Osteoporosis overview
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Osteoporosis Microchapters |
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Diagnosis |
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Treatment |
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Medical Therapy |
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Case Studies |
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Osteoporosis overview On the Web |
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American Roentgen Ray Society Images of Osteoporosis overview |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Eiman Ghaffarpasand, M.D. [2]
Overview
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Osteoporosis was first discovered by John Hunter, British surgeon, in 1800's. Osteoporosis divided to primary and secondary diseases, upon classification based on disease origin. While, it becomes divided to osteopenia, osteoporosis, and severe osteoporosis, upon classification based on disease severity. The pathophysiology of osteoporosis basically involves an imbalance between bone resorption and bone formation. Major factors that contribute to the development of osteoporosis include estrogen deficit and aging. The main pathway, through which these factors might lead to osteoporosis is reactive oxygen species (ROS) damage to osteocytes. Decreasing the capability of autophagy in osteocytes is another important issue; which make them vulnerable to oxidative stresses. Genes involved in the pathogenesis of osteoporosis are many genes that majorly can categorized in four main groups, include the osteoblast regulatory genes, osteoclast regulatory genes, bone matrix elements genes, and hormone/receptor genes. Osteoporosis must be differentiated from other diseases that cause decreasing in bone mineral density (BMD), such as idiopathic transient osteoporosis of hip, osteomalacia, scurvy, osteogenesis imperfecta, multiple myeloma, homocystinuria, and hypermetabolic resorptive osteoporosis. Osteoporosis is a major health problem involving 43.9% (43.4 million) of male and female population in the United States. The disease rate increased as people's age raised. The most prevalent age group of patients is 80 years and older. White females and African-American males have the highest frequency among the other races. Risk factors for osteoporosis disease are of two types, including non-modifiable and modifiable (potentially) factors. Non-modifiable risk factors are age, sex, menopause, and family history. Modifiable (potentially) factors are smoking, alcohol consumption, immobility, glucocorticoid abuse, and proton pump inhibitor (PPI). Today, risk of fracture due to osteoporosis is threatening one out of two postmenopausal women and also one out of five older men. The 10-year risk for any osteoporosis-related fractures in 65-year-old white woman with no other risk factor is 9.3%. Upon the guidelines of USPSTF, all women ≥ 65 years old along with women < 65 years old with high risk of fracture are target of screening for osteoporosis; but there is not any recommendation to screen men for the disease. There are two major methods, that is suggested to use for screening osteoporosis, include dual energy x-ray absorptiometry (DXA) of both hip and lumbar spine bones, and quantitative ultrasonography of the calcaneus. If left untreated, most of patients with osteoporosis may progress to develop fracture. With appropriate and timely usage of medications along with calcium and/or vitamin D supplementation, the outcome of osteoporosis is usually good. Apart from risk of death and other complications, osteoporotic fractures are associated with a reduced quality of life due to immobility; emotional problems may also raised as a consequence. As studies suggested, the impact of osteoporosis and also osteoporotic fractures on public life would be worse than lots of life threatening diseases; especially with aging. There are various lifestyle modifications that can be implemented to help prevent the development or even treatment of osteoporosis. They are including calcium and vitamin D supplementation, diet, exercise, smoking quit, alcohol consumption, and also fall prevention. The mainstays of treatment in primary osteoporosis disease are based on in lifestyle modifications. Most of the time in high risk patients and people with past history of osteoporotic fracture, medical therapy is necessary. Bisphosphonates are the first line treatment for osteoporosis disease. Raloxifene is the second line treatment of osteoporosis in postmenopausal women, for both treatment and prevention. Denosumab is a human monoclonal antibody designed to inhibit RANKL (RANK ligand), a protein that acts as the primary signal for bone removal. It is used to treat osteoporosis in elder men and postmenopausal women. Teriparatide and Abaloparatide are human recombinant parathyroid hormones used to treat postmenopausal woman with osteoporosis at high risk of fracture or to increase bone mass in men with osteoporosis. |
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Historical Perspective
Osteoporosis was first discovered by John Hunter, British surgeon, in 1800's. He found that bones in the human body are turning over continuously; when some old or dysfunctioned bone tissue become eroded and eliminated, the new fully functioned one being substituted. Nowadays, the process is called remodeling, the most important issue in osteoporosis pathophysiology. Jean Lobstein, a French pathologist of 1830's, found that there are normal holes in every bone; but some people's bones from specific age and diseases may have larger holes than normal ones. He eventually named this kind of bones as porous, and the disease got its name; osteoporosis.
Classification
Osteoporosis may be classified into several subtypes based on disease origin and disease severity. Osteoporosis divided to primary and secondary diseases, upon classification based on disease origin. While, it becomes divided to osteopenia, osteoporosis, and severe osteoporosis, upon classification based on disease severity. Osteoporosis in children and adolescents is rare, usually is due to some comorbidities or medications, secondary osteoporosis. Surprisingly, no significant causes have been found for rare cases, idiopathic osteoporosis.
Pathophysiology
The pathophysiology of osteoporosis basically involves an imbalance between bone resorption and bone formation. Major factors that contribute to the development of osteoporosis include estrogen deficit and aging. The main pathway, through which these factors might lead to osteoporosis is reactive oxygen species (ROS) damage to osteocytes. Decreasing the capability of autophagy in osteocytes is another important issue; which make them vulnerable to oxidative stresses. Genes involved in the pathogenesis of osteoporosis are many genes that majorly can categorized in four main groups, include the osteoblast regulatory genes, osteoclast regulatory genes, bone matrix elements genes, and hormone/receptor genes.
Causes
Osteoporosis may be caused by any condition, which could lead to the disturbed balance between bone formation and bone resorption. The most common conditions include but not limited to aging, menopause, nutritional deficiency of calcium and/or vitamin D, chronic renal failure, immobility, hyperparathyroidism, and chronic glucocorticoid abuse.
Differentiating Osteoporosis from other Diseases
Osteoporosis must be differentiated from other diseases that cause a decrease in the bone mineral density (BMD), such as idiopathic transient osteoporosis of hip, osteomalacia, scurvy, osteogenesis imperfecta, multiple myeloma, homocystinuria, and hypermetabolic resorptive osteoporosis.
Epidemiology and Demographics
Osteoporosis is a major health problem involving 43.9% (43.4 million) of male and female population in the United States. The disease rate increased as people's age raised. The most prevalent age group of patients is 80 years and older. White females and African-American males have the highest frequency among the other races.
Risk Factors
Risk factors for osteoporosis disease are of two types, including non-modifiable and modifiable (potentially) factors. Non-modifiable risk factors are age, sex, menopause, and family history. Modifiable (potentially) factors are smoking, alcohol consumption, immobility, glucocorticoid abuse, and proton pump inhibitor (PPI).
Screening
Today, the risk of fracture due to osteoporosis is threatening one out of two postmenopausal women and also one out of five older men. The 10-year risk for any osteoporosis-related fractures in a 65-year-old white woman with no other risk factor is 9.3%. Upon the guidelines of USPSTF, all women ≥ 65 years old along with women < 65 years old with a high risk of fracture are the target of screening for osteoporosis, but there is not any recommendation to screen men for the disease. There are two major methods, that is suggested to use for screening osteoporosis: dual energy x-ray absorptiometry (DXA) of both hip and lumbar spine bones, and quantitative ultrasonography of the calcaneus.
Natural History, Complications and Prognosis
If left untreated, most of the patients with Osteoporosis may progress to develop a fracture. With the appropriate and timely usage of medications along with calcium and/or vitamin D supplementation, the outcome of osteoporosis is usually good. Apart from the risk of death and other complications, osteoporotic fractures are associated with a reduced quality of life due to immobility; emotional problems may also arise as a consequence. As studies suggested, the impact of osteoporosis and also osteoporotic fractures on public life would be worse than lots of life threatening diseases; especially with aging.
Diagnosis
History and symptoms
Osteoporosis, actually has not any acute symptoms, until the patient experiences an osteoporotic fracture. The hallmark of osteoporotic fracture is bone pain. Following osteoporotic fractures, the major signs appeared, gradually; which include immobility, bed sores, shortness of height, and stooped posture.
Physical examination
Osteoporosis is generally asymptomatic during initial years; until the bone mass loss leads to a fracture. These fractures could be divided into acute and chronic ones; mostly involve the femoral neck and vertebral bones, respectively. The main feature of femoral fracture is immobilization and the main feature of vertebral fracture is Dowager's hump appearance. Any other secondary causes of the disease (e.g., chronic corticosteroid use or hyperthyroidism) may have their own symptoms; signifying a risk factor for osteoporosis.
Laboratory findings
There is a limited role for laboratory tests in diagnosis of osteoporosis; however, they may be used for differentiating primary versus secondary causes of the disease. Lab tests for the diagnosis of osteoporosis include some baseline tests like complete blood count (CBC), serum calcium, phosphate, alkaline phosphatase, and 25-(OH)-vitamin D. There are also tests for diagnosing secondary osteoporosis, which include 24 hr serum calcium, serum protein electrophoresis, and serum thyroid hormones.
Electrocardiogram
There are no electrocardiogram (ECG) findings associated with osteoporosis.
X-ray
X-ray may be helpful in the diagnosis of osteoporosis. The main finding on x-ray suggestive of osteoporosis is bone mass loss, identified with decreased bony trabecula in primary stages and then decreased cortical thickness. The most common bones monitored for osteoporosis evidences are femoral neck, lumbar vertebrae, and calcaneus. Plain radiography needs at least 30-50% of bone loss to demonstrate decreased bone density; therefore, it is not a very sensitive modality.
CT scan
High resolution CT (hrCT) and micro CT (μCT) may be helpful in the diagnosis of osteoporosis. Despite that bone mineral density (BMD) measurement may provide so much information about osteoporosis and also osteoporotic fracture risk, but some researchers suggest that it has a limited role in bone strength description. In order to describe the bone strength more precisely, it seems necessary to do quantitative assays such as dual energy X-ray absorbtiometery (DXA) and CT scan (especially volumetric quantitative CT (vQCT)). Modalities for assessing osteoporotic fracture risk, without any destruction or invasion, include high resolution CT (hrCT) and micro CT (μCT). The only tests that is possible in vivo are hrCT and vQCT.
MRI
Regarding that magnetic resonance imaging (MRI) technique is very precise in measuring trabecular bone structure, it could be a suitable surrogate for multiple sites bone biopsy. On the other hand, although 20% of skeleton consist of trabecular bones, but they have highest impression from metabolic stimuli; thus, in contrast with DXA which is measure both trabecular and cortical at the same time, MRI would be better choice. The most impressing aspect of MRI in diagnosing osteoporosis is the ability to take in vivo images of trabecular bones. The plain resolution starts at about 150 μm and slice thickness starts at 300 μm; measuring trabecular bones precisely.
Echocardiography/Ultrasound
There are no echocardiography findings associated with osteoporosis. Quantitative ultrasound may be helpful in the diagnosis of osteoporosis. The main finding on an ultrasound that may be diagnostic of osteoporosis is bone mass loss, mainly trabecular bone that is the major bone type involving in osteoporosis. Problems with DXA method have led to choose some methods with fewer harms and limitations, such as ultrasound (especially quantitative), which could diagnose osteoporosis with lower radiation, lower price, and also higher availability. Most common site of ultrasound application is peripheral parts, such as calcaneus and phalanges.
Other imaging findings
The most important modality for measuring bone mineral density (BMD), that every osteoporosis diagnostic and therapeutic decision are based on, is dual energy X-ray absorptiometry (DEXA). DEXA is a 2-dimensional image of a 3-dimensional subject, mainly depends on the size of the bone which is studied. Regarding the vast advantages of DEXA, it seems that DEXA will remain the masterpiece of fracture risk assessment and also osteoporosis diagnosis in the future. Finite element modeling (FEM) is basically an engineering computer-based simulation software. FEM typically simulate the physical loading effects on materials. The effects may be strain or compression, while the subject determined as net-like elements connected to each other. BMD is focused on density and does not imply for microstructure or architecture of bones. One of the most powerful methods to determine the microstructure is the trabecular bone score (TBS) as a complementary method for DEXA.
Other diagnostic studies
There are no additional diagnostic findings for osteoporosis.
Treatment
Medical therapy
Life style modification
There are various lifestyle modifications that can be implemented to help prevent the development or even treatment of osteoporosis. They are including calcium and vitamin D supplementation, diet, exercise, smoking cessation, alcohol consumption, and also fall prevention. The patient should consume 1200 to 1500 mg of calcium daily, either via dietary means (e.g., 8 oz glass of milk contains approximately 300 mg of calcium) or via supplementation. New vitamin D intake recommendations are adults up to age 50, 400-800 IU daily and those over 50, 800 - 1,000 IU daily. Multiple studies have shown that aerobics, weight lifting, and resistance exercises can all maintain or increase BMD in postmenopausal women. In addition to maintaining adequate vitamin D levels and physical activity, as described above, several strategies have been demonstrated to reduce falls.
Pharmacotherapy
The mainstays of treatment in primary osteoporosis disease are based on in lifestyle modifications. Most of the time in high risk patients and people with past history of osteoporotic fracture, medical therapy is necessary. Bisphosphonates are the first line treatment for osteoporosis disease. Raloxifene is the second line treatment of osteoporosis in postmenopausal women, for both treatment and prevention. Denosumab is a human monoclonal antibody designed to inhibit RANKL (RANK ligand), a protein that acts as the primary signal for bone removal. It is used to treat osteoporosis in elder men and postmenopausal women. Teriparatide and Abaloparatide are human recombinant parathyroid hormones used to treat postmenopausal woman with osteoporosis at high risk of fracture or to increase bone mass in men with osteoporosis.
Surgery
Surgery is not the first-line treatment option for patients with osteoporosis. Vertebroplasty, kyphoplasty, lordoplasty, and vesselplasty are procedures that usually reserved for patients with either pathological or osteoporotic vertebral fractures in patients, refractory to medical therapy. Surgery options for osteoporosis are very limited. In case of hip fracture, open reduction internal fixation or in rare cases total hip replacement surgery are the options.
Primary Prevention
In osteoporosis, some of lifestyle modification strategies would be beneficial for both primary prevention and also initial treatment; because osteoporosis majorly depends on life style, in every stage of the disease. Lifestyle modification, as well as calcium supplementation, are the best early and long-term measures for the prevention of osteoporosis. There are also medications available that can be used to prevent worsening of osteoporosis. The primary prevention of osteoporosis is particularly important because the micro-architectural changes that occur in osteoporosis are largely irreversible.
Secondary Prevention
Effective measures for the secondary prevention of osteoporosis include pharmacological therapy and also lifestyle modification as soon as osteoporosis is diagnosed.
Cost-Effectiveness of Therapy
44 million people of more than 50 years old in the US are suffering from osteoporosis, more than half of over 50 years people. Remaining the current conditions and utilities, it is estimated that more than 61 million people in 2020 will be involved in osteoporosis. Women are 80% of the osteoporotic population. PTH analogues (teriparatide and abaloparatide) have more prices and QALYs in contrast with zoledronate. Teriparatide and abaloparatide are $43,440 and $22,061 more costly than zoledronate. In Europe the whole cost of medical therapies for osteoporosis in 2010 was €37 billion, in which 66% was for acute fractures management, 29% was for long-term fracture outcome management, and 5% was for medical prevention. On the other hand, the holistic burden of osteoporosis in Europe assumed to be the loss of 1,180,000 life years (quality adjusted (QALY)), most of them because of prior osteoporotic fractures. Regarding that one QALY is equal value of 2xGDP, it is assumed that the total burden of osteoporosis become €60.4 billion, in 2010. Surprisingly, the QALY number will rise from 1.2 million in 2010 to about 1.4 million years in 2025, with 20% increase.
Future or Investigational Therapies
Some future antiresorptive drugs that are not yet improved by FDA, include calcitriol, genistein, other bisphosphonates (etidronate, pamidronate, and tiludronate), PTH (1-84), sodium fluoride, strontium ranelate, and also tibolone.