Biomaterials.info - Resources for Engineers

Record 2081 to 2100

Focal adhesion quantification - a new assay of material biocompatibility? Review
Owen, G. R., D. O. Meredith, et al. (2005), Eur Cell Mater 9: 85-96; discussion 85-96.
Abstract: The development of novel synthetic biomaterials is necessitated by the increasing demand for accelerated healing of tissues following surgical intervention. Strict testing of such materials is necessary before application. Currently, before any material can be marketed, approval by regulatory organisations such as the FDA is required. Presently, in vitro testing is performed as a prerequisite to in vivo evaluation. The in vitro techniques currently employed do not reflect the progress in our understanding of extra and intra-cellular processes, with far more sensitive in vitro evaluations now available. Obtaining quantifiable data is increasingly relevant to evaluating events occurring in vivo. Quantifying cell adhesion to surfaces provides some of this data as an initial assessment method. Major developments in this field are occurring but many investigators still use less than optimal methods for assessing biomaterials. The relevance of using cell adhesion assays to help determine biomaterial biocompatibility is reviewed. Additionally, current in vitro methods of evaluating biomaterials are discussed in the context of novel testing concepts developed by the authors.

Folate conjugated fluorescent silica nanoparticles for labeling neoplastic cells
Santra, S., B. Liesenfeld, et al. (2005), J Nanosci Nanotechnol 5(6): 899-904.
Abstract: We describe a novel technique of using fluorescent silica nanoparticles (FSNPs) to detect over-expressed folate receptors, as typical for certain malignancies (metastatic adenocarcinoma, pituitary adenoma and others). Using Stober's method with some modification, 135 nm size FSNPs were synthesized by a hydrolysis and co-condensation reaction of tetraethylorthosilicate (TEOS), fluorescein labeled (3-aminopropyl)triethoxysilane (APTS) and a water-dispersible silane reagent, (3-trihydroxysilyl)propyl methylphosphonate (THPMP) in the presence of ammonium hydroxide catalyst. Folic acid (folate) was covalently attached to the amine modified FSNPs by a carbodiimide coupling reaction. The characterization of folate-FSNPs was performed using a variety of spectroscopic (UV-VIS and fluorescence), microscopic (transmission electron microscopy, TEM) and light scattering techniques. Folate conjugated FSNPs were then targeted to human squamous cancer cells (SCC-9). Laser scanning confocal images successfully demonstrated the labeling of SCC-9 cells and the efficacy of FSNP based detection system.

Force measurement for antigen-antibody interaction by atomic force microscopy using a photograft-polymer spacer
Idiris, A., S. Kidoaki, et al. (2005), Biomacromolecules 6(5): 2776-84.
Abstract: To determine the intermolecular force on protein-protein interaction (PPI) by atomic force microscopy (AFM), a photograft-polymer spacer for protein molecules on both surfaces of the substrate and AFM probe tip was developed, and its effectiveness was assessed in a PPI model of a pair of human serum albumin (HSA) and its monoclonal antibody (anti-HSA). A carboxylated photoiniferter, N-(dithiocarboxy)sarcosine, was derivatized on both surfaces of the glass substrate and AFM probe tip, and subsequently water-soluble nonionic vinyl monomers, N,N-dimethylacrylamide (DMAAm), were graft-polymerized on them upon ultraviolet light irradiation. DMAAm-photograft-polymerized spacers with carboxyl groups at the growing chain end but with different chain lengths on both surfaces were prepared. The proteins were covalently bound to the carboxyl terminus of the photograft-polymer chain using a water-soluble condensation agent. The effects of the graft-spacer length on the profile of the force-distance curves and on the unbinding characteristics (unbinding force and unbinding distance) were examined in comparison with those in the case of the commercially available poly(ethylene glycol) (PEG) spacer. The frequency of the nonspecific adhesion force profile was markedly decreased with the use of the photograft spacers. Among the force curves detected, a high frequency of single-peak curves indicating the unbinding process of a single pair of proteins and a very low frequency of multiple-peak profiles were observed for the photograft spacers, regardless of the graft chain length, whereas a high frequency of no-force peaks was noted. These observations were in marked contrast with those for the PEG spacer. The force peak values determined ranged from 88 to 94 pN, irrespective of the type of spacer, while the standard deviation of force distribution observed for the photograft spacer was lower than that for the PEG spacer, indicating that the photograft spacers provide a higher accuracy of force determination.

Formaldehyde from POM brackets
Zilberman, U. (2005), Am J Orthod Dentofacial Orthop 128(2): 147-8; author reply 148-9.

Formation and resolution of ankylosis under application of recombinant human bone morphogenetic protein-2 (rhBMP-2) to class III furcation defects in cats
Takahashi, D., T. Odajima, et al. (2005), J Periodontal Res 40(4): 299-305.
Abstract: OBJECTIVES: Periodontal regeneration under application of bone morphogenetic protein (BMP) is compromised by ankylosis. Ankylosis disappearance following application of BMP has been observed in the case of a small defect, which might be beneficial change for periodontal regeneration. However, the histological observation of ankylosis disappearance has not been demonstrated in a large defect. The purpose of this present study was to confirm resolution of ankylosis during periodontal regeneration by recombinant human BMP-2 (rhBMP-2) applied to class III furcation defects. MATERIAL AND METHODS: Class III furcation defects were created in the premolars of six adult cats. The rhBMP-2 material, prepared by applying rhBMP-2 to a combination of polylactic acid-polygricolic copolymer and gelatin sponge (PGS; 0.33 microg rhBMP-2/mm(3) PGS) or control material containing only PGS, was implanted into each defect. The cats were killed at 3, 6 or 12 weeks after surgery and serial sections were prepared for histological and histometrical observation. RESULTS: Ankylosis was observed in some of the rhBMP-2/PGS group at 3 and 6 weeks, but not at 12 weeks. At 6 weeks, osteoclast-like cells were visible in the rhBMP-2/PGS group with ankylosis. Residual PGS was evident between the bone and root surface in the rhBMP-2/PGS group without ankylosis at 3 weeks. CONCLUSIONS: Resolution of ankylosis by osteoclast-like cells possibly occurred under application of rhBMP-2. Residual PGS might play an important role in preventing ankylosis formation.

Formation characterization of hydroxyapatite on titanium by microarc oxidation and hydrothermal treatment
Liu, F., Y. Song, et al. (2005), J Biosci Bioeng 100(1): 100-4.
Abstract: Microarc oxidation (MAO) was performed on titanium in an electrolyte containing calcium glycerphosphate (Ca-GP) and calcium acetate (CA) using a direct current power supply. It was found that the MAO method is suitable forming a ceramic coating containing Ca and P using titanium, and that films display a porous and rough structure on their surface. Samples with a Ca/P ratio of 1.71 were hydrothermally treated in water solution whose pH was adjusted to 7.0-11.0 by adding NaOH at 190 degrees C for 10 h in an autoclave. Hydroxyapatite crystals were precipitated on the film surface after the hydrothermal treatment, and the amount of hydroxyapatite precipitated increased with increasing pH of water solution. The oxide film composition was semiquantitatively analyzed with an electron probe microanalyzer. The microstructures on the sample surfaces were observed by scanning electron microscopy before and after the hydrothermal treatment. The topography of the oxide film was imaged with an atomic force microscope. Its cross section was observed by scanning electron microscopy after being coated with a thin Au film. The surface structures of the films were analyzed by X-ray diffraction.

Formation of core-shell type biodegradable polymeric micelles from amphiphilic poly(aspartic acid)-block-polylactide diblock copolymer
Arimura, H., Y. Ohya, et al. (2005), Biomacromolecules 6(2): 720-5.
Abstract: Poly(aspartic acid)-block-polylactide diblock copolymers (PAsp-b-PLAs) having both hydrophilic and hydrophobic segments of various lengths were synthesized. These PAsp-b-PLA diblock copolymers formed polymeric micelles consisting of a hydrophobic PLA core and a hydrophilic, pH-sensitive PAsp shell in aqueous solution. The effects of the segment length of both the PLA and the PAsp portions and the pH of the solution on the shapes and sizes of the PAsp-b-PLA polymeric micelles were investigated. The results indicated a balance between the effects of electrostatic repulsion, hydrogen bonding in the PAsp shell layer, and hydrophobic interactions in the PLA core determine the sizes of the PAsp-b-PLA polymeric micelles. Moreover, the PAsp-b-PLA polymeric micelles did not possess any cytotoxic activity against L929 fibroblast cells. The obtained polymeric micelle should be useful for biodegradable biomedical materials such as drug delivery vehicle.

Formation of embryoid bodies by mouse embryonic stem cells on plastic surfaces
Konno, T., K. Akita, et al. (2005), J Biosci Bioeng 100(1): 88-93.
Abstract: Mouse embryonic stem (ES) cells were cultured on artificial polymeric biomembranes with a phospholipid polymer (phosphatidylcholine, PC) surface. ES cells aggregated to form an embryoid body (EB) on the PC surface immediately after seeding. Single EBs formed on the PC surface after 3 d, and their size was depended on the initial number of cells that were seeded. In contrast, many small EBs with a nonuniform shape formed on a conventional hydrophobic nontreated polystyrene surface. RT-PCR assays of the EBs indicated that cell-cell interactions were enhanced in EBs that formed on the PC surface compared with EBs that formed on the polystyrene surface. The transcription factor Pax6, which is a marker of the differentiation of ES cells to neurons, was not expressed in EBs that formed on the PC surface; however, EBs that formed on the polystyrene surface did express Pax6, indicating that they were undergoing differentiation into neurons. When stimulated with retinoic acid (an inducer of differentiation into neurons), EBs on the PC surface expressed Pax6. We also observed that the adhesion of ES cells to the PC surface was reduced. Thus, the formation of large EBs on the PC surface was due to enhanced cell-cell interaction and inhibition of nonspecific differentiation to neurons.

Formation of focal contacts by osteoblasts cultured on orthopedic biomaterials
Puleo, D. A. and R. Bizios (1992), J Biomed Mater Res 26(3): 291-301.
Abstract: The nature of the contact sites formed during the adhesion of osteoblasts to orthopedic implant materials was investigated by fluorescence microscopy. More specifically, the cytoskeletal organization of and the focal contact formation by neonatal rat calvarial osteoblasts attaching to and spreading on 316L stainless steel, Ti-6Al-4V, Co-Cr-Mo, Synamel (hydroxyapatite), alumina, and borosilicate glass were examined. Focal contacts are regions where the plasma membrane approaches the substrate to within 10-15 nm and where bundles of cytoskeletal microfilaments terminate. Fluorescent-labeling of F-actin-containing microfilaments demonstrated a typical sequence of events as rounded, suspended osteoblasts spread onto the substrates. Immunofluorescent-labeling of the protein vinculin, which is found at the cytoplasmic face of focal contacts, initially showed the formation of streak-like focal patches. On the biomaterials, the vinculin staining subsequently extended up and along, but ventral to, the microfilament bundles. The fibrillar patterns observed at later times may evidence the formation of extracellular matrix contacts.

Formation of hydroxyapatite/biopolymer biomaterials. I. Microporous composites from solidified emulsions
Ritzoulis, C., N. Scoutaris, et al. (2004), J Biomed Mater Res A 71(4): 675-84.
Abstract: Microporous materials of controlled pore size were prepared by means of a three-step process involving in situ hydrochemical preparation of a hydroxyapatite-sodium caseinate (HAp-Cas) composite material into a Cas-stabilized oil-in-water emulsion, subsequent concentration and drying of the composite-emulsion, and removal of the oil by means of supercritical carbon dioxide extraction. The resulting composite materials were found to contain micron-sized pores in the space previously occupied by the oil droplets. In order to elucidate the structure of the resulting porous product, its Cas-HAp composition was studied in the corresponding nonporous composite material. In nonporous samples, a protein assay by means of visible spectroscopy suggested equilibrium between the Cas that was trapped in the composite structure and the Cas that remained in solution after precipitation. This observation was confirmed by separate thermogravimetric analysis and Fourier transform IR spectroscopy measurements.

Formation of Propionibacterium acnes biofilms on orthopaedic biomaterials and their susceptibility to antimicrobials
Ramage, G., M. M. Tunney, et al. (2003), Biomaterials 24(19): 3221-7.
Abstract: Failure to treat and eradicate prosthetic hip infection with systemic antibiotic regimens is usually due to the fact that the infection is associated with biofilm formation and that bacterial cells growing within a biofilm exhibit increased resistance to antimicrobial agents. In this in vitro study, we investigated the susceptibility of prosthetic hip Propionibacterium acnes and Staphylococcus spp. isolates growing within biofilms on polymethylmethacrylate (PMMA) bone cement to a range of antibiotics. All P. acnes isolates in the biofilm mode of growth demonstrated considerably greater resistance to cefamandole, ciprofloxacin and vancomycin. In contrast, only four of the eight P. acnes isolates demonstrated an increase in resistance to gentamicin. All ten Staphylococcus spp. isolates in the biofilm mode of growth exhibited large increases in resistance to gentamicin and cefamandole with eight of the ten isolates also exhibiting an increase in resistance to vancomycin. However, only three of the ten Staphylococcus spp. isolates exhibited an increase in resistance to ciprofloxacin. Biofilms were also formed on three different titanium alloys and on PMMA bone cement using P. acnes, Staphylococcus epidermidis and Staphylococcus aureus strains to determine if the underlying biomaterial surface had an effect on biofilm formation and the antimicrobial susceptibility of the bacteria growing within biofilms. Although differences in the rate at which the three strains adhered to the different biomaterials were apparent, no differences in biofilm antibiotic resistance between the biomaterials were observed. In the light of these results, it is important that the efficacy of other antibiotics against P. acnes and Staphylococcus spp. prosthetic hip isolates growing within biofilms on orthopaedic biomaterials be determined to ensure optimal treatment of orthopaedic implant infection.

Formation of TiO2 nanoparticles by reactive-layer-assisted deposition and characterization by XPS and STM
Song, Z., J. Hrbek, et al. (2005), Nano Lett 5(7): 1327-32.
Abstract: Stoichiometric TiO2 nanoparticles (1-5 nm) were prepared by reactive-layer-assisted deposition (RLAD), in which Ti was initially deposited on a multilayer of H2O (or NO2) on a Au(111) substrate at approximately 90 K. The composition and atom-resolved structure of the nanoparticles were studied by XPS and STM. The approximately 5 nm TiO2 particles had either a rutile or anatase phase with various crystal facets. STS of the nanoparticles suggests size-dependent electronic structure. These well-defined nanoparticles can be used in molecular-level studies of the reactions and mechanisms of photocatalytic processes on TiO2 nanoparticle surfaces.

Formulation and evaluation of novel tableted chitosan microparticles for the controlled release of clozapine
Agnihotri, S. A. and T. M. Aminabhavi (2004), J Microencapsul 21(7): 709-18.
Abstract: Controlled release formulations of clozapine microparticulated tablets were prepared by using chitosan. Microparticles were characterized for particle size and size distribution. Microparticles were compressed into tablets using the directly compressible excipients. SEM photographs of the fractured part of the tablet revealed the presence of discrete particles in the tablets, suggesting that the system chosen is ideal for tableting. Drug release from the tableted microparticles exhibited an initial burst effect, but the release decreased with increasing extent of cross-linking. Tablets were coated with chitosan or cellulose acetate, which significantly lowered the initial burst effect when compared to uncoated tablets. Drug release from chitosan-coated tablets was slightly higher than the tablets coated with cellulose acetate. Tablets prepared were effective in delivering clozapine over a period of 12 h.

Formulation and process parameters affecting protein encapsulation into PLGA microspheres during ethyl acetate-based microencapsulation process
Cho, M. and H. Sah (2005), J Microencapsul 22(1): 1-12.
Abstract: The objective of this study was to investigate formulation and process parameters affecting protein encapsulation into PLGA microspheres during an ethyl acetate-based double emulsion microencapsulation process. Lysozyme was used as a model protein throughout this study. An aqueous lysozyme solution was emulsified in ethyl acetate containing 0.6 approximately 1.2 g PLGA75: 25. The primary emulsion was then transferred quickly to an aqueous phase to make a water-in-oil-in-water emulsion. Ethyl acetate quenching was performed on the double emulsion stirred for 5, 15, 30 or 45 min. The resultant microspheres were further hardened, collected and dried overnight under vacuum. The bicinchoninic acid assay was carried out to determine the quantity of lysozyme present in the aqueous continuous phase and inside the microspheres. While the primary emulsion was stirred without quenching, lysozyme in the inner water phase continued diffusing across the ethyl acetate phase into the aqueous continuous phase. Emulsion droplets were also broken into smaller ones with ongoing stirring; this event also contributed to lysozyme leaking out of the inner water phase. The amount of lysozyme leaching to the aqueous continuous phase ranged from 4.79 +/- 2.1 to 51.9 +/- 5.3% under the experimental condition. Ethyl acetate quenching stopped the primary emulsion droplets from being fragmented into smaller ones and caused PLA75: 25 precipitation to form microspheres. As a result, the rate of ethyl acetate removal influenced lysozyme encapsulation efficiency, as well as microsphere size. Depending on the timing of ethyl acetate quenching, lysozyme encapsulation efficiencies were found to be 9.89 +/- 4.53 approximately 75.82 +/- 6.55%. Optimization of the onset of ethyl acetate quenching and formulations could permit attainment of a desirable protein encapsulation efficiency.

Founder's award for the 27th Annual Meeting of the Society for Biomaterials, St. Paul, MN, April 24-9, 2001. The teaching of biomaterials
Hulbert, S. F. (2001), J Biomed Mater Res 57(4): 475-6.

Founder's Award, 25th Annual Meeting of the Society for Biomaterials, perspectives. Providence, RI, April 28-May 2, 1999. Tissue heart valves: current challenges and future research perspectives
Schoen, F. J. and R. J. Levy (1999), J Biomed Mater Res 47(4): 439-65.
Abstract: Substitute heart valves composed of human or animal tissues have been used since the early 1960s, when aortic valves obtained fresh from human cadavers were transplanted to other individuals as allografts. Today, tissue valves are used in 40% or more of valve replacements worldwide, predominantly as stented porcine aortic valves (PAV) and bovine pericardial valves (BPV) preserved by glutaraldehyde (GLUT) (collectively termed bioprostheses). The principal disadvantage of tissue valves is progressive calcific and noncalcific deterioration, limiting durability. Native heart valves (typified by the aortic valve) are cellular and layered, with regional specializations of the extracellular matrix (ECM). These elements facilitate marked repetitive changes in shape and dimension throughout the cardiac cycle, effective stress transfer to the adjacent aortic wall, and ongoing repair of injury incurred during normal function. Although GLUT bioprostheses mimic natural aortic valve structure (a) their cells are nonviable and thereby incapable of normal turnover or remodeling ECM proteins; (b) their cuspal microstructure is locked into a configuration which is at best characteristic of one phase of the cardiac cycle (usually diastole); and (c) their mechanical properties are markedly different from those of natural aortic valve cusps. Consequently, tissue valves suffer a high rate of progressive and age-dependent structural valve deterioration resulting in stenosis or regurgitation (>50% of PAV overall fail within 10-15 years; the failure rate is nearly 100% in 5 years in those <35 years old but only 10% in 10 years in those >65). Two distinct processes-intrinsic calcification and noncalcific degradation of the ECM-account for structural valve deterioration. Calcification is a direct consequence of the inability of the nonviable cells of the GLUT-preserved tissue to maintain normally low intracellular calcium. Consequently, nucleation of calcium-phosphate crystals occurs at the phospholipid-rich membranes and their remnants. Collagen and elastin also calcify. Tissue valve mineralization has complex host, implant, and mechanical determinants. Noncalcific degradation in the absence of physiological repair mechanisms of the valvular structural matrix is increasingly being appreciated as a critical yet independent mechanism of valve deterioration. These degradation mechanisms are largely rationalized on the basis of the changes to natural valves when they are fabricated into a tissue valve (mentioned above), and the subsequent interactions with the physiologic environment that are induced following implantation. The "Holy Grail" is a nonobstructive, nonthrombogenic tissue valve which will last the lifetime of the patient (and potentially grow in maturing recipients). There is considerable activity in basic research, industrial development, and clinical investigation to improve tissue valves. Particularly exciting in concept, yet early in practice is tissue engineering, a technique in which an anatomically appropriate construct containing cells seeded on a resorbable scaffold is fabricated in vitro, then implanted. Remodeling in vivo, stimulated and guided by appropriate biological signals incorporated into the construct, is intended to recapitulate normal functional architecture.

Founder's Award, Society for Biomaterials. Sixth World Biomaterials Congress 2000, Kamuela, HI,May 15-20, 2000. Really smart bioconjugates of smart polymers and receptor proteins
Hoffman, A. S., P. S. Stayton, et al. (2000), J Biomed Mater Res 52(4): 577-86.
Abstract: Over the past 18 years we have been deeply involved with the synthesis and applications of stimuli-responsive polymer systems, especially polymer-biomolecule conjugates. This article summarizes our work with one of these conjugate systems, specifically polymer-protein conjugates. We include conjugates prepared by random polymer conjugation to lysine amino groups, and also those prepared by site-specific conjugation of the polymer to specific amino acid sites that are genetically engineered into the known amino acid sequence of the protein. We describe the preparation and properties of thermally sensitive random conjugates to enzymes and several affinity recognition proteins. We have also prepared site-specific conjugates to streptavidin with temperature-sensitive polymers, pH-sensitive polymers, and light-sensitive polymers. The preparation of these conjugates and their many fascinating applications are reviewed in this article.

Four years of clinical experience with an adverse reaction unit for dental biomaterials
Vamnes, J. S., G. B. Lygre, et al. (2004), Community Dent Oral Epidemiol 32(2): 150-7.
Abstract: OBJECTIVES: We describe the function of, and results from, the Norwegian National Dental Biomaterials Adverse Reaction Unit after 4 years of activity from 1993 to 1997. METHODS: During this period of time, 296 patients were examined at the unit, which is located at the Dental School, University of Bergen. The most prevalent age group was 40-49 years, and 70% were women. Dental amalgam was the primary reason for referral to the unit for nearly 85% of the patients, followed by metals in crowns and bridges (11%). Materials in removable dentures, resin-based filling materials and cements, endodontic materials, and others, including temporary materials, were also involved. Nearly all (96%) patients reported general subjective symptoms, such as muscle and joint pain, fatigue, and memory problems. Complaints involving the orofacial region (lips, face, temporomandibular joint) and intraoral subjective symptoms were also common. RESULTS: Of the patients who were patch tested with substances in dental materials, 23% were positive to gold, 28% to nickel, 14% to cobalt, 9% to palladium, 6% to mercury, and 8% to one or more components of resin-based materials. Mercury concentrations in blood and urine were statistically higher in the patients with amalgam fillings compared with those without. CONCLUSIONS: Generally, we could not establish a straightforward cause-and-effect relationship between the presence of dental biomaterials and general symptoms. Twenty patients were advised to replace restorative materials because of contact lesions. Another 20 patients were recommended replacement of materials because of allergy verified with positive patch tests. The complex nature of most of the reactions requires a multidisciplinary approach to the care taking of patients who are concerned about reactions from dental materials, particularly amalgam.

Fourier transform infrared imaging for high-throughput analysis of pharmaceutical formulations
Chan, K. L. and S. G. Kazarian (2005), J Comb Chem 7(2): 185-9.
Abstract: Fourier transform infrared (FTIR) spectroscopic imaging with infrared array detectors has recently emerged as a powerful materials characterization tool. We report a novel application of FTIR imaging for high-throughput analysis of materials under controlled environment. This approach combines the use of spectroscopic imaging with an attenuated total reflection (ATR)-IR cell, microdroplet sample deposition system, and a device that controls humidity inside the cell. By this approach, it was possible to obtain "chemical snapshots" from a spatially defined array of many different polymer/drug formulations (more than 100) under identical conditions. This method provides direct measurement of materials properties for high-throughput formulation design and optimization. Simultaneous response (water sorption, crystallization, etc.) of the array of formulations to the environmental parameters was studied. Implications of the presented approach range from studies of smart polymeric materials and sensors to screening of pharmaceuticals and biomaterials.

Four-year follow-up of poly-L-lactic Acid cages for lumbar interbody fusion in goats
van Dijk, M., P. J. van Diest, et al. (2005), J Long Term Eff Med Implants 15(2): 125-38.
Abstract: BACKGROUND: New applications of bioabsorbable polymer implants demand for histologic evaluation because a host tissue response is elicited and late complications after polymer implantation have been reported. Furthermore, in load-bearing regions an accelerated polymer degradation and foreign body reaction may be observed. METHODS: Lumbar interbody fusion procedures were performed using poly-L-lactic acid (PLLA) and titanium cages in 43 goats. At 3, 6, 12, 24, 36, and 48 months after surgery, sequential histologic analysis of instrumented motion segments, lymph nodes, and nervous structures was performed. Blood samples were retrieved for laboratory analysis. RESULTS: No adverse local or distant histologic or systemic effects were observed during the absorption of the poly-L-lactic acid cages. Interbody fusion was maintained, and only a very mild inflammatory response was observed. In half the specimens complete absorption was observed, and in the remaining specimens an estimated 1-10% of the original PLLA was present at the 3-year follow-up. At the 4-year follow-up, five out of seven PLLA specimens showed no PLLA particles under polarized light microscopy. In the remaining two specimens an estimated 1% of the original PLLA could be observed. CONCLUSIONS: Poly-L-lactic acid cages are feasible for lumbar interbody fusion, and the biocompatibility under high load bearing conditions is excellent during the complete absorption of the PLLA interbody fusion cages.

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