• Clinical science

Osteoporosis

Abstract

Osteoporosis is a skeletal condition in which the loss of bone mineral density leads to decreased bone strength and an increased susceptibility to fractures. The disease typically affects postmenopausal women and the elderly, as an abrupt decrease in estrogen and age-related processes play a key role in the development of osteoporosis. Further risk factors include inactivity, smoking, and alcohol consumption. Osteoporosis usually remains asymptomatic until the first occurence of fragility fractures (following minor trauma), particularly of the vertebrae. After repeated vertebral fractures, patients may also develop thoracic hyperkyphosis and lose height. Osteoporosis is diagnosed through a bone density test (dual-energy X-ray absorptiometry), while fractures are usually confirmed through conventional x-ray. Management of osteoporosis includes prophylactic measures and medical therapy. The prophylaxis consists mainly of adequate intake of calcium and vitamin D and regular physical activity with strengthening exercises. Both help to maintain or even increase bone mass and improve balance, thereby reducing the risk of falling. Medical therapy is indicated in cases of severely reduced bone density or osteoporotic fractures. The most commonly used drugs are bisphosphonates, which inhibit bone resorption and can significantly decrease the risk of fractures. There are several other possible medical therapies (e.g., teriparatide, raloxifene), which may be indicated in special cases (e.g., severe osteoporosis, breast cancer prophylaxis required) or if patients have contraindications to bisphosphonates.

Definition

  • Osteoporosis: insufficient bone strength with increased susceptibility to fractures
  • Osteopenia: decreased bone strength but less severe than osteoporosis

Epidemiology

  • Sex: > (∼ 4:1)
  • Age of onset: 50–70 years
  • Demographics: higher incidence in individuals of Asian, Hispanic and northern European ancestry than in black populations

References:[1]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

References:[1][2][3][4][5]

Clinical features

  • Mostly asymptomatic
  • Pathological fractures: spontaneous fracture following mild physical exertion or minor trauma (e.g., lifting something, bending over, or sneezing/coughing)
    • Localizations: vertebral (most common) > femoral neck > distal radius (Colles) fracture, fractures of the long bones (e.g., humerus)
    • Vertebral compression (crush) fractures are commonly asymptomatic, but may cause acute back pain and possible point tenderness without neurological symptoms
    • Long-term findings after repeated vertebral compression fractures
      • Decreased height (loss of 2–3 cm with each fracture)
      • Thoracic hyperkyphosis → stooped posture with a “dowager's hump”

References:[1][6][7]

Diagnostics

  • DXA (dual-energy X-ray absorptiometry)
    • Calculates bone mineral density (BMD) in g/cm2
    • Indications
      • General recommendation for women ≥ 65 years and men ≥ 70 years
      • In younger individuals if additional risk factors are present (e.g., prolonged glucocorticoid use, low BMI (< 21 kg/m2) or weight < 127 lb, alcohol use, smoker, amenorrhea)
    • Sites: lumbar spine, (entire) femur, femoral neck are measured
    • Results: T-score
  • Quantitative computed tomography (QCT): measurement of true volume density in g/cm3
  • Plain radiography
    • If osteoporosis is diagnosed: radiographic assessment of the whole skeletal system is recommended, particularly if a fracture is already suspected or height loss has occurred
    • Increased radiolucency is detectable in cortical bones once 30–50% of bone mineral has been lost
    • Osteoporosis can be diagnosed if vertebral compression fractures are present
      • Commonly an incidental finding because such fractures are typically asymptomatic
  • Clinical chemistry: usually normal (see Laboratory evaluation of bone disease), but some markers may be used for assessing risk of fracture
  • Pathology:

Osteoporosis is diagnosed if T-score ≤ -2.5 SD and/or a fragility fracture is present.

References:[1][8][9][10]

Differential diagnoses

References:[1]

The differential diagnoses listed here are not exhaustive.

Treatment

Lifestyle measures

  • Diet
    • Avoid alcohol and nicotine
    • Sufficient intake of calcium and vitamin D
  • Physical activity with strength and balance training
  • Avoid or minimize glucocorticoids

Medical therapy

Bisphosphonates should be taken in the morning and evening at least 30 minutes before meals to prevent bisphosphonates from forming complexes with calcium. To prevent esophagitis, they should also be taken with plenty of water and an upright position should be maintained for at least 30 minutes following intake!

References:[1][11][12][5]