bubble_chart Overview

Osteoporosis refers to a decrease in the amount of bone tissue per unit. The growth and development of bones begin during the embryonic stage and continue for more than 20 years after birth. In adults, the amount of bone no longer changes, but bone metabolism continues without interruption, meaning the processes of bone formation and bone resorption remain in balance. After the age of 40, bone formation remains unchanged, but bone resorption increases. Decades later, the amount of bone tissue is only half of what it was at age 30. Once bone density decreases to the point where it can no longer withstand the stresses of daily life, pathological fractures occur.

bubble_chart Etiology

[Etiology of Diseases]

1. Postmenopausal and senile osteoporosis
2. Hereditary osteoporosis
   1. Osteogenesis imperfecta
   2. Homocystinuria
3. Osteoporosis caused by endocrine disorders
   1. Hypogonadism
   2. Hyperthyroidism
   3. Hyperparathyroidism
   4. Hyperadrenocorticism
4. Diet-related osteoporosis
   1. Calcium deficiency
   2. Vitamin D deficiency
   3. Vitamin C deficiency
   4. Chronic alcoholism
5. Drug-induced osteoporosis
   1. Long-term use of heparin
   2. Long-term use of methotrexate
6. Disuse osteoporosis
7. Osteoporosis caused by other diseases
   1. Various chronic sexually transmitted diseases
   2. Various intramedullary tumors: multiple myeloma, lymphoma, and leukemia
8. Idiopathic osteoporosis
   1. Idiopathic juvenile osteoporosis
   2. Idiopathic adult osteoporosis

[Pathological Changes]

Many factors can affect the quantity of bone tissue.

1. Systemic diseases: Malabsorption, liver and kidney diseases, alcoholism, corticosteroid use, and insufficient sunlight exposure can disrupt bone metabolism.
2. Race and heredity: White women, especially those from Northwestern Europe, have a higher incidence of osteoporosis-related fractures, while Black women have a lower incidence.
3. Nutritional status: Related to the intake of calcium and vitamin D₃. Children should consume 400–700mg of calcium daily, adolescents in the growth phase 1300mg, menopausal women 700mg, pregnant women 1500mg, lactating women 2000mg, and postmenopausal women need 1500mg of calcium daily to prevent bone loss. Dairy products and leafy green vegetables are the main dietary sources of calcium, while high-protein diets and emaciation due to improper food can increase urinary calcium loss. Doubling protein intake increases urinary calcium loss by 50%. Half of the body's vitamin D₃ comes from food, and the other half from sunlight exposure. Elderly individuals with insufficient sunlight exposure may develop vitamin D₃ deficiency. Young adults require 400 IU of vitamin D daily, while the elderly need 800 IU.
4. Age and gender: After epiphyseal closure, the morphology of bones changes, with increases in both periosteal and endosteal surface areas. After age 40, the endosteal surface area increases rapidly, cortical bone gradually decreases, and trabecular bone also diminishes, with women being more affected than men. On average, bone mass decreases by 0.5% annually. The rate of decline differs significantly between genders: men lose 0.5–0.75% per year, while women lose 1.5–2%, and sometimes as much as 3%.
5. Endocrine factors: Postmenopausal osteoporosis is related to low estrogen levels. Estrogen has been proven to play a key role in bone metabolism. Osteoporosis is also linked to parathyroid hormone (PTH). In the elderly, the renal production of 1,25-(OH)₂D₃ in response to PTH is weakened, while osteoclasts remain highly responsive to endogenous PTH, which is associated with estrogen deficiency.
6. Activity and Load: Mechanical loading stress is the primary external factor affecting bone development and remodeling. Inactive individuals are more prone to osteoporosis than active ones. During spaceflight, bone tissue loss can also occur due to weightlessness. After 84 days in a weightless environment, the degree of fracture and osteoporosis closely resembles disuse osteoporosis. It is now also believed that the loss of muscle contraction is a major cause of osteoporosis. Examples include Gypsum immobilization after a fracture, nerve and spinal cord injuries, and prolonged bed rest.

bubble_chart Diagnosis

Osteoporosis patients lose 30% of their bone mass from the spine, which is why they often seek medical attention due to spine fracture or proximal femur fracture. Spine fractures can be classified into three types:

1. thoracolumbar vertebral compression fracture. Minor trauma can lead to acute compression of the thoracolumbar vertebral body, and spontaneous vertebral compression may even occur without obvious trauma.
2. compression fracture of the lower lumbar spine.
3. diffuse spinal pain, which may be caused by multiple micro-fractures.

Proximal femur fractures include intracapsular femoral neck fractures and intertrochanteric fractures. The former is more common in individuals aged 65–75, while the latter occurs more frequently in older individuals, typically between 75–85 years of age.

X-ray findings show decreased bone density, with at least 30–50% of bone tissue already lost before the decrease in bone density becomes apparent; vertebral bodies become biconcave; the cortex of tubular bones thins, and the medullary cavity enlarges. Singh classified osteoporotic fractures into six grades based on changes in the trabeculae of the proximal femur. Grade 6 is normal, grades below 5 indicate osteoporotic fractures, and grades below 3 indicate grade III osteoporotic fractures.

After a vertebral compression fracture occurs, the following four manifestations may be observed:

1. biconcave central compression fracture;
2. anterior wedge-shaped compression fracture;
3. symmetrical transverse compression fracture;
4. mixed-type fracture.

﹝Auxiliary Examination﹞

Laboratory tests generally show normal serum calcium and phosphorus levels, with a slight increase in serum alkaline phosphatase in cases of fracture.

Several methods for measuring bone loss:

1. Singh index: as previously described.
2. Plain radiography of the hand to measure the cortical thickness of the midshaft of the second metacarpal bone. Normally, the cortical thickness should account for at least half of the diameter at that site.
3. Nosland-Cameson single-photon absorptiometry: using 125I as a monoenergetic photon source, differences in photon absorption between bone and soft tissues can be measured to determine bone tissue content in limbs. For example, in the radius, the proximal metaphysis normally consists of 95% cortical bone and 5% trabecular bone, while the distal metaphysis consists of 75% cortical bone and 25% trabecular bone. Dual-photon absorptiometry has recently been introduced, which can distinguish between fat and soft tissue components in bone.
4. Dual-energy quantitative CT scanning: quantitative CT scanning can differentiate fat, soft tissue, and bone tissue, while dual-energy quantitative CT scanning can further distinguish soft tissue components (bone marrow) within bone tissue.
5. In vivo neutron activation analysis: high-energy neutrons activate calcium in the body from Ca48 to Ca49, and a gamma-ray counter measures the decay of Ca48. Since 99% of the body's calcium is stored in bones, this method is highly accurate for determining whether total bone mass is reduced.
6. Iliac bone biopsy: involves three steps:
   1. Step 1: Oral administration of 750 mg tetracycline daily for 3 days to label bone tissue.
   2. After 3 days, an iliac bone biopsy is performed.
   3. The bone sample is obtained without decalcification, and ultrathin sections (5–10μ) are prepared for morphological measurement. This method is not suitable as a routine examination.

bubble_chart Treatment Measures

1. Acute Phase Treatment

Once a vertebral fracture occurs, the patient should rest on a hard bed with a pillow placed under the knees to reduce mild purgation and stress on the lumbar region. Pay attention to bedsore care. Painkillers may be used. Exercise should begin once the pain subsides, with activity levels gradually increasing daily. Patients with severe pain may wear a brace.

2. Methods to Increase Bone Tissue

1. Oral Calcium Supplements: Calcium carbonate, calcium phosphate, calcium lactate, and calcium gluconate can all be used. Patients should be encouraged to drink plenty of water after taking oral calcium supplements to prevent urinary stones.
2. Vitamin D Supplementation: It must be noted that large dose supplementation of vitamin D can cause hypercalcemia. For women around menopause, the daily dose is 400 units.
3. Estrogen Supplementation: Suitable for women around menopause. The dose is 0.6mg daily, but long-term use may carry a risk of cancer and should not be used as a routine treatment.
4. Exercise: At least 30 minutes of walking daily is recommended, which can serve as weight-bearing exercise and also facilitate sunlight absorption.
5. Sodium Fluoride Method: Take sodium fluoride orally at 1mg/kg daily, divided into 36 doses. Calcium supplements must be taken simultaneously. Overdosing can lead to fluoride poisoning. After 18 months of application, 90% of cases no longer experience fractures.
6. Other Medications: Include bisphosphonates, calcitonin, and anabolic steroids such as stanozolol.