THEosteoporosis is currently a major public health problem. Indeed, the proportion of women affected by the disease is increasing and the repercussions on the quality of life are significant. In this article we will focus on trabecular osteoporosis or post-menopausal menopause.
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A few reminders about osteoporosis
Le skeleton, framework of the body, consists of 2 types of bones : L 'cortical bone, dense; and thetrabecular bone, more airy and lighter. Both are made up of comparable basic elements: the bone lamellae. These 2 types of bones combine to form the constituent parts of the skeleton.
THEcortical bone, which is more resistant to mechanical stresses, represents approximately 80% of bone mass in young adults. It occupies the periphery of the diaphysis (or body of the long bones). It also enters into the constitution of short bones and flat bones.
THEcancellous bone or the trabecular is present in the ends of the long bones, i.e. the epiphyses.
It is also found in the metaphysis, the transition zone between the epiphysis and the diaphysis, where it forms a system of irregular bone lamellae, the trabeculae. It is also present in vertebral bodies.
Trabecular bone represents only 20% of bone mass. The bone spans formed by the lamellae intersect and are arranged in the same direction as the pressure and traction forces exerting stresses on the bone.
Trabecular bone, although quantitatively less abundant, renews approximately 5 times faster than cortical bone. For this reason, osteoporosis manifests clinically in sites where there is a relatively large proportion of trabecular bone, primarily in the spine, hip and forearm.
osteoporosis
THEosteoporosis is a diffuse skeletal disease characterized by decrease in bone mass and deterioration of the microarchitecture of bone tissue. It is responsible for bone fragility predisposing to fractures.
It's about a double alteration du bone tissue : decrease in the amount of bone mass and modification of the quality of the trabecular meshwork without abnormal mineralization (unlike osteomalacia where mineralization is abnormal).
Osteoporosis corresponds to an exaggeration of physiological bone aging in such a way that the fracture threshold will be crossed. Thus, fractures will appear with minimal trauma, or even spontaneously. If you want to know more about osteoporosis, I invite you to click here.
Focus on trabecular or post-menopausal type 1 osteoporosis
It's here common formde theosteoporosis. It mainly affects women, in the post-menopausal period, between 50 and 65 years old.
It results in a thinning of the bone spans and a poor connection between them.
For good reason, the excess resorption at the level of the trabecular bone is linked to an estrogen deficiency. This situation simultaneously causes an increase in bone remodeling and a stimulation of bone resorption (destruction of bone tissue).
Trabecular osteoporosis is expressed mainly by vertebral fractures and incidentally by Pouteau Colles fractures (of the wrist).
Bone remodeling and bone loss
Bone is living tissue. It is constantly being overhauled. Two types of cells are responsible for the breakdown and synthesis of bone matrix. On the one hand, osteoclasts which destroy bone tissue (osteoresorption), and on the other hand, osteoblasts which build new bone tissue (osteoformation).
All of these phenomena constitute the bone remodeling. The balance is ensured by several factors, including bone cells, circulating hormones, growth factors, etc. Among these, hormones, especially estrogens, play a decisive role. All bone diseases are due to dysfunction of bone remodeling.
La estrogen deficiency causes a abnormal decrease in trabecular bone mass. This is due to hyperremodeling of the numerous foci of osteoclastic resorption causing the thinnest spans to disappear irreversibly. This results in a loss of connectivity of the trabecular meshwork.
Consequences of estrogen deficiency at the skeletal level
As we age, the amount of bone deposited during each remodeling cycle decreases. On the other hand, the depth of the resorption gaps dug by the osteoclasts would remain the same or decrease.
The result is a negative bone balance in each remodeling unit.
During osteoporosis, the depth of the resorption gaps is also not modified. On the contrary, the decrease of the amount of bone deposited during every remodeling cycle is more important.
Moreover, there is, at the time of menopause, an acceleration in the frequency of activation of bone remodeling resulting in an increase in the number of osteoclasts along the bone trabeculae.
Postmenopausal or trabecular osteoporosis occurs in the 5 to 15 year period following menopause. She's there result du estrogen deficiency consecutive to the cessation of ovarian activity. Bone loss primarily affects trabecular bone. During osteoporotic processes, the architecture of the cancellous bone trabeculae changes, the separation of the bony trabeculae increases, thus leading to their disjunction.
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