Guest Author - Denise Howard, M.D., M.P.H.

Osteoporosis is a disorder of the skeletal system that results in decreased bone strength and subsequent susceptibility to fractures. It is a major epidemiologic problem and the prevalence is rapidly increasing due to an aging population. Osteoporotic bones are easily fractured and minimal trauma could cause breakage. The hip and spine are the areas commonly affected. Hip fractures can lead to death and disability and is a common reason that older individuals lose their independence. It is important to understand normal bone structure and the abnormalities that lead to this disorder in under to understand prevention and treatment.

Bone strength is determined by bone density and bone quality. Components of this are structural and material in nature. Structural properties include bone shape, size, and microarchitecture. Material properties include mineralization, collagen composition and damage accumulation.

Bone maintains its strength and quality by having a balance between bone resorption and formation. This is called remodeling. Old, damaged bone is resorbed and new bone is formed. Bone cells called osteoclasts remove the old structures and osteoblasts lay down the material for new bone formation. Osteoporosis develops when this balance is disrupted and there is more bone resorption than formation.

Bone mineral density testing is the standard way to measure bone integrity. This testing is performed using dual-energy x-ray absorptiometry (DEXA). It is the gold standard for diagnosing osteoporosis. The World Health Organization (WHO) has defined criteria for normal and abnormal results. The T score is utilized and describes the number of standard deviations (SD) in which a person’s results exceeds (positive score) or falls below (negative score) the mean of a young adult group of the same sex.

A diagnosis of Osteoporosis is given when the value falls 2.5 standard deviations (T score of -2.5) or more below the mean. Osteopenia or low bone density occurs when the T score is -1.0 to -2.5. If the score is greater than -1.0, one’s bones are considered to be of normal density. These ranges were developed to identify individuals who are at increased risk of fractures. The goal of early diagnosis and prevention is to minimize the incidence of fracture and other morbidity as they can have life threatening and life altering consequences.

Please look for upcoming articles that will discuss the problem of osteoporosis, treatment and prevention.