Osteoporosis

Upon completion of this chapter, the reader will be able to:

• Differentiate primary and secondary osteoporosis and understand the medical conditions and medications associated with secondary osteoporosis.

• Understand how to determine individual fracture risk by identifying risk factors and secondary causes and determining bone mineral density.

• Interpret bone mineral density measurements and understand their use in predicting fracture risk and determining the need for drug therapy.

• Understand recommendations from the U.S. Preventive Services Task Force and the National Osteoporosis Foundation for bone density testing.

• Understand recommendations for calcium and vitamin D intake and how to determine if a patient requires supplementation.

• Describe the drugs currently approved for primary and secondary prevention, their effectiveness in preventing fractures, and potential adverse effects.

CASE 1 Harold Jackson

Harold Jackson is a 73-year-old widower who gets intermittent care from the local hospital emergency room and sometimes an urgent care office. His wife brings him to the walk-in clinic you cover occasionally because he has fallen “again.” Mr. Jackson says he has emphysema but evidently he still smokes. They have lived in the old family farmhouse for many years, and don’t get out much. He does not drive following an arrest for driving while intoxicated, his wife says. He takes a taxi home from the bar on his evenings out with his cronies. Last year Mr. Jackson fell at home and broke his wrist. It’s still stiff and swollen. He did not follow up after his wrist was splinted in the emergency room. Tonight, he has dirty cuts up his arm and on his knee, and his back hurts. He looks dry and undernourished. He has a cough which is “nothing” he says; he has just come to get cleaned up because his hand is bleeding and to get a tetanus shot. He is unkempt, ill shaven, and has lost 11 pounds since his last visit to the same clinic 9 months ago. You ask about his wheezy cough, which he says is just his usual. “I used to take prednisone.” Mrs. Jackson says, “He don’t eat right.” He says he has a bad stomach, and takes antacid pills and over-the-counter ranitidine, which relieves his symptoms. On examination he has some prolonged expiratory wheezes and basal crackles.

1. What can you and Mrs. Jackson do to prevent Mr. Jackson from falling again and sustaining a more serious fracture?

2. What aspects of his history put him at risk of osteoporosis?

3. Does he already have osteoporosis?

4. What are his chances of dying after a hip fracture?

Prevalence and impact

Osteoporosis is a systemic skeletal condition characterized by low bone mass and microarchitectural deterioration of bone tissue that increases bone fragility and risk for fractures.¹ It is diagnosed on the basis of the presence of a fragility fracture or by bone mass measurement criteria. A fragility fracture results from forces that would not normally cause a fracture, such as a hip or wrist fracture from falling from standing height or a vertebral compression fracture. In the absence of a fracture, osteoporosis can be diagnosed by measuring bone mineral density (BMD). Results are expressed as a T-score, which is the difference between an individual’s BMD measurement and normal values from a young healthy reference group. The World Health Organization developed definitions for normal, low, and osteoporotic levels of BMD based on T-scores for the spine, hip, or wrist for postmenopausal women and men age 50 and older.² By these criteria, bone density is normal for T-scores of −1.0 and higher; low for T-scores between −1.0 and −2.5 (also referred to as osteopenia), and osteoporotic for T-scores of −2.5 or lower (Box 43-1). However, T-scores identify only one aspect of the condition. Other important components, such as the rate of bone loss and quality of bone, are not currently measured.

BOX 43-1 BONE DENSITY T-SCORES

T-score is the difference between an individual’s bone density and the normal value of a reference group. It is expressed as the number of standard deviations above or below the mean of the normal values. T-score is used to classify bone density results into normal, low, and osteoporotic categories. These groupings were determined by the World Health Organization based on bone density measurements at the spine, hip, or forearm, and apply only to postmenopausal women and men age 50 and older.

If T-score is:	Bone density is:
−1.0 and higher	Normal
Between −1.0 and −2.5	Low (osteopenic)
−2.5 and lower	Osteoporotic

Low bone density, osteoporosis, and related fractures are common in older adults. Estimates in 2012 indicated that as many as 50% of Americans older than age 50, or 12 million individuals, would be at risk for osteoporotic fractures during their lifetimes.¹ Fracture rates for women are higher than for men, and rates are highest in whites compared to other racial groups, although rates for all demographic groups increase with age.^3–5

Osteoporosis-related fractures occur at many anatomic sites but are most common at the vertebrae, hip (proximal femur), and wrist (distal radius). All types of fractures are associated with increased mortality.6–8 Approximately one third of men with hip fractures will die during the subsequent year, a higher rate than for women.⁹ Nonfatal fractures at any site can impair function and quality of life, cause chronic pain and disability, and result in high costs for health care and lost productivity.

All types of fractures are associated with increased mortality.

CASE 2 Georgia and Ann Pound (Part 1)

Georgia Pound is an 81-year-old woman whose only child, Ann, has cared for her for more than 20 years. Ann had always been there for her parents, seeing them Sundays and Fridays and holidays and staying over whenever either of them were ill. When Mr. Pound suddenly died when Ann was in her early 40s, she left her office job in a local bank and moved in to help her mother. Over the years they became a familiar sight, Mrs. Pound in her wheelchair and Ann bent over pushing her up the hill to the church and down again to the old family home. If you passed them on the street, two identical smiles looked up at you. They increasingly looked like sisters, Ann, 63, and Mrs. Pound, 81.

The two of them come to see you in your office. They had not been in for a long time. Mrs. Pound is in a bad mood. Ann is finding her mother more and more difficult; she complains by day and wakes confused in the night. “It’s my back, I’m in pain goddammit!” says Mrs. Pound.

Mrs. Pound staggers out of her wheelchair that she has used constantly since breaking her hip 7 years ago. Her legs are edematous and her knees stiff from years of “resting.” You examine her back, and it is tender around L2 to L4; standing, her kyphosis is more obvious and she says she has “shrunk.”

1. What is the first thing to do to help Mrs. Pound’s mood?

2. Mrs. Pound’s problem list includes previous hip fracture, hypertension, and osteoarthritic knees. What three chronic illnesses can already be added to her list?

3. What needs to be done for Ann?

Risk factors and pathophysiology

Bone mass is determined by genetic factors, nutrition, physical activity, and general health, and it peaks during early adulthood. Bone health is maintained by the process of bone remodeling, in which old bone is replaced by new. Bone loss occurs when bone removal outpaces replacement. This process also causes alterations in the trabecular plates of bone, which further weakens bone structure (Figure 43-1). Bone loss progresses with aging and may be particularly active for women during menopause. Although bone loss and structural fragility are important causes of fracture, several others are contributory, such as the factors influencing falls (Figure 43-2).

Figure 43-1 Micrographs of normal (A) versus osteoporotic (B) bone. (From National Osteoporosis Foundation. Physicians’ guide to prevention and treatment of osteoporosis. http://www.nof.org.)

Figure 43-2 Fractures result from multiple contributing components relating to risk of fall, force of impact, and strength of bone.

Differential diagnosis and assessment

Reassess risks for osteoporosis and fractures periodically; changes in health status influence the risk.

Osteoporosis and fractures may result from several contributing causes, and it is important to understand a patient’s overall medical condition before planning interventions, particularly drug therapy. Individual risks for osteoporosis and fractures need to be reassessed periodically because changes in health status, such as the diagnosis of a new condition or initiation of a new medication, can influence a patient’s risk profile.

Fracture history

Previously undetected vertebral fractures easily seen on x-rays are important in establishing the diagnosis of osteoporosis.

Patients with previous osteoporosis-related fractures are at high risk for subsequent fractures and are the most likely to benefit from osteoporosis drugs. Most patients are able to recall having had a previous fracture that required medical attention. Fractures are usually well documented in medical records and validated by radiographs. Tracking follow-up care is usually more difficult because it often occurs outside of the immediate care setting. As a result, evaluations for osteoporosis are often missed, drug therapy is frequently not prescribed, and rates of subsequent fractures are generally high.¹⁰^,¹¹ Fractures that do not require immediate medical attention are often not recognized, particularly the majority of vertebral fractures with mild or no symptoms. Nonetheless, undetected vertebral fractures are also important in establishing the diagnosis of osteoporosis and determining needs for drug therapy, and can easily be seen on vertebral x-rays. The National Osteoporosis Foundation (NOF) recommends vertebral imaging for older men and women.¹²

Patients remember fractures and they are usually documented on x-ray films. However, bone density testing for osteoporosis is often not done, and avoidable fractures, disability, and even death can result.

CASE 2 Georgia and Ann Pound (Part 2)

For Mrs. Pound you prescribe acetaminophen, 650 mg, three times a day, as well as advising a heat-in-the-microwave pad.

Mrs. Pound allows you to x-ray her lumbar spine and, sure enough, the bones are thin, and the vertebral bodies of L2 and L3 are crushed, quite recently. Her vitamin D is at deficient levels. She agrees to take vitamin D so you start with 50,000 international units (IU) once a week.

You glance at quiet, worried Ann. Like mother, like daughter. Ann’s back is also kyphotic even though she is only 63. Is it already too late to prevent her from breaking a hip one day and suffering vertebral fractures? You order BMD testing for Ann.

1. What else is needed for Mrs. Pound? Should she be persuaded to take additional medication? What will you add first? Does she need more tests?

2. How can Ann prevent her own osteoporotic fractures?

3. What more should be done about Mrs. Pound’s cognition?

Identification of secondary causes and risk factors

Osteoporosis may occur without a known cause (primary osteoporosis) or can occur as the result of another condition (secondary osteoporosis). It is important to identify potential secondary causes before determining the need for osteoporosis drugs. Common secondary causes include dietary deficiencies of calcium or vitamin D; medications (including glucocorticoids); health conditions such as rheumatoid arthritis; and several others that are often undetected (Box 43-2). Metabolic bone diseases other than osteoporosis, such as hyperparathyroidism or osteomalacia, may be associated with a low BMD. Tests to diagnose secondary causes include complete blood counts and blood chemistries, liver function, thyroid stimulating hormone (TSH), serum 25(OH)D, parathyroid hormone (PTH), and 24-hour urine calcium, as well as special studies in selected patients.

BOX 43-2

SECONDARY CAUSES OF OSTEOPOROSIS

^*At levels of 5 mg daily or more of prednisone or equivalent for 3 or more months.

U.S. Department of Health and Human Services. Bone health and osteoporosis: A report of the Surgeon General. Rockville, MD: U.S. Department of Hearth & Human Services. Office of the Surgeon General; 2004.

If a secondary cause is found, it is of course addressed. Bone density monitoring and osteoporosis treatment can be considered if the bone density is low or there is a fracture, depending on the underlying condition, the severity of osteoporosis, other aspects of the patient’s health, and the patient’s preferences.

Risk factors are also useful in determining needs for bone density testing and osteoporosis drugs. Several methods to calculate a patient’s individual risk for fracture based on key risk factors derived from epidemiologic studies have been developed and tested. Although models vary, most are modest predictors of fractures, and the results of simple versus complex models are similar.¹³ The Fracture Risk Assessment Model (FRAX), developed by the World Health Organization,¹⁴ calculates a patient’s 10-year probabilities of either a major osteoporotic fracture (spine, hip, or wrist) or, specifically, a hip fracture based on 11 risk factors (Box 43-3). FRAX has been validated for both men and women. Calculations can be made with and without bone density results using a publicly accessible web-based calculator.¹⁵ The NOF has issued treatment recommendations based on specific 10-year risk thresholds calculated by FRAX (20% and higher risk for major osteoporotic fractures; 3% and higher risk for hip fracture).¹² However, this approach has not been tested in drug trials, and it is not yet known how effective these thresholds would be in reducing fractures in actual patients.