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Figure 5 shows the force needed to pull stainless steel wires through two sub- merged silicone pads that have been compressed with 500 g of force quality penegra 50mg. The wire that was coated with Teflon buy cheap penegra 50 mg on-line, a lubricious yet very hydrophobic material, required about half the force of an uncoated wire to pull it through the fixture. In comparison, the wire that had a lubricious, hydrophilic, photoimmobilized polymer coating required less than a tenth of the force of an uncoated wire. The hydrophilic coating was durable for many cycles of the test. A wide range of biomaterials have been modified with photoimmobilized hydrophilic polymers and tested against various surfaces. Lubricious surfaces on medical devices reduce the force required to manipulate medical devices during a surgical procedure. This in turn has the benefit of reducing the time required for any given procedure. In addition, lubricious catheters can negotiate tortuosities in the vasculature that are not possible with unmodified devices, thus expanding the range of potential treatment sites within the body using procedures such as arthroscopic surgery, balloon catheter angioplasty, or site-directed drug delivery. As an example of the benefits of the photoimmobilized hydrogel lubricious surface, a model in vitro system was devised using pinched fresh bovine aortas. This simulation of a narrowed artery was used to compare unmodified mock polyethylene (PE) catheters with those modified using a photoreactive mixture of polyacrylamide and polyvinylpyrrolidone. The force required to push catheters through the pinched aorta was carefully measured using a force gauge; the results (Fig. Passivation When a medical device is subjected to the harsh in vivo environment, its surface is exposed to the body’s natural defense systems. Minerals, fatty acids, proteins, host cells, macromolecules, Figure 5 Reduction of friction by using a PhotoLink lubricious coating on a stainless steel wire compared to uncoated and Teflon coated wires. Forces were measured by pulling the wires through SR pads. Surface Modification of Biomaterials 105 Figure 6 Reduction of crossing force using surface-modified catheters. The pinched aorta model for measuring lubricity was used to compare unmodified and modified catheters. Mock PE catheters were either coated with a common silicone lubricant or with photoreactive hydrogel polymer while submerged in heparinized bovine blood. Adsorption of proteins or lipids can contribute to (1) initiation of blood coagulation, complement activation, and platelet adherence on intravascular devices; (2) fouling and plugging of microporous contact lenses or dialysis membranes; (3) opacification of the visual axis on IOLs, contact lenses, or keratoprostheses; and (4) bacterial colonization on almost any implantable product. Surfaces modified with photoimmobilized hydrophilic polymers have been shown to effec- tively reduce protein adherence, bacterial colonization, and lipid deposition. By controlling the polymeric composition and the extent of crosslinking, hydrogel matrices can be designed to provide optimal passivation characteristics for enhancing the particular biomaterial and device performance. Further discussion of passivating coatings can be found in Section IV, ‘‘Surface Modification to Improve Blood Compatibility of Medical Devices,’’ and Section V, ‘‘Antimicro- bial Coatings. SURFACE MODIFICATION TO IMPROVE BLOOD COMPATIBILITY OF MEDICAL DEVICES Improved compatibility with blood is a desired feature for a variety of medical devices that must contact blood during clinical use. It is difficult, however, to achieve this improvement by altering the bulk materials used for fabricating the devices. Because of the diversity of blood- contacting medical devices, which range in complexity from syringe needles to artificial hearts and in duration of use from seconds to years, it is unlikely that sufficient ‘‘blood-compatible’’ bulk materials will be identified to serve the needs of the many devices currently used or in development. A more straightforward method is to apply a thin-film coating to the surface of 106 Anderson et al. For many years, researchers have been developing coatings to improve the blood compatibility of medical devices. It is recognized that it is unlikely that a single surface modification will solve the broad spectrum of blood compatibility issues, and therefore it is essential to develop and test a variety of potential surface modification agents. Heparin-based coatings have been demonstrated to substantially improve the performance of a variety of blood-contacting medical devices. Recently, nonheparin- based, synthetic coatings have also been shown to be promising for medical device applications where biological molecules are not desired or appropriate. The notion of using surface modifications to improve the blood compatibility of medical device materials is not new. Synthetic processes have been developed to immobilize (1) fibrin cascade inhibitors [6,7]; (2) passivating polymers, such as hydrogels [8–11] and polyethylene oxide [12,13]; (3) albumin binding agents [14–17]; (4) membrane mimics; (5) platelet inhibitors; and (6) sulfonated polymers [20–22] onto polymers and metals. However, these processes generally are limited to one or a few types of substrates, require harsh chemical reaction conditions, or are time or labor intensive. In contrast, surface modification using the photochemical coupling technology described above has several significant advantages over previous methods: (1) a broad spectrum of materials can serve as substrates for immobilization; (2) many types of molecules (including all of the classes listed above) can be immobilized using analogous protocols; and (3) the processing steps are simple, short, and devoid of severe chemical treatments. Photoimmobilized Heparin Surface Modifications Heparin is a pharmaceutical that has been used clinically for decades as an intravenous anticoagu- lant to treat inherent clotting disorders and to prevent blood clot formation during surgery and interventional procedures. Heparin molecules are polysaccharides with a unique chemical structure that gives them specific biological activity. When heparin is derivatized with photo- chemical coupling agents and immobilized onto the surface of a medical device material, it improves the performance of the material when in contact with blood in several ways: (1) providing local catalytic activity to inhibit several enzymes critical to the formation of fibrin (which holds thrombi together); (2) reducing the adsorption of blood proteins, many of which lead to undesirable reactions on the device surface; and (3) reducing the adhesion and activation of platelets, which are a primary component of thrombus. Heparin-containing coatings have been assessed using a variety of in vitro and in vivo test systems. These tests include the verification of the heparin presence, uniformity, and stability on the surface as well as in vitro and in vivo function. Presence and Uniformity The presence and uniformity of photoheparin on material surfaces has been assessed by staining with toluidine blue, electron spectroscopy for chemical analysis (ESCA), static secondary ion mass spectrometry (SSIMS), and scanning electron microscopy with atomic x-ray analysis (SEM/ EDAX).
There are many causes of anterior knee pain discount 100mg penegra, some of Patellofemoral Malalignment them related to PFM and many more not related There are some uncommon injuries (e cheap penegra 50 mg free shipping. Likewise, we should bear in mind that chondritis dissecans [OCD] of the patellofemoral there are teenage patients with anterior knee groove, or painful bipartite patella) that result pain who lack evidence of organic pathology from PFM but that do not require specific treat- (i. Mori and col- pain, emphasizing the fact that not all malalig- leagues35 regard overuse and the excessive lat- ments are symptomatic. As with any other pathology, it is eral retinacular release to be an effective treat- necessary to make an accurate diagnosis before ment for these patients. In our own series, we embarking on a specific treatment plan. An have two cases of OCD of the patellofemoral 115 116 Etiopathogenic Bases and Therapeutic Implications groove associated with PFM that were treated Furthermore, the pain experienced by with an Insall’s proximal realignment, with sat- patients with a bipartite patella is, according to isfactory clinical results, leading to the healing Mori and colleagues,36 a result of excessive trac- of the osteochondral lesion, as shown by MRI tion by the vastus lateralis and the lateral reti- (Figure 7. Osteochondritis dissecans of the patellofemoral groove in a patient with symptomatic PFM (a–c). The MRI shows the chondral lesion healed a year and a half after realignment surgery (d&e). These authors have observed that a trauma,6 intra-articular hemangioma,3,41 osteoid modified lateral retinacular release eliminates osteoma15 (Figure 7. These lesions can cause confusion and trauma,40,52 saphenous nerve entrapment,42 stress hence lead to an incorrect diagnosis resulting in fractures in the region of the knee34,38,51 (Figure an erroneous treatment. Bipartite patella of a volleyball player with excessive lateral pressure syndrome. Moreover, a affected by the delay in diagnosis or by an inap- high proportion of primary aggressive benign or propriate invasive procedure that can result in malignant bone tumors occur in the same age extension of the tumor and may close the door group than anterior knee pain syndrome, and on a limb-salvage surgery. According Moreover, a careful, thorough physical exam- to Muscolo and colleagues,37 poor-quality radi- ination is very important to rule out referred ographs and an unquestioned original diagnosis pain arising from the lumbosacral spine (e. When a femoral neck, stress fractures of the femoral musculoskeletal tumor is initially misdiagnosed neck, slipped femoral epiphysis). Associated as a sports injury, its treatment may be adversely numbness or tingling suggests a lumbar Figure 7. Intramuscular hemangioma of the vastus medialis obliquus muscle (a). Referred pain from the hip usually where for an anterior knee pain syndrome and affects the anterior aspect of the distal thigh and functional patellofemoral instability with “asso- knee, and generally there is decreased internal ciated psychological factors” was in actual fact rotation and pain on hip motion. For instance, a found to have a calcar osteoid osteoma. Once patient in our series who was being treated else- the tumoral lesion was addressed, both the Figure 7. Localized pigmented villonodular synovitis of the Hoffa’s fat pad. Heterogeneous enhancement lesion into the Hoffa’s fat pad. A subperiostial osteoid osteoma on the anterior aspect of the proximal end of the tibia is an extremely rare cause of anterior knee pain. Axial T2-weighted MR image (with fat suppression) (b). Note a well-defined edematous area without significant extraosseous involvement. Currently (9 years later), the source of the anterior knee pain may be in this patient is in a physically very demanding the posterior aspect of the knee47 (see patient 1 job, which he manages to do without any prob- under Case Histories). MRI shows a mass in the popliteal aspect with bone involvement. Biopsy revealed a nonspecific chronic synovitis of the popliteal aspect. Symptoms of the anterior aspect of the knee disappeared after the resec- tion of the lesion. In conclusion, as a general rule, the more infrequent causes of anterior knee pain should be considered in the differential diagnosis of a painful knee when the treatment of the most fre- quent ones has proved ineffective. Treat the Patient, Not the Image: Advances in Diagnostic Imaging Do Not Replace History and Physical Examination In some cases, a distinction should be drawn between instabilities caused by an ACL tear and those caused by the patella. In our series there is a patient who was referred to us with knee insta- bility secondary to indirect trauma caused by a skiing accident. The patient’s MRI result was compatible with an ACL rupture (Figure 7. Clinical examination revealed a normal ACL, Figure 7. Sagittal FSE PDW Fat Sat MRI showing an intra-articular which was confirmed arthroscopically. Another patient, for anterior right knee pain and functional referred to our department with knee pain and patellofemoral instability. In the CT scan we can instability, previously diagnosed by CT-scan to see a correct patellofemoral congruence of the have PFM, actually had an ACL rupture as well as right knee and an osteolytic area in the lateral a bucket handle tear of the medial meniscus Figure 7. Iliotibial friction band syndrome in a female surfer. Note the bone exostosis of the lateral femoral condyle (arrow), which leads to an impingement on the iliotibial tract. Stress fracture in the proximal tibia in a patient who consulted for anterior knee pain without traumatism.
The serum glucose concentration is 48 mg/dl generic penegra 50 mg overnight delivery, the serum insulin level is high order penegra 100 mg with mastercard, and test results are negative for insulin antibodies. The C-peptide level is low, and tests for sulfonylurea and meglitinides are negative. Which of the following is the most likely diagnosis for this patient? Noninsulinoma pancreatogenous hypoglycemia syndrome (NIPHS) D. Insulin autoimmune hypoglycemia Key Concept/Objective: To be able to recognize the patient with factitial hypoglycemia Factitial hypoglycemia is more common in women and occurs most often in the third or fourth decade of life. Many of these patients work in health-related occupations. Factitial hypoglycemia results from the use of insulin or drugs that stimulate insulin secretion, such as sulfonylureas or meglitinides. The possibility of factitial hypoglycemia should be con- sidered in every patient undergoing evaluation for a hypoglycemic disorder, especially when the hypoglycemia has a chaotic occurrence—that is, when it has no relation to meals 3 ENDOCRINOLOGY 15 or fasting. The diagnosis of factitial hypoglycemia can usually be established by measur- ing serum insulin, sulfonylurea, and C-peptide levels when the patient is hypoglycemic. In a patient whose hypoglycemia results from covert use of a hypoglycemic agent, the agent will be present in the blood. In insulin-mediated factitial hypoglycemia, the serum insulin level is high and the C-peptide level is suppressed, usually close to the lower limit of detec- tion, as seen in this patient. A 38-year-old man is brought to the emergency department after a generalized seizure. The complete blood count and results of a blood chemistry 7 panel are normal, with the exception of a low glucose level. A head CT is negative, and a lumbar puncture reveals no evidence of infection. After the patient is stabilized and able to give a history, he tells you that he has been experiencing episodes of dizziness, confusion, headache, blurred vision, and weakness for the past month. The episodes always occur about 2 hours after he eats. He has no other significant medical his- tory and takes no medications. Which of the following is the probable diagnosis for this patient? Insulin autoimmune hypoglycemia Key Concept/Objective: To be able to distinguish NIPHS from insulinoma NIPHS is a recently described entity. Like insulinoma, it affects patients across a broad age range (16 to 78 years) and causes severe neurohypoglycemia, with loss of consciousness and, in some cases, generalized seizures. Unlike insulinoma, it occurs predominantly in males (70%). Histologic analysis of pancreatic tissue from patients with NIPHS shows cells budding off ducts, seen best by chromogranin A immunohistochemical staining. No gross or microscopic tumor has been identified in any patient with NIPHS. Symptoms of NIPHS occur primarily in a postprandial state, usually 2 to 4 hours after eating. Although patients with insulinoma may experience symptoms postprandially, they also have symptoms during food deprivation. It is extremely rare for insulinoma patients to have symptoms solely in the postprandial state. Results of super- vised 72-hour fasts have always been negative in NIPHS patients. A negative 72-hour fast in a patient with insulinoma is a rare occurrence. Gradient-guided partial pancreatectomy has been effective in relieving symptoms in patients with NIPHS, though recurrence of hypoglycemia after a few symptom-free years has been reported in a few patients. A 42-year-old white woman comes to your office to establish primary care. She reports no previous med- ical history except "fibroids," for which she underwent a vaginal hysterectomy. Other than the fact that she appears obese, there are no pertinent findings on physical examination. You are concerned with the long-term implications related to her being overweight. On the basis of the available data, what is the calculated body mass index (BMI) for this patient? This form of measurement has been replaced by a classification system that attempts to allow comparison of weights independent of stature across populations. It is based on the BMI, which is calculated by dividing the body weight (in kilograms) divided by height (in meters) squared. In nonselected populations, BMI does correlate with percentage of body fat, but this relationship is independently influenced by sex, age, and race. In this patient, BMI is calculated as follows: 82 kg ÷ (1. A 38-year-old woman who is a longtime patient of yours comes to the clinic for her annual appointment. Despite multiple attempts at dietary and behavior modification, she has been gaining weight regularly since she was 23 years of age. In addition to obesity, she has moderately controlled hypertension and glucose intolerance and worsening osteoarthritis in her knees bilaterally.
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