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PubMed2005

Biocompatibility and degradation of poly(DL-lactic-co-glycolic acid)/calcium phosphate cement composites.

Injectable calcium phosphate (Ca-P) cement materials exhibit favorable osteocompatible behavior but are resorbed slowly because of a lack of a bone ingrowth-enabling macroporosity. In this study, poly(DL-lactic-co-glycolic acid) (PLGA) microparticles (average size 66 +/- 25 microm) were incorporated into Ca-P cement to obtain a macroporous Ca-P cement scaffold after PLGA hydrolysis in vivo. Preset PLGA/Ca-P cement composite discs of various weight ratios (0/100, 15/85, 30/70, and 50/50) were implanted subcutaneously and in cranial defects in rats for 12 weeks. Histological analysis revealed that all macropores in the PLGA-containing composites (average pore size 73 +/- 27 microm) were filled with fibrous tissue and blood vessels (subcutaneous implants) and/or bone (cranial implants). Histologically, bone formation appeared most abundant and most consistent in the 30/70 PLGA/Ca-P cement composites. Histomorphometrical evaluation revealed a significant increase in defect fill in the 15/85 and 30/70 PLGA/Ca-P cement composites. Finally, subcutaneous and cranial 50/50 PLGA/Ca-P cement composites had degraded to a large extent, without adequate replacement by bone in the cranial implants. Therefore, we conclude that PLGA/Ca-P cement composites enable tissue ingrowth and show excellent osteocompatibility in weight ratios of 15/85 and 30/70 PLGA/Ca-P cement. In this model, 30/70 PLGA/Ca-P cement composites showed the most favorable biological response.

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PubMed2003

Repair of a proximal femoral bone defect in dogs using a porous surfaced prosthesis in combination with recombinant BMP-2 and a synthetic polymer carrier.

Total hip arthroplasty (THA) has become an almost standard procedure for the treatment of various hip lesions. However, one of the limitations has been the mechanical loosening of the prosthesis, a condition termed peri-prosthetic osteolysis. Consequently, at revision surgery, various grades of bone defect are often noted. Alternative approaches aimed at overcoming this problem have included a special design of the revision prosthesis and allo- or autogeneic bone grafting in combination with or without biomaterials. In a further attempt to address the loosening of the prosthesis, we have combined human bone morphogenetic protein-2, produced by DNA recombination (rhBMP-2) with a new synthetic biodegradable polymer (poly-D,L-lactic-acid-para-dioxanone-polyethyleneglycol block co-polymer; PLA-DX-PEG). We present data on the efficacy of the rhBMP-2 laden prosthesis to reconstruct a bone defect in a canine model. In this model, medial half of the proximal femur was surgically resected to create a bone defect that was repaired with the rhBMP-2/PLA-DX-PEG composite. Twelve weeks after implantation, the original bone defects in the rhBMP-2 treatment groups had been repaired. Thus, this type of 'hybrid' prosthesis may provide a new modality to repair bone defects or restore lost bone mass encountered in revision arthroplasty.

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PubMed2003

Failure to induce supracrestal bone growth between and around partially inserted titanium implants using bone morphogenetic protein (BMP): an experimental study in dogs.

The effect of bone morphogenetic protein on supracrestal bone growth around partially inserted implants in a dog model is described. The lower premolar teeth (P1, P2, P3 and P4) were extracted on both sides of the mandible in six dogs. At a surgical exposure 12 weeks later, two 10-mm turned titanium implants were partially inserted, approximately 15 mm apart, in the areas of the P1 and P3 in each side of the mandible, allowing five threads to protrude from the bone crest. A titanium mesh was fastened to the coronal aspect of the two fixtures and the space beneath the mesh was filled with bone morphogenetic protein (S300 BMP) in combination with an insoluble bone matrix carrier, or with the carrier alone. The mesh was covered with an ePTFE membrane. Thus, a space for potential bone formation was created between the two implants. The surgical flaps were coronally positioned and secured with vertical mattress sutures. After 16 weeks of healing, biopsy specimens were retrieved and examined histologically. Bone was not formed around the protruding implants or in the created space between the implants in any case. The carrier was incompletely resorbed. We conclude that supracrestal bone growth beyond the crestal limit with or without BMP in such a large space as in this experimental design may not be possible.

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PubMed2004

[Biologic tissue response to sutures].

The search for the ideal suture material has continued for decades. Implantation of foreign materials, including surgical sutures causes cellular response. Use of materials of natural origin is connected with a more pronounced reaction than that caused by synthetic sutures. The above review summarizes properties of suture materials that may be useful for choosing indication of the appropriate material in varying surgical situations.

Absorbable Implants↗

PubMed2005

Histological analysis of regeneration of temporomandibular joint discs in rabbits by using a reconstituted collagen template.

The aim of this study was to design a biodegradable implant, in the form of a reconstituted collagen template in order to promote and support regeneration of the temporomandibular joint disc. Bovine collagen (Major Type I) was pepsinized, reduced by beta-mercaptoethanol, and reconstituted by glutaraldehyde. The reconstitution of the collagen increased the resistance to biological degradation by collagenase, optimized the pore size and possessed maximum biological activity for tissue regeneration. Forty-four New Zealand rabbits underwent either sham surgical procedures or partial temporomandibular joint discectomy. In animals that underwent partial discectomy, the discs were replaced by either reconstituted collagen templates or subdermal grafts. Some of the surgerized animals did not receive any type of implant or disc substitute. Gross and histological examination of the surgerized temporomandibular joints was carried out at 1-, 2-, and 3-month intervals after surgery on the selected groups of animals. Marked arthritic changes were observed after 3 months in the partially discectomized joints without implantation. In contrast, the discs, which received a reconstituted collagen template or subdermal graft exhibited regeneration and nearly normal morpology. No foreign body response was observed in experimental groups 3 months after implantation. This study demonstrated that the reconstituted collagen did as well as subdermal grafts in supporting and facilitating regeneration of the disc and the former was found to have some advantages over the latter.

Absorbable Implants↗

PubMedDate not supplied

Manufacturing techniques of biodegradable implants intended for intraocular application.

Polylactic acid and polylactic-co-glycolic acid are biocompatible and biodegradable polymers with wide utility for the design of controlled release systems for drugs. Regarding intraocular application, polymeric sustained-drug release systems are being studied to treat vitreoretinal diseases. Our work aimed to compare the influence of two implant manufacturing techniques, compression and hot molding, on the in vitro degradation of the polymeric matrices and on the release of dexamethasone acetate. The results showed that the manufacturing technique highly influences degradation and drug release processes. The compressed systems degraded faster and allowed one faster release of the drug.

Absorbable Implants↗

PubMedDate not supplied

Laboratory and field evaluation of biodegradable polyesters for sustained release of isometamidium and ethidium.

An overview is presented of the results obtained with biodegradable sustained release devices (SRDs) containing a mixture of polymers and either isometamidium (ISMM) or ethidium. Under controlled laboratory conditions (monthly challenge with tsetse flies infected with Trypanosoma congolense) the protection period in SRD treated cattle could be extended by a factor 2.8 (for ethidium) up to 4.2 (for ISMM) as compared to animals treated intramuscularly with the same drugs. Using a competitive drug ELISA ISMM concentrations were detected up to 330 days after the implantation of the SRDs, whereas after i.m. injection the drug was no longer present three to four months post treatment. Two field trials carried out in Mali under heavy tsetse challenge showed that the cumulative infection rate was significantly lower in the ISMM-SRD implanted cattle than in those which received ISMM intramuscularly. Using ethidium SRD, however, contradictory results were obtained in field trials in Zambia and in Mali. The potential advantages and inconvenients of the use of SRDs are discussed and suggestions are made in order to further improve the currently available devices.

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PubMed2003

[A degradable artificial nerve guide to bridge peripheral nerve defects].

The standard technique for bridging a peripheral nerve defect is an autologous nerve graft if the nerve ends cannot be sutured. Recent evidence indicates that an alternative procedure-application of a degradable nerve guide-may be feasible. Currently the use of such a degradable nerve guide for the recovery of peripheral nerve defects in the hand is being tested in a multicenter trial. Conventional suturing as well as autologous nerve grafting are accepted methods in the control group within the protocol of the multicenter study. In the first two patients to receive the implant, a 28-year-old man and a 50-year-old women with tendon and nerve injury due to glass cuts, the operation was technically successful. Functional nerve recovery will be assessed in due course.

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PubMed2003

Creating bioabsorbable Schwann cell coated conduits through tissue engineering.

Enormous effort has been devoted to the generation of a synthetic guidance conduit for nerve repair instead of utilizing autograft. Several studies show neural guidance conduit is more effective when coated with Schwann cells. In this study, we synthesized bioabsorbable conduit consist of L-lactide and epsilon-caprolactone which was useful clinically and examined adhesion of Schwann cells to bioabsorbable conduits. In vivo studies were done in which these polymer conduits coated with Schwann cells were implanted across a 12 mm gap in the rat sciatic nerve. Silicone conduits were implanted across the same gap as control. At 12 weeks, axonal regeneration was observed in the midconduit region of these polymer conduits and was not in control. This study assesses the feasibility of a tissue engineering approach to constructing bioabsorbable conduits coated with Schwann cells.

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PubMed2001

Enhancement of bone regeneration using resorbable ceramics and a polymer-ceramic composite material.

The aim of this experimental study was to evaluate the use of resorbable implants for the repair of nonloaded skeletal defects. Porous ceramic implants of alpha-TCP, of glass-ceramic, and of solid composite implants of glass-ceramic/polylactic acid 8 mm in diameter and 2 mm in thickness were fabricated and implanted pressfit into biparietal, full-thickness defects of the calvaria of 60 adult rats. Twenty rats received unfilled defects and served as controls. Fluorochrome labeling of bone formation was performed during the observation period. Five animals from each group were evaluated after 6, 13, 26, and 52 weeks. The control defects showed incomplete regeneration, with bone formation extending 1.66 mm, on average, into the defect after 52 weeks. In the group of alpha-TCP implants, histologic evaluation indicated that the bone formed during initial stages had undergone resorption later on, so that bone repair after 52 weeks was not significantly enhanced, with an average depth of 1.83 mm of bone ingrowth. The glass-ceramic implants exhibited extensive bone formation and nearly complete repair of the calvarial defect, with 3.90 mm of bone ingrowth into the implant pores. Degradation of the ceramic was nearly complete, with a few remaining particles surrounded by soft tissue. The composite implants showed a negligible bone ingrowth of 0.63 mm, on average. Soft tissue had invaded the polylactic acid implant body, but no bone formation had taken place at the surface of the embedded ceramic particles. Degradation of the polymer was not complete after 52 weeks. It is concluded that the balance between degradation and bone formation is delicate and that chemical events and cellular reaction during degradation may counteract complementary bone ingrowth.

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PubMed2005

A new anti-adhesion film synthesized from polygalacturonic acid with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide crosslinker.

The most commonly used anti-adhesion device for separation and isolation of wounded tissues after surgery is the polymeric film. In this study, a new anti-adhesion membrane based on polygalacturonic acid (PGA) has been synthesized, and its biocompatibility and anti-adhesion capabilities evaluated. The PGA film was reacted with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) to obtain a cross-linked PGA film with an 86% gel content and a 47% water content when immersed in aqueous solution. This PGA-EDC film did not show any evidence of cytotoxic effects since it did not induce any significant increase in cytoplasmic LDH release from the L929 cells in contact with it. When implanted into rats, the PGA-EDC film exhibited a most promising anti-adhesion potential with only 1 out of 21 rats operated not forming any tissue adhesion. This anti-adhesion potency is significantly higher than that found for Seprafilm and untreated rats where 11 out of 21 and 18 out of 21 operated rats, respectively, formed tissue adhesions. The implanted PGA-EDC film did not elicit any acute inflammatory reaction based on the results of histological examination and peritoneal fluid leukocytes analysis. The newly developed PGA-EDC film thus has a great potential for future use in clinical applications.

Absorbable Implants↗

PubMed2005

Efficacy of bioabsorbable antibiotic containing bone screw in the prevention of biomaterial-related infection due to Staphylococcus aureus.

Impregnation of antimicrobial agents within biodegradable orthopedic implants provides a possibility for local antimicrobial prophylaxis of biomaterial-related infections. The objective of this study was to evaluate the efficacy of a bioabsorbable ciprofloxacin containing bone screw (Ab-PLGA) in the prevention of biomaterial-related infection due to Staphylococcus aureus in a rabbit model. Animals in Group I (n=8) received a Ab-PLGA screw contaminated with S. aureus, while animals in Group II (n=8) received a stainless steel (SS) screw contaminated with S. aureus. In two negative control groups, the animals received a Ab-PLGA screw (Group III, n=4) or a SS screw (Group IV, n=4) without bacterial contamination. 18F-FDG-PET imaging, performed at 6 weeks, was applied as a novel quantitative in vivo imaging modality of implant-related infection. Infection was verified by swab cultures, direct cultures of the retrieved implant, and quantitative cultures of pulverized bone. The concentrations of ciprofloxacin in serum and local bone tissue were determined by a high performance liquid chromatographic (HPLC) method with fluorescence (FLD) detection. In the group of contaminated Ab-PLGA screws, all cultures were negative. In the group of contaminated SS screws, all cultures of retrieved implants and six cultures out of eight of pulverized bone were positive for inoculated S. aureus. In negative control groups, all cultures were negative except one contaminant (S. cohnii) found in a SS screw culture. Verified infection of contaminated SS screws was collaborated by the increased 18F-FDG-PET uptake (P=0.004 compared with the group of contaminated Ab-PLGA screws). The mean bone tissue concentration of ciprofloxacin varied from 2.54 to 0.83 microg/g bone as a function of distance from the implantation site. The serum concentration of ciprofloxacin remained undetectable and below the resolution of the analytic method (<5.0 ng/ml). This study confirmed the in vivo efficacy of bioabsorbable antibiotic containing bone screw in the prevention of biomaterial-related infection due to S. aureus.

Absorbable Implants↗

PubMed2003

Deproteinized bovine bone and gentamicin as an adjunct to GTR in the treatment of intrabony defects: a randomized controlled clinical study.

OBJECTIVES: To evaluate whether Bio-Oss used as an adjunct to guided tissue regeneration (GTR) improves the healing of 1- or 2-wall intrabony defects as compared with GTR alone, and to examine whether impregnation of Bio-Oss with gentamicin may have an added effect. MATERIAL AND METHODS: Sixty patients, with at least one interproximal intrabony defect with probing pocket depth (PPD) > or =7 mm and radiographic evidence of an intrabony component (IC) > or =4 mm, were treated at random with either a resorbable membrane (GTR), a resorbable membrane in combination with Bio-Oss impregnated with saline (DBB-), a resorbable membrane in combination with Bio-Oss impregnated with gentamicin (DBB+), or with flap surgery (RBF). RESULTS: All treatment modalities resulted in statistically significant clinical improvements after 1 year. Defects treated with GTR alone presented a probing attachment level (PAL) gain of 2.9 mm, a residual PPD (PPD12) of 4.9 mm, a radiographic bone level (RBL) gain of 3.1 mm, and a residual IC (IC12) of 2.7 mm. GTR combined with Bio-Oss did not improve the healing outcome (PAL gain: 2.5 mm; PPD12: 4.9 mm; RBL gain: 2.8 mm; IC12: 3.3 mm). Impregnation of the Bio-Oss with gentamicin 2% mg/ml resulted in clinical improvements (PAL gain: 3.8 mm; PPD12: 4.2 mm; RBL gain: 4.7 mm; IC12: 2.1 mm), superior to those of the other treatment modalities, but the difference was not statistically significant. Defects treated with only flap surgery showed the most inferior clinical response (PAL gain: 1.5 mm; PPD12: 5.1 mm; RBL gain: 1.2 mm; IC12: 4.2 mm) of all groups. CONCLUSION: The results failed to demonstrate an added effect of Bio-Oss implantation in combination with GTR on the healing of deep interproximal 1- or 2-wall, or combined 1- and 2-wall intrabony defects compared with GTR alone. Local application of gentamicin, on the other hand, improved the treatment outcome but not to an extent that it was statistically significant.

Absorbable Implants↗

PubMed1999

The effect of pentosan polysulphate on bone healing of rat cranial defects.

The purpose of the study was to determine the efficacy of pentosan polysulphate, used in combination with guided bone regeneration on rat skull defects. The study was conducted on 45 adult Wistar rats. On each animal two symmetrical 6 mm wide, full-thickness, skull defects were created in the parietal regions. The right defect was chosen as the experimental site and the left one was left empty to provide a control. Each experimental site was covered by an inner and outer polytetrafluoroethylene membrane. The 45 rats were divided into 3 groups: in group I (n = 15), carboxymethyl cellulose, used as a delivery vehicle, was injected between the two membranes; in group II (n = 15), 1 mg of pentosan polysulfate was added to the carboxymethyl cellulose vehicle; in group III (n = 15), purified micronized eggshell powder was added to the mixture of pentosan polysulfate and carboxymethyl cellulose between the two membranes. In each group, the animals were sacrificed at 42 days. The harvested specimens were processed for contact radiography and standard histological examination. The results were assessed by a Fisher's exact test. All animals, except one, healed uneventfully. In group I, partial bone healing was observed in 14 out of 15 animals. In group II, partial bone healing was observed in 13 out of 15 animals, and complete bone healing in 1 out of 15 cases. In group III, partial resorption of the eggshell implant was observed with a partial bone healing in only 2 cases (P < 0.001). In conclusion, significant bone regeneration was observed with the membranes alone. The use of pentosane polysulphate did not result in additional bone gain. The use of particulate material as a space maintainer is also questionable.

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PubMed2004

Drug-eluting bioabsorbable magnesium stent.

Current stent technology is based on the use of permanent implants that remain life long in the vessel wall, far beyond the time required for the prosthesis to accomplish its main goals of sealing dissection and preventing wall recoil. With the possibility to implant long vessel segments using antiproliferative drugs to prevent restenosis, the practice of transforming the coronary vessels into stiff tubes with a full metal jacket covering all side branches and being unable to adjust to the long-term wall changes, including wall remodeling with lumen ectasia becomes a serious concern. In this article, we describe the first biodegradable stent based on a magnesium alloy that allows controlled corrosion with release to the vessel wall and the blood stream of a natural body component such as magnesium with beneficial antithrombotic, antiarrhythmic, and antiproliferative properties. We also discuss the animal experiments and the initial clinical applications in 20 patients with implants below the knee, with final results soon to be released, and the plans for the first coronary study. The results of these last two studies will indicate whether the absence of a permanent implant and the antiproliferative properties shown in animals are sufficient to prevent the restenotic process in humans or whether the prosthesis must be modified by adding the biodegradable coating with conventional antiproliferative drugs.

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PubMed2006

An allogenic cell-based implant for meniscal lesions.

BACKGROUND: Meniscal tears in the avascular zones do not heal. Although tissue-engineering approaches using cells seeded onto scaffolds could expand the indication for meniscal repair, harvesting autologous cells could cause additional trauma to the patient. Allogenic cells, however, could provide an unlimited amount of cells. HYPOTHESIS: Allogenic cells from 2 anatomical sources can repair lesions in the avascular region of the meniscus. STUDY DESIGN: Controlled laboratory study. METHODS: Both autologous and allogenic chondrocytes were seeded onto a Vicryl mesh scaffold and sutured into a bucket-handle lesion created in the medial menisci of 17 swine. Controls consisted of 3 swine knees treated with unseeded implants and controls from a previous experiment in which 4 swine were treated with suture only and 4 with no treatment. Menisci were harvested after 12 weeks and evaluated histologically for new tissue and percentage of interface healing surface; they were also evaluated statistically. RESULTS: The lesions were closed in 15 of 17 menisci. None of the control samples demonstrated healing. Histologic analysis of sequential cuts through the lesion showed formation of new scar-like tissue in all experimental samples. One of 8 menisci was completely healed in the allogenic group and 2 of 9 in the autologous group; the remaining samples were partially healed in both groups. No statistically significant differences in the percentage of healing were observed between the autologous and allogenic cell-based implants. CONCLUSION: Use of autologous and allogenic chondrocytes delivered via a biodegradable mesh enhanced healing of avascular meniscal lesions. CLINICAL RELEVANCE: This study demonstrates the potential of a tissue-engineered cellular repair of the meniscus using autologous and allogenic chondrocytes.

Absorbable Implants↗

PubMed2004

Microscopic evaluation of the natural coral (Porites spp.) post-implantation in sheep femur.

The study was carried out with the aim to evaluate natural coral (Porites spp.) implanted in sheep femur microscopically. Twelve adult, male sheep were used in this study. The defect area was implanted with coral and monitored for up to 12 weeks. The sheep were euthanased at 2,4,8, and 12 weeks post-implantation. Microscopically, natural coral implanted into bone tissue have shown gradual resorption and progressively replaced by new bone. At 12 weeks post-implantation, the implanted site was almost completely surrounded by mature bone. The results showed that natural coral was found to be a biodegradable and osteo-conductive biomaterial, which acted as a scaffold for a direct osteoblastic apposition.

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PubMed2007

Combined radiofrequency ablation and doxorubicin-eluting polymer implants for liver cancer treatment.

Previously, biodegradable polymer implants (polymer millirods) to release chemotherapeutic agents directly into tumors have been developed. The purpose of this study is to evaluate local drug distribution from these implants in liver tumors treated with radiofrequency (RF) ablation and determine if the implants provide a therapeutic improvement over RF ablation alone. Cylindrical implants were fabricated using 65% poly(D,L-lactide-co-glycolide) (PLGA), 21.5% NaCl, and 13.5% doxorubicin. Control or drug-containing millirods were implanted inside VX2 liver tumors (11 mm diameter) in rabbits after RF ablation. Therapeutic efficacy was assessed 4 and 8 days after treatment using tumor size, histology, and fluorescence measurement of drug distribution. Tumors in both test groups recurred at the boundary of the ablated region. Therapeutic doxorubicin concentrations were found in more than 80% of the ablated area, but concentrations declined rapidly at the boundary between normal and ablated tissue. This region was characterized by a developing fibrous capsule with resolving inflammation, which restricted drug transport out of the ablated zone. The intratumoral doxorubicin implants delivered high concentrations of drug within the ablated region but only limited amounts outside the ablation zone. Future studies will focus on overcoming the fibrotic transport barrier and enhancing drug delivery to the periphery of the ablation region to prevent tumor progression.

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