Complications of osteoporosis

Pathomechanism: why do bones break?

Osteoporosis is not an isolated nosological entity. It is the end result of multiple pathological processes in which bone destruction (resorption) begins to quantitatively exceed its formation. Bone strength, which drops catastrophically in this disease, depends on the integration of two parameters:

1. Mineral density (BMD) — the amount of mineral per unit of area or volume.
2. Bone quality — its architecture, level of mineralization, rate of bone turnover, and the presence of accumulated microfractures.

In osteoporosis, bone trabeculae gradually thin and may disappear completely. The remaining elements attempt compensatory thickening in response to mechanical stress. The cortical layer undergoes endosteal resorption and thins, while in states with high bone turnover, intracortical tunneling and porosity are observed.

Fragility fractures as the main complication

Osteoporotic bone loses the ability to withstand even standard mechanical loads. As a result, fragility fractures (fragility fractures) develop — fractures resulting from inadequate, minimal trauma.

The decrease in density initially affects areas of the skeleton rich in spongy (trabecular) tissue. Therefore, typical localization sites are distinguished:

• Spine (the axial skeleton is affected first).
• Proximal femur.
• Distal forearm.
• Later, changes encompass the appendicular skeleton (pelvis, ribs, sternum).

Fractures are always accompanied by intense pain and lead to pronounced deformities. Important clinical nuance: the presence of at least one fragility fracture in a patient automatically indicates severe osteoporosis, even if densitometry shows normal results or osteopenia.

Prognosis and consequences of hip fracture

Complications of osteoporosis are inextricably linked with severe socio-economic consequences and profound disability, especially amid population aging. The greatest threat to life is posed by a hip fracture.

Outcome statistics for this localization are extremely unfavorable:

• About 20% of victims die within the first year after sustaining the trauma.
• Another 20% of patients permanently lose the ability to care for themselves and require constant care (e.g., become residents of nursing homes).

Causes and risk factors for complications

The risk of developing complications largely depends on the etiology of the pathological process. The disease is divided into two major groups:

1. Primary osteoporosis (always generalized in nature):

• Type I (postmenopausal): Develops in women due to a drop in estrogen levels. Osteoblasts respond to hormone deficiency by producing cytokines IL-1 and IL-6, which leads to powerful stimulation of osteoclasts.
• Type II (involutional): Associated with natural aging.
• Rare forms: Idiopathic in young adults and juvenile.

2. Secondary osteoporosis (as a symptom of other diseases):

• Endocrine: hyperparathyroidism, hyperthyroidism, glucocorticoid excess.
• Alimentary: malabsorption syndrome (celiac disease), alcoholism, scurvy (vitamin C deficiency).
• Hereditary: osteogenesis imperfecta, Marfan syndrome.
• Hematological: thalassemia, sickle cell anemia, leukemia in children.

Diagnosis before fractures occur

Conventional radiography has serious limitations: the images reveal only far-advanced bone mass loss. The term "demineralization" is incorrect here, as both minerals and collagen are lost in osteoporosis.

The "gold standard" for preventive diagnostics is dual-energy X-ray absorptiometry (DXA). According to WHO classification, the diagnosis is made based on the T-score:

• Normal: BMD ≥ -1 SD.
• Osteopenia: from < -1 to > -2.5 SD.
• Osteoporosis: BMD ≤ -2.5 SD.

Class and exam questions

What else to study on this topic

• Parameters and evaluation rules of the Z-score in densitometry
• Hyperparathyroidism and the formation of "brown tumors"
• Avascular necrosis of the femoral head ("double line" sign)
• Transient osteoporosis and regional migratory osteoporosis syndrome
• Ischiofemoral impingement syndrome

Other topics in the section "Chapter 22. Diseases of the Musculoskeletal System"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.