O cimento ósseo, utilizado para a fixação de componentes protéticos nas cirurgias de substituição articular, mais resistente às forças de compressão do que às forças de tração, tem suas propriedades mecânicas alteradas por vários fatores entre esses a formulação comercial e o método de preparação empregado. É o objetivo deste trabalho avaliar comparativamente as propriedades mecânicas à compressão de duas formulações comerciais de cimento ósseo preparadas manualmente e a vácuo, segundo as instruções do fabricante. Um conjunto de moldagem confeccionado em aço inoxidável permitiu preparar 48 corpos de prova para cada grupo experimental, totalizando 192 corpos de prova, que foram testados na Máquina Universal de Ensaios, tendo as especificações baseadas nas normas ISO 5833 e ASTM F451-86. A elaboração do diagrama tensão x deformação de cada grupo experimental analisou as propriedades mecânicas do cimento ósseo quanto ao módulo de elasticidade, tensão e deformação no limite de proporcionalidade, entre grupos de mesma formulação comercial e entre os grupos com mesmo método de mistura. Analisados estatisticamente pelo método de Variança de Kruskal-Wallis (p ≤0,001) e pelo método de Dunn's (p ≤0,05). Quanto ao módulo de elasticidade, o grupo 2M foi o que apresentou maior módulo, 1563 MPa, valor estatisticamente significante (p ≤ 0,05) em relação aos grupos 1M, 1V e 2V. Para a tensão no limite de proporcionalidade os grupos 1M (39,40 MPa) e 2V (39,65 MPa) foram os maiores valores de tensão no limite de proporcionalidade, não havendo diferença estatisticamente significante entre eles, mas essas diferenças foram significativas quando comparadas aos grupos 1V e 2M. A deformação no limite de proporcionalidade de maior valor percentual foi para o grupo 1M, 3,36%, sendo esta diferença estatisticamente significante quando comparado ao grupo 2M. Os testes de resistência à compressão do cimento nacionalizado e importado, preparados manualmente e a vácuo, mostraram não haver diferença importante entre os dois tipos de cimento ósseo, nem entre as duas formas de misturá-los. / The bone cement used for the fixation of the prosthetic components in the surgeries of joint replacement, more resistant to the compression than to the traction, has its mechanical properties altered by several factors among those the commercial formulation and preparation employee's method. It is the objective of this work to evaluate the mechanical properties to the compression of the two commercial formulas of bone cement manually prepared and using vacuum, according to the manufacturer's instructions. A molding set was made in stainless steel and it allowed for the preparation of 48 bodies of proof for each experimental group, adding up to 192 proof bodies total which were tested in the Universal Rehearsal Machine, with the specifications based on the ISO 5833 and the ASTM F451-86 regulations. The elaboration of the diagram "tension vs. deformation" of each of the experimental group analyzed the mechanical properties of the bone cement in relation to the elasticity module, tension and deformation on the proportional limit among the groups with the same commercial formula and among the groups with the same mixture method. Analyzed statistically, by Kruskal-Wallis's method of the variation (p ≤0.001) and by the Dunn’s method (p ≤0.05). Regarding the elasticity, the group 2M was the one with the highest module, 1563 MPa, a statistically significant value (p ≤0.05) in relation to the groups 1M, 1V and 2V to the tension at the limit of the proportionality, there is no significant differences among them, but these differences were relevant when compared to groups 1V and 2M. The deformation at the limit of the proportionality of the highest percentage was to group 1M, 3.36%, being this the relevant statistical difference when compared to group 2M. The resistance tests to the compression of the national and international cement prepared manually and by vacuum show that there is no important difference between the two kind of bone cement, and neither between the two ways of mixing them.

O cimento ósseo, utilizado para a fixação de componentes protéticos nas cirurgias de substituição articular, mais resistente às forças de compressão do que às forças de tração, tem suas propriedades mecânicas alteradas por vários fatores entre esses a formulação comercial e o método de preparação empregado. É o objetivo deste trabalho avaliar comparativamente as propriedades mecânicas à compressão de duas formulações comerciais de cimento ósseo preparadas manualmente e a vácuo, segundo as instruções do fabricante. Um conjunto de moldagem confeccionado em aço inoxidável permitiu preparar 48 corpos de prova para cada grupo experimental, totalizando 192 corpos de prova, que foram testados na Máquina Universal de Ensaios, tendo as especificações baseadas nas normas ISO 5833 e ASTM F451-86. A elaboração do diagrama tensão x deformação de cada grupo experimental analisou as propriedades mecânicas do cimento ósseo quanto ao módulo de elasticidade, tensão e deformação no limite de proporcionalidade, entre grupos de mesma formulação comercial e entre os grupos com mesmo método de mistura. Analisados estatisticamente pelo método de Variança de Kruskal-Wallis (p ≤0,001) e pelo método de Dunn's (p ≤0,05). Quanto ao módulo de elasticidade, o grupo 2M foi o que apresentou maior módulo, 1563 MPa, valor estatisticamente significante (p ≤ 0,05) em relação aos grupos 1M, 1V e 2V. Para a tensão no limite de proporcionalidade os grupos 1M (39,40 MPa) e 2V (39,65 MPa) foram os maiores valores de tensão no limite de proporcionalidade, não havendo diferença estatisticamente significante entre eles, mas essas diferenças foram significativas quando comparadas aos grupos 1V e 2M. A deformação no limite de proporcionalidade de maior valor percentual foi para o grupo 1M, 3,36%, sendo esta diferença estatisticamente significante quando comparado ao grupo 2M. Os testes de resistência à compressão do cimento nacionalizado e importado, preparados manualmente e a vácuo, mostraram não haver diferença importante entre os dois tipos de cimento ósseo, nem entre as duas formas de misturá-los. / The bone cement used for the fixation of the prosthetic components in the surgeries of joint replacement, more resistant to the compression than to the traction, has its mechanical properties altered by several factors among those the commercial formulation and preparation employee's method. It is the objective of this work to evaluate the mechanical properties to the compression of the two commercial formulas of bone cement manually prepared and using vacuum, according to the manufacturer's instructions. A molding set was made in stainless steel and it allowed for the preparation of 48 bodies of proof for each experimental group, adding up to 192 proof bodies total which were tested in the Universal Rehearsal Machine, with the specifications based on the ISO 5833 and the ASTM F451-86 regulations. The elaboration of the diagram "tension vs. deformation" of each of the experimental group analyzed the mechanical properties of the bone cement in relation to the elasticity module, tension and deformation on the proportional limit among the groups with the same commercial formula and among the groups with the same mixture method. Analyzed statistically, by Kruskal-Wallis's method of the variation (p ≤0.001) and by the Dunn’s method (p ≤0.05). Regarding the elasticity, the group 2M was the one with the highest module, 1563 MPa, a statistically significant value (p ≤0.05) in relation to the groups 1M, 1V and 2V to the tension at the limit of the proportionality, there is no significant differences among them, but these differences were relevant when compared to groups 1V and 2M. The deformation at the limit of the proportionality of the highest percentage was to group 1M, 3.36%, being this the relevant statistical difference when compared to group 2M. The resistance tests to the compression of the national and international cement prepared manually and by vacuum show that there is no important difference between the two kind of bone cement, and neither between the two ways of mixing them.

Introdução: O tratamento dos tumores ósseos benignos é frequentemente realizado por abordagem intralesional com curetagem do tumor e preenchimento da falha óssea com substâncias biológicas ou sintéticas. Entre as biológicas estão os vários tipos de enxertos e o maior representante das sintéticas é o cimento ósseo ou polimetilmetacrilato (PMMA). O uso do cimento ósseo compacto pode apresentar problemas devido à necrose térmica, ao afrouxamento asséptico, à incapacidade de remodelação e à elasticidade inadequada em relação ao osso normal. O desenvolvimento de um cimento ósseo esponjoso que atenda a estas demandas mecânicas e biológicas e que seja de fácil manipulação no ambiente cirúrgico tem estimulado alguns pesquisadores. Basicamente, é possível formar poros no interior do cimento por mistura de substâncias hidrossolúveis ou por reação química produtora de gás. Objetivo: Desenvolver e caracterizar fisicamente e mecanicamente um cimento ósseo com poros intercomunicantes de aspecto estrutural esponjoso. Material e métodos: A produção de cimento esponjoso foi realizada misturando-se o PMMA com bicarbonato de sódio e ácido cítrico. Foram confeccionados 90 corpos de prova com 40 mm de altura por 20 mm de diâmetro distribuídos em 6 grupos (n=15): G1 formado por cimento esponjoso em que antes da polimerização do cimento foram adicionados bicarbonato de sódio e ácido cítrico na proporção de 10% em relação ao componente sólido do cimento (polímero); G2 - cimento esponjoso na proporção de 20%; G3 - cimento esponjoso na proporção de 30%; G4 - cimento ósseo de PMMA compacto; G5 - formado por cimento de poliuretana de mamona (Bioósteo®) na proporção de 20%; G6 formado de corpos de prova cilíndricos de osso esponjoso extraído com trefina de côndilos tibiais proximais de bovinos. A qualidade do cimento esponjoso foi avaliada por macroscopia, cálculo de densidade, imersão em azul de metileno, tomografia computadorizada, microscopia eletrônica de varredura e ensaio mecânico de compressão. Resultados: A melhor forma de produção de cimento esponjoso foi pela mistura de PMMA e componentes efervescentes. O teste da imersão em azul de metileno mostrou que os G2 e G3 apresentaram melhor intercomunicabilidade. As análises com o microscópio eletrônico de varredura (MEV) mostraram uma ampla variação no tamanho e distribuição dos poros que medem de 50m a 3mm. Em relação aos ensaios mecânicos não houve diferenças significativas entres os grupos de cimento esponjoso G1, G2 e G3. Estes grupos apresentaram valores pouco inferiores aos do grupo G6 de osso esponjoso bovino. O grupo G4 (PMMA compacto) apresentou valores extremamente altos quando comparado ao osso esponjoso bovino e ao cimento esponjoso. O grupo G5 de cimento ósseo de mamona não atingiu os valores aceitáveis de resistência mecânica. Conclusão: Foi possível desenvolver um cimento esponjoso à base de polimetilmetacrilato pela mistura com os aditivos efervescentes, bicarbonato de sódio e ácido cítrico, que apresenta características físicas e mecânicas desejadas como substituto ósseo esponjoso nas curetagens para tratamento de tumores ósseos benignos. O cimento de mamona esponjoso na forma testada mostrou-se inadequado para os fins pretendidos. / Introduction: Benign bone tumors are usually treated by intralesional curettage. The bone defect may be filled with synthetic or biological substitutes. Polymetylmethacrylate (PMMA) is the most popular synthetic substitute and the solid form is associated to thermal necrosis, aseptic loosening, bone remodeling prevention and distinct elasticity. Research of porous cement that solves these drawbacks and can be molded intraoperatively has encouraged many authors. For surgical purposes, porosity can be achieved by mixing hydrosoluble substances or by gas-foaming reactions. Objective: Development and physical and mechanical characterization of a bone cement with interconnecting pores and cancellous bone like structural aspect. Methods: Porous cement was produced by adding the effervescent components sodium bicarbonate and citric acid to PMMA. Six groups of fifteen cylindrical samples (40 mm height, 20 mm diameter) were compared. G1, G2 and G3 groups consisted of porous cement specimens of PMMA with 10%, 20% and 30% of effervescent components respectively. G4 consisted of solid PMMA cement specimens. G5 group consisted of porous ricinic polyurethane cement (Bioósteo®) with 20% effervescent components specimens. The control group G6 consisted of bovine cancellous bone samples. The porous cements were characterized in terms of porosity, density, pore interconnectivity and compressive strength. Macroscopic evaluation and measuring, methylene blue immersion, Scanning Electron Microscopy (SEM), mechanical testing and a special computed tomography reading software were employed for these evaluations. Results: The pilot study showed that adding effervescent components to PMMA was the best solution for porous cement production. The methylene blue immersion test showed that G2 and G3 groups had better pore interconnection. Scanning electron microscopy (SEM) showed a wide variation in pore size, from 50m to 3mm, and pore distribution. No significant differences between G1, G2 and G3porous cement groups were found regarding to mechanical strength and Young Modulus. Cancellous bovine bone, G6, was slightly stronger and less elastic than these groups. This property is potentially beneficial considering osteointegration as a consequence of Wolfs law. Solid PMMA is extremely strength and inelastic. These properties do not match with cancellous bone. The porous ricinic polyurethane cement (Bioósteo®) is unacceptably weak. Conclusion: Porous cement was developed by adding effervescent components, sodium bicarbonate and citric acid, to polymethylmetacrylate. Physical and mechanical properties are very similar to cancellous bone. Further investigations to evaluate its bone substitute potential should be encouraged. The porous ricinic polyurethane cement (Bioósteo®) is inadequate these purpose.

Vertebroplasty is a new technique in orthopedic surgery for stabilizing fractured vertebra. In this technique acrylic bone cement as a biocompatible material is injected through a cannula inside of vertebra. There are several concerns in this technique that the most serious one is cement leakage out of vertebra. The main reasons are improper viscosity and lack of visibility. Clinicians who practice vertebroplasty use commercial highly concentrated radiopaque acrylic bone cement (more than 25%BaSO[subscript 4] or ZrO[subscript 2]) or a cement with manually added radiopaque agents. High density materials with attenuation under X-ray are good alternatives compared to conventional radiopaque agents (BaSO[subscript 4] or ZrO[subscript 2]) in acrylic bone cement for application in vertebroplasty. In the first part of this study, thermal and rheological properties of modified acrylic bone cement with conventional radiopaque agent (Barium Sulfate, BaSO[subscript 4]) are studied. Additions of barium sulfate are in the form of substitute or excess. In substitute formulation, barium sulfate is replaced with the same weight of powder and liquid to powder ratio kept constant. In the excess formulation, barium sulfate added as excess and liquid to powder ratio decreased. In the second part of this study, high density radiopaque agents are used as alternative radiopacifier. Experimental design technique is used to study the effect of X-ray conditions, concentration, type, and size of radiopaque agents on the visibility of bone cement. The visibility of bone cement was quantified by the measurement of contrast index. In the first project, it was found that the setting time increased with the increase of concentration of radiopacifier in substitute formulation of barium sulfate bone cement. With increase of barium sulfate concentration, excess formulations showed higher residual monomer but for substitute cement, we had a decreasing trend. Acrylic bone cements with excess formulation had higher initial viscosity compared to reference or substitute but the variation of viscosity with time was lower for substitute formulation and cements had higher working time. In the second project, contrast index was the same for barium sulfate, tungsten, and zirconium in the lower voltage but in higher voltage of X-ray lamp, tungsten and zirconium gave higher contrast index. Variation of current in X-ray lamp changed the contrast index of cement slightly compared to the effect of voltage. Bone cement with nano tungsten had higher contrast index compared to the cement with micro size tungsten although micro size zirconium as radiopacifier gave higher contrast index than nano size zirconium.

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Infection is one of the major causes of increased morbidity and the escalating costs associated with orthopedic surgery. The areas that are infected are often difficult to reach and thus difficult to treat. In some surgeries antibiotic-loaded bone cements are used to control infection. Polymethylmethacrylate (PMMA) and calcium phosphate-based bone cements (CPC) are usually used as bone fillers. CPC are bioresorbable and biocompatible (unlike PMMA cements), but can only be used in non- or low-load bearing areas and are thus more applicable in cranio-and maxilla-facial surgeries. Several in vitro and in vivo trials have been conducted on the incorporation of antibiotics and other therapeutic agents into CPC and the release of these agents. As with any solid matrix, release is defined by specific parameters, i.e. matrix porosity, solubility of the drug and interaction of the drug with the cement. The increase in antibiotic-resistant pathogens, mainly as a result of overuse of antibiotics, has a major impact on the choice of antibiotics that are used in the treatment of bacterial infections. The search for alternative antimicrobial compounds that are active against resistant pathogens, is thus of utmost importance. Antimicrobial peptides (bacteriocins) produced by lactic acid bacteria may pose a possible alternative to antibiotics. Some of these peptides are active against antibiotic-resistant pathogens. Bacteriocins are small cationic, hydrophobic, or amphiphilic peptides active against a narrow range of target organisms. Most of these peptides are active in the nanomolar range. It may then be advantageous to incorporate bacteriocins into CPC to evaluate if they may be used as an alternative to antibiotics. The aim of the project was to evaluate if bacteriocins could be successfully incorporated into self seting brushite bone cement and remain effective in vivo without altering basic cement characteristics. Incorporation of bacteriocins into CPC is a novel concept. The low setting temperature and pH of CPC renders it the ideal matrix for incorporation of antimicrobial peptides. In this study, peptide ST4SA, a class IIa broad-spectrum bacteriocin, has been incorporated into brushite bone cement and characterized in vitro. Incorporation of the peptide did not have a significant effect on the crystal entanglement or setting reaction of the cement. Peptide ST4SA was rapidly released and inhibited the growth of the target strain effectively. In another experiment, peptide ST4SA was suspended in poly (lactide-co-glycolide) and electrosprayed to form micro particles that were entrapped in brushite cement. Association of the peptide with microparticles resulted in a delayed release from the cement, followed by a constant release. Nisin F, a class Ia bacteriocin was also incorporated into brushite cement and its activity studied in vitro and in vivo. Similar results were observed in vitro as recorded with peptide ST4SA incorporated into brushite cement. Small cylinders of brushite cement loaded with nisin F were implanted into subcutaneous pockets in mice and each pocket infected with a bioluminescent strain of Staphylococcus aureus (Xen 36). Nisin F in the bone cement prevented the growth of S. aureus in the wound and controlled infection. With this study we have shown that antimicrobial peptides that differ in structure (classes I and II) could be incorporated into bone cement and control the growth of S. aureus in vivo and in vitro. The mode of action of these peptides differs from antibiotics in that they form a permanent pore in the cell membrane of the target organism. This minimizes the chance of a strain becoming resistant to the peptide. Incorporation of antimicrobial peptides into bone cement may be a possible alternative to antibiotics in the control of bacterial infections associated with implants. / AFRIKAANSE OPSOMMING: Infeksie is een van die grootste bydraende faktore tot sterftes en verhoogde kostes in ortopediese chirurgie. Geinfekteerde areas is dikwels moeilik bereikbaar en dus ook moeilik om te behandel. In sommige operasies word antibiotika-gelaaide beensement gebruik om infeksie te beheer. Polymetielmetakrilaat (PMMS) en kalsium fosfaat gebaseerde beensement (KFS) word gebruik as been vullers. KFS is bioverenigbaar en bio-absorberend (in teenstelling met PMMS), maar kan slegs in geen- of liggewig-draende areas gebruik word en is dus van groter toepassing in skedel-, kaak- gesig- en mondchirurgie. Verskeie in vitro en in vivo toetse is al gedoen op die inkorporering van antibiotika en ander terapeutiese middels in KFS en die vrystelling daarvan uit die matriks. Soos met enige soliede matriks is vrylating van die geinkorporeerde bestanddeel afhanklik van sekere parameters, onder andere porositeit, oplosbaarheid van die middel, en die interaksie van die middel met beensement. Die toename in antibiotika-weerstandbiedende patogene plaas geweldige druk op die keuse van antibiotika wat gebruik word in die beheer van bakteriese infeksie. Die soeke na alternatiewe antimikrobiese middels aktief teen bestande patogene is dus van kardinale belang. Antimikrobiese peptiede (bakteriosiene) gepproduseer deur melksuur bakteriee mag dalk . alternatief tot antibiotika wees. Sommige van hierdie peptiede is aktief teen verskeie weerstandbiedende patogene. Bakteriosiene is kationiese, hidrofobiese of amfifiliese peptiede wat naverwante bakteriee inhibeer of doodmaak. Die meeste van hierdie peptiede is aktief op nanoskaal vlak. Dit mag dalk dus voordelig wees om bakteriosiene in been sement te evalueer as moontlike alternatiewe tot antibiotika. Die doel van die proejek was om te evaleer of bakteriosiene suksesfol in "brushite" sement geïnkorporeer kan word en steeds effektief in vivo bly sonder om die basiese eienskappe van die sement te verander. Inkorporasie van bakteriosiene in KFS is 'n nuwe konsep. Die lae stollingstemperatuur en pH van KFS maak dit moontlik om bakteriosiene daarin te inkorporeer. In hierdie studie is peptied ST4SA, . klas IIa wye-spektrum bakteriosien, in "brushite" sement geïnkorporeer en in vitro bestudeer. Die toevoeging van die peptied het nie 'n beduidende effek op die stolreaksie of kristal verstrikking van die sement gehad nie. Peptied ST4SA is effektief vrygelaat en het die groei van die teikenorganisme suksesvol onderdruk. In 'n ander eksperiment is peptied ST4SA in poli (D,L-laktied-ko-glikolied) gesuspendeer en met behulp van elektrosproeiing tot mikropartikels omvorm en is in "brushite" sement geïnkorporeer. Assosiasie van die peptied met mikropartikels het die inisiële vrylating van die peptied vertraag, gevolg deur 'n konstante vrylating. Nisien F, . klas Ia lantibiotikum, is ook in "brushite" sement geïnkorporeer en die aktiwiteit daarvan in vitro en in vivo bestudeer. Die in vitro eienskappe is soortgelyk aan die eienskappe wat vir peptied ST4SA-gelaaide sement waargeneem is. Klein stafies "brushite" sement, waarin nisien F geïnkoproreer is, is in onderhuidse sakkies in muise geplaas en die area met 'n bio-liggewende bakterie (S. aureus Xen 36) geïnfekteer. Nisien F in die beensement het die groei van S. aureus in die wond onderdruk en infeksie beheer. Met hierdie studie het ons bewys dat bakteriosiene wat struktureel van mekaar verskil (klasse I en II) in beensement geïnkorporeer kan word en die groei van S. aureus in vitro en in vivo kon beheer. Die wyse waarop hierdie peptiede die groei van sensitiewe organismes inhibeer verskil van die van antibiotika deurdat dit porieë in die selmembraan vorm. Die moontlikheid dat organismes weerstandbiedend raak tot die peptied is dus heelwat skraler. Die insluit van antimikrobiese peptiede in beensement mag dalk 'n alternatief tot antibiotika wees in die voorkoming van bakteriële infeksie geassosieer met ortopediese chirurgie.

Acrylic bone cement is widely used as a structural material in orthopaedics, dentistry, and orofacial surgery. Although bone cement celebrates four decades of success, it remains susceptible to fatigue fracture. This type of failure can directly lead to implant loosening, revision surgery, and increased healthcare expenditures. The mechanism of fatigue failure is divided into three stages: 1) fatigue crack initiation, 2) fatigue crack propagation, and 3) fast, brittle fracture. Adding reinforcing fibers and particles to bone cement is a proposed solution for improving fatigue performance. The mechanical performance of these reinforced bone cements is limited by fiber ductility, fibermatrix de-bonding, elevated viscosity, and mismatch of fiber size and scale of fatigue induced damage. In this dissertation, I report that adding small amounts (0% - 10% by weight) of multiwall carbon nanotubes (MWNTs) enhances the strength and fatigue performance of single phase bone cement. MWNTs (diameters of 10-9 10-8 m; lengths of 10-6 10-3 m) are a recently discovered nanomaterial with high surface area to volume ratios (conferring MWNT bone cement composites with large interfaces for stress transfer) that are capable of directly addressing sub-microscale, fatigue induced damage. MWNTs (2wt%) significantly increased the flexural strength of single phase bone cement by a modest 12%; whereas, similar additions of MWNTs dramatically enhanced fatigue performance by 340% and 592% in ambient and physiologically relevant conditions, respectively. Comparing the fatigue crack propagation behaviors of reinforced and unreinforced single phase bone cements revealed that the reinforcing mechanisms of MWNTs are strongly dependent on stress intensity factor, K, a numerical parameter that accounts for the combinatorial effect of the applied load and the crack size. As the crack grows the apparent stress at the crack tip intensified and the MWNTs lost their reinforcing capabilities. For that reason, it is likely that the predominant role of the MWNTs is to reinforce the bone cement matrix prior to crack initiation and during the early stages of crack propagation. Therefore, MWNTs are an excellent candidate for improving the clinical performance of bone cement, thereby improving implant longevity and reducing patient risk and healthcare costs.

The third generation of hip resurfacing commenced in the U.K. in the 1990’s with the Birmingham Hip Resurfacing system and is now becoming more commonplace as an attractive alternative for young and active patients due to premature failure in total hip replacement in this patient group. However the Swedish National Hip Arthroplasty Register (2010) suggests that premature failure of resurfacing arthroplasty may be more prevalent than first expected. The aim of this study is to investigate, through Finite Element Analysis, the short, medium and long term performance of Poly Methyl Methacrylate (PMMA) bone cement of the femoral component in hip resurfacing arthroplasty. The study takes a forensic engineering approach, analysing the performance of PMMA bone cement in order to provide understanding, awareness and an insight into lifestyle options. Finite Element Analysis explores and models the effect of resting periods during daily activities, patients’ bone quality and PMMA bone cement Young’s modulus on the PMMA bone cement stresses within the femoral hip resurfacing component. Mechanical tests are used to illustrate the use of the Finite Element Analysis results. Contributing to knowledge, this study verifies the significance of high metal-on-metal friction due to resting periods, developing a dynamic FEA model to quantify the premature fatigue failure of PMMA bone cement, within the femoral component of hip resurfacing arthroplasty. A decrease in bone quality added to the effect of resting periods increase the risk of PMMA fatigue failure and PMMA-metal interface failure due to an increase of PMMA tensile and shear stresses, suggesting that patients with low bone quality should avoid hip resurfacing procedures. The use of low PMMA Young’s modulus could greatly enhance the long term success of hip resurfacing arthroplasty generally and specifically reduce the risk of interface failure and PMMA bone cement failure due to resting periods and patient bone quality. Moreover, this study shows that the consequence of PMMA fatigue failure and PMMA-metal interface failure must be included in the design, patient selection, screening process, post-operative rehabilitation and long term lifestyle attributes. This study suggests that occupational therapists and patients with hip resurfacing arthroplasty should be aware of high metal-on-metal friction situations, which could lead to early failure indicated by this research. The deleterious effect of resting periods indicated by this research could be alleviated by appropriate re-initiation of synovial lubrication by movement prior to full loading. Recommendations for further work include the compilation of a PMMA bone-cement fatigue properties database and further development of the FEA modelling technique for application upon other arthroplasty procedures.

O envelhecimento promove o aparecimento de doenças crônicodegenerativas, entre elas a osteoartrose. Artroplastia Total de Quadril (ATQ) tem sido procedimento comumente frequentemente com uso de cimento ósseo metilmetacrilato (MTC). Por outro lado, importantes alterações hemodinâmicas são descritas durante o procedimento de cimentação. A raquianestesia é um procedimento anestésico que produz menores efeitos hemodinâmicos e melhor analgesia pós-operatória em comparação a anestesia geral para a ATQ. Entretanto, especificamente neste procedimento cirúrgico tais alterações permanecem a ser investigadas. Buscamos avaliar os efeitos hemodinâmicos através da técnica de cardioimpedância em pacientes idosos submetidos à cirurgia de ATQ com o uso de MTC e raquianestesia. Utilizamos um estudo transversal, observacional, comparativo, inter-metodológico e com intervenção ativa. Método: Doze pacientes de ambos os sexos, > 65 anos, com indicação ortopédica para ATQ foram estudados. Os sujeitos receberam avaliação pré-anestésica e realizaram exames laboratoriais préoperatórios. Foram submetidos à cirurgia de ATQ com utilização de raquianestesia e implante de cimento de MTC. Os pacientes foram monitorados hemodinamicamente por meio da cardiografia de impedância, da saturação de oxigênio e pressão arterial, no intra-operatório, no momento acordado, durante a indução anestésica, na colocação do MTC e após este procedimento. Após a expansão volêmica observamos que houve aumento do DC quando comparado a raquianestesia, cimentação, inserção, redução da prótese e ao final da cirurgia (P<0,05). Tais resultados foram de certa forma, atenuados na presença de efedrina. No entanto, o VS sofreu alterações nos eventos supracitados na presença ou não da droga. Por outro lado, a FC, o IC e a RVS sofreu poucas alterações durante os eventos estudados. O DC, IC e o VS se correlacionaram com a massa corporal (r = 0,81, 0,60 e 0,67 respectivamente), o VS se correlacionou negativamente com a idade (r = -0.67), o IC se correlacionou negativamente com a classe funcional pela NYHA (r = -0,61) e o DC se correlacionou positivamente com a quantidade de efedrina administrada (r = 0,70). Conclusão: O procedimento cirúrgico de ATQ com MTC sob raquianestesia produz alterações hemodinâmicas e a cardioimpedância foi um instrumento útil para guiar os procedimentos e conduta do intraoperatório, configurando-se como uma técnica interessante para monitorização não invasiva. / Aging promotes the onset of chronic diseases, including osteoarthritis. Hip arthroplasty procedure has been commonly often the use of methylmethacrylate bone cement (MMA) has been used in the surgical procedure. On the other hand, significant hemodynamic changes are described in the cementation procedure. Spinal anesthesia is an anesthetic that produces less hemodynamic effects and better postoperative analgesia compared to general anesthesia for surgery arthroplasty. However, this particular surgical procedure (hip arthroplasty) such changes remain to be investigated. To evaluate the hemodynamic effects through cardioimpedance technique in elderly patients undergoing surgery for hip arthroplasty with the use of MMA for prosthetic hip and spinal. Twelve patients of both sexes, > 65 years, with orthopedic indication for hip arthroplasty were studied. The subjects received preanesthetic evaluation and underwent preoperative laboratory. From then underwent surgery for hip arthroplasty with use of spinal anesthesia and MMA cement. Patients were haemodynamically monitored by impedance cardiography, oxygen saturation and blood pressure intraoperative, when awake, during anesthesia induction, installing the MMA cement and after this procedure. After volume expansion, we observed that there was increase in CO when compared to spinal anesthesia, cementing, insertion, and reduction of the prosthesis at surgery (P<0.05). These results were somewhat attenuated in the presence of ephedrine. However, the SV underwent changes at aforementioned event on the presence or not of drugs. On the other hand, HR, CI and SVR has a few changed during the studied event. The CO, CI and the SV was correlated with body mass (r = 0.81, 0.60 and 0.67 respectively), SV was negatively correlated with age (r = -0.67), the CI was negatively correlated with NYHA functional class (r = -0.61) and CO was positively correlated with the amount of ephedrine administered (r = 0.70).Conclusion: The surgical procedure for hip arthroplasty under spinal anesthesia with MMA produces haemodynamic changes and cardioimpedance was a useful tool to guide the procedures and conduct of the intraoperative considering as interesting technique for noninvasive monitoring.

Os cimentos de fosfato de cálcio (CFCs) formam uma pasta viscosa após a mistura de uma fase sólida (sal de fosfato de cálcio) com uma fase líquida (água ou uma solução aquosa). Esta pasta endurece, dando lugar a um precipitado que contenha um ou mais fosfatos de cálcio, que graças à sua formação à temperatura corporal evita uma resposta imunológica negativa do organismo. Embora uma das caraterísticas mais importantes dos cimentos de -TCP seja sua reabsorbilidade pelo organismo, a taxa de reabsorção In Vivo pode ser lenta devido à ausência de macroporos abertos. No presente trabalho foram obtidas estruturas macroporosas com presença de interconexões a partir da mistura de cimento de -TCP com uma fase líquida espumada. A fase líquida foi constituída de diferentes concentrações de hidrogenofosfato de sódio e um surfactante (Lutensol ON 110 ou Lauril Sulfato de Sódio), sendo espumada por agitação manual num sistema composto por 2 seringas conectadas por uma válvula de PVC. Após, foi acrescentado o pó de cimento, o qual foi misturado com a espuma no mesmo sistema. Verificou-se que as soluções com Lutensol apresentaram maior espumabilidade (218 – 400%) que as soluções com Lauril (63 – 209%). A difração de raios X evidenciou a transformação de -TCP em Hidroxiapatita deficiente em cálcio em todas as amostras após a imersão em solução de Ringer. As amostras preparadas com Lutensol apresentaram macroporos abertos com diâmetros maiores a 100m. Além disso foi observado que a macroestrutura final e o tamanho dos macroporos dos cimentos espumados varia em função das concentrações de fosfato e surfactante, além da proporção L/P. Por outro lado, a resistência a compressão das amostras macroporosas diminuiu com o aumento da porosidade total. Finalmente, foi observada a formação de uma camada continua de apatita sobre a superfície dos cimentos após imersão em SBF durante 21 dias. Este estudo sugere que as amostras de cimento de fosfato de cálcio espumadas com Lutensol possuem potencial para uso como arcabouços (scaffolds) para crescimento de tecidos. / Calcium phosphate cements (CPCs) form a viscous paste after mixing a solid phase (a calcium phosphate salt) with a liquid phase (water or an aqueous solution). This paste hardens, forming a precipitate with one or more calcium phosphates, which thanks to their formation at body temperature prevent a negative immune response. Even though one of the most important characteristics of -TCP cements is their resorbability in the body, their In Vivo resorption rate is low due to the lack of open macropores. In the present work, macroporous interconnected structures were obtained by mixing the -TCP cement with a foamed liquid phase. The liquid phase was composed of different concentrations of sodium hydrogenphosphate and a surfactant (Lutensol ON 110 or Sodium Lauril Sulfate), and it was foamed by manual agitation in a system of two syringes connected by a PVC valve. The cement powder was then added to the system and mixed with the foam likewise. Solutions with Lutensol showed better foamability (218 - 400%) than solutions with Lauril (63 - 209%). X-ray diffraction showed the transformation of -TCP into Calcium Deficient Hydroxyapatite in every sample after immersion in Ringer’s solution. Samples prepared with Lutensol showed open macropores with diameters greater than 100m. It was found that final macrostructure and size of macropores in the foamed cements vary according to phosphate and surfactant concentrations, as well as to the L/P ratio. It was also found that compressive strength of the macroporous samples decreased with the increase of the total porosity. Finally, a continuous apatite layer was observed on the surface of the cements after immersion in SBF for 21 days. This study suggests that the calcium phosphate cement samples foamed with Lutensol have potential to be applied as scaffolds for bone tissue regeneration.

Orientador: João Guilherme Padilha Filho / Banca: Claudia Acosta Duarte / Banca: Fabrício Bernardo de Jesus Brasil / Banca: Júlio Carlos Canola / Banca: Márcia Rita Fernandes Machado / Resumo: Foi utilizado na presente pesquisa o ultra-som pulsado de baixa intensidade, com a finalidade de avaliar, experimentalmente, seus efeitos sobre a reparação de falhas ósseas produzidas em rádio de coelhos, preenchidas ou não com o cimento de fosfato de cálcio adicionado com fibras de náilon. Foram utilizados 12 coelhos, raça Nova Zelândia, separados em dois grupos experimentais iguais (n=6) e escolhidos aleatoriamente (Grupo Tratado- GT e Grupo Controle-GC). As falhas ósseas de aproximadamente oito milímetros de extensão foram produzidas na diáfise de ambos os rádios, sendo as do membro direito preenchidas com o cimento de fosfato de cálcio sob a forma granulada e as do esquerdo, não preenchidas. Os animais do grupo tratado receberam estímulo pelo ultra-som pulsado de baixa intensidade durante 15 minutos nos primeiros cinco dias e dez minutos nos cinco dias seguintes, em ambos os membros. Os animais do grupo controle não foram estimulados pelo ultra-som. O controle radiográfico foi realizado no pós-operatório imediato e aos sete, 15 e 30 dias, de acordo com o tempo de observação de cada subgrupo (15 e 30 dias). Após o sacrifício, as áreas que continham as falhas ósseas foram processadas para a avaliação histopatológica. Os resultados das análises radiográfica e histolopatológica revelaram uma evolução mais rápida e intensa da proliferação de tecido ósseo nas falhas, preenchidas ou não pelo cimento, porém que receberam estímulo pelo ultra-som. Os resultados obtidos neste trabalho mostraram que o ultra-som pulsado de baixa intensidade é ser um recurso extremamente eficaz na aceleração do processo de ossificação e que, associado ao cimento de fosfato de cálcio com fibras de náilon, tem este processo intensificado, demonstrando, assim, o poder osteoindutor deste biomaterial. / Abstract: The present experimental research evaluated the effects of low intensity pulsed ultrasound for repair bone defects produced in rabbit's radius, filled in or not with calcium phosphate cement incorporated with nylon fibers. Twelve rabbits, from the New Zealand lineage, were randomly allocated in two equal experimental groups. An eight millimeters bone gap was surgically produced in the radius bone diaphysis and filled with the cement (right radius). The left limb bone gap remained empty. Animais were submitted to dessions of pulsed ultrasonic stimulus for 15 minutes during five days and ten minutes during more five days, in both radius. Radiological examinations were performed in the immediate postoperative and seven, 15 and 30 days after surgery (according with the postoperative follow-up -15 and 30 days). The bone defects were collected and submitted to optical microscopy. The results showed an increase and faster evolution of ossification's process in the bone defects, filled or not with the bone cement, but that received stimulus by ultrasound when compared to the control group. These results suggest that low-intensity pulsed ultrasound is an effective resource for acceleration of the ossification process and, when combined with calcium phosphate cement, this effect was increased. / Doutor