres may be useful in repair of dermal, dental, cardiovascular and orthopaedic defects.

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The compressive mechanical properties of untreated and chemically and physically treated nasal septum homografts were determined. Mechanical properties of control, saline-, thimerosal (Merthiolate)- and Alcide-treated specimens were similar. At high strains, the stiffness of treated cartilage ranged from 12.8 to 22.5 MPa and was unaffected by storage time. In comparison, irradiated and freeze-dried nasal septum exhibited stiffnesses of 35 and 37.5 MPa, respectively, after approximately 1 month of storage. These values of stiffness were significantly different from controls at a 0.95 confidence level. On the basis of these results, it was concluded that Alcide and Merthiolate treatment did not alter the compressive mechanical properties of cartilage and that a combination of these treatments may adequately sterilize and preserve nasal septum homografts.

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Scanning and transmission electron microscopy are of clinical value in assessing the interaction between biomaterials and ingrowing tissues. Ultrastructural information allows the clinician and biomaterials specialist to determine events occurring during wound healing and the biocompatibility of prosthetic devices. This paper reviews some of the experimental and clinical studies done in our laboratory on the use of natural and reconstituted collagen as replacements for connective tissues. Consideration is given to collagen flakes used for the treatment of dermal ulcers, a collagen fiber prosthesis used for tendon and ligament replacement, the effects of chemical preservatives on cartilage used for replacement of tissues during plastic surgery and the growth and orientation of nerve cells on reconstituted collagen fibers. Our results show that reconstituted collagen can be prepared into prosthetic devices which encourage cell attachment and orientation thereby facilitating healing of injured tissues. Furthermore chemical preservation of cartilagenous tissues kills chondrocytes resulting in eventual resorption by inflammatory cells.

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