By H. Will. New Saint Andrews College. 2018.
Of the many Co–Cr alloys available cheap zithromax 100 mg mastercard antibiotic resistance vertical horizontal, the two most com- Corrosion and Biocompatibility of Implants 73 74 Hallab et al cheap zithromax 250 mg free shipping antibiotic resistance update. Others approved for implant use include one that incorporates tungsten (Co–Cr–Ni–W, ASTM F-90) and another with iron (Co–Ni–Cr–Mo–W-Fe, ASTM F-563). Co–Ni–Cr–Mo alloys that contain large percentages of Ni (25–37%) promise increased corrosion resistance yet raise concerns of possible toxicity and/or immunogenic reactivity (discussed later) from released Ni. The biologic reactivity of released Ni from Co–Ni–Cr alloys is cause for concern under static conditions. Due to their poor frictional (wear) properties, Co–Ni–Cr alloys are also inappropriate for use in articulating components. Therefore the dominant implant alloy used for total joint components remains Co–Cr–Mo (ASTM F-75). Titanium Alloys While CPTi is most commonly used in dental applications, the stability of the oxide layer formed on CPTi (and consequently its high corrosion resistance) and its relatively higher ductility (i. Generally, Ti-6Al-4V (ASTM F-136) is used for joint replacement components because of its superior mechanical properties in comparison to CPTi (Table 3). The Ti-6Al-4V alloy (also known as Ti-6-4) is composed of grains of two phases: an HCP phase and a BCC phase, referred to as the alpha and beta phases, respectively. The microstructure and mechanical properties of this alloy are highly dependent on the thermomechanical processing treatments. The Ti-6Al-4V alloy microstructure is generally composed of a fine-grained HCP phase with a sparse distribution of the BCC phase. If the material is cooled too slowly the BCC phase becomes more prominent and lowers the strength and corrosion resistance of the alloy. Titanium alloys are particularly good implant materials because of their high corrosion resistance compared with stainless steel and Co–Cr–Mo alloys. A passive oxide film (primarily of TiO2) protects both Ti-6Al-4V and CPTi. This stable and adherent passive oxide film protects Ti alloys from pitting corrosion, intergranular corrosion, and crevice corrosion attack and in large part is responsible for the excellent biocompatibility of Ti alloys. Generally the strength of Ti-6Al-4V exceeds that of stainless steel, with a flexural rigidity roughly half of stainless steel and Co–Cr–Mo alloys. The torsional and the axial stiffness (moduli) of Ti alloys are therefore closer to bone and theoretically provide less stress shielding than do Co alloys and stainless steel. This attribute, along with excellent biocompatibility and corrosion resistance, is primarily responsible for the popularity of titanium alloys in fracture fixation devices (plates, screws), spinal fixation devices, and total hip replacement femoral components. Ti-6Al-4V alloy is an example of a material which can be approximately 15% softer than Co–Cr–Mo alloys, yet when used in bearing applications results in significantly more (15% greater) wear than Co–Cr–Mo, e. Thus, Ti alloys are seldom used as materials where resistance to wear is a primary concern [1,16–20]. Zirconium and Tantulum Alloys Zirconium (Zr) and tantalum (Ta) are characterized as refractory metals (others include molybde- num and tungsten) because of their relative chemical stability (passive oxide layer) and high melting points. Zr and Ta alloys are currently in use and may be gaining popularity as orthopedic metals. Because of the surface oxide layer stability, Zr and Ta (like Ti) are highly corrosion Corrosion and Biocompatibility of Implants 75 76 Hallab et al. Corrosion resistance generally correlates with biocompatibility (although not always) because more stable metal alloys tend to be less chemically active and less participatory in biologic reactions. Additionally, these refractory metals generally possess high levels of hardness (12 Gpa) and wear resistance (approximately ten fold that of Co and Ti alloys, using abrasion testing), which makes them well suited for bearing surface applications. The thickness of the surface oxide layer (approximately 5 m) and ability to extend ceramic-like material properties (i. As difficulties associated with forming and machining these metals are overcome the use of these materials is expected to grow [2,16,18–20]. PRIMARY MECHANISMS OF IMPLANT CORROSION There are significant clinical problems relating to the corrosion of implant alloys in the current state-of-the-art implants which will likely continue to be a potential hazard for the near future, one of which is corrosion observed in the taper connections of retrieved modular joint replacement components.
Improvements in appearance included reduction in the appearance of skin dimpling buy zithromax 250mg on line antimicrobial wipes, improvement in the overall contour of the limb generic 250 mg zithromax with mastercard virus martin garrix, and improvement in overall skin texture. Patients enjoyed the procedure and found it to be relaxing, with no side effects. There was no signiﬁcant change in either BMI or percent body fat. This suggests that TM observed improvement were due to the action of the TriActive device. It also suggests TM that the TriActive device provides localized treatment, without an apparent systemic effect on the body. Many patients are interested in treatments that improve the appearance of cellulite. TM We have found that the TriActive device offers a unique and unmatched combination of low energy irradiation, contact cooling, and dynamic suction massage to treat this unpleasant condition of the skin and subcutaneous tissue, leading to improvement in the appearance of cellulite. This therapy was ﬁrst performed in Argentina (1) and later in France, in the thermal waters station of Royat, near Clermont Ferrand (2). There, a group of cardiologists from the hospital of Clermont Ferrand began to treat patients with peripheral organic and func- tional arteriopathies (atherosclerotic, Buerger’s disease, Raynaud’s disease, etc. In 1953, the cardiologist Jean Baptiste Romuef published a paper about his 20 years of experience in using subcutaneous injections of CO2 for treatments (3). Later, the Parisian cardiologist Jerome Berthier, along with Luigi Parassoni from Gaillard A, started to apply it in patients with cellulite (4). Until 1983, 402,000 patients had been treated in Royat. The large number of patients conﬁrms the popularity and perhaps the efﬁcacy of this therapeutic method. CO2 is an odorless, colorless gas, ﬁrst discovered by Van Helmont in 1648. Many years ago in France, Clermont Ferrand used thermal CO2 (CO2 99. When administered subcutaneously, CO2 immediately diffuses at the cutaneous and muscular microcirculatory level. After the administration of 200 cc of CO2 in the subcu- taneous thigh tissue of a canine, CO2 is detected in the femoral venous blood in approxi- mately 5 minutes, with a maximum time lag of 30 minutes. This demonstrates the ability of CO2 to diffuse across fasciae and reach the underlying muscles (6). Most of the gas is elimi- nated through the lungs (expiration), while a smaller portion is converted into carbonic acid in tissues and is eliminated through the kidneys. At the vascular level, CO2 increases vascular tone and produces active microcircula- tory vasodilatation. CO2-induced vasodilatation results from the direct action of CO2 on arteriole smooth-muscle cells (7). In addition, this promotes Bohr’s effect, a mechanism that allows the transfer of tissue CO2 to the lungs and lung O2 to tissues through the oxyhemoglobin dissociation 197 198 & LEIBASCHOFF curve. When administered through an external route, CO2 promotes this mechanism, resulting in a higher tissue oxygenation and neoangiogenesis (Fig. Figure 1 Change in oxygenation and neoangiogenesis after administration of CO2. Although it is toxic when inhaled (10% in air may cause asphyxia), subcutaneous or intra-abdominal administration of CO2 has not shown any toxic effects, even at high doses (2–10 L). It differs from other gases because no nitrogen embolisms arise, unlike those that occur in oxygen–ozone therapy. Organic or functional peripheral arteriopathies (10) b. Erectile dysfunction, associated with microangiopathies CARBOXYTHERAPY & 199 Figure 2 Before and after CO2 treatments to correct skin graft surgery. Figure 3 Before and after CO2 treatments to improve liposculpture results.
Physical examination is notable for lymphadenopathy and splenomegaly zithromax 250mg without a prescription antibiotics for uti yahoo answers. Laboratory data reveal a moderately decreased hemoglobin level order 500mg zithromax fast delivery antibiotic tooth infection, thrombocytopenia, and a moderate leukocytosis. Which of the following statements is the most accurate regarding cure of ALL? A combination of vincristine, prednisone, and daunorubicin cures about one third of patients with Philadelphia positive (Ph+) ALL B. A combination of L-asparaginase and cyclophosphamide cures about one third of patients with Ph+ ALL C. Allogeneic stem cell transplantation cures about one third of patients with Ph+ ALL D. There are currently no regimens that are known to cure this disease Key Concept/Objective: To know the regimen that is associated with cure of Ph+ ALL Ph+ ALL is identified by the t(9;22)(q34;q22) or the bcr-abl fusion gene. It is currently the major challenge in curing ALL because it makes up 25% to 30% of adult cases and perhaps one half of B-lineage ALL. Approximately 70% of patients achieve CR, but the remission durations are markedly shorter (median, 7 months) for Ph+ cases than for those without a Ph chromosome (remission of almost 3 years). As yet, no chemotherapy regimen alone appears to have the potential to cure this group of patients. In contrast, allogeneic stem cell transplantation cures about one third of patients with Ph+ ALL. The probability of relapse after transplantation is approximately 30% to 50%, further attesting to the thera- py-resistant nature of this disease. The treatment for Ph+ ALL should include an intensive remission-induction chemotherapy program, followed by allogeneic stem cell transplan- tation in the first CR if a donor is available. Considerable interest exists in investigating new agents, especially the tyrosine kinase inhibitor imatinib mesylate, in this high-risk group of patients. A 50-year-old man is referred to your clinic by the blood bank for a positive HTLV-I serology. What advice would you give this patient at this time? He has a 20% lifetime risk of developing leukemia B. He has a 40% lifetime risk of developing leukemia C. He is unlikely to have any medical problems associated with this virus E. He is at risk for developing an AIDS-like illness Key Concept/Objective: To be able to recognize that most patients exposed to the HTLV-I virus will not develop leukemia Blood banks commonly screen donated blood for HTLV-1. This virus had been linked to acute T cell leukemia and cutaneous T cell lymphoma in adults. However, most people with antibodies to HTLV-I remain free of these associated diseases, which suggests a multifactor- ial process in the development of leukemia. Burkitt lymphoma is associated with Epstein- Barr virus. Which of the following groups has an increased incidence of acute leukemia? All of the above Key Concept/Objective: To know the risk factors for acute leukemia All of the groups listed have a higher risk of developing acute leukemia than does the gen- eral population. Other risk factors include Jewish ethnicity, prior exposure to ionizing radi- ation (either through environmental exposure or as part of a treatment regimen), exposure to some industrial chemicals, several chemotherapy agents, a genetic predisposition, and the presence of specific diseases such as Down syndrome. Which of the following statements is more commonly associated with acute myeloid leukemia (AML) than with ALL? It accounts for the majority of cases of acute leukemia in adults B. Patients are more likely to have hepatosplenomegaly and lym- phadenopathy at presentation D. Maintenance chemotherapy generally lasts 1 to 3 years E. The Philadelphia chromosome–positive (Ph+) variant is more resistant to standard treatment Key Concept/Objective: To know the differences between AML and ALL in adults AML accounts for about 80% of acute leukemias in adults and is most likely to present with hemorrhage or infection. Standard induction therapy with cytarabine and daunoru- bicin (7 + 3 regimen) is followed by consolidation chemotherapy but generally no long- term maintenance regimen.
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