These are common words associated with bone health. If the word you are looking for is not listed, check the index for pages where you can find additional information.

 

Anabolics: medicines that turn on the bone-builder cells (osteoblasts) to promote formation of new bone. Forteo is the sole member of the anabolic group.

Antiresorptives: medicines that target the bone-breakdown cells (osteoclasts). These include the bisphosphonate class of medicines (Actonel, Atelvia, Boniva, Fosamax, generic alendronate, and Reclast), as well as calcitonin, estrogens, Evista, and Prolia. Decreasing bone breakdown results in slowing bone loss and improving bone density.

Bone Mineral: the crystalline component of bone made up of calcium and phosphorus in the form of hydroxyapatite.

BMD (Bone Mineral Density): bone mass is quantified by measurement of bone mineral. Bone mineral density predicts fracture risk.

Bone densitometry or bone density scan: the measurement of bone mass; the current gold standard device is the DXA machine, which quantifies bone mineral density of various skeletal sites, including the lower (lumbar) spine, hip, and forearm.

Bone scan: In contrast to a bone density scan, a bone scan is a nuclear medicine study. Any area of bone that has increased metabolic activity (fracture, tumor, or infection) will show increased uptake of the radioisotope.

Bone formation: the building of bone mass by cells called osteoblasts.

Bone remodeling: the continual process of bone-breakdown cells and bone-formation cells working in concert to keep bone repaired. An imbalance in bone remodeling causes problems. When bone breakdown exceeds new bone formation, such as with loss of estrogen in the menopause transition, bone loss occurs.

Bisphosphonates: synthetic compounds of the natural phosphorus that binds to the bone mineral. The name refers to the chemical structure of these phosphorus compounds: two phosphonate groups linked by a carbon atom. The structure of the side chains that branch from the carbon atom differentiates the various bisphosphonates. Fosamax, generic alendronate, Actonel, Atelvia, Boniva, and Reclast make up this class. Bisphosphonates block the breakdown of the bone by physically interfering with the bone-breakdown cells, or osteoclasts.

Cancellous bone: the spongy or trabecular bone tissue of the inner parts of the bones found in the vertebrae (spine), pelvis, and end sections of the long bones. This type of bone resembles a rigid sponge with a plate-like meshwork of beams. The plates within this kind of bone are called “trabeculae.” These act like cross braces that support and prevent collapse of the structure.

Compact bone or cortical bone: the hard, dense bone tissue of the shafts of the long bones of the arms and legs and the outer shell of all bones in the body. It comprises about 80 percent of the skeleton.

DXA (dual-energy x-ray absorptiometry): the full name is descriptive of the technique. The dual-energy x-ray part of the name accounts for the use of two different energy levels of x-ray. Absorptiometry refers to radiation passing through various body tissues that have different patterns of absorption. The differences in the two beams of radiation that pass through the body's tissues allow subtraction of the bone measurement from the measurement of the surrounding tissues. The results are usually reported as bone mineral density (BMD), which is a calculated measure in grams per square centimeter (g/cm²). Diagnosis is based on standardized T-scores or Z-scores, depending on age and sex.

Femoral neck or neck of femur: the narrowest portion of the hip; located between the femur's ball head and shaft. This area is a common site of hip fracture.

Femur: thighbone; the bone between the hip and knee joints.

Fracture: broken bone; the structural failure of bone.

FRAX: the fracture risk calculator developed by the World Health Organization. The FRAX tool incorporates results of the hip (femoral neck) bone density with personal risk factors to calculate your ten-year fracture probability. Treatment guidelines use the results of the ten-year probability of fracture for individuals with low bone mass or “osteopenia.”

Kyphoplasty: a technique for treatment of an acute painful spine fracture. A balloon is inflated inside the bone (vertebral body) to create a space and then cement is injected to stabilize the fracture.

NHANES (National Health and Nutrition Examination Survey): a program of studies designed to assess the health and nutritional status of adults and children in the US by studying representative samples from different parts of the country.

Nonvertebral fracture: a fracture that occurs in bones other than the spine.

Osteoblasts: cells that form new bone in the bone remodeling cycle.

Osteoclasts: cells that break down bone in the bone remodeling cycle.

Osteocytes: cells within the structure of the bone that form an interconnected network.

Osteomalacia: a disease that means “soft bones.” A very low vitamin D level, generally 15 ng/ml or less, is the most common cause. This results in an inadequate supply of calcium and phosphorus, both of which are essential for maintaining the hardness and strength of bone through a process called mineralization. If new bone does not mineralize, it is soft and rubbery.

Osteopenia: low bone mass; the World Health Organization criteria define osteopenia as bone mineral density T-scores between -1 and -2.5 measured at the lumbar spine, total hip, femoral neck, or forearm. “Low bone mass” is now the preferred name for this range of bone density.

Osteoporosis: a disease characterized by progressive and silent loss of bone that makes your bones thinner and weaker so that they are more likely to fracture or break. The World Health Organization criteria define osteoporosis as bone mineral density T-scores of -2.5 or less measured at the lumbar spine, total hip, femoral neck, or forearm.

Parathyroid and parathyroid hormone (PTH): the parathyroid consists of four small glands that are located in the neck, usually on the backside of the thyroid. The parathyroid's sole role is to regulate calcium in the body by producing parathyroid hormone.

RANKL (receptor-activating nuclear factor [kappa]B ligand): the intermediary messenger that regulates the bone remodeling cycle. Produced by osteoblasts, RANKL regulates the creation of osteoclasts and their activity by binding to receptor sites (RANK) on the surface of the precursor cells of osteoclasts and immature osteoclasts.

Resorption: the breakdown of bone by osteoclasts; this is followed by bone formation in the bone remodeling cycle.

SERM (Selective Estrogen Receptor Modulator): also called an Estrogen Agonist/Antagonist (EAA); this “designer estrogen” has a split personality. In some tissues it works like estrogen and in other tissues it has the opposite effect. Evista is the only SERM approved by the FDA for prevention and treatment of osteoporosis.

Trabecular bone: the spongy bone tissue of the inner parts of the pelvis, the end sections of the long bones, and the bones found in the vertebrae (spine). This bone, also referred to as cancellous bone, resembles a rigid sponge with a plate-like meshwork of beams. The plates within this kind of bone are called “trabeculae.” These act like cross-braces to support and prevent collapse of the structure.

T-score: the standardized measurement of bone mineral density; compares an individual's measured bone mineral density with a reference database of same-sex young adults whose average scores are representative of peak bone mass. T-scores are applicable for diagnosis in postmenopausal women and men over the age of fifty.

Vertebra (Vertebrae, plural): the individual bone in the spine. Each level is comprised of a central portion called the vertebral body, a bony arch that goes around the spinal cord, and several projections for attachment of muscles.

Vertebral fracture: a structural failure of the vertebral body. Vertebral fractures may either be “silent” (not associated with any symptoms; usually identified by x-ray) or “clinical” (painful; usually diagnosed by a doctor).

Vertebral Fracture Assessment (VFA): a DXA scan of the upper and lower areas of the spine to detect vertebral fractures.

Vertebroplasty: a procedure for treatment of an acute painful spine fracture. Cement is injected inside the vertebral body to stabilize the fracture.

Z-score: standardized comparison of an individual's measured bone mineral density with same-age individuals from a reference database. Z-scores are used to diagnose low bone mass in younger adults, premenopausal women, men under the age of fifty, and children.