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Results for “Absorbable Implants”

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PubMed2003

In vivo promoted growth of mice hair follicles by the controlled release of growth factors.

This study is an investigation to evaluate how the controlled release of different growth factors modifies the hair follicle growth of mice. For the controlled release, basic fibroblast growth factor or hepatocyte growth factor was incorporated into a biodegradable gelatin hydrogel, while vascular endothelial growth factor was incorporated into a biodegradable collagen hydrogel. After subcutaneous implantation of the two different hydrogels incorporating growth factors into the backs of mice, hair follicle growth was evaluated photometrically and histologically 10 days later. The darkness of the reverse side of skin implanted with every hydrogel incorporating growth factor was significantly higher than that of skin injected with the corresponding growth factor in the solution. Implantation of the hydrogel incorporating growth factor increased the area of the hair follicles to a significantly greater extent than other control groups, whereas no effect on the skin thickness was observed. The length of hair shaft elongated was significantly high by the hydrogel incorporating every growth factor. Neither empty gelatin nor collagen hydrogels affected hair follicle growth. These findings indicate that the controlled release enabled the growth factor to positively act on the hair growth cycle of mice.

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PubMed2003

Holding power of bioabsorbable self-reinforced poly-L/DL-lactide 70/30 tacks and miniscrews in human cadaver bone.

Several bioabsorbable internal fixation systems are currently in use in the field of bone surgery. To test the mechanical properties of recently developed amorphous self-reinforced poly-L/DL-lactide [SR-P(L/DL)LA] 70/30 tacks in comparison with commercially available SR-P(L/DL)LA 70/30 (BioSorbFX; Bionx Implants Ltd) miniscrews, SR-P(L/DL)LA miniscrews (length = 6.0 mm, core diameter = 1.5 mm, thread diameter = 2.0 mm) and tacks (length = 5.4 mm, core diameter = 1.5 mm, thread diameter = 2.0 mm) were applied to human cadaveric metatarsal (MT) bones (6 pairs of fourth MT bones and 6 pairs of fifth MT bones from donors who were from 29 to 56 years of age at the time of death). Pullout force was measured using a mechanical testing machine. Forty-eight pullout tests were carried out for each implant type. The Student test, Mann-Whitney test, and Spearman coefficient were used for statistical evaluation. The pullout force of tacks was 135.0 +/- 26.1 N, and that of the miniscrews was 119.3 +/- 26.1 N ( = 0.04, statistically significant difference). Accordingly novel SR-P(L/DL)LA 70/30 tacks have a statistically better pullout strength than the SR-P(L/DL)LA 70/30 miniscrews when tested in cadaver MT bones.

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PubMed2003

Expandable bioresorbable endovascular stent. I. Fabrication and properties.

A bioresorbable, expandable poly(L-lactic acid) stent has been designed, based on a linear, continuous coil array principle, by which multiple furled lobes convert to a single lobe upon balloon expansion, without heating. Stent strength and compliance are sufficient to permit deployment by a conventional balloon angioplasty catheter. Several multiple lobe configurations were investigated, with expansion ratios ranging from 1.4 to 1.9 and expanded diameters ranging from 2.3 to 4.7 mm. Compression resistance of the expanded stent is dependent on fiber coil density and fiber ply. A range sufficient for endovascular service was obtained, with less than 4% elastic recoil in six day saline incubation studies. Surface plasma treatment with di(ethylene glycol) vinyl ether significantly reduced platelet adhesion in a 1 h porcine arteriovenous shunt model. Patency was maintained in one week implant studies in the porcine common femoral artery. However, a strong inflammatory response, and significant reduction of the vascular lumen were observed following two weeks implantation. The design principles and fabrication techniques for this bioresorbable stent are sufficiently versatile that a broad range of applications can be addressed. Much work remains to be done, including long-term evaluation of the inflammatory response, and of polymer degradation. The results of this study demonstrate the feasibility of expandable biodegradable stent design and deployment by conventional means.

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PubMed2007

A novel poly(ethylene glycol)-fibrinogen hydrogel for tibial segmental defect repair in a rat model.

The aim of this study is to investigate regeneration in a segmental bone defect using a novel fibrinogen-based hydrogel material. The use of hydrogels made from poly(ethylene glycol) (PEG) conjugated to fibrinogen for this purpose may be better to conventional fibrin-based materials as it offers an additional degree of control over the structural characteristics and biodegradation of the material. At the same time, it maintains some of the inherent biofunctionality of the fibrinogen molecule. PEGylated fibrinogen hydrogels with various degrees of proteolytic resistance based on PEG and fibrinogen composition were designed for slow, intermediate, and fast biodegradation. The hydrogels were implanted into 7-mm segmental rat tibial defects without additional osteoinductive factors with the rationale that the ingrowth matrix will displace the normal fibrin clot while sustaining a similar healing effect for a longer duration. Histological and X-ray results confirmed that the extent and distribution of newly formed bone in the defect after 5 weeks strongly parallels the biodegradation pattern of the implanted material. When compared to nonunions in animals treated with the fast-degrading implants and untreated control animals, the rats implanted with the intermediate-degrading material exhibited osteoneogenesis. This data supports the hypothesis that the perseverance of the PEGylated fibrinogen material can be synchronized with the optimal healing characteristics of a segmental osseous defect and that the consequent sustained release of fibrinogen fragments facilitates the osteogenic response at the injury site. The PEGylated fibrinogen material may, therefore, be a highly efficacious material for promoting the healing of bone defects and especially nonunion fractures.

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PubMed2006

MRI study of bioabsorbable poly-L-lactic acid devices used for fixation of fracture and osteotomies.

BACKGROUND: The overall clinical results of bioabsorbable fixation devices made of poly-L-lactic acid (PLLA) used for fixation of fractures, bone grafting, and osteotomies have been favorable. However, clinical studies demonstrated no sign of normal bony architecture restored after surgery, although implant channels had been filled with fibrous tissue. The purpose of the present retrospective study was to examine the extent of structural changes in PLLA devices (PLLA-Ds) for fixation of rotational acetabular osteotomies and displaced malleolar ankle fractures using magnetic resonance imaging (MRI). METHODS: Altogether, 14 patients with osteoarthritis of hip joints and 15 with displaced malleolar ankle fractures were operated on using PLLA-D (NEOFIX). Of these patients, 22 were finally enrolled in the study, and the period from operation to the time of the study ranged from 17 to 78 months. The postoperative radiographic findings were evaluated for union, and changes around the implant holes were classified as sclerosis, resorption, or no change. MRI was carried out to estimate changes in the PLLA-Ds. RESULTS: Bone union was obtained in all cases; clinical complications such as infection, joint effusion, soft tissue irritation due to PLLA-D deviation, and motion pain in the joints were not observed. The MRI study suggested that water content in PLLA-D increased mainly due to biodegradation and that implants were not replaced by bony tissue. CONCLUSIONS: The PLLA-Ds were degraded but were not replaced by bony tissue during the observation period. Considering these findings and the assumption that in bony tissues mechanical strength of PLLA-D decreases with time, attention should be paid to mechanical insufficiency, which may occur when the cross-sectional area of a PLLA-D extends beyond the cross-sectional area of the osteosynthesis site.

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PubMed2005

Dissolution and mineralization of sintered and thermally sprayed hydroxy-fluoroapatites.

Hydroxyapatites are commonly used as bone cement, coatings on implants for dental and orthopaedic applications, but also as middle ear implants. These applications all require a different tissue healing response that can be attained by different manufacturing processes or by chemically modifying the composition. During implantation apatites undergo a process of dissolution and mineralization. The degree of dissolution is dependent upon the manufacturing process & is higher for thermally sprayed implant materials. This allows them to integrate to the natural bone. This study tests the dissolution and mineralization of fluoride containing hydroxyapatites through immersion in simulated body fluid. It shows that mineralization occurs more readily in hydroxyapatites than fluorapatites because of their higher dissolution rate. Mineralization was detected most readily by image analysis using scanning electron microscopy than by weight changes using a microbalance. Microscopy allowed small heterogeneous precipitates to be observed during the initial stages of mineralization.

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PubMed2005

Culturing of skin fibroblasts in a thin PLGA-collagen hybrid mesh.

A thin biodegradable hybrid mesh of synthetic poly(DL-lactic-co-glycolic acid) (PLGA) and naturally derived collagen was used for three-dimensional culture of human skin fibroblasts. The hybrid mesh was constructed by forming web-like collagen microsponges in the openings of a PLGA knitted mesh. The behaviors of the fibroblasts on the hybrid mesh and PLGA knitted mesh were compared. The efficiency of cell seeding was much higher and the cells grew more quickly in the hybrid mesh than in the PLGA mesh. The fibroblasts in the PLGA mesh grew from the peripheral PLGA fibers toward the centers of the openings, while those in the hybrid mesh also grew from the collagen microsponges in the openings of the mesh resulting in a more homogenous growth. The proliferated cells and secreted extracellular matrices were more uniformly distributed in the hybrid mesh than in the PLGA mesh. Histological staining of in vitro cultured fibroblast/mesh implants indicated that the fibroblasts were distributed throughout the hybrid mesh and formed a uniform layer of dermal tissue having almost the same thickness as that of the hybrid mesh. However, the tissue formed in the PLGA mesh was thick adjacent to the PLGA fibers and thin in the center of the openings. Fibroblasts cultured in the hybrid mesh were implanted in the back of nude mouse. Dermal tissues were formed after 2 weeks and became epithelialized after 4 weeks. The results indicate that the web-like collagen microsponges formed in the openings of the PLGA knitted mesh increased the efficiency of cell seeding, improved cell distribution, and therefore facilitated rapid formation of dermal tissue having a uniform thickness. PLGA-collagen hybrid mesh may be useful for skin tissue engineering.

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PubMed2000

Tissue responses of calcium phosphate cement: a study in dogs.

The in vivo properties of a new kind of calcium phosphate cement were investigated in this study. Calcium phosphate cement was implanted as paste into femoral bone and dorsal muscle of dogs for 3 and 6 months, and as prehardened form into thigh muscles of dogs for 1, 2 and 6 months. Histology was performed on thin un-decalcified sections. No foreign body reaction, no inflammation and no necrosis were found both in bony site and in muscles. There was no connective tissue layer between the cement and bone when cement paste was implanted in the bone. A creeping substitution of cement by bone, in which osteoclast-like cells resorbed the cement as if the cement is a part of bone and new bone was formed directly on the resorption line of calcium phosphate cement, was found. Bone formation was found histomorphologically in pores and deep rugged surface of cement samples (both paste and prehardened form) implanted in muscles of dogs. The induced bone was also identified with backscattered scanning electron microscopy (BSE) and by energy-dispersive X-ray micro-analysis (EDX). The results suggest that the calcium phosphate cement used in this study is biocompatible, resorbable in a manner of creeping substitution, osteoconductive and osteoinductive. It seems that an ideal bone substitute can be developed by using this type of calcium phosphate cement.

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PubMed2006

Safety and pharmacokinetics of an intravitreal biodegradable implant of dexamethasone acetate in rabbit eyes.

The treatment of vitreoretinal diseases is limited and, nowadays, new drug delivery approaches have been reported in order to increase drug bioavailability. The objective of the current study was to determine the pharmacokinetic profile of a biodegradable dexamethasone acetate implant inserted into the vitreous of rabbits and to evaluate its potential signs of toxicity to the rabbits' eyes. The results showed that the intravitreous drug concentration remained within the therapeutic range along the 8-week period of evaluation. The system under study was not toxic to the normal rabbit retina, and no significant increase in intraocular pressure was observed.

Absorbable Implants↗

PubMed2005

Biodegradation of differently cross-linked collagen membranes: an experimental study in the rat.

The aim of the present study was to compare the biodegradation of differently cross-linked collagen membranes in rats. Five commercially available and three experimental membranes (VN) were included: (1) BioGide (BG) (non-cross-linked porcine type I and III collagens), (2) BioMend (BM), (3) BioMendExtend (BME) (glutaraldehyde cross-linked bovine type I collagen), (4) Ossix (OS) (enzymatic-cross-linked bovine type I collagen), (5) TutoDent (TD) (non-cross-linked bovine type I collagen, and (6-8) VN(1-3) (chemical cross-linked porcine type I and III collagens). Specimens were randomly allocated in unconnected subcutaneous pouches separated surgically on the back of 40 wistar rats, which were divided into five groups (2, 4, 8, 16, and 24 weeks), including eight animals each. After 2, 4, 8, 16, and 24 weeks of healing, the rats were sacrificed and explanted specimens were prepared for histologic and histometric analysis. The following parameters were evaluated: biodegradation over time, vascularization, tissue integration, and foreign body reaction. Highest vascularization and tissue integration was noted for BG followed by BM, BME, and VN(1); TD, VN(2), and VN(3) showed prolongated, while OS exhibited no vascularization. Subsequently, biodegradation of BG, BM, BME and VN(1) was faster than TD, VN(2), and VN(3). OS showed only a minute amount of superficial biodegradation 24 weeks following implantation. Biodegradation of TD, BM, BME, VN(2), and VN(3) was associated with the presence of inflammatory cells. Within the limits of the present study, it was concluded that cross-linking of bovine and porcine-derived collagen types I and III was associated with (i) prolonged biodegradation, (ii) decreased tissue integration and vascularization, and (iii) in case of TD, BM, BME, VN(2), and VN(3) foreign body reactions.

Absorbable Implants↗

PubMed2002

Resorbable polymer implants in unilateral transforaminal lumbar interbody fusion.

OBJECT: Sixty patients underwent instrumentation-assisted posterior transforaminal lumbar interbody fusion (TLIF) with resorbable polymer cages and autograft bone for degenerative disease. This article discusses the technique of TLIF and its early outcomes. METHODS: Although the follow-up period is short and results are preliminary, no adverse events or complications were attributed to the resorbable polymer. CONCLUSIONS: Further multicenter clinical studies are underway with a minimum 2-year follow-up period chosen as an endpoint to provide insight as to the future of biodegradable polymers as spinal interbody devices.

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PubMed1999

Biocompatibility testing of a new bioabsorbable X-ray positive SR-PLA 96/4 urethral stent.

PURPOSE: Recently a first X-ray-positive bioabsorbable urethral stent was developed by our group. The stent is made from self-reinforced poly-L,D-lactic acid (SR-PLA 96/4) blended with barium sulfate. The aim of this study was to evaluate the biocompatibility properties of the new stent materials. MATERIALS AND METHODS: Rods made from pure SR-PLA 96/4 and SR-PLA 96/4 blended with barium sulfate were inserted into the dorsal muscles of a rabbit. Rods made from latex and silicone were used as positive and negative controls. To evaluate the long-term effect of BASO4 after the bioabsorption of the polymer, fast degrading SR-PGA (self-reinforced polyglycolic acid) and SR-PLA + BASO4 rods were used as controls. Urethral stents made from SR-PLA 96/4 and X-ray-positive SR-PLA 96/4 stents were inserted cystoscopically into the rabbit urethra. Metal stents were used as controls. The animals were sacrificed after 1 week, 1 month or 6 months. RESULTS: In the muscle implantation samples acute tissue reactions due to operative trauma were seen in all specimens at 1 week. After 6 months chronic inflammatory changes and foreign body reaction were seen only in the positive controls. The stent worked well in the rabbit urethra, its biocompatibility was good and there was less encrustation than in the metal stents. CONCLUSIONS: This first X-ray-positive bioabsorbable urethral stent showed no toxic tissue effects.

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PubMed2005

Shape-memory polymers as stimuli-sensitive implant materials.

Shape-memory polymers are stimuli-responsive materials. Upon exposure to an external stimulus, e.g. an increase in temperature, they have the capability of changing their shape. The shape-memory effect results from the polymer's structure and morphology in combination with a certain processing and programming technology. Stimuli-sensitive implant materials have a high potential for applications in minimally invasive surgery. A group of biodegradable implant materials with shape-memory has been developed for applications in biomedicine. These implant materials are not a single polymer but polymer systems that allow the variation of different macroscopic properties over a wide range by only small changes in the chemical structure. In this way, it is possible to implement a variety of different applications with tailor-made polymers of the same family. Two different types of degradable shape-memory polymer systems, covalently cross-linked polymer networks and thermoplastic elastomers, are presented and examples are given for each case.

Absorbable Implants↗

PubMed2006

Vertical ridge augmentation by means of deproteinized bovine bone block and recombinant human platelet-derived growth factor-BB: a histologic study in a dog model.

The primary objective of this proof-of-principle study was to evaluate the outcome of vertical ridge augmentation in a standardized dog model by combining purified recombinant platelet-derived growth factor (rhPDGF-BB) and a block of deproteinized cancellous bovine bone. The secondary objective was to determine the value of a resorbable barrier membrane to improve the efficacy of the procedure. Six adult foxhounds were committed to bilateral surgical extraction of all four mandibular premolars. A vertical alveolar ridge defect was created at the time of the extractions. Three months later, the artificially created defects were grafted: Group A used a deproteinized bovine bone block in combination with a collagen barrier membrane, group B used a deproteinized bovine bone block infused with rhPDGF-BB only, and group C included a deproteinized bovine bone block infused with rhPDGF-BB, plus a collagen resorbable barrier membrane. After 4 months, the animals were sacrificed. Histologic examination of group B revealed a large amount of newly formed bone, and a large amount of bone-to-implant contact was visible in the areas of bone regeneration extending over the top of the implant cover screw. The results of this preclinical canine study provide proof-of-principle that rhPDGF-BB, used in combination with a deproteinized bovine block without placement of a barrier membrane, has the potential to regenerate significant amounts of new bone in severe mandibular ridge defects. In addition, the results seem to point to the importance of the periosteum as a source of osteoprogenitor cells in growth factor-mediated regenerative procedures.

Absorbable Implants↗

PubMed2002

Bioresorbable polymer implants in the unilateral transforaminal lumbar interbody fusion procedure.

Sixty patients from two centers have undergone instrumented transforaminal posterior lumbar interbody fusion (TLIF) with bioresorbable polymer cages and autograft bone for degenerative indications. This article discusses the technique of TLIF and its early outcomes. Although follow-up is short and results are preliminary, no adverse events or complications may be attributed to the bioresorbable polymer. Further multicenter clinical studies are underway with a minimum of 2 years of follow-up chosen as an endpoint to provide insight as to the future of biodegradable polymers as spinal interbody devices.

Absorbable Implants↗

PubMed2005

Ectopic osteoinduction and early degradation of recombinant human bone morphogenetic protein-2-loaded porous beta-tricalcium phosphate in mice.

The present study investigated the ectopic osteoinduction and early degradation of recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded porous beta-tricalcium phosphate (beta-TCP) in mice. The porous beta-TCP with 50 microg of rhBMP-2 (n = 25) and porous beta-TCP (control group, n = 25) were implanted into muscle pouches in the right and left thigh of 28-day-old mice (n = 25), respectively. At every time point (3, 7, 14, 21 and 28 days after implantation), five mice were euthanized and the histological examinations of implantation sites were performed. In addition, the alkaline phosphatase (ALP) activity was also quantitatively analyzed. For the rhBMP-2-loaded group, blood vessel formation and immature cartilage was observed within the porous beta-TCP 3 days after implantation. Mature cartilage was observed 7 days after implantation of rhBMP-2-loaded porous beta-TCP. Newly formed woven bone, lamellar bone as well as marrow were observed 14 and 21 days after implantation of the rhBMP-2-loaded porous beta-TCP. Lamellar bone and marrow were observed 28 days after implantation of the rhBMP-2-loaded porous beta-TCP. For the control group, no bone or cartilage was observed at all time points. However, multinucleated giant cells and fibrous tissues were observed in the control group at 7 and 28 days after implantation, respectively. At 21 and 28 days after implantation, porous beta-TCP was observed to fragment indicating early degradation of the porous beta-TCP in both groups. In addition, ALP was observed to be significantly higher in the rhBMP-2-loaded beta-TCP as compared to the control beta-TCP. It was concluded from this study that the rhBMP-2-loaded porous beta-TCP induced blood vessel and ectopic bone formation.

Absorbable Implants↗

PubMedDate not supplied

Evaluation of in vitro drug release, pH change, and molecular weight degradation of poly(L-lactic acid) and poly(D,L-lactide-co-glycolide) fibers.

Biodegradable fibers of poly(L-lactic acid) (PLLA) and poly(D,L-lactide-co-glycolide) (PLGA) that encapsulated a water-soluble drug were created by a patented technique consisting of wet-spinning a water-in-oil emulsion. These fibers are 2.4% by mass drug, which is slowly released, making these fibers potential candidates for implantation as drug delivery devices and/or tissue-engineering substrates. Drug release kinetics and changes in molecular weight were investigated over time. This study demonstrated that drug release rates and molecular weight degradation are a function of the amount of aqueous phase added as an emulsion during fabrication. The type of polymer used (PLLA or PLGA) determines the molecular weight degradation rates, but has little effect on drug release kinetics.

Absorbable Implants↗

PubMedDate not supplied

Autogenous bone versus beta-tricalcium phosphate graft alone for bilateral sinus elevations (2- and 3-dimensional computed tomographic, histologic, and histomorphometric evaluations): preliminary results.

The aim of this research was to compare 2 different graft materials, beta-tricalcium phosphate (Cerasorb) and autogenous bone, used in the same patient. Bilateral sinus grafting was performed on 4 selected patients; Cerasorb only was used on the experimental side, and autogenous bone only was used on the control side. In all 4 patients, the maxilla was atrophied to such an extent that the reconstruction included not only sinus grafting but also onlay plasty. The procedure was followed by implant placement 6 months later. In addition to routine panoramic radiographs, 2- and 3-dimensional computed tomographic (CT) examinations were performed pre- and postoperatively and after implantation. Information from CTs is necessary when alveolar bone atrophy is extensive, complications appear probable, and in difficult cases, when exact documentation is important. A total of 16 bone biopsies were taken at the time of implant placement. The histologic and histomorphometric results indicated that when the formation of new bone was slow, it was slow on both sides; when it was fast, then it was fast on both sides. Individual patient factors strongly influenced the fates of the various graft materials in the organism. Comparisons of the present results with the findings of other investigators demonstrated that beta-tricalcium phosphate is a satisfactory graft material, even without autogenous bone.

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