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By N. Mason. Jackson State University.

The computer simulation indicates that increasing the pulse duration (and/or amplitude) produced an increase in the magnitude of the maximum external and maximum internal rotation angles that occur during knee flexion order fildena 25mg visa. Also cheap fildena 150mg line, positions of the maximum external rotation angles were slightly affected by the pulse amplitude and/or duration. A two-point contact condition was maintained until about 66° of knee flexion. From there on, and until 90° of flexion, a one-point contact was predicted on the medial side. This motion is expected and can be thought of as a result of the femur rotating externally over fixed plateaus which causes the medial tibial contact point to move anteriorly and the lateral tibial contact point to move posteriorly. The analysis show that the position of separation in the lateral compartment was slightly affected by the amplitude and/or duration of the forcing pulses. However, the motion pattern of the medial and lateral femoral and tibial contact points was independent of both pulse amplitude and pulse duration. Henceforth, the medial shift velocity increased, reaching a maximum at 90° of knee flexion. Then, the varus velocity increased, reaching a maximum between 40 and 50° of knee flexion; henceforth, the velocity decreased reaching zero between 60 and 65° of knee flexion. The valgus velocity increased again achieving a maximum around 80° of knee flexion. Then, the external rotation velocity began to increase reaching a maximum at around 8° of knee flexion and decreased, reaching zero around 20° of knee flexion. From this point, the internal rotation velocity increased to a maximum between 45 and 60° of knee flexion then decreased as the knee flexion increased. The remaining results related to contact and ligamentous forces are shown for pulses of different amplitudes and a constant duration of 0. These two figures show that increasing the pulse amplitude caused a decrease in the magnitude of the medial and lateral contact forces; similar results were obtained when the pulse duration was increased while the pulse amplitude was kept unchanged. As the flexion angle increased, this tension decreased while tension in the anterior fibers increased and became dominant. The maximum forces in the anterior and deep fibers occurred between 40 and 50° of knee flexion, while the maximum force in the oblique fibers occurred at approximately 5° of knee flexion. The results show that the patterns of change in the ligamentous forces were not generally affected by changing the characteristics of the applied pulsing loads. However, increasing pulse amplitude (and/or duration) slightly affected the magnitude of the forces in the different ligamentous fibers. The procedure is then repeated at different positions to cover a range of knee motions. However, these quasi-static models cannot predict the velocity or acceleration of the different segments forming the joint. Also, these models are further limited in that they cannot determine the effects of the dynamic inertial loads (which occur in many daily living activities) on joint kinematics and joint loads. In this chapter, a © 2001 by CRC Press LLC FIGURE 1. The system of equations forming an anatomical quasi-static knee model is a system of nonlinear algebraic equations. These equations are solved iteratively using a Newton-Raphson iteration tech- nique,20-23,129,130 discretized and solved using the finite element method9 or rewritten as a potential energy function that can be minimized using an optimization method such as the steepest descent optimization technique. Solving a DAE system is more difficult than solving an algebraic system. Several techniques have been proposed to solve the DAE system that describes the two-dimensional dynamic response of the knee joint. Using the Differential/Algebraic System Solver software (DASSL) developed at the Lawrence Livermore National Laboratory, the latter and more complex DAE system was solved, thus describing the three-dimensional dynamic response of the knee joint. The integration scheme implemented in DASSL employs variable order and variable size multistep backward differentiation formulas (BDFs). It is hard to validate the present model predictions because of the limited experimental data available in the literature that describe the dynamic behavior of the human knee joint. The dynamic response of the joint must be described in terms of the loads exerted on the joint; the six components of the three- dimensional motion of the tibia with respect to the femur; the deformations of the different components forming the joint, including the ligaments, menisci and cartilage. Varus-Valgus Rotation Model predictions show that varus rotation occurred in association with internal tibial rotation while the knee was flexed. These results are in agreement with van Kampen et al. Also, the results reported here are within the varus-valgus rotation’s envelope of passive knee motion reported by Blankevoort et al. However, the model predictions are not in agreement with the data reported by Blankevoort et al. This difference may be due to the omission of the menisci in this model. Mills and Hull92 reported that the valgus rotation coupled with the internal tibial rotation is due to the medial condyle’s ride over the medial meniscus. When an internal moment of 3 N-m was applied by van Kampen et al. Tibial Rotation Model calculations show that as the knee was flexed from 15 to 90°, it underwent internal tibial rotation. This rotation indicates that the tibia was subjected to internal moments caused by tension forces in the lateral collateral ligament and/or the anterior fibers of both the anterior and posterior cruciate ligaments. The predicted tibial rotations lay within the envelope of passive knee motion defined earlier. These results indicate that external tibial rotation occurs with knee extension.

On examination safe 150mg fildena, the patient has 4/5 strength in the proximal muscles and 5/5 strength distally cheap fildena 50 mg with amex; otherwise, the examination is normal. Refer the patient to a muscular dystrophy clinic D. Perform the ischemic forearm test Key Concept/Objective: To understand the use of MRI in improving the diagnostic accuracy of biopsy Involvement of muscles in polymyositis is often patchy. In recent years, the use of MRI of the proximal muscles has demonstrated the patchy nature of the disease and aided in the localization of biopsy. This is the most likely reason for this patient’s normal biopsy. An MRI scan will probably demonstrate the extent and location of muscle disease, and rebiop- sy of involved sites will most likely demonstrate myositis. A 47-year-old woman presents to your clinic complaining of crampy abdominal pain and diarrhea; she also has been experiencing progressive dyspnea on exertion and constant chest pain that is worse when she leans forward. She has had these symptoms for the past several days. She also reports arthralgias and has now developed a rash. On physical examination, the patient is mildly tachypneic, but her vital signs are otherwise stable. Pulmonary examination reveals dullness to percussion and decreased breath sounds over the right lower lung field, with no egophony. Cardiac and abdominal examinations are unremark- able. Lower extremities are notable for purpura and trace edema below the knees. Evaluation of her diarrhea reveals an eosinophilic gastroenteritis. You suspect that her underlying problem is Churg-Strauss syndrome (CSS). Which of the following components of this patient’s medical history would be most supportive of the diagnosis of CSS? Polymyalgia rheumatica Key Concept/Objective: To understand the importance of history in the diagnosis of Churg- Strauss syndrome CSS displays clinical similarities to Wegener granulomatosis (WG) in terms of organ involvement and pathology, especially in patients with upper or lower airway disease or glomerulonephritis. CSS differs most striking- ly from WG in that the former occurs in patients with a history of atopy, asthma, or aller- gic rhinitis, which is often ongoing. In the prevasculitic atopy phase, as well as during the systemic phase of the illness, eosinophilia is characteristic and often of striking degree (≥ 1,000 eosinophils/mm3). When eosinophilia is present in WG, it is usually more modest (~500 eosinophils/mm3). Chronic sinusitis can be seen in both CSS and WG, although it is more characteristic in the latter than the former. Polymyalgia rheumatica is not associat- ed with either CSS or WG; there is, however, a clear association between polymyalgia rheumatica and temporal arteritis. A preceding streptococcal or viral infection has been seen occasionally with both WG and CSS. A 54-year-old man is brought to the emergency department by his family. They report that several days ago, the patient began complaining of arthralgias, myalgias, and subjective fevers. He thought that he had the flu and remained home from work. Yesterday he developed swelling and a rash on his legs. According to his family, yesterday evening the patient started acting funny, and today he has been some- what confused. On physical examination, the patient’s temperature is 99. He is able to answer questions but is easily dis- tracted during the examination. Pulmonary, cardiovascular, and abdominal examinations are normal. On musculoskeletal examination, petechiae and purpura are noted on the upper and lower extremities, with 1+ pitting edema in the lower extremities. Laboratory values reveal a white blood cell count of 24,000, a platelet count of 550,000, and a hematocrit of 35%. Blood urea nitrogen and creatinine levels are 120 mg/dl and 4. You admit the patient to the hospital for further workup. A serum test for perinuclear antineutrophil cytoplasmic antibodies (p-ANCAs) with antimyeloperoxidase specificity is positive. Which of the following vasculitides is most likely responsible for this man’s illness? Wegener granulomatosis (WG) Key Concept/Objective: To know the clinical presentation and laboratory findings for MPA Glomerulonephritis, particularly rapidly progressive glomerulonephritis, and alveolar hemorrhage are common in MPA and absent, by definition, in classic PAN. Constitutional symptoms such as fever, asthenia, and myalgias are common in both PAN and MPA. Elevated acute-phase reactants, thrombocytosis, leukocytosis, and the anemia of inflam- matory disease are common, although they are not uniformly present. The diagnosis of MPA and PAN should ideally be based on histopathologic demonstration of arteritis and the clinical pattern of disease. A biopsy specimen of clinically involved, nonnecrotic tissue that demonstrates the presence of arteritis of muscular arteries is the ideal supportive find- ing for the diagnosis of arteritis of a medium-sized vessel, but such a finding is not always possible.

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In pain 25 mg fildena with mastercard, so other pathophysiological processes must fact buy 50mg fildena with visa, the number of realignment surgeries has exist. Moreover, PFM theory cannot adequately dropped dramatically in recent years, due to explain the variability of symptoms experienced a reassessment of the paradigm of PFM. Moreover, we know that such procedures are, Finally, we must also remember that it has been in many cases, unpredictable and even danger- demonstrated that there are significant differ- ous; they may lead to reflex sympathetic dys- ences between subchondral bone morphology trophy, medial patellar dislocations, and and geometry of the articular cartilage surface of iatrogenous osteoarthrosis (see Chapters 20 the patellofemoral joint, both in the axial and and 21). We should recall here a phrase by doc- sagittal planes6 (Figure 1. Therefore, a radi- tor Jack Hughston, who said: “There is no ographical PFM may not be real and it could problem that cannot be made worse by sur- induce us to indicate a realignment surgery than gery” (see Chapters 20 to 23). Among problems could provoke involuntarily an iatrogenic PFM with the knee, this statement has never been leading to a worsening of preoperative symptoms. Moreover, this emphasize the importance of a correct diagno- could explain also the lack of predictability of sis (see Chapters 6 and 7) and nonoperative operative results of realignment surgery. Critical Analysis of Long-term Follow-up Criticism of Insall’s Proximal Realignment for The great problem of the PFM concept is that not all malalignments, even of significant propor- PFM: What Have We Learned? Halsted, I think that the may be symptomatic and the other not, even operating room is “a laboratory of the highest though the underlying malalignment is entirely order. On the other hand, and realignment surgery is not an exception, Figure 1. CT at 0° from a patient with anterior knee pain and functional patellofemoral instability in the right knee; however, the left knee is completely asymptomatic. Background: Patellofemoral Malalignment versus Tissue Homeostasis 9 Figure 1. CT at 0° from a patient with severe anterior knee pain and patellofemoral instability in the left knee (a). This knee, which was operated on two years ago, performing an Insall’s proximal realignment, was very symptomatic in spite of the correct patellofemoral congruence. Nevertheless, the right knee was asymptomatic despite the PFM. Conventional radiographs were normal and the patella was seen well centered in the axial view of Merchant (b). Axial stress radiograph of the left knee (c) allowed us to detect an iatro- genic medial subluxation of the patella (medial displacement of 15 mm). The symptomatology disappeared after surgical correction of medial subluxation of the patella using iliotibial tract and patellar tendon for repairing the lateral stabiliz- ers of the patella. Scheme of gadolinium-enhanced MR arthrotomogram of the left knee in the axial plane. Note patellofemoral incongruence of the osseous contours (b). Furthermore, I have not found, in the basic tenets and may devise clinical research to long-term follow-up, a relation between the test the underlying hypothesis, in our case the result, satisfactory versus nonsatisfactory, and PFM concept. In this way we have evaluated retrospectively I postulate that PFM could influence the home- 40 Insall’s proximal realignments (IPR) per- ostasis negatively, and that realignment surgery formed on 29 patients with isolated sympto- could allow the restoring of joint homeostasis matic PFM. Realignment surgery temporarily is presented in detail in Chapter 2. Moreover, lyze whether there is a relationship between the according to Dye, rest and physical therapy are presence of PFM and the presence of anterior most important in symptoms resolution than knee pain or patellar instability. Once we have achieved joint In my experience IPR provides a satisfactory homeostasis, these PFM knees can exist happily centralization of the patella into the femoral within the envelope of function without symp- trochlea in the short-term follow-up. Moreover, in my series, 12 patients pre- this satisfactory centralization of the patella is sented with unilateral symptoms. In 9 of them the lost in the CT scans performed in the long-term contralateral asymptomatic knee presented a PFM follow-up in almost 57% of the cases. That is, IPR and only in 3 cases was there a satisfactory cen- does not provide a permanent correction in all tralization of the patella into the femoral trochlea. Nonetheless, this loss of centralization We can conclude that not all patellofemoral does not correlate with a worsening of clinical malaligned knees show symptoms, which is not surprising, as there are numerous examples of asymptomatic anatomic variations. Therefore, e We define the term “isolated symptomatic PFM” as ante- PFM is not a sufficient condition for the onset rior knee pain or patellar instability, or both, with abnormal- of symptoms, at least in postoperative patients. History and physical exam must Background: Patellofemoral Malalignment versus Tissue Homeostasis 11 point toward surgery and imaging only to allow they are living, metabolically active systems. This theory attributes pain to a physiopatholog- ical mosaic of causes such as increase of osseous Relevance of our Findings remodeling, increase of intraosseous pressure, To think of anterior knee pain or patellar insta- or peripatellar synovitis that lead to a decrease bility as somehow being necessarily tied to of what he called “Envelope of Function” (or PFM is an oversimplification that has posi- “Envelope of Load Acceptance”). The great danger in using describes a range of loading/energy absorption PFM as a diagnosis is that the unsophisticated that is compatible with tissue homeostasis of an or unwary orthopedic surgeon may think that entire joint system, that is, with the mechanisms he or she has a license or “green light” to cor- of healing and maintenance of normal tissues. Within the Envelope of Function is the region termed Zone of Homeostasis Tissue Homeostasis Theory (Figure 1. Loads that exceed the Envelope of In the 1990s, Scott F. Dye, of the University of Function but are insufficient to cause a California, San Francisco, and his research group, macrostructural failure are termed the Zone of came up with the tissue homeostasis theory. If The initial observation that led to the develop- sufficiently high forces are placed across the ment of the tissue homeostasis theory of patellofemoral system, macrostructural failure patellofemoral pain was made by Dye, when a can occur (Figure 1. The bone scan of that (dynamic control of the joint involving propri- individual manifested an intense diffuse patellar oceptive sensory output, cerebral and cerebellar uptake in the presence of normal radiographic sequencing of motor units, spinal reflex mecha- images. This finding revealed the presence of a nisms, and muscle strength and motor control); covert osseous metabolic process of the patella in (3) physiological factors (the genetically deter- a symptomatic patient with anterior knee pain mined mechanisms of molecular and cellular and normal radiographic findings.

In acoustic microscopy buy fildena 50mg mastercard, short pulses are necessary to ensure that incident and reflected waves do not interfere buy discount fildena 150mg online. A transducer that has short pulse lengths has a short “ring down time” because it oscillates through fewer numbers of cycles per excitation. A Historical Perspective of the Study of Bone with Acoustic Microscopy The first practical scanning acoustic microscope was developed and built for materials analysis by Lemons and Quate. Since then, scanning acoustic microscopy has become a major nondestructive evaluation tool involving imaging and the characterization and detection of defects in structural materials. Although acoustic microscopy has been used for over 3 decades in industry to analyze solid materials, only recently have scientists applied scanning acoustic microscopy to the fields of biology and medicine, where “soft” materials are prevalent. Experiments involving the technique have been used to study the acoustic velocity, acoustic attenuation, density, and thickness of tissues, and even cells. To measure the acoustic impedance of a material, one collects the amplitude of the first echo of a longitudinal sound wave reflected from the surface of the specimen. By varying transducer design, other sonic waves can be generated and used for material properties analysis. Rayleigh waves are surface waves; however, bone poorly supports Rayleigh wave propagation. High signal attenuation occurs because of the porosity of bone. Low Rayleigh velocities result, and given the angle at which the signal returns to the transducer, it is not possible for the transducer to receive the signal. The same group measured surface skimming waves from horse radial bone. A high frequency point focus lens was used and surface waves were measured every 150 microns in a line. The averaged velocities were used to calculate a mean elastic coefficient. Other investigators have also used the velocities measured with acoustic microscopy to calculate the material properties of bone. They observed a significant decrease in the velocity of sound in osteoporotic bone compared to age-matched normal bone. Three other recently published studies have addressed the material property contributions that mineral and collagen provide for bone, and all three research groups utilized a scanning acoustic microscope. All the techniques demonstrated decreased material properties with demineralization. They also compared the elastic constants generated with bulk transmission ultrasound against the constants gen- erated with velocities measured with an acoustic microscope. Orthotropic symmetry was assumed, and © 2001 by CRC Press LLC a good agreement with both techniques was observed, except for specimens oriented 30° to the longitu- dinal axis of the bone. This deviation supports the hypothesis that the principal orientation of the secondary lamellar bone collagen is 30° to the long axis of the bone. This concept was further supported by the anisotropy ratio data generated in this study. The most recent work from Turner’s laboratory23 makes use of the collagen and mineral orientation data in a composite model for the ultrastructure of osteonal bone. A two-phase composite model was developed and the acoustic data played a key role in testing hypotheses regarding amounts of intrafibular vs. A scanning acoustic microscope with a similar transducer was used in the studies by Hasegawa,20 Turner,22 Pidaparti,23 and Broz. In all four studies, acoustic velocity measurements were made at multiple locations on each specimen and then averaged for a mean velocity. Bulk density measurements were made using Archimedes’ principle for the entire specimen and bulk elastic stiffness coefficients were calculated. These data were used to calculate the bulk elastic stiffness coefficients of the specimens. Thus, a relatively high resolution velocity measurement tool was used to measure multiple velocities, and a mean velocity was used to calculate bulk properties in all four studies. Specimen Preparation In all the experiments to be described, fresh or imbedded bone was tested. The imbedded bone goes through a dehydration and clearing process before imbedding in polymethylmethacrylate. After imbed- ding, the specimens are sectioned with a diamond saw and polished with fine sized grit until a 600 grit (approximately 15 µm) finish is attained. In all scanning experiments, deionized water was used as a couplant. An optical reflection microscope was used to examine the quality of the polishing and detect any defects or cracks that would affect the acoustic measurements. Once the specimen was aligned in the instrument, the parallelism assured that the wave front was always perpendicular to the specimen. Finally, each section was placed in an ultrasonic cleaner for 5 minutes to clear the bone of any grit that may have entered the pores during the polishing process. The Acoustic Microscope The acoustic microscope used in the low frequency studies consisted of a Panametrics 5052UA ultrasonic analyzer, Matec SR-9000 pulser receiver, a differential amplifier, and a 12-bit A/D converter. The speci- mens were mounted in a water bath and scanned in a raster fashion with a 50 MHz spherically focused transducer (Panametrics Inc. It drove the scanning of the specimen, it acquired the data through an A/D converter (a 256 × 256 array of points per image is stored), and it presented the results visually.

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