By T. Goran. West Virginia University Parkersburg.

The identification and localization of a ial compartment is distracted whereas the lateral compart- displaced meniscal fragment can be important in the pre- ment is compressed discount lasuna 60caps on-line. Medial distraction means that the operative planning of arthroscopic surgery lasuna 60caps fast delivery. Lateral compression means sile stress can avulse the capsule away from the menis- that the lateral meniscus is at risk for entrapment and tear cus (meniscocapsular separation), with or without a along the free margin. Meniscocapsular injury avulsed at sites where they are fixed, but can escape in- may be an important cause of disability that can be jury in regions where they are mobile. Compared to the treated surgically by primary reattachment of the cap- lateral meniscus, the medial meniscus is more firmly at- sule. Since the capsule stabilizes the medial meniscus, tached to the capsule along its peripheral border, and is meniscocapsular separation or peripheral meniscal avul- far less mobile. Normal knee motion involves greater sion can cause persistent pain and lead to posteromedi- translation of the femorotibial contact point in the lateral al instability with eventual degenerative change. In order to shift with the condyle and avoid images, meniscocapsular injury is more difficult to injury, the lateral meniscus requires a looser capsular at- identify than meniscal tear. Since with scarring and apparent reattachment of the capsule the medial meniscus is tightly secured by menis- to meniscus. Similarly, small avulsed corners of menis- cofemoral and meniscotibial ligaments along the joint cus may be difficult to identify unless a directed search line, it is subjected to greater tensile stress with lesser de- is made for them. Imaging of the Knee 33 The same valgus force that distracts the medial com- Therefore, depending on knee position and the direction partment also compresses the lateral compartment. Since of mechanical load, different structures are functioning the lateral meniscus is loosely applied to the joint cap- synergistically to stabilize the joint. During axial load across the lateral compartment, the meniscus is sometimes crushed, which Medial Collateral Ligament and Medial splays and splits the free margin, creating a radial (trans- Meniscus verse) tear. Radial tears of the lateral meniscus usually originate at the junction of anterior and middle meniscal The medial collateral ligament complex comprises super- thirds. They are most difficult to identify on coronal im- ficial and deep capsular fibers. The superficial compo- ages since they are vertically orientated in the coronal nent, also called tibial collateral ligament, resists both plane.

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Fick’s law states that the rate of gas diffusion is inversely related to membrane thickness buy cheap lasuna 60caps. This means that the diffu- Alveolus sion of a gas will be halved if membrane thickness is dou- Start of End of bled cheap lasuna 60 caps fast delivery. Fick’s law also states that the rate of diffusion is di- capillary capillary rectly proportional to surface area (As). If two lungs have the same oxygen diffusion gradient and membrane thick- ness but one has twice the alveolar-capillary surface area, the rate of diffusion will differ by 2-fold. Alveolar Under steady state conditions, approximately 250 mL of level oxygen per minute are transferred to the pulmonary circu-. The ratio VCO2/VO2 is the respiratory ex- change ratio (R) and, in this case, is 0. Capillary Blood Flow Limits Oxygen Uptake From Alveoli Exercise CO Pulmonary capillary blood flow has a significant influence on oxygen uptake. The time required for the red cells to move through the capillary, referred to as tran- Uptake of N2O, O2, and CO by pulmonary FIGURE 21. Gas transfer is affected by gas tension in the blood equilibrates with the alveolar gas pulmonary capillary blood flow. For example, when cardiac output increases, blood through the pulmonary capillaries is 0. The vertical axis in- flow through the pulmonary capillaries increases, but transit dicates gas tension in the pulmonary capillary blood and the top of the vertical axis indicates gas tension in the alveoli. Nitrous oxide (N O) is used to illustrate how gas 2 nitrous oxide (laughing gas), a common dental anesthetic, transfer is limited by blood flow; carbon monoxide (CO) illus- is breathed. Nitrous oxide (N2O) is chosen because it dif- trates how gas transfer is limited by diffusion. The profile for oxy- fuses across the alveolar-capillary membrane and dissolves gen is more like that of N2O, which means oxygen transfer is lim- in the blood, but does not combine with hemoglobin.

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As the disease advances generic lasuna 60 caps on line, the synovium becomes greatly thickened 60caps lasuna free shipping, Ulnar deviation of the phalanges with or without asso- with enlargement of the synovial villi. The by proliferation of fibrovascular connective tissue distal phalanx of the thumb is characteristically hyper- known as pannus. Pannus is responsible for the charac- extended, giving rise to the “hitchhiker thumb” defor- teristic marginal erosions that first occur in the so- mity. The carpus is characteristically rotated towards called bare areas between the peripheral edge of the the ulna. Ultimately, pannus grows over and destroys the surface of the articular cartilage. Juvenile Rheumatoid Arthritis (Still’s Disease) In general, the younger the patient, the more likely the Roentgenographic Observations disease is monoarticular, particularly involving a large joint such as the knee, ankle, or wrist. The disease may The initial manifestations are soft-tissue swelling, sym- be limited to a few major joints. If it begins in an old- metrical narrowing of the joints, periarticular osteoporo- er child, there is more likely to be symmetrical in- sis, and marginal erosions. Radiographic manifestations volvement of the smaller peripheral joints, as in an of the disease are present in 66% of patients 3 to 6 adult. There is interference with skeletal maturation, months after the onset of disease and in 85% of those af- usually manifested as acceleration of maturation, with fected for 1 year. The pre- Peripheral Arthritis 145 mature fusion leads to shortening of the digits. Reiter’s Syndrome Involvement of the spine is much more common in children than in adults. The involvement may be mani- Reiter’s syndrome is characterized by urethritis, conjunc- fested by atlantoaxial subluxation and erosions and tivitis, and mucocutaneous lesions in the oropharynx, eventually by bony ankylosis of the facet joints in the tongue, glans penis, and skin, as well as arthritis.