Chapter 89: Osteoporosis

Osteoporosis, which literally means porous bone, is reduced bone mass per unit volume (see FIG. 89.1), thus predisposing the person with it to an increased risk of fracture. It also refers to the increased bone fragility that accompanies ageing and many illnesses. Following menopause, women begin to lose calcium from their bone at a much faster rate than men, presumably in response to low levels of oestrogen. By the age of 65 the rate of fractures in women has increased to 3–5 times that of men.¹ However, a third of all hip fractures in the community occur in men.

In recent decades osteoporosis was largely prevented by correction of oestrogen deficiency through the use of hormone replacement therapy but the balance has changed since the controversial association of HRT with breast cancer was reported.

Primary

Type 1: Postmenopausal (vertebral or distal forearm fractures between the ages of 51 and 75). Due to increased osteoclast activity. It is six times more common in women than men.

Type 2: Involutional or senile osteoporosis (fracture of proximal femur and other bones). It affects patients over 60 years and is twice as common in women as in men.

Idiopathic osteoporosis: Occurs in children and young adults of both sexes with normal gonadal function.

Secondary

Secondary to various endocrine disorders, malabsorption and malignancies. Various causes and risk factors are presented in TABLE 89.1.

• Plain radiography is of limited value. Osteoporosis is not detectable until 40–50% of bone is lost.

• 25-hydroxy vitamin D (most useful test): normal range 75–250 nmol/L.

• Plasma calcium, phosphate and alkaline phosphatase, parathyroid hormone (usually normal).

• Thyroid stimulating hormone.

• Parathyroid hormone.

• Consider tests for multiple myeloma in an osteoporotic area.

• Densitometry can predict an increased risk of osteoporosis and fracture, the best current modality being dual energy X-ray absorptiometry (DEXA scan) in a facility with high-standard quality control.³ The spine and femoral neck are targeted: the femoral neck is the most useful index.

DEXA, T scores and Z scores⁵

DEXA is the current gold standard for the diagnosis of osteoporosis. It assesses both whole-body and regional bone mass (lumbar spine and proximal femur). Bone mass is measured as bone mineral density (BMD) in g/cm² and the lower the BMD, the higher the risk of fracture. There are actually different normal ranges of BMD for each bone and for each type of DEXA measuring machine.

The BMD ‘T score’ is the number of standard deviations (SD) away from the mean BMD of a 30-year-old adult (see TABLE 89.2). Osteopenia (low bone density) is 1–2.5 SDs below the young adult standard mean. Osteoporosis is >2.5 SD below this mean. This is a strong indicator of bone fragility. Consider treatment if T score is <−2.5.

The BMD ‘Z score’ is the number of SDs away from the age- and sex-matched mean BMD. The Z score is used to express bone density in patients <50 years, premenopausal women, younger men and children. If low (<−2) it indicates prompt investigation for underlying causes of a bone deficit.

BMD is subsidised under the MBS⁶ for:

• people over the age of 70 years (2- or 5-yearly screening, depending on first T score)

• diagnosis of osteoporosis following a low-impact fracture

• screening for people with specific medical conditions or treatments likely to cause osteoporosis (annual)

• subsequent monitoring of low BMI

The decision whether to measure BMD in non-subsidised situations, and whether to treat a low BMD, may also be guided by an assessment of absolute fracture risk. The FRAX tool is commonly used, although somewhat controversially was developed by manufacturers of osteoporosis medication.⁷

The management of osteoporosis starts with restoring mobility and instituting measures to prevent falls. Underlying diseases that may be responsible for increased bone fragility should be identified and treated where possible. Carefully consider deprescribing medications adding to the risk of osteoporosis and falls.

The goal of drug treatment is to prevent osteoporosis or reduce further loss. Eliminate risk factors where possible and focus on optimal lifestyle measures as a baseline for management. No treatment has been shown to replace lost bone effectively. Anabolic agents such as nandrolone decanoate may reduce further loss but the side effects are problematic. The list of recent recommendations from the American College of Physicians is noteworthy.

Recommendations of American College of Physicians⁵

• Treat women who have known osteoporosis with alendroate, risedronate, zoledronic acid or denosumab to reduce the risk for hip and vertebral fractures

• Treatment should last 5 years (oral) or 3 years (annual IV), then usually cease unless recent fracture

• Menopausal hormone therapy should not be prescribed to treat osteoporosis in women

• BMD monitoring during the 5-year treatment period is not advised as evidence suggests that women see fracture reduction benefits regardless of BMD changes

• Offer bisphosphonate therapy to men with clinically recognised osteoporosis

• For osteopenic women ≥65 at high fracture risk, decisions to treat should take into account patient preference, fracture-risk profile, benefits, harms and price of medications

• Denosumab can cause hypocalcaemia which could lead to heart failure

Medications of value in decreasing further loss³

The following medications may be valuable in preventing further bone loss, possibly reversing the osteoporosis process and preventing further fractures.

• HRT (long-term use is not recommended but weigh potential benefits versus harms with female patients)⁸

  or

• bisphosphonates (decrease bone absorption)³—can be used alone or combined with other agents (take care with potential adverse effects of oesophagitis and osteonecrosis of jaw):

  • – alendronate 70 mg (o) once weekly on an empty stomach (take care with potential side effect of oesophagitis)

  • – risedronate 150 mg (o) once monthly or 35 mg (o) once weekly or in combination therapy with calcium carbonate ± vitamin D

  • – zoledronic acid, single annual IV injection

• raloxifene (a selective oestrogen-receptor modulator) (SERM) 60 mg (o) daily

• teriparatide (a synthetic form of human parathyroid hormone) increases bone formation—give 20 mcg SC once daily

• denosumab (a monoclonal antibody) 60 mg SC, once every 6 months, once calcium intake and vitamin D levels are optimal—a potential risk factor for osteonecrosis of the jaw especially in patients with bone cancer

The choice depends on the clinical status, such as the age of the patient and the extent of disease, the patient’s tolerance of drugs and further clinical trials of these drugs.

Recommendations for prevention^3,7,8,9

• lifestyle factors: stop smoking, limit caffeine and alcohol (2 SDs/day)

• maintain adequate nutrition: aim for ideal body weight with recommended waist measurements (preferable) or BMI 18–25

• adequate dietary intake of calcium:

  • – at least 1000 mg/day in women <50 years and men <70 years; 1300 mg in women >50 years and men >70 years

  • – dairy food is the main source of dietary calcium and people should meet their requirements with a good diet; supplementation in non-institutionalised people is not required

  • – oral calcium supplements may be necessary where a person’s diet does not meet their daily calcium requirements, particularly in postmenopausal women

• calcium citrate is better absorbed than carbonate³—recommend: calcium citrate 2.38 g (= 500 mg elemental calcium) daily

  or

  calcium carbonate 1.5 g (= 600 mg elemental calcium) daily with food

• calcium-rich foods include low-fat calcium-enriched milk (500 mL contains 1000 mg), other low-fat dairy products (e.g. yoghurt or cheese), fish (including tinned fish such as salmon with the bone), citrus fruits, sesame and sunflower seeds, almonds, brazil nuts and hazel nuts

• vitamin D deficiency and sunlight^9,10: there is evidence we need significant exposure to sunlight of the face, bare arms and hands to produce natural vitamin D (e.g. for those at risk—in summer 6–7 minutes mid-morning or mid-afternoon; in winter 7–40 minutes at noon with as much bare skin as possible). Refer to regional recommendations.¹¹ Measure serum 25-hydroxy vitamin D and ideally maintain it at >50 nmol/L. Mild deficiency is 30–49 nmol/L, moderate 12.5–29, severe <12.5. If supplementation is required use cholecalciferol 25–50 mcg (1000–2000 IU) (o) daily.³

• exercise: moderate exercise against gravity—walking (brisk walking for 30 minutes 4 times a week) or jogging may make a small contribution to retarding bone loss, but also help reduce falls. Highly osteogenic exercise includes basketball, tennis, dancing and gymnastics.

• attention to falls prevention, including avoiding falls (refer to CHAPTER 8)¹²

• ‘hip protectors’ for osteoporotic patients at increased falls risk have some weak evidence, but adherence can be poor

An Australian review investigating the effect of natural remedies on BMD commented that there is good evidence that exercise increases BMD in postmenopausal women with osteoporosis, little good-quality empirical evidence to support the use of natural progesterone cream and insufficient evidence to support the use of boron, cod liver oil or chelated calcium supplements (as opposed to calcium carbonate).¹³

There is no evidence that complex mineral preparations have added benefit and often they contain less elemental calcium than simple preparations.³

Recommendations are to measure BMD at the lumbar spine and hip:

• 2 years after therapy begins

• 1–2 years after therapy changes significantly or where high risk of bone loss (long-term glucocorticoids or post-transplant)

The main problem in children is secondary osteoporosis, which is usually related to chronic inflammatory disorders which require treatment with corticosteroids and/or cause reduced mobility. Other medical causes are malignancy, malabsorption syndromes, poor nutrition, anorexia nervosa and hypogonadism. Use DEXA to assess and monitor BMD and Z scores. Refer for treatment, which may be based on bisphosphonates.

Refer to CHAPTER 110.

• Refer postmenopausal women and older men to a specialist according to individual needs

• Osteoporosis appears to be secondary to an underlying illness

• Advice is required about the management of a patient with pathological osteoporotic fractures or loss of height

Hand-out sheets from Murtagh’s Patient Education 7th edition:

• Osteoporosis

NICE Fragility fracture risk (2012). <https://www.nice.org.uk/guidance/CG146>, accessed April 2018.