Definition

Osteoporosis, or porous bone, is a disease characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased susceptibility to fractures, especially of the hip, spine and wrist, although any bone can be affected. According to Dorland’s Medical Dictionary osteoporosis is the abnormal rarefraction of bone.

Etiology

Osteoporosis has many different causes.
It can be idiopathic or secondary to other disease such as thyrotoxicosis. ( Dorland’s Medical Dictionary)
Senile osteoporosis can occur in men as postmenopausal osteoporosis can occur in women. ( Goodman and Snyder) Prolonged immobilization can cause osteoporosis. ( Donatelli and Wooden)
Bones constantly change and are affected by diet and exercise. Until about the age of 30 you build and store bone efficiently. Then as you age, your bones begin to break down faster then new bone forms. In women bone loss accelerates after menopause- because less estrogen is produced. Estrogen is a hormone that protects one from bone loss.
( National Osteoporosis Foundation , http://www.nof.org)
Certain people are more likely to develop osteoporosis than others. Factors that increase the likelihood of developing osteoporosis are called "risk factors."

Risk Factors

• Personal history of fracture after age 50
• Current low bone mass
• History of fracture in a 1° relative
• Being female
• Being thin and/or having a small frame
• Advanced age
• A family history of osteoporosis
• Estrogen deficiency as a result of menopause, especially early or surgically induced
• Abnormal absence of menstrual periods (amenorrhea)
• Anorexia nervosa
• Low lifetime calcium intake
• Vitamin D deficiency
• Use of certain medications, such as corticosteroids and anticonvulsants
• Presence of certain chronic medical conditions
• Low testosterone levels in men
• An inactive lifestyle
• Current cigarette smoking
• Excessive use of alcohol
• Being Caucasian or Asian, although African Americans and Hispanic Americans are at significant risk as well

Prevalence

Women can lose up to 20 percent of their bone mass in the five to seven years following menopause, making them more susceptible to osteoporosis. ( National Osteoporosis Foundation , http://www.nof.org) Osteoporosis is a major public health threat for an estimated 44 million Americans, or 55 percent of the people 50 years of age and older. In the U.S. today, 10 million individuals are estimated to already have the disease and almost 34 million more are estimated to have low bone mass, placing them at increased risk for osteoporosis. Of the 10 million Americans estimated to have osteoporosis, eight million are women and 2 million are men. Thirty-four million Americans have low bone mass, which puts them at increased risk of developing osteoporosis and related fractures. One in two women and one in four men over age 50 will have an osteoporosis-related fracture in her/his remaining lifetime. Significant risk has been reported in people of all ethnic backgrounds. While osteoporosis is often thought of as an older person's disease, it can strike at any age.

Women

Eighty percent of those affected by osteoporosis are women. Five percent of non-Hispanic black women over age 50 are estimated to have osteoporosis; an estimated additional 35 percent have low bone mass that puts them at risk of developing osteoporosis. Ten percent of Hispanic women aged 50 and older are estimated to have osteoporosis, and 49 percent are estimated to have low bone mass. Twenty percent of non-Hispanic white and Asian women aged 50 and older are estimated to have osteoporosis, and 52 percent are estimated to have low bone mass.

Men

Twenty percent of those affected by osteoporosis are men. Seven percent of non-Hispanic white and Asian men aged 50 and older are estimated to have osteoporosis and 35 percent are estimated to have low bone mass. Four percent of non-Hispanic black men aged 50 and older are estimated to have osteoporosis and 19 percent are estimated to have low bone mass. Three percent of Hispanic men aged 50 and older are estimated to have osteoporosis and 23 percent are estimated to have low bone mass. (National Osteoporosis Foundation, http://www.nof.org)

Fractures

One in two women and one in four men over age 50 will have an osteoporosis-related fracture in their remaining lifetime. Osteoporosis is responsible for more than 1.5 million fractures annually, including:( National Osteoporosis Foundation , http://www.nof.org)

• over 300,000 hip fractures; and approximately
• 700,000 vertebral fractures
• 250,000 wrist fractures and 300,000 fractures at other sites.

Cost

The estimated national direct expenditures (hospitals and nursing homes) for osteoporotic and associated fractures was $17 billion in 2001 ($47 million each day) and the cost is rising. (National Osteoporosis Foundation, http://www.nof.org)

Symptoms

Osteoporosis is often called the "silent disease" because bone loss occurs without symptoms. People may not know that they have osteoporosis until their bones become so weak that a sudden strain, bump or fall causes a fracture or a vertebra to collapse. Collapsed vertebrae may initially be felt or seen in the form of severe back pain, loss of height, or spinal deformities such as kyphosis or stooped posture.

Detection/Diagnosis

Specialized tests called bone mass measurement or bone density tests can measure bone density in various sites of the body. A bone density test can:

• Detect osteoporosis before a fracture occurs.
• Predict your chances of fracturing in the future.
• DXA BMD can determine your rate of bone loss and/or monitor the effects of treatment.

(National Osteoporosis Foundation, http://www.nof.org) Diagnosing osteoporosis in men is complicated by a lack of consensus on how it should be defined. Significant risk factors for osteoporosis or fracture include low bone mineral density, previous fragility fracture, maternal history of fracture, marked hypogonadism, smoking, heavy alcohol intake or alcoholism, low calcium intake, low body mass or body mass index, low physical activity, use of bone-resorbing medication such as glucocorticoids, and the presence of such conditions as hyperthyroidism, hyperparathyroidism, and hypercalciuria (Wojciech P., et al ,Accepted 21 November 2003. Available online 25 February 2004)

Prevention and Treatment

By about age 20, the average woman has acquired 98 percent of her skeletal mass. Building strong bones during childhood and adolescence can be the best defense against developing osteoporosis later. There are four steps, which together, can optimize bone health and help prevent osteoporosis. They are:

• A balanced diet rich in calcium and vitamin D
• Weight-bearing exercise
• A healthy lifestyle with no smoking or excessive alcohol intake and Bone density testing and medication when appropriate.
• Medications- see information below

(National Osteoporosis Foundation , http://www.nof.org)

Pathophysiology and Fractures

The demineralization of bone due to the disease can lead to pain, particularity in the back, deformities such as loss of stature and kyphosis and pathological fractures. ( Dorland’s Medical Dictionary) The most typical sites of fractures related to osteoporosis are the hip, spine, wrist and ribs, although the disease can affect any bone in the body. The rate of hip fractures is two to three times higher in women than men; however the one year mortality following a hip fracture is nearly twice as high for men as for women. A woman's risk of hip fracture is equal to her combined risk of breast, uterine and ovarian cancer. In 1991, about 300,000 Americans age 45 and over were admitted to hospitals with hip fractures. Osteoporosis was the underlying cause of most of these injuries. An average of 24 percent of hip fracture patients aged 50 and over die in the year following their fracture. One-fourth of those who were ambulatory before their hip fracture require long-term care afterward. At six months after a hip fracture, only 15% of hip fracture patients can walk across a room unaided. White women 65 or older have twice the incidence of fractures as African-American women. (National Osteoporosis Foundation , http://www.nof.org)

Osteopenia versus Osteoporosis

Osteopenia according to Dorlands Medical Dictionary states osteopenia is reduced bone mass due to a decrease in osteoid synthesis. Strength of bone can be considered biomechanically and densiometrically. Strength of bone depends on intrinsic stiffness and architectural spatial distribution of mineralized tissue. To determine a differential diagnosis between disuse, primary, or secondary bone disturbance one must look at anthropometic test measures which take into account bone and muscle masses to determine osteopenia versus cross sectional tests of bone structure and strength to determine osteoporosis. Currently, densitometrists distinguish osteopenia as below -1.0 on densitometric t- score of areal BMD tests versus one below -2.5 as an osteoporosis. ( Ferretti, et al, 2003) Overall , low bone density is termed osteopenia. Low bone density that seems to have neared the “fracture threshold” of below -2.5 on the densitometric test is termed osteoporosis.

Medications

There appears to be some debate on these points please reference Feretti et al. 2003, for a more detailed description of this debate. Although there is no cure for osteoporosis, the following medications are approved by the FDA for postmenopausal women to prevent and/or treat osteoporosis:

Bisphosphonates

• Alendronate (brand name Fosamax®)
• Risedronate (brand name Actonel®)

Calcitonin (brand name Miacalcin®)

Estrogen/Hormone Therapy

• Estrogens (brand names, such as Climara®, Estrace®, Estraderm®, Estratab®, Menostar™, Ogen®, Ortho-Est®, Premarin®, Vivelle®, and others)
• Estrogens and Progestins (brand names, such as Activella™, FemHrt®, Premphase®, Prempro®, and others)

Parathyroid Hormone

• Teriparatide (PTH (1-34) (brand name Fortéo®)

Selective Estrogen Receptor Modulators (SERMs)

• Raloxifene (brand name Evista®)
• Alendronate is approved as a treatment for osteoporosis in men and is approved for treatment of glucocorticoid (steroid)-induced osteoporosis in men and women. Risedronate is approved for prevention and treatment of glucocorticoid-induced osteoporosis in men and women.
• Parathyroid hormone is approved for the treatment of osteoporosis in men who are at high risk of fracture.
• Treatments under investigation include sodium fluoride, vitamin D metabolites, and other bisphosphonates and selective estrogen receptor modulators.

References:

Ferretti, J, et al., Bone mass, bone strength, muscle-bone interactions, osteopenias, and osteoporosis. Mechanisms of Ageing and Development. Vol 124,;3. 2003
National Osteoporosis Foundation. http://www.nof.org/osteoporosis.
Dorlands Medical Dictionary. 1981, WB. Saunders Company pg 943.
Differential Diagnosis in Physical Therapy. 2000, WB. Saunders Company, Goodman and Snyder.,
Orthopedic Physical Therapy. 1989. Churchill Livingstone Inc. Donatelli and Wooden.
Wojciech, P. et al., Osteoporosis in men: Epidemiology, diagnosis, prevention, and treatment. Ovid online review Feb 2004.
Information compiled by Cindy Tumbleson PT.