Density of Bone

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Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Cameron, John R.; James G. Skofronick & Roderick M. Grant. Physics of the Body. Second Edition. Madison, WI: Medical Physics Publishing, 1999: 96. "The density of compact bone is surprisingly constant through out life at about 1900 kg/m3" 1900 kg/m3
(density)
Jones, Larry. Density notes. "All density values in the following table are units of g/cm3" 1600 kg/m3
(density)
The Skeletal System. Oxford Text Book of Medicine. Third edition, Third volume. New York, Medical publications, 1996: 3066. "The measurement of bone mineral density (BMD) by dual x-ray absorptiometry. The shaded areas represents the changes of BMD with age. [Value appears in a graph.]" 1000–1200 g/cm2
(BMD)
Bonnick, Sydney Lou. Osteoporosis, The Hand Book. Third edition.Texas, Cooper Square Press, 2000: 147. "A DXA spine bone density report showing the image of the spine, the measured bone density, and comparisons to a young adult and individual of the same age. [Value appears in a graph.]" 1000 g/cm2
(BMD)

The musculoskeletal system is made of bones, muscles, tendons and cartilage. Bones have a wide range of uses within our body. One of the most important functions is the support of organs. Other functions include storing calcium (which is needed for the brain), producing red cells, white cells and platelets. The bone is made of a hard layer and a mineral layer. One of the structures which makes up the mineral layer of the bone that resembles tubes, is called the Haversian canal. This structure carries organic nourishment required by the bone system. Thin plates called lamellae that contain the marrow of the bone surround the Haversian canal. The yellow marrow is fat and the red marrow is made of tissue that includes the blood cells. The hard layer of the bone is made of collagen. This layer makes up 70% of the density of bone in adults, and 30% in children. Three cells make up the function portion of the bone. They include osteoblasts, osteocytes, and osteoclasts. The osteoblasts create collagen and strengthen the bone. The osteocytes control the mineral balance within the body. Osteoclasts destroy bone mineral tissue in the process called bone turnover.

Osteoporosis is a disease that results from excess bone turnover. In this disease the bone weakens from the inside, as more tissue is destroyed then hard bone created. It does not affect the density of the hard section of the bone, however. The function of the bone begins to fault with age. People who have osteoporosis are at a high risk of fractures in the spinal, hip, and wrist areas. Those who are most susceptible to loosing bone mass are women, Europeans, and those over fifty. Several procedures have been created which monitor the bone turnover process. One such process is called the Dual-Energy X-ray Absorptiometry (DXA). In this procedure a computer controls an X-ray tube that is not radioactive. The machine measures the bone mineral density of the tissue of the bone. The DXA process graphs a persons bone mass per area in contrast to a normal for that patient's category. The results end up in terms of standard deviation from the normal. Bone mineral density is dependent upon sex, age, and the part of the body. A range for the mineral density of the bone of the spine region is from 1000 to 1200 g/cm2. The range of bone mineral density for the forearm is from 700 to 800 g/cm2. Young's modulus of elasticity has been used to calculate the density of hard bone, that is know to be a constant of 1900 kg/m3.

Anna Yarusskaya -- 2002

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Lohman, Timothy G. Advances in Body Competition Assessment. University of Arizona, 1992: 32. "Estimation of mineral content of fat-free body. Estimated total bone mineral density for males is: 1990 -- 3.88 g/cm2 for females -- 2.90 g/cm2, in 1984 -- males is 4.24 g/cm2, and for females it is 3.47 g/cm2, and in 1991 for women it is 3.11 g/cm2." 3.114.24 g/cm2
Susan Ott, MD. About Osteoporosis. Osteoporosis and bone physiology. University of Washington. 2002. "Using standardized bone density measurements of the total hip, 'normal' bone is greater than 833 mg/cm2. 'Osteopenia' is between 833 and 648 mg/cm2. Osteoporosis is lower than 648 mg/cm2, and 'Severe (established) osteoporosis' is when there has been a fragility fracture." > 0.833 g/cm2
(normal)

0.8330.648 g/cm2
(osteopenia)

< 0.648 g/cm2
(osteoporosis)
Mary B. Laya. Bone Density Measurements Basics. Osteoporosis Education. 2002. [diagram] 0.40 g/cm2
Adams, P. and Jowey, J. Bone Mineral Metabolism -- An experimental study in endocrinology. 1967: 735-40. "During this interval, the mean lumbar spine bone mineral increased from an initial value of 1.01 g/cm2 to 1.07 g/cm2, an increase of 6.6% per year." 1.011.07 g/cm2

Bone density is the amount of bone tissue in a certain volume of bone (g/cm3). It is usually hard to determine so we normally use bone mineral density (g/cm2). Bone mineral density (BMD) is a test that measures the amount of calcium in a special region of bones. From this information, an estimate of the strength of the bones can be made. BMD helps predict the risk of a future fracture of the bone, measures the amount of bone mass, and also monitors the effectiveness of treatment. BMD can be measured using a special x-ray technique called a quantitative computed tomography (QCT) or dual energy x-ray absorptiometry (DEXA).The normal, average bone mineral density is around 3.88 g/cm2 in males and 2.90 g/cm2 in females. Individuals with a BMD lower than 1.0 g/cm2 need certain care.

BMD measurements normally decrease with age. White and black females are the highest individuals at risk of osteoporosis, or any bone disease, as they grow older, rather than white or black males. Osteoporosis is the most common bone disease in the United States. This disease affects 25 million people in this country and half of all women over the age of 45. Osteoporosis causes more than 1.3 million fractures, including 500,000 spinal fractures, 250,000 hip fractures and 240,000 wrist fractures. If the body does not have enough Calcium, it will take it from the bones in the body, which causes damage. A person acquiring Osteoporosis will have a T-score of less than -1. A BMD more than 2.5 standard deviations below the mean for a young healthy white woman is 30% of all postmenopausal women having osteoporosis.

Kathy Donina -- 2002


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