Osteoporosis
last authored: Nov 2011, David LaPierre
last reviewed:
Introduction
Osteoporosis is a decrease in bone density and quality, leading to issues with bone strength and leading to increased risk of fragility fracture.
It was previously a disease characterized by spinal compression fractures, though is now defined radiologically by T score (see ////// S.TD.GQCEbelow) of >2.5 SD.bwrzzbb/E>/.r/..s.............z
Similar to other diseases, osteoporosis identification and treatment may be approached from a risk reduction strategy.
Osteoporosis affects 1:4 women and 1:8 men over 50. Over 1.4 million Canadians will be affected during their lifetime. After menopause, women have a 40% chance of an osteoporotic fracture. White and Asian people are more affected than blacks people.
Fragility fractures are those that occur spontaneously, or following a minor trauma such as a fall from a standing height.
The Case of...
a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.
Causes and Risk Factors
key risk factors include:
- low calcium intake
- low bone mineral density
- prior fragility fracture
- age
- family history
other major risk factors include:
- age over 65
- vertebral compression fracture
- kidney problems, leading to problems with vitamin D activation
- fragility fracture after age 40
- family history
- systemic glucocorticoid therapy over 3 mo
- Cushing's
- malabsorption syndrome
- persistent anovulation
- hyperparathyroidism
- propensity to fall
- x-ray appearance of osteopenia
- hypogonadism (testosterone is bone protective)
- early menopause (before age 45)
minor risk factors:
- Caucasian
- hyperthyroidism, past or present
- low BMI
- smoking
- rheumatoid arthritis
- chronic heparin therapy
- chronic anticonvulsant therapy
Pathophysiology
Can have primary osteoporosis, secondary, or other rarer forms.
main risk factor is loss of estrogen in women
Aggravated by general or regional inactivity; bone is very dynamic, and maintained bone loading is important.
Trabeculae orient along the lines of stress
osteoclasts have estrogen receptors and likely respond to a loss of the hormone.
women over 75 have accelerated loss of bone density
- glucocorticoids cause increased bone resorption; after 3 mo, vitamin D action is antagonized
- calcium excretion is also increased
- also acts on pituitary to suppress LH/FSH
- promotes apoptosis of osteoblasts
Signs and Symptoms
- history
- physical exam
History
Identify risk factors for low BMD, future fractures and falls:
- prior fragility fractures
- parental hip fracture
Suspect osteoporosis in women with new onset back pain, a decrease in height (vertebral fractures), or thoracic kyphosis.
Physical Exam
Investigations
- screening
- lab investigations
- diagnostic imaging
Screening
Mass screening is not recommended.
Hip and spine are most commonly screened.
Women over 65, any post-menopausal women, or people with one major or two minor risk factors.
The United States Preventive Services Task Force suggests that women over age 65 years or at any age if their 10-year risk of fracture exceeds 10% should be screening.
One American study (Gourlay 2012) suggests screening intervals for older women should be as follows:
- normal or mild osteopenia - every 15 years
- moderate osteopenia - at age 70
- severe osteopenia - annually, or until bisphosphonate treatment is started
Lab Investigations
Bone biochemical markers can be used to identify people losing bone at an increased rate:
- nonspecific markers: alkaline phosphatase, urinary calcium/creatinine, hydroxyproline/creatinine
- specific markers: serum bone-specific AP
- osteocalcin
- procollagen I extension peptides
- plasma TRAP
- urine pyridinoline and deoxypyridinoline
Bloodwork screening for causes include:
- CBC
- creatinine TSH
- 25-OH vit D
Diagnostic Imaging
Bone density can be assessed in many ways. Radiographs can provide information about lucency. Dual energy x-ray absorptiometry (DEXA) can be used to detect small changes over time.
Imaging of the femoral neck is helpful, as it is a cortical bone.
Regarding DEXA scans:
status |
T-score |
normal |
+ 2.5 to -1.0 |
osteopenia |
- 1.0 to - 2.5 |
osteoporosis |
< -2.5 |
severe osteoporosis |
< -2.5 and fragility fracture |
Falsely elevated values can occur in cases of sclerosis or compression fractures.
Other imaging modalities include:
- quantitative CT
- ultrasound densitometry
- single or double photon absorptiometry
- bone biopsy
- other
Differential Diagnosis
Risk Stratification
Glucocorticoids taken over 3 months, move people into a higher risk category.
such as:
- prev wrist fracture
- spine T score much lower than...
Treatments
Conservative treatment
Regardless of risk factors, all patients should be encouraged to take calcium (1,000-1,500 mg per day TOTAL, or 0-500mg daily supplementation) and vitamin D (800-1000 IU per day). VIt D decreases muscle strength and balance, leading to increased risk of falls.
Regular physical activity (e.g., weight-bearing and muscle-strengthening exercises) are critical.
Smoking cessation and alcohol minimization are also helpful. As well, excessive caffeine should be recommended (true?)
Gait stabilization exercises (eg, Tai-Chi, yoga) assistive devices, and home safety practices can be used to prevent falls. Hip protectors can be used in certain populations to reduce fractures.
Medications
Medications should be used if patients are high risk, or moderate risk with special concerns.
First line for treatment of osteoporosis is bisphosphonates - risedronate, alendronate, or etidronate daily or weekly, or zolendronic acid monthly/yearly. Bisphosphonates work by inhibiting osteoclast resorption in bone.
Concerns may include:
- esophageal cancer
- osteonecrosis of the jaw
- atrial fibrillation
- atypical femur fractures
For many people, a drug holiday after a few years, if there is no clinical evidence of fracture, is likely safe.
Second-line treatment is raloxifene, a selective estrogen receptor modulators (SERMs). Raloxifene increases BMD and decreases risk of fracture. It also appears to benefit lipid profile and decrease breast cancer, though with increased risk of DVT, PE, and hot flashes.
Hormone replacement therapy increases BMD, though the side effects (DVT, PE, CVD, cancer) outweigh benefits for most people. Use only in people with severe osteoporosis.
Calcitonin increases BMD and may decrease acute vertebral fracture pain, though evidence is controversial in regards to fracture reduction. It acts by reducing the number of osteoclasts.
Strontium may be used to inhibit bone resorption and increase bone formation.
Teriparatide is a PTH analog, providing short-lived increase osteoblast function and bone formation.
Anabolic steroids, pulsatile growth hormone, or parathyroid hormone therapy (experimental).
Follow-up
Follow-up of BMD should be offered 1-3 years after treatment is started. If condition is improving, interval can be extended.
Consequences and Course
Risk stratification of patients suggests overall risk of fracture.
Twenty percent of women and 34% of men with hip fracture die within the first year, and 1/4 require long term care.
Resources and References
Osteoporosis Canada Clinical guidelines
Society of Obstetricians and Gynecologists of Canada's 2006 Osteoporosis guidelines
Topic Development
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