Bone result

Vitamin D is really a small family of closely related molecnles that prevent the bone disease rickets in children and osteomalacia in adnlts. In both cases, inadeqnate mineralization of bone results in bone deformation and weakness. Calcinm, Ca +, homeostasis is one goal of vitamin D activity, a goal it shares with parathyroid hormone and calcitonin. Calcium is intimately involved in bone mineralization and distnrbances of calcium levels in the blood can resnlt in inadeqnate bone mineralization or excessive calcification of other tissues. 

Back pain may be associated with osteoporosis and pregnancy. Osteomalacia refers to insufficient mineralisation of the bones, resulting in soft bones. 

Hemimelia—absence of any of the long bones, resulting in a shortened limb... 

Cortical bone, also called compact or lamellar bone, is remodelled from woven bone by means of vascular channels that invade the embryonic bone from its periosteal and endosteal surfaces. It forms the internal and external tables of flat bones and the external surfaces of long bones. The primary structural unit is an osteon, also known as a Haversian system, a cylindrical shaped lamellar bone surrounding longitudinally oriented vascular channels (the Haversian canals). Horizontally oriented canals (Volkmann canals) connect adjacent osteons. The mechanical strength of cortical bone results from the tight packing of the osteons. 

Rickets is characterized improper mineralization during the development of the bones resulting in soft, pliable bones. 

Up to 6% of boys in high school, including a number of nonathletes, have used anabolic steroids at least once. A particular problem with anabolic steroid use in adolescents is early closure of the growth plates at the ends of bones, resulting in permanent short stature. Other side effects are common to both adolescents and adults. 

Skeletal changes due to cadmium accumulation are probably related to calcium loss, which can be influenced by diet and hormonal status. These skeletal changes include osteomalacia (softening of bone resulting from loss of minerals) and pseudofractures. In Japan, people who ate fish contaminated with cadmium experienced skeletal changes, especially in their backs. This very painful effect was called the Itai-Itai ( ouch-ouch ) disease. Postmenopausal women with low calcium and vitamin D intake were apparently most susceptible. 

Hypervitaminosis A and D have also been associated with bone abnormalities. Vitamin D can cause resorption of calcium from bone. Chronic vitamin D intoxication may result in increased mineralization on bone and metastatic calcifications including joints, periarticular, and the kidney. Excessive vitamin D intake can cause demineralization of bone resulting in multiple fractures from very slight trauma. 

The answer is d. (Murray, pp 627-661. Scriver, pp 3897-3964. Sack, pp 121-138. Wilson, pp 287—320.) People with bowed legs and other bone malformations were quite common in the northeastern United States folio-wing the industrial revolution. This was caused by childhood diets lacking foods "with vitamin D and by minimal exposure to sunlight due to the da-wn-to-dusk working conditions of the textile mills. Vitamin D is essential for the metabolism of calcium and phosphorus. Soft and malformed bones result from its absence. Liver, fish oil, and egg yolks contain vitamin D, and milk is supplemented "with "vitamin D by law. In adults, lack of sunlight and a diet poor in "vitamin D lead to osteomalacia (soft bones). Dark-skinned peoples are more susceptible to "vitamin D deficiency. 

Bone Toxicity. Beta emissions from radiostrontium bound to bone resulted in various bone lesions (trabecular osteoporosis, sclerosis, osteolytic lesions), particularly in animals that were exposed chronically (Book et al. 1982 Clarke et al. 1972 Momeni et al. 1976). In young rats and rabbits exposed orally to 90Sr, necrotic effects on the vasculature of developing bone secondarily disrupted the process of osteogenesis (Casarett et al. 1962 Downie et al. 1959). Disruption in the metaphyseal microvasculature disorganized the transformation of cartilage into bone, so that chondrocytes inappropriately resumed active proliferation. 

These drugs cross the fetal-placental barrier and can chelate calcium in developing bones, resulting in a decrease in bone integrity. 

VITAMIN D DEFICIENCY Vitamin D deficiency is associated with inadequate absorption of calcium and phosphate. The resulting decrease in Ca stimulates PTH secretion, which acts to restore plasma Ca + at the expense of bone. Plasma phosphate concentration will remain low due to the phosphaturic effect of PTH. In children, the failure to mineralize newly formed bone results in rickets, a growth disorder in which the long bones may be bowed due to inadequate calcification. 

Finally, we have the whole bone itself constructed of osteons and portions of older, partially destroyed osteons (called interstitial lamellae) in the case of humans or of osteons and/or plexiform bone in the case of mammals. This we denote the macrostructural level The elastic properties of the whole bone results from the hierarchical contribution of each of these levels. 

Even at a low level of exposure, the replacement of Ca by Cd in bones results in poor mineralization and leads to fragility and risk of bone fracture. Because Cd " " is a good chemical analog for Zn, Cd can also substitute for Zn in the active center of many Zn-enzymes and block their activity. It seems, for example, that the substitution of Cd for Zn in alkaline phosphatase—an important Zn enzyme in bone formation—may contribute to bone demineralization [31]. 

Infection within the bone results in extensive marrow oedema, and typically with associated soft tissue oedema. The appearances of the oedema can be similar to that of a fracture and differentiation between infection and an undisplaced fracture may be difficult. Obviously, the clinical features and mode of presentation will often discriminate. 

There has been a report of Kienbock disease (osteonecrosis of the lunate bone) resulting from local glucocorticoid injections in a 51-year-old man [13" ]. 

Rickets does not often occur in adults although an adult counterpart, osteomalacia, now mercifully rare, may occur in women living mostly indoors and consuming a diet containing inadequate amounts of calcium and vitamin D, and subjected to frequent childbearing. Demineralization of the bones, resulting from these circumstances, may cause gross deformities. 

Although absorbable plates have been relatively successful for these applications, there are limitations. Deforming the polymer plates prematurely can cause damage and weaken plates, and absorbable screws often require tapping of the bone resulting in over-tapping of drilled holes for screw insertion (9). Another concern is the application of excessive torsional forces that result in the failure between the head of the screw and the shaft. 

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