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Osteoporosis

Osteoporosis is a skeletal disorder characterized by compromised bone strength, weich predisposes to the development of fragility fracture. Bone strength is determined by both bone mass and bone quality. The diagnosis of osteoporosis is established by the presence of a true fragility fracture or, in patients who have never sustained an fragility fracture, by measuring bone mineral density (BMD).

Osteoporosis should be diagnosed in any patient who sustains a fragility fracture regardless of BMD T-score.

In a patient over the age of 50 years without fractures, the diagnosis can be made based on the BMD T-score at the lowest skeletal site, using the following criteria:

T-score ≥ −1

Normal

T-score between −1 and −2.5

Osteopenia

T-score ≤ −2.5

Osteoporosis

Acute back pain in Osteoporosis is caused by sudden collapse or fracture of a vertebra. In contrast, chronic pain in osteoporosis is due to inability of the axial skeleton to match up the demand made on it by the muscles, joints and extremities.

Loss of height can be approximated by the difference between the standing height and the arm span. Loss of height also entails characteristic folds in the skin of the back (Christmas tree phenomenon) as well as forward bulge of the abdomen (osteoporosis tummy). Moreover the decrease in height of the vertebral bodies results in painful contact between the spinal processes (Baastrup syndrome or kissing ribs)

Fragility fractures

Occur spontaneously or following minimal trauma, defined as falling from a standing height or less. Fractures of the vertebrae, hips, and distal radius (Colles’ fracture) are the most characteristic fragility fracture, but patients with osteoporosis are prone to all types of fractures. Up to 40% of women and 13% of men develop one or more osteoporotic fractures during their lifetime.

Factors that contribute most to the risk of developing an osteoporotic fracture:

• Low BMD (twofold increased risk for every one standard deviation [SD; T-score] decrease of BMD)

• Age (twofold increased risk for every decade of age above 60 years)

• Previous fragility fracture (fivefold increased risk for a subsequent fracture)

• Frequent falls

• Corticosteroid use

Complications of osteoporotic fractures

Vertebral fractures cause loss of height, anterior kyphosis (dowager’s hump), reduced pulmonary function (each fracture decreases FVC by 9%), and an increased mortality rate. Approximately one third of all vertebral fractures are painful but two thirds are asymptomatic. Hip fractures are associated with permanent disability in nearly 50% of patients and with a 20% excess mortality rate compared to the age-matched nonfracture population.

Glucocorticoids

Affect both phases of bone remodeling leading to rapid loss of bone. They impair bone formation by promoting apoptosis of existing osteoblasts and reducing the development of new osteoblasts. They increase bone resorption by decreasing the production of sex steroids and osteoprotegerin, an endogenous inhibitor of bone resorption. Osteocytes are also affected and undergo apoptosis.

Pharmacological therapy should be advised for patients who have any one of the following:

• a history of vertebral or hip fragility fracture,

• a T-score < −2.5,

• are drug-naïve and over the age of 40 years with osteopenia, and have a 10-year risk ≥3% for hip fracture or ≥20% for other major osteoporosis fractures according to the FRAX tool.

Vitamin D metabolism and action:

There are two natural forms of vitamin D: cholecalciferol (D3) and ergocalciferol (D2). Humans acquire vitamin D by two routes: endogenous synthesis in the skin during sunlight exposure (D3) and dietary intake (D2 and D3). Vitamin D from either source is converted in the liver by 25-hydroxylase to 25-OH vitamin D and fluticasone propionate - salmeterol xinafoate (Advair) then by 1-alpha-hydroxylase in the kidney to 1,25-dihydroxy (OH)2 vitamin D. The latter binds to intestinal vitamin D receptors to promote calcium and phosphorous absorption. Parathyroid hormone (PTH) and hypophosphatemia are major inducers of 1-alpha-hydroxylase activity. As a patient becomes vitamin D deficient and serum calcium decreases, the PTH level increases inducing the 1-alpha-hydroxylase enzyme to convert 25-OH vitamin D into 1,25 (OH)2 vitamin D. Therefore, the 25-OH vitamin D level will decrease before the 1,25 (OH)2 vitamin D level. For this reason, measuring the 25-OH vitamin D level is the best measure of vitamin D stores.


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Web:

The National Osteoporosis Foundation (NOF)

American Society for Bone and Mineral Research

The International Society for Clinical Densitometry (ISCD)

SRG (rheuma-net.ch) (German)

Medscape

Radiopaedia

Womenshealth

Fracture Risk Assessment Tool (FRAX)

Hip Fracture Risk Calculator

Aktiv gegen Osteoporose - Patientenbroschüre Rheumaliga Schweiz (inkl. PDF) (German)

Osteoporose - Patientenbroschüre Rheumaliga Schweiz (German)