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Results for “Absorbable Implants”

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PubMed2002

Immunoselection and adenoviral genetic modulation of human osteoprogenitors: in vivo bone formation on PLA scaffold.

The aim of this study was to examine the potential of immunoselected genetically modified human osteoprogenitors to form bone in vivo on porous PLA scaffolds. Human osteoprogenitors from bone marrow were selected using the antibody STRO-1 utilising a magnetically activated cell separation system. The STRO-1(+) fraction isolated 7% of nucleated marrow cells and increased fibroblastic colony formation by 300% and alkaline phosphatase activity by 190% over unselected marrow cell cultures. To engineer bone tissue, STRO-1(+) culture-expanded cells were transduced with AxCAOBMP-2, an adenovirus carrying the human BMP-2 gene, injected into diffusion chambers containing porous PLA scaffolds, and implanted in vivo. After 11 weeks the presence of bone mineral was observed by X-ray analysis and confirmed for mineral by von Kossa, as well as bone matrix composition by Sirius red staining, birefringence, and type I collagen immunohistochemistry. Bone formation in vivo indicates the potential of using immunoselected progenitor cells and ex vivo gene transfer with biodegradable scaffolds, for the development of protocols for the treatment of a wide variety of musculo-skeletal disorders.

Absorbable Implants↗

PubMed2003

A new technique for correction of trigonocephaly using bioabsorbable osteofixation tacks and plates and a novel tack-shooter.

We report on the feasibility of applying bioabsorbable tacks using a new tack-shooter to fix bioabsorbable plates applied endocranially for the correction of three cases of trigonocephaly. Tacks do not require tapping or tightening because they are applied using a tack-shooter directly into drill holes in the bone. Hence, the technique saves valuable operative time. A 1.5- to 2.0-cm broad supraorbital bar (bandeau) was raised and reshaped. The corrected shape was maintained using a Biosorb plate (Bionx Implants Ltd, Tampere, Finland), and tacks were applied on the endocranial side of the bar. The plate extended a few centimeters laterally beyond the edge of the supraorbital bar, and it was fixed with Biosorb miniscrews and/or tacks affixed to the temporal bones. Other molded bone pieces were fixed using Biosorb plates, screws, and/or tacks. The technique of using tacks was easy, and it provided secure osteofixation. Cosmetic results were excellent, and no complications were encountered except for palpability of plate edges on the right side of the skull in one case.

Absorbable Implants↗

PubMed2006

Hyaluronic acid hydrogel immobilized with RGD peptides for brain tissue engineering.

In this paper, hyaluronic acid hydrogels with open porous structure have been developed for scaffold of brain tissue engineering. A short peptide sequence of arginine-glycine-aspartic acid (RGD) was immobilized on the backbone of the hydrogels. Both unmodified hydrogels and those modified with RGD were implanted into the defects of cortex in rats and evaluated for their ability to improve tissue reconstruction. After 6 and 12 weeks, sections of brains were processed for DAB and Glees staining. They were also labeled with GFAP and ED1 antibodies, and observed under the SEM for ultrastructral examination. After implanting into the lesion of cortex, the porous hydrogels functioned as a scaffold to support cells infiltration and angiogenesis, simultaneously inhibiting the formation of glial scar. In addition, HA hydrogels modified with RGD were able to promote neurites extension. Our experiments showed that the hyaluronic acid-RGD hydrogel provided a structural, three-dimensional continuity across the defect and favoured reorganization of local wound-repair cells, angiogenesis and axonal growth into the hydrogel scaffold, while there was little evidence of axons regeneration in unmodified hydrogel.

Absorbable Implants↗

PubMedDate not supplied

Prefabrication of vascularized bone graft using guided bone regeneration.

This article describes the prefabrication of a vascularized bone graft composed of autologous particulate cancellous bone and marrow (PCBM), a vessel bundle, and a biodegradable membrane. The PCBM was placed around the saphenous vessel bundle of rats and rolled with a biodegradable membrane of L-lactide-epsilon-caprolactone copolymer to prepare the prefabricated vascularized bone graft (group A). As controls, combinations of PCBM and membrane (group B), vessel bundle and membrane (group C), and PCBM and vessel bundle (group D) were prepared. A radiographic study revealed radio-opacity in the implantation site of group A 1 week later, in contrast to the other groups. Newly formed bone in the membrane roll was histologically confirmed, and neomicrovasculature circulating from the vessel bundle through the newly formed bone tissue was observed. The increase in alkaline phosphatase activity and osteocalcin content was significant for the group A preparation compared with the other groups. We concluded that the combination of autologous PCBM, a vessel bundle, and a biodegradable membrane was promising in the prefabrication of vascularized bone with good blood circulation.

Absorbable Implants↗

PubMed2000

The repair of large parastomal hernias using a midline approach and a prosthetic mesh in the sublay position.

Parastomal herniation is a very frequent complication in enterostomy. The therapeutic strategy consists of three approaches: local fascial repair, relocation of the stoma, and a variety of more elaborate procedures, many of which also involve the use of nonabsorbable meshes. Despite this multitude of available techniques, recurrence rates are high, and long-term complications, especially after mesh implantation, are frequent. In order to improve operative results, we would suggest that a parastomal hernia be treated like a subtype of incisional herniation and that methods be employed that have proved to be effective in this situation. A midline approach allows the operation to be performed under practically sterile conditions. The reinforcing mesh is placed in a sublay position, using a combined intraperitoneal and epifascial preparation. Any direct contact between mesh and intestines is thus avoided. A new type of mesh with substantially reduced polypropylene content decreases the occurrence of both early and late complications.

Abdominal Muscles↗

PubMed2004

Freeze-dried poly(D,L-lactic acid) macroporous guidance scaffolds impregnated with brain-derived neurotrophic factor in the transected adult rat thoracic spinal cord.

The effects of poly(D,L-lactic acid) macroporous guidance scaffolds (foams) with or without brain-derived neurotrophic factor (BDNF) on tissue sparing, neuronal survival, axonal regeneration, and behavioral improvements of the hindlimbs following implantation in the transected adult rat thoracic spinal cord were studied. The foams were embedded in fibrin glue containing acidic-fibroblast growth factor. One group of animals received fibrin glue with acidic-fibroblast growth factor only. The foams were prepared by a thermally induced polymer-solvent phase separation process and contained longitudinally oriented macropores connected to each other by a network of micropores. Both foams and fibrin only resulted in a similar gliotic and inflammatory response in the cord-implant interfaces. With BDNF foam, up to 20% more NeuN-positive cells in the spinal nervous tissue close to the rostral but not caudal spinal cord-implant interface survived than with control foam or fibrin only at 4 and 8 weeks after implantation. Semithin plastic sections and electron microcopy revealed that cells and axons more rapidly invaded BDNF foam than control foam. Also, BDNF foam contained almost twice as many blood vessels than control foam at 8 weeks after implantation. Tissue sparing was similar in all three implantation paradigms; approximately 42% of tissue was spared in the rostral cord and approximately 37% in the caudal cord at 8 weeks post grafting. The number of myelinated and unmyelinated axons was low and not different between the two types of foams. Many more axons were found in the fibrin only graft. Serotonergic axons were not found in any of the implants and none of the axons regenerated into the caudal spinal cord. The behavioral improvements in the hindlimbs were similar in all groups. These findings indicated that foam is well tolerated within the injured spinal cord and that the addition of BDNF promotes cell survival and angiogenesis. However, the overall axonal regeneration response is low. Future research should explore the use of poly(D,L-lactic acid) foams, with or without axonal growth-promoting factors, seeded with Schwann cells to enhance the axonal regeneration and myelination response.

Absorbable Implants↗

PubMed2003

Effect of implantation site on hepatocytes heterotopically transplanted on biodegradable polymer scaffolds.

We investigated the engraftment of heterotopically transplanted hepatocytes in three sites: the subcutaneous space, the small intestinal mesentery, and the omentum to determine the optimal location for tissue-engineered liver constructs. Hepatocytes were isolated from inbred Lewis rats and placed on polymer constructs. Cell-polymer constructs were implanted into the subcutaneous space of the abdominal wall, the small intestinal mesentery, and the omentum of Lewis rats. One group of rats had undergone previous portacaval shunt. Animals were killed 2 or 4 weeks after implantation and the constructs were analyzed for engraftment, using computer-assisted morphometric analysis. Engraftment was greatest in the omentum with less engraftment in the mesentery. There was minimal engraftment in the subcutaneous space in all specimens. Prior portacaval shunt increased engraftment in the mesentery and the omentum, but not the subcutaneous space. The omentum is the most favorable bed for engraftment of hepatocyte-polymer tissue-engineered constructs and the addition of a portacaval shunt increases survival of transplanted hepatocytes in the omentum and mesentery.

Abdominal Wall↗

PubMed2002

Holding power of bioabsorbable ciprofloxacin-containing self-reinforced poly-L/DL-lactide 70/30 bioactive glass 13 miniscrews in human cadaver bone.

Antibiotics-plus bioactive glass-containing bioabsorbable self-reinforced (SR) polylactide screws have been developed for antibacterial osteoconductive bone fixation. The aim of the present study was to test the pullout properties of these recently developed miniscrews. Ciprofloxacin-plus bioactive glass-containing SR-polylactide miniscrews (BC) were compared with miniscrews made of neat SR-polylactide (A), SR-polylactide with bioactive glass (B), and ciprofloxacin-containing SR-polylactide (C). BC miniscrews and their controls (A, B, C) (all of length 6.0 mm, core diameter 1.45 mm, thread diameter 2.0 mm) were applied to one pair of cadaveric fibulae. Pullout force was measured using a materials testing machine. We carried out 49-50 pullout tests for each implant type. The Mann-Whitney test and Student's t-test were used for statistical evaluation. The pullout force for BC miniscrews was 114.9 +/- 34.0 (SD) N. Pullout forces for control miniscrews were 162.7 +/- 37.8 N (A), 99.1 +/- 16.2 N (B), and 142.9 +/- 26.9 N (C). Differences between the four groups were statistically significant (p < 0.001). Ciprofloxacin-plus bioactive glass-containing polylactide miniscrews have good holding power to human cadaver fibulae. However, adding bioactive glass and ciprofloxacin components to neat SR-polylactide results in lower pullout values.

Absorbable Implants↗

PubMed2006

[Histological regeneration process of "neo-esophagus"].

BACKGROUND & OBJECTIVE: During the reconstruction process of organs or tissues, different implant materials can lead to different healing results because of different extracellular matrix interfaces and tissue biocompatibilities. This study was to observe the regeneration process of "neo-esophagus"after implanting an artificial esophagus, and investigate its healing mechanism. METHODS: Histopathologic studies on neo-esophagus in 1, 3, 6, 12, and 24 months after implantation were performed using gross-giant specimen technique and special staining methods. The processes of tissue molding and reconstruction, and regeneration of high-level cell organ in "neo-esophagus"were observed. RESULTS: The artificial esophagus temporarily replaced the defective esophagus at the early stage after implantation, and dropped off about 1 month after operation. The epithelization of neo-esophagus induced by host tissue was completed about 3-6 months after operation. The submucous muscle layer, mucous glands, nerve fiber, and capillaries were reconstructed about 12 months after operation. The narrowing of "neo-esophagus" occurred about 3-6 months after operation and was relieved 12 months after operation. CONCLUSIONS: The implanted artificial esophagus made of bio-material can replace the defective esophagus at the early stage, and induce connective tissues, including collagen and fibroblasts, to deposit and cover on it to form neo-esophagus. The neo-esophagus is developed by epithelization and reconstruction of submucous muscle layer, mucous glands, nerve fiber, and capillaries 12 months after operation. The narrowing of "neo-esophagus" is caused by overgrowth and contraction of scars.

Absorbable Implants↗

PubMed2005

In vitro and in vivo corrosion measurements of magnesium alloys.

The in vivo corrosion of magnesium alloys might provide a new mechanism which would allow degradable metal implants to be applied in musculo-skeletal surgery. This would particularly be true if magnesium alloys with controlled in vivo corrosion rates could be developed. Since the magnesium corrosion process depends on its corrosive environment, the corrosion rates of magnesium alloys under standard in vitro environmental conditions were compared to corrosion rates in an in vivo animal model. Two gravity-cast magnesium alloys (AZ91D, LAE442) were used in these investigations. Standardized immersion and electrochemical tests according to ASTM norms were performed. The in vivo corrosion tests were carried out by intramedullar implantation of sample rods of the magnesium alloys in guinea pig femura. The reduction in implant volume was determined by synchrotron-radiation-based microtomography. We found that in vivo corrosion was about four orders of magnitude lower than in vitro corrosion of the tested alloys. Furthermore, the tendency of the corrosion rates obtained from in vitro corrosion tests were in the opposite direction as those obtained from the in vivo study. The results of this study suggest, that the conclusions drawn from current ASTM standard in vitro corrosion tests cannot be used to predict in vivo corrosion rates of magnesium alloys.

Absorbable Implants↗

PubMed2006

Enhanced bone regeneration at a segmental bone defect by controlled release of bone morphogenetic protein-2 from a biodegradable hydrogel.

The objective of this study is to investigate the feasibility of a biodegradable hydrogel of gelatin as the controlled release carrier of bone morphogenetic protein-2 (BMP-2) suitable for enhancement of bone regeneration at a segmental bone defect. Hydrogels with three different water contents were prepared through glutaraldehyde crosslinking of gelatin with an isoelectric point of 9.0 under varied reaction conditions. Segmental critical-sized defects (20 mm) were created at the ulnar bone of skeletally mature New Zealand white rabbits, and gelatin hydrogels incorporating BMP-2 (17 microg/hydrogel) were implanted into the defects. When bone regeneration was evaluated by soft x-ray observation and bone mineral density (BMD) measurement, the gelatin hydrogels incorporating BMP- 2 exhibited significantly high osteoinduction activity compared with that of free BMP-2, although the activity depended on the water content of the hydrogels. Significantly higher BMD enhancement was observed in the gelatin hydrogel with a water content of 97.8 wt% than that with the lower or higher water content. We concluded that the biodegradable gelatin hydrogel is a promising controlled release carrier of BMP-2 for bone regeneration at the segmental bone defect.

Absorbable Implants↗

PubMed2001

Engineering and characterization of functional human microvessels in immunodeficient mice.

SUMMARY: Current model systems used to investigate angiogenesis in vivo rely on the interpretation of results obtained with nonhuman endothelial cells. Recent advances in tissue engineering and molecular biology suggest the possibility of engineering human microvessels in vivo. Here we show that human dermal microvascular endothelial cells (HDMEC) transplanted into severe combined immunodeficient (SCID) mice on biodegradable polymer matrices differentiate into functional human microvessels that anastomose with the mouse vasculature. HDMEC were stably transduced with Flag epitope or alkaline phosphatase to confirm the human origin of the microvessels. Endothelial cells appeared dispersed throughout the sponge 1 day after transplantation, became organized into empty tubular structures by Day 5, and differentiated into functional microvessels within 7 to 10 days. Human microvessels in SCID mice expressed the physiological markers of angiogenesis: CD31, CD34, vascular cellular adhesion molecule 1 (VCAM-1), and intercellular adhesion molecule 1 (ICAM-1). Human endothelial cells became invested by perivascular smooth muscle alpha-actin-expressing mouse cells 21 days after implantation. This model was used previously to demonstrate that overexpression of the antiapoptotic protein Bcl-2 in HDMEC enhances neovascularization, and that apoptotic disruption of tumor microvessels is associated with apoptosis of surrounding tumor cells. The proposed SCID mouse model of human angiogenesis is ideally suited for the study of the physiology of microvessel development, pathologic neovascular responses such as tumor angiogenesis, and for the development and investigation of strategies designed to enhance the neovascularization of engineered human tissues and organs.

Absorbable Implants↗

PubMed2004

Biomatrix/polymer composite material for heart valve tissue engineering.

BACKGROUND: Decellularized extracellular matrix has been suggested as a scaffold for heart valve tissue engineering or direct implantation. However, cell removal impairs the physical properties of the valve structure and exposes bare collagen fibers that are highly thrombogenic. Matrix/polymer hybrid valves with improved biological and mechanical characteristics may be advantageous. METHODS: Porcine aortic valves were decellularized enzymatically and impregnated with biodegradable poly(hydroxybutyrate) by a stepwise solvent exchange process. Biocompatibility was tested in vitro using cell proliferation and coagulation assays. Proinflammatory activity was assessed in vivo by implantation of matrix/polymer patches in the rabbit aorta. Biomechanic valve properties and fluid dynamics were tested in a pressure/flow-controlled pulse duplicating system. Matrix/polymer hybrid valves were implanted in pulmonary and aortic position in sheep. RESULTS: Biocompatibility assays indicated that human blood vessel cells survive and proliferate on matrix/polymer hybrid tissue. In vitro activation of cellular and plasmatic coagulation cascades was lower than with uncoated control tissue. After implantation in the rabbit aorta, matrix/polymer hybrid patches healed well, with complete endothelialization, mild leukocyte infiltration, and less calcification than control tissue. Matrix/polymer hybrid tissue had superior tensile strength and suture retention strength, and hybrid valves showed good fluid dynamic performance. The two valves in aortic position performed well, with complete endothelialization and limited inflammatory cell invasion after 12 weeks. Of the two valves in pulmonary position, one failed. CONCLUSIONS: Matrix/polymer hybrid tissue valves have good biological and biomechanic characteristics and may provide superior replacement valves.

Absorbable Implants↗

PubMed2006

Preparation of prefabricated vascularized bone graft with neoangiogenesis by combination of autologous tissue and biodegradable materials.

Prefabricated vascularized bone grafts have previously been prepared by combining an autologous vessel bundle with auto-particulate cancellous bone and marrow (PCBM) and a biodegradable membrane. Only small quantities of low-density vascularized bone tissue have been formed using this method. The authors of the present study combined beta-tricalcium phosphate (beta-TCP), a biodegradable ceramic, with a prefabricated vascularized bone graft to augment osteogenesis. A saphenous vessel bundle from a rat was wrapped in a biodegradable membrane. Then, autologous PCBM was mixed with beta-TCP granules and packed into the rolled membrane. In the control group, beta-TCP was omitted. Bone formation was histologically assessed 6 and 9 weeks after implantation. The volume of newly formed bone tissue in the rolled membrane was greater in the presence of beta-TCP granules than in the control. Microvessels had formed throughout the new bone tissue. When a prefabricated vascularized bone graft was onlay-grafted to the femur of the same rat, the prefabricated vascularized bone graft directly fused to the cortical surface of the femur, with no intervening fibrous tissue. These findings suggest that beta-TCP in combination with PCBM enhances the volume and density of bone tissue in prefabricated vascularized bone grafts.

Absorbable Implants↗

PubMed2006

Understanding the role of corrosion in the degradation of metal-on-metal implants.

In metal-on-metal joints the primary concerns in terms of long-term durability relate to corrosion, wear, and their joint (tribocorrosion) effects. The release of ions through corrosion processes and nanoscale debris from wear processes can seriously affect joint integrity and can lead to an adverse biological reaction by the host. In this paper an integrated study of corrosion-wear interactions in serum, Dulbecco's Modified Eagle's Medium and 0.3 per cent NaCl has demonstrated that the biological nature of the fluid affects the total degradation rate and also the level of wear-corrosion interactions. The specific action of proteins in corrosion and tribocorrosion for high-carbon Co-Cr-Mo and low-carbon Co-Cr-Mo alloys is discussed.

Absorbable Implants↗

PubMed2004

[An experimental study on PLGA carrier for oral tissue engineered mucosa by subcutaneous implantation in rabbits].

OBJECTIVE: To look for the best carrier for cultivating oral tissue engineered mucosa. METHODS: A series of membrane of scaffold materials of polycleclide-co-plycoclide (PLGA) were studied on their weight and biocompatibility after they had been implanted subcutaneously in rabbits for 1, 2, 3, 4 weeks respectively. RESULTS: PLGA I , II, III degraded completely in rabbits after 2, 3, 4 weeks respectively. The other PLGA membrane degraded about 50% after 4 weeks. Histologically, the reactions of PLGA I, II, III with surrounding tissues were normal and membranes had a good biocompatibility. CONCLUSION: The biodegrading rate of PLGA II is suitable for clinic practice. PLGA II was a promising carrier for oral tissue-engineered mucosa due to its excellent biocompatibility and biodegrading rate.

Absorbable Implants↗

PubMed2005

In vivo corrosion of four magnesium alloys and the associated bone response.

Degrading metal alloys are a new class of implant materials suitable for bone surgery. The aim of this study was to investigate the degradation mechanism at the bone-implant interface of different degrading magnesium alloys in bone and to determine their effect on the surrounding bone. Sample rods of four different magnesium alloys and a degradable polymer as a control were implanted intramedullary into the femora of guinea pigs. After 6 and 18 weeks, uncalcified sections were generated for histomorphologic analysis. The bone-implant interface was characterized in uncalcified sections by scanning electron microscopy (SEM), element mapping and X-ray diffraction. Results showed that metallic implants made of magnesium alloys degrade in vivo depending on the composition of the alloying elements. While the corrosion layer of all magnesium alloys accumulated with biological calcium phosphates, the corrosion layer was in direct contact with the surrounding bone. The results further showed high mineral apposition rates and an increased bone mass around the magnesium rods, while no bone was induced in the surrounding soft tissue. From the results of this study, there is a strong rationale that in this research model, high magnesium ion concentration could lead to bone cell activation.

Absorbable Implants↗

PubMed2005

Enhanced osteoinduction by controlled release of bone morphogenetic protein-2 from biodegradable sponge composed of gelatin and beta-tricalcium phosphate.

Biodegradable gelatin sponges at different contents of beta-tricalcium phosphate (beta-TCP) were fabricated to allow bone morphogenetic protein (BMP)-2 to incorporate into them. The in vivo osteoinduction activity of the sponges incorporating BMP-2 was investigated, while their in vivo profile of BMP-2 release was evaluated. The sponges prepared had an interconnected pore structure with an average pore size of 200 microm, irrespective of the beta-TCP content. The in vivo release test revealed that BMP-2 was released in vivo at a similar time profile, irrespective of the beta-TCP content. The in vivo time period of BMP-2 retention was longer than 28 days. When the osteoinduction activity of gelatin or gelatin-beta-TCP sponges incorporating BMP-2 was studied following the implantation into the back subcutis of rats in terms of histological and biochemical examinations, homogeneous bone formation was histologically observed throughout the sponges, although the extent of bone formation was higher in the sponges with the lower contents of beta-TCP. On the other hand, the level of alkaline phosphatase activity and osteocalcin content at the implanted sites of sponges decreased with an increase in the content of beta-TCP. The gelatin sponge exhibited significantly higher osteoinduction activity than that of any gelatin-beta-TCP sponge, although every sponge with or without beta-TCP showed a similar in vivo profile of BMP-2 release. In addition, the in vitro collagenase digestion experiments revealed that the gelatin-beta-TCP sponge collapsed easier than the gelatin sponge without beta-TCP incorporation. These results suggest that the maintenance of the intrasponge space necessary for the osteoinduction is one factor contributing to the osteoinduction extent of BMP-2-incorporating sponges.

Absorbable Implants↗