Osteoporosis is a disease characterized by reduced bone mass, degradation of bone microstructure, and decreased bone strength, resulting in an increased risk of fracture. A study in the United States showed that fragility fractures caused by minor violence in the elderly accounted for 75% of proximal humerus fractures, 80% of hip fractures, 60% of tibia and ankle fractures, and 50% of distal radius fractures. The sex composition ratio of the occurrence of osteoporotic fractures has more significant clinical features. Females accounted for 68.32% and males 31.68%. The main reason why women are significantly higher than men is that after menopause, with the decline of estrogen levels, women lose bone mass rapidly, while men show a slow loss process. This different change in bone metabolism due to different changes in sex hormones in men and women has formed the gender characteristics of osteoporotic fractures.
I. Factors of osteoporotic fracture occurrence
1. Decrease in bone mass and increase in bone fragility
Decreased bone mass and increased bone fragility due to ageing are the main reasons for increased susceptibility to osteoporotic fractures. The results of clinical epidemiology and bone mass measurement studies confirm that low bone mass at the fracture site is the most important factor for fracture occurrence. Bone transformation takes place on the surface of bone trabeculae, and cancellous bone trabeculae have a large surface area; therefore, bone tissues rich in cancellous bone, such as vertebral bodies of vertebrae, distal radius, and proximal femur, lose bone mass faster during aging, and the structural integrity of bone tissue is easily damaged, making them more susceptible to fracture. The internal cause of osteoporotic fractures is the decrease in the mechanical strength of the bone, i.e., the weakened ability of the bone to withstand and resist external forces. Bone strength is 80% dependent on bone mineral density, and low bone density is strongly associated with a high incidence of osteoporotic fractures. cummings et al. reported that for each standard deviation decrease in low femoral neck bone density, the age-adjusted risk of hip fracture would increase 2.6-fold. Previous epidemiological studies have firmly established that low bone density is the single most important risk factor for osteoporotic fractures.
2. Altered bone geometry
This is another important cause of osteoporotic fractures. The risk of hip fracture increases 13-fold in the elderly from 60 to 80 years of age, but the decrease in bone density at this stage only increases the risk of fracture by a factor of 1. Therefore, there must be other factors such as bone structure, distribution, muscle strength, body balance stability and falls. Many studies in recent years have confirmed that osteoporotic fractures are caused by changes in bone structure in addition to a decrease in bone mass. The pathological changes of osteoporosis are not only the change of bone volume, i.e. the decrease of bone density, but also the change of bone structure, and this change of bone structure obviously affects the strength of bones.
The pathological changes of osteoporosis are thinning of bone trabeculae and reduction of their number, resulting in increased loading of the residual trabeculae, which reduces the strength of the trabeculae. The geometry of bone determines the structural mechanical characteristics of bone, while the microstructure of bone directly affects the material mechanical properties of bone, and a small change in bone structure can significantly decrease the strength of bone. Yan Jinglong et al. found that the trabeculae in the proximal tibial epiphysis of rats after ovariectomy became significantly thinner, some trabeculae were interrupted and gradually resorbed, the distance between trabeculae widened, and the trabecular junction was destroyed. The above changes will certainly lead to a decrease in the overall mechanical strength of cancellous bone, which may be the main cause of fibrous fractures.
One of the four characteristics of bone biomechanics is the degree of microstructural integrity. Steel is stronger than bone but its life span is shorter than that of bone because it is unable to repair itself resulting in constant microdamage within the material. Microcracks in bone tissue can be completely repaired by bone reconstruction under normal circumstances. However, if they are produced too quickly and in too large numbers, exceeding the ability of the bone tissue to repair itself, fatigue fractures can occur. Therefore, osteoporosis also causes fractures because the repair function of microfractures is reduced, resulting in an accumulation of microfractures that can produce fractures when subjected to minor external forces.
Studies have concluded that osteoporosis is prone to fractures due to (1) repetitive mechanical micro-injuries and increased intensity of inappropriate labor. (2) Delayed repair process. Vertebral hematopoietic bone marrow normal about 75% , the proliferation of bone cells determined by the number of such hematopoietic stem cells, with the increase of age, the elderly calcium metabolism impairment, hematopoietic marrow cells is only half of the normal, osteoblasts decreased, empty bone traps increased, after 70 years of age Ha’s system has 35% of empty bone traps, the performance of endosteal resorption, the expansion of the medullary cavity, cortical bone thinning, trabecular bone and cortical bone into equal proportion to reduce the resistance to The bone strength of fracture is significantly reduced, and the rate of bone repair is less than the incidence of minor injuries. (3) The absolute volume of bone is reduced. The loss of trabecular bone increases the weight-bearing of the remaining bone, which is more likely to cause micro-injury.
3.Other factors
Some scholars believe that the frequency and extent of falls are also fundamental factors in the occurrence of osteoporotic fractures. More than 90% of hip fractures are caused by falls. The elderly are prone to falls, and the first force on the hip is the direct cause of fracture. courtney et al. found that the strength and energy absorption capacity of the femur in the elderly are only half and one-third of those in young people, respectively, meaning that a simple fall in the elderly can put them at risk of femur fracture. Factors that increase the risk of fracture include: direct impact at or near the greater trochanter; lack of protective measures, such as extending the upper extremity to prevent a fall; and inadequate local soft tissue energy absorption . There are many causes of fall-prone elderly, such as age-related vision loss, visual impairment due to cataracts and diabetic retinopathy, hypertension and hypotension, as well as Meniere’s syndrome, cerebrovascular lesions, cervical spondylosis and lumbar degeneration, which involve multidisciplinary diseases.
II. Intervention and prevention measures for osteoporotic fracture
1. Identify high-risk groups and help assess osteoporotic fracture risk factors
Risk factors for osteoporotic fracture include advanced age, postmenopausal women, family history of fracture, low body weight, inadequate calcium and vitamin D intake, poor lifestyle (smoking, excessive alcohol consumption, excessive coffee and carbonated beverages, lack of physical activity and physical exercise, and diseases affecting bone metabolism (such as hyperthyroidism, diabetes) or long-term use of drugs affecting bone metabolism (such as glucocorticoids and diuretics). Take fracture risk assessment for them, help them analyze the factors that may induce fracture and propose fracture prevention measures.
2. Safety protection guidance for high-risk groups
For elderly people with osteoporosis, we should provide them with safety protection guidance, inform them of the adverse consequences of falls and preventive measures, such as going to the toilet, getting up, bathing, etc., to stand firmly before moving and improve coordination of movements. Hold the handrail when going up and down the stairs or taking the bus. The floor should not be too wet, and wear comfortable and non-slip shoes to prevent falls caused by slippery floors. Elderly patients with osteoporosis should go less often to places where people gather to reduce collisions. Elderly people with unstable walking and poor muscle strength of lower limbs should have crutches to assist them. Usually pay attention to maintain good posture, avoid weight-bearing, and use lumbar girth when necessary, which is helpful to prevent vertebral fractures.
3.Elderly exercise and environmental requirements
The mechanism of the effect of exercise on bone mass is more complicated. It is reported that it may be related to the fact that exercise can increase the serum level of sex hormones; sunlight during exercise can increase the level of 1,25(OH)2D3 in the body and promote the absorption of calcium and phosphorus in the intestine; exercise can promote the deposition of calcium ions in bone tissue, improve the stress stimulation of the whole body bones and reduce the level of PTH in the blood of postmenopausal women. Elderly people without serious chronic diseases and mobility disorders can appropriately participate in outdoor group activities. Exercise should be measured and gradual, such as walking, jogging, tai chi and other suitable for the elderly, outdoor activities can open up the chest, breathing fresh air; sun exposure to the skin is conducive to the synthesis of vitamins and calcium absorption in the body. It is best to go out with a partner. If there is a danger of falling, you can remind each other. The living environment should be suitable for the characteristics of the elderly, with bright indoor lighting, even light distribution, flat floors and non-slip low tiles to avoid collisions and slips. Items should not be placed too high, so that they can be easily retrieved and placed. The bathroom should be equipped with a toilet and handrails, and the height of the bed should be considered for the convenience of the elderly. Avoid falls caused by living environment factors.
4.Intervention treatment of osteoporosis
Adequate intake of calcium and vitamin D from the diet, the main sources of calcium are dairy products, soy products, seafood, such as milk, sea fish, tofu, sesame, vegetables, etc. Studies have proven that calcium and active vitamin D can improve motor coordination in the elderly. Caregivers should scientifically instruct patients to take calcium and vitamin D correctly , but with caution to prevent adverse consequences. Scientific selection of anti-osteoporosis drugs and their regular application under the guidance of physicians can effectively reduce the incidence of osteoporotic fractures.