By T. Merdarion. Saint Louis Christian College.
Thus cheap 150mg zyban otc anxiety frequent urination, Ti alloys are seldom used as materials where resistance to wear is a primary concern [1 order 150mg zyban amex depression years,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. With the large and growing number of total joint designs that use modular connec- tions (i. Retrieval studies [21,22] have shown that severe corrosion attack can take place in the crevices formed by these tapers in vivo (see Fig. It has been postulated that this corrosion process is the result of a combination of stress and motion at the taper connection and the crevice geometry of the taper. The stresses resulting from use cause fracturing and abrasion of the oxide film covering these passive metal surfaces. This, in turn, causes significant changes in the metal surface potential and in the crevice solution chemis- try as the oxides are continuously fractured and repassivate. These changes may result in deaera- tion (loss of O2) of the crevice solution and a lowering of the pH in the crevice as is expected in crevice corrosion attack. The ultimate result of this process is a loss of the oxide film and its kinetic barrier effect and an increase in the rate of corrosive attack in the taper region. Figure 4 Retrieved joint replacement components showing corrosion around the rims of early model conical taper connections. Both fretting and crevice corrosion are responsible for generating this type of implant degradation. Corrosion and Biocompatibility of Implants 77 Severe corrosion attack has been associated with Co–Cr alloy modular taper connections. While less common, corrosion attack of titanium alloy stems can also occur. In general, Co–Cr alloys undergo intergranular corrosion, etching, selective dissolution of cobalt, and the formation of Cr-rich particles that are most likely oxides or oxychlorides. The corrosion products generated at the taper connections can migrate into periprosthetic tissues and in between articulating poly- meric surfaces. In the past there have been instances where retrieved implants have corroded to such an extent that intergranular corrosion resulted in fatigue failure in the neck of Co–Cr stems. It is to be emphasized that it is the mechanical integrity of the oxide films that form on these alloys that determines long-term stability and performance of metallic components. Rela- tively little is known about the mechanical stability of oxide films and the electrochemical reactions which occur when an oxide film is fractured. What is known is that when the oxide films of these orthopedic alloys are abraded or removed from the surface by fretting the open circuit potential can decrease to values as low as 500 mV (vs. These potential excursions may be significant enough and prolonged enough to cause changes in the oxide structure and stability by bringing the interface potential into the active range of the alloy, thereby dramatically accelerating the corrosion rate. Known corrosion properties of popular implant alloys are listed in Table 4 and discussed in the following sections.
HSV-2 is transmitted more effi- ciently from males to females than from females to males order zyban 150 mg with mastercard depression xanax withdrawal. Autoinoculation to other skin sites also occurs purchase zyban 150 mg without a prescription depression untreated, more often with HSV-2 than with HSV-1. Extragenital lesions 7 INFECTIOUS DISEASE 85 develop during the course of primary infection in 10% to 18% of patients. Aseptic meningitis is not uncommon with primary genital herpes, particularly in women; in rare instances, herpetic sacral radiculomyelitis occurs. Primary finger infections, or whitlows, usually involve one digit and are characterized by intense itching or pain fol- lowed by the formation of deep vesicles that may coalesce. Among the general public, whitlows are most often caused by HSV-2, whereas among medical and dental person- nel, HSV-1 is the principal culprit. A 70-year-old male patient who has diabetes and hypertension presents with a complaint of severe flank pain. He was in his usual state of health until 5 days ago, when he developed intermittent, severe, lan- cinating pain that radiated from his midchest to his right flank and then to his right middle back. He denies having undergone any trauma or having hematuria, dysuria, fever, chills, weight loss, or a histo- ry of renal stones. He also states that his shirt has been "sticking to his back" during this period. On phys- ical examination, the patient is afebrile and has a diffuse vesicular eruption in a T4 distribution with severe pain to palpation. Which of the following statements regarding varicella-zoster virus (VZV) infection is true? Primary varicella infection is communicable and can result in her- pes zoster infection in a contact B. Hospitalized patients with varicella or herpes zoster infection should be isolated to prevent spread of the virus to other susceptible persons C. There is no available medical therapy for herpes zoster eruptions D. Ramsay Hunt syndrome is a herpes zoster eruption in the first branch of the trigeminal nerve Key Concept/Objective: To know the clinical concepts and features of VZV infection Herpes zoster results from the reactivation of VZV infection. Varicella in one patient cannot produce herpes zoster in another; however, persons who are exposed to patients who have herpes zoster can contract varicella. Thus, hospitalized patients with varicella or herpes zoster should be iso- lated to prevent spread of the virus to other susceptible persons. High-dose oral acy- clovir (800 mg five times daily for 7 days), when begun early, may shorten the course and reduce the severity of herpes zoster in otherwise healthy hosts. Oral valacyclovir (1 g three times daily) or famciclovir (500 mg three times daily) may also be used. Ramsay Hunt syndrome is an infection of the geniculate ganglion of the seventh cranial nerve that produces facial paralysis; vesicles on the eardrum and side of the tongue can also occur. A 22-year-old man presents to your clinic with complaints of fever, sore throat, marked fatigue, and myalgias. He denies having had contact with anyone who was sick, and he denies ever having unprotected sexual intercourse. He has had only one sexual partner, with whom he has been having sexual relations for sever- al months. His sore throat has been improving, and he denies hav- ing cough or sputum production. On physical examination, mod- erate pharyngeal injection without exudates is noted, and the spleen tip is palpable and slightly tender. Laboratory testing shows a normal WBC, mild elevations of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, a differential with 10% atypical lymphocytes, and a negative result on heterophil antibody screening. Which of the following statements regarding cytomegalovirus (CMV) infection is true?
Immediate referral should be made because botulism can be life threatening purchase zyban 150mg otc anxiety yahoo. Double Vision Double vision zyban 150 mg generic anxiety 411, or diplopia, is the condition in which the extraocular muscles do not work in a coordinated manner and the patient sees one object as two. There are a variety of causes for diplopia, including both neurological and muscular disorders. History For the complaint of double vision, it is important to fully analyze the symptom, deter- mining how severe the visual disturbance is, when it occurs, and so on. Determine any associated symptoms, such as other weaknesses, headache, or pain. Explore whether the diplopia most commonly occurs in certain circumstances, including particular times of day. Ask about substance use/abuse, including alcohol intake. Identify any history of systemic disorders, including neuromuscular, endocrine, and neurological diseases. Physical Examination The physical examination should start with visual acuity testing. Determine whether the diplopia occurs only when the patient uses both eyes or whether it is limited to only one eye. Carefully assess the placement and symmetry of the eyes, performing a cover/uncover test and observing for the corneal light reﬂex. Note any lack of conjugate movement as the patient follows an object through the six cardinal ﬁelds of gaze. PROPTOSIS AND EXOPHTHALMOS Proptosis is the general term used to describe anterior displacement of the eye, whereas exophthalmos is used speciﬁcally to describe proptosis related to endocrinopathy, usually thyroid disease. In thyroid disorders, the eye muscles thicken and thereby move the eyes forward so that their ability to move conjugately is affected, and the lids may fail to close completely. Movement in all directions may be affected, although most commonly the patient ﬁnds it difficult to look upward. In addition to diplopia, patients may experience dry eyes, ulcerations, and diminished vision. Less common causes of proptosis include infections and tumors. The patient may complain of signs of thyroid disease, primarily those of hyperthy- roidism, such as nervousness, anxiety, weight loss, and so on. The thyroid may be nodular or enlarged, the heart rate elevated, and a ﬁne tremor may be present. A fever may accom- pany the proptosis, regardless of whether the cause is from thyroid disease or infection. There may also be complaints of visual disturbances in addition to the diplopia, a dry/gritty sensation, and eye tenderness. The initial tests would be to assess thyroid function, with complete blood count and other studies obtained subsequently, as needed. A Hertel exophthalmometer can be used to measure the degree of anterior displacement. OCULOMOTOR NERVE DISORDERS Lesions of the third, fourth, or sixth cranial nerves may result in diplopia, either verti- cal or horizontal. The third, fourth, or sixth cranial nerve palsies are usually benign, self- limited, and resolve in weeks to months. They commonly occur in patients who have hypertension and/or diabetes. However, a mass-occupying lesion should be excluded. If the third cranial nerve is affected, there is usually accompanying ptosis, so that the lid obscures the vision in the affected eye and the patient’s main complaint may not be dou- ble vision. If the fourth nerve is involved, the diplopia will be vertical, whereas sixth cra- nial nerve palsy results in horizontal diplopia. Depending on the cause, the patient may exhibit signs or complaints consistent with herpes zoster, other infections, or neurological involvement.
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