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Theoretical Strength Comparison of Bioabsorbable PLLA Plates and Conventional Stainless Steel and Titanium Plates Used in Internal Fracture Fixation, Ajit Nazre & S Lin, Jan 1994, ASTM Issue 1217
Abstract
Description
Describes the clinical use of bone plates as well as their mechanical properties from both clinical and engineering points of view. Metabollic plates as well as the experimental plates made of bioabsorbable materials are covered. 12 papers in 4 sections:
• Screws
• Materials and Design
• Testing Methods
• Clinical Application
... The complete degradation of pure-phase β-TCP in humans and animal models occurs within a 6-12-month period [47], which is far quicker than PDLLA (12-30 months) [7,48,49] and β-TCP/PDLLA (9-19 months) [50,51]. The rapid resorption will provide more space for tissue ingrowth and release large amounts of Ca 2+ and P 5+ ions into the milieu, which are essential for osteoblast maturation and bone formation [52]. ...
... This was consistent with a previous study based on calcium phosphate and polymer composite [46]. The complete degradation of pure-phase β-TCP in humans and animal models occurs within a 6-12-month period [47], which is far quicker than PDLLA (12-30 months) [7,48,49] and β-TCP/PDLLA (9-19 months) [50,51]. The rapid resorption will provide more space for tissue ingrowth and release large amounts of Ca 2+ and P 5+ ions into the milieu, which are essential for osteoblast maturation and bone formation [52]. ...
This study was performed to examine the applicability of the newly developed nano-biocomposite, β-tricalcium phosphate (β-TCP)/u-HA/poly-d/l-lactide (PDLLA), to bone defects in the oral and maxillofacial area. This novel nano-biocomposite showed several advantages, including biocompatibility, biodegradability, and osteoconductivity. In addition, its optimal plasticity also allowed its utilization in irregular critical bone defect reconstructive surgery. Here, three different nano-biomaterials, i.e., β-TCP/PDLLA, β-TCP, and PDLLA, were implanted into critical bone defects in the right lateral mandible of 10-week-old Sprague–Dawley (SD) rats as bone graft substitutes. Micro-computed tomography (Micro-CT) and immunohistochemical staining for the osteogenesis biomarkers, Runx2, osteocalcin, and the leptin receptor, were performed to investigate and compare bone regeneration between the groups. Although the micro-CT results showed the highest bone mineral density (BMD) and bone volume to total volume (BV/TV) with β-TCP, immunohistochemical analysis indicated better osteogenesis-promoting ability of β-TCP/PDLLA, especially at an early stage of the bone healing process. These results confirmed that the novel nano-biocomposite, β-TCP/PDLLA, which has excellent biocompatibility, bioresorbability and bioactive/osteoconductivity, has the potential to become a next-generation biomaterial for use as a bone graft substitute in maxillofacial reconstructive surgery.
... Depending on the exact type used, it breaks down inside the body within 6 months to 2 years. This gradual degradation is desirable for a support structure, because it gradually transfers the load to the body (e.g. the bone) as that area heals [7]. ...
Collagen and Polylactic Acid (PLA) as biomaterials in the tissue engineering have been investigated for the structure and function in considerably large progress. From a viewpoint of its electronic structures in the subnano-meter range, we investigate the bonding nature for five models of the type I collagen, PLA models and the bimolecular interaction between the models by using Density Functional Theory (DFT) calculations with Frontier MO theory. In order to confirm the accuracy of the models, we compare the simulated IR and C1s X-ray photoelectron spectra with experimental results. Especially, the interaction between PLA and (AspHypGly)-collagen models was obtained as the chemical bond energy (1540 kJ/mol), and the results of PLA-other four collagen bimolecular models were given as intermolecular bond energies of 30 ∼ 81 kJ/mol. The intermolecular interaction is due to inter-H-bond of –OH---O=, -NH---O=, and –CH---O= functional groups, respectively, using MO calculations.
... bones in case of bone remodelling) while the treated area heals. 12 PLA is subjected to a bulk hydrolytic degradation mechanism that means that the degradation rate is faster inside the polymer bulk than on its surface; hence, the implant keeps its shape, up to the last steps of its life-time before fragmentation and complete degradation. ...
Microbial colonization on biomaterials is the main cause of failure of a successful
implantation. In fact, local infections can eventually evolve in severe sepsis that might finally end up in a multi-organ failure and death of the patient. Besides, infection has become one of the toughest problems in the medical world, as microorganisms become more resistant to known drugs. Scientific research has been focussing on exploring new strategies to combat this life-threatening problem. In this review, information was collected about currently used polymeric biomaterials in the medical field and the main bacterial infections associated with their implantation. Furthermore, drug-free strategies to overcome this complication are explored, and the existing methodology required for assessment of the antibacterial activity is also described.
... However, the applications of resorbable materials are restricted where the loads are moderated [61]. To improve mechanical properties, the resorbable polymers are modified with variety of non-resorbable materials including carbon [62][63][64][65][66] and polyamide [67][68] fibers and they are classified as partially resorbable composites. ...
Presently, the concept of ‘Green Chemistry for Sustainable Development’ is a guiding source for development of next generation materials, known as composite green polymers. Green composite polymers are used for development of hard tissue implants, such as, artificial bone, spine instrumentation, knee hip replacement and bone cement etc. Moreover green composite polymers are used for soft tissue replacements and implantations, such as, ureter prosthesis, catheters, vascular grafts, tendons and ligaments instead of conventional metal alloy and ceramic. The present chapter represents various applications of green composite polymers in medical technology with special interest on development of artificial organs.
... Also, the hydrolysis properties of PDMMLAs confer a particular quality compared to other polyesters described in the literature and used as stent-coating, particularly PLA. The interest in PDMMLA as promising coating-stent is even more important that the PLA with a hydrophobic character and slow degradation rate that can reach two years [34] and [35]. ...
In-stent restenosis is currently treated with drug eluting stents based on biodegradable polymers which can deliver a therapeutic agent and be degraded in a few months preventing the risk of thrombosis. Poly([R,S]-3,3-dimethylmalic acid) (PDMMLA) is a new and original biodegradable and biocompatible polymer which contains a carboxylic acid functional group in its side chain. This gives it the particularity to be chemically modified and custom-synthesized to meet an adequate degradation time. It was prepared in order to develop new coating exhibiting different groups in its side chain and give natural and non-toxic primary products after a complete degradation. Herein we present the study of hydrolytic degradation of PDMMLAs under physiological conditions for a 6-month period. The most important factors that influence the kinetic degradation of polymers (molecular weight, nature and stability of functional groups, natural biological enzymes, pH and temperature) were studied in order to understand the behavior of PDMMLAs hydrolysis. It has been shown that the different PDMMLA polymers were degraded according to a bulk or erosion-surface profiles. Therefore, a hydrophilic loaded side chain, high temperature, high pH and the presence of specific enzyme accelerated the degradation rate of PDMMLAs with an erosion-surface profile. Since these new biomaterials as promising coating-stent will be in direct contact with the arterial wall, their biocompatibility was evaluated in this study in human vascular endothelial cells which are essential for the repair of the arterial wall to inhibit multiple processes leading to in-stent restenosis. The products of long-term degradation of PDMMLA polymers were non-cytotoxic.
In this second edition of the Biocomposites chapter, the latest advanced mechanics theories for analyzing the mechanical properties of biocomposites reinforced with various reinforcing structures including continuous fibers, short fibers, and particles are presented. The stiffness properties as well as internal stresses in the fiber, standing for the reinforcement, and the matrix of the composite are calculated through unified, rigorous, and analytical micromechanics Bridging Model. These stresses are homogenized or approximated values. They must be converted into true quantities before the failure and strength behavior of the composite can be estimated. Rigorous conversion formulae from the homogenized to the true stresses are summarized in the article. An Excel table for running all of the formulae has been programmed, which is available upon request. From this table, one can automatically obtain all of the conversion coefficients by specifying the fiber and matrix properties and the fiber related geometric parameters only. The other issues addressed are essentially the same as those in the first edition of the article. They include reinforcing fibers and matrices suitable to make biocomposites, typical applications of composite materials to human engineering, biocompatibility, and fabrication and characterization methods for biocomposites.
Les fucoïdanes sont des polysaccharides sulfatés d’origine marine portant des activités biologiques diverses et comparables au glycosaminoglycanes (GAGs) endogènes. Leur utilisation comme agents thérapeutiques dans le traitement de maladies cardiovasculaires est envisagée. L’hétérogénéité structurelle liée à leur diversité naturelle et aux méthodes d’extraction et de purification, induisent des variations dans leurs propriétés physicochimiques et leurs effets biologiques. Le but de cette thèse est d’une part, d’établir études structure-fonction de fucoïdanes extraits de l’algue Ascophyllum nodosum sur leurs effets pro-angiogéniques in vitro (migration et formation de réseau vasculaire en 2D par des cellules endothéliales humaines, HUVECs) et le rôle des GAGs endogènes ; et d’autre part, l’étude du potentiel régénératif d’un biofilm de fucoïdane/VEGF appliqué sur des prothèses de valves cardiaques porcines acellularisées. Dans notre première étude, nos résultats montrent que la fraction de fucoïdane de bas poids moléculaire (LMWF, 4900 g/mol) induit des effets pro-angiogéniques plus importants qu’une fraction de moyen poids moléculaire (MMWF, 26700 g/mol) sur les HUVECs. De plus, le LMWF garde un potentiel proangiogénique avec des cellules HUVECs n’exprimant pas de GAGs endogènes et peut être internalisé par une endocytose dépendante de la clathrine dans laquelle les GAGs seraient partiellement impliqués. Dans notre deuxième étude, nos analyses démontrent que l’application d’un biofilm de fucoïdane/VEGF sur des valves pulmonaires porcines acellularisées induit un potentiel antithrombotique et permet l’adhérence et la survie des HUVECs. Ces travaux suggèrent que ce procédé permettrait la ré-endothélialisation de valves acellulaires pour le développement de bioprothèses auto-régénératives.
Hybrid materials constituted by hydroxyapatite (HAp) and both biodegradable and natural polymers have a great interest that mainly covers the biomedical field in applications relative to tissue-engineering and even drug delivery systems. On the other hand, polylactide (PLA) is one of the most employed biodegradable polymers due to its good properties, the capability to be synthesized from renewable resources, and even the possibility to tune some properties through the change in its stereoisomeric composition. The present review concerns to the specific developments that recently have been carried out with PLA/HAp composites. These include, for example, their use as representative systems of bone repairing with good biocompatibility and the research on carrier systems that release osteogenic drugs for orthopedic treatments.
Various aspects of biocomposites are addressed in this chapter. Stiffness and strength formulae of unidirectional (UD) composites only using original properties of their constituent fiber and matrix materials are presented at first. Reinforcing fibers and matrices suitable to make biocomposites are summarized in Section 9.06.3. Typical applications of composite materials to human engineering in the current literature mainly attempted in three areas, i.e., soft tissues, hard tissues, and body assistances or body check-ups have been reviewed in Section 9.06.4. Biocompatibility is an issue that should be taken into account before any biomaterial is developed. What are the rules or principals for a biocomposite to follow up is highlighted in Section 9.06.5. A number of fabrication methods for making biocomposites are given in Section 9.06.6, in which both destructive and nondestructive techniques to characterize mechanical, physical, and morphological properties of them are also shown. Section 9.06.7 focuses on structure–property relationship of biocomposites reinforced with different fibrous structures. Essentially, any such structure is subdivided into a series of UD composites whose stiffness and strength properties are estimated from those of the fiber and matrix materials. In Section 9.06.8, effects of processing and environment on biocomposite behaviors are briefly discussed. Some designing examples for biocomposite products are presented in Section 9.06.9, followed by a foreseeing for future advancement.
An overview of various biomedical applications of polymer-composite materials reported in the literature over the last 30 years is presented in this paper. For the benefit of the readers, general information regarding structure and function of tissues, types and purpose of implants/medical devices, and various other materials used, are also briefly presented. Different types of polymer composite that are already in use or are investigated for various biomedical applications are presented. Specific advantages of using polymer-composite biomaterials in selected applications are also highlighted. The paper also examines the critical issues and scientific challenges that require further research and development of polymer composite materials for their increased acceptance in the biomedical industry.
In the internal fixation of fractured bone by means of bone-plates fastened to the bone on its tensile surface, an on-going concern has been the excessive stress shielding of the bone by the excessively-stiff stainless-steel plate. The compressive stress shielding at the fracture-interface immediately after fracture-fixation delays callus formation and bone healing. Likewise, the tensile stress shielding in the layer of bone underneath the plate can cause osteoporosis and decrease in tensile strength of this layer. In this study a novel forearm internal fracture fixation plate made from short carbon fibre reinforced plastic (CFRP) was used in an attempt to address the problem. Accordingly, it has been possible to analyse the stress distribution in the composite plates using finite-element modelling. A three-dimensional, quarter-symmetric finite element model was generated for the plate system. The stress state in the underlying bone was examined for several loading conditions. Based on the analytical results the composite plate system is likely to reduce stress-shielding effects at the fracture site when subjected to bending and torsional loads. The design of the plate was further optimised by reducing the width around the innermost holes.
1. The probable greatest bending moment applied to a plated or nailed fracture of the tibia during restricted weight-bearing is estimated to be, in men, up to about 79 Newton metres (58 poundsforce feet). The maximum twisting moment is estimated to be about 29 Newton metres (22 poundsforce feet).
2. Twenty-two human tibiae were loaded in three-point bending and broke at bending moments of from 57·9 to 294 Newton metres (42·7 to 216 poundsforce feet) if they had not previously been drilled; tibiae which had holes made through both cortices with a c. 3-millimetre (⅛-inch) drill broke at from 32·4 to 144 Newton metres (23·8 to 106 poundsforce feet). Tibiae loaded in torsion broke at twisting moments of from 27·5 to 892 Newton metres (20·2 to 65·8 poundsforce feet) when not drilled, 23·6 to 77·5 Newton metres (l7·3 to 57·1 poundsforce feet) when drilled.
3. When bent so as to open the fracture site, the 14-centimetre Stamm was the strongest of all the single plates tested (reaching its elastic limit at a bending moment of 17·6 Newton metres (13 poundsforce feet) and 5 degrees total angulation at 22·6 Newton metres (16·6 poundsforce feet)), while the Venable was the weakest (elastic limit 4·9 Newton metres (3·6 poundsforce feet) and 5 degrees at 7·9 Newton metres (5·8 poundsforce feet)). A 13-millimetre Küntscher nail reached its elastic limit at 42·2 Newton metres (31·1 poundsforce feet) and 5 degrees total angulation at 49 Newton metres (36 poundsforce feet).
4. In torsion the 15-centimetre Hicks was the strongest ofthe plates (elastic limit 27·5 Newton metres (20·2 poundsforce feet) and 5 degrees rotation at 16·7 Newton metres (l2·3 poundsforce feet)).
5. Küntscher nails in bones provided no dependable strength in torsion.
6. In both bending and torsion, a preparation of one Venable plate on each of the two anterior surfaces was stronger than any single plate, and was as strong as the weaker drilled tibiae.
7. The three currently available metallic materials (stainless steel, cobalt-chrome and titanium) have static mechanical properties so similar that the choice between them can be made on other grounds.
8. The highest load applied to a screw during bending tests was about half that needed to pull a screw out of even a thin-walled tibia.
9. Screws beyond four for one plate are mechanically redundant at the moment of implantation but may be necessary as an insurance against subsequent deterioration in strength.
10. Countersinks in plates are a source of significant weakness, and should preferably be as shallow as possible.
11. An unoccupied screw hole in the centre of a plate is a source of serious weakness.
12. Only the strongest implants tested were strong enough to withstand the bending or twisting moments to be expected in restricted weight-bearing. In two-plate preparations a danger is introduced by the fact that these moments are similar to those required to Ireak a drilled tibia.
Design and Analysis of Absorbable and Semi-absorbable Composite Fracture Fixation Devices
- M C Zimmermann
Poly(L-Lactide Acid) Orthopaedic Fixation Devices
- S Lin
Composites Design”, Think Composites
- S W Tsai